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  • Artikel: DFG Deutsche Nationallizenzen  (4.221)
  • 1985-1989  (4.221)
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  • 1988  (4.221)
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  • Kidney
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  • Artikel: DFG Deutsche Nationallizenzen  (4.221)
Materialart
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  • 1985-1989  (4.221)
  • 1980-1984
  • 1965-1969
  • 1930-1934
  • 1890-1899
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  • 1
    Digitale Medien
    Digitale Medien
    Binding sites of atrial natriuretic peptide in human renal tissue — Quantification by in vitro receptor autoradiography (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 303-307 
    Details
    ISSN: 1432-1440
    Schlagwort(e): ANP ; Human ; Kidney ; Receptor autoradiography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Specific binding sites for atrial natriuretic peptide (99–126) in different areas of normal human renal tissue were quantified by in vitro autoradiography. Our data represent the first characterization of ANP binding sites in different structures of the human kidney. Characterization of ANP binding revealed by Scatchard plot analysis a single class of high affinity binding sites in the glomeruli (K d 0.53±0.11 nM;B Max 74.4±17.86 fmol/mg protein), the vasculature (K d 0.18±0.014 nM;B Max 91.6±25.02 fmol/mg protein), and the medulla (K d 0.34±0.13 nM;B Max 106.0±30.61 fmol/mg protein). These sites may play a key role in the actions of the cardiac hormone in human kidney and in the ameliorating effects of ANP in the recovery from acute renal failure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01727517
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  • 2
    Digitale Medien
    Digitale Medien
    Age-related occurrence of simple renal cysts studied by ultrasonography (1988)
    Springer
    Journal of molecular medicine 66 (1988), S. 385-387 
    Details
    ISSN: 1432-1440
    Schlagwort(e): Aging ; Kidney ; Simple cyst ; Ultrasonography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Three hundred forty-eight outpatients without evidence of renal disease were examined by ultrasound. Their ages ranged from 18 to 83 years. Unexpected renal cysts of more than 1 cm were found in 47 patients (13.5%). No cysts were demonstrated in patients less than 23 years old; thereafter the number of patients with cysts increased significantly with age. The cyst diameter also tended to increase with age, but the correlation with age was not significant. There was no statistical difference of cyst occurrence between the right and left kidney, or between males and females. The upper portion of the kidney was most often affected in the equally divided three portions along the long axis. These results confirm that the development of simple renal cysts is age-related.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01737941
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  • 3
    Digitale Medien
    Digitale Medien
    Lowered plasma erythropoietin in hypoxic rats with kidney tubule lesions (1988)
    Springer
    Annals of hematology 57 (1988), S. 317-321 
    Details
    ISSN: 1432-0584
    Schlagwort(e): Erythropoietin ; Kidney ; Ureterligation ; Tubules ; Gentamicin ; Hypoxia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The role of the kidney tubules in the renal formation of erythropoietin is incompletely understood. Therefore, the capability to produce erythropoietin in response to hypoxia was studied in rats with tubular lesions. Nephron damage was induced in two different ways. First, rats were treated with the nephrotoxic aminoglycoside gentamicin (67.5 mg/kg and day) for 14 days. The animals were then subjected to simulated altitude (6,800 m) for 6 h. The resulting plasma erythropoietin concentration was significantly lower (0.5 IU/ml) than in saline treated control rats exposed to hypoxia (1.0 IU/ml). Second, unilateral hydronephrosis was induced by ureteral ligation. The contralateral kidney was removed immediately before the animals were exposed to siulated altitude for 6 h. The plasma erythropoietin concentration in the ureterligated rats did not increase above the value (0.3 IU/ml) in hypoxia exposed anephric rats. These results indicate that the production of erythropoietin is reduced following tubular injury. Tubule cells may diretly produce the hormone or interfere with the O2-sensing mechanisms controlling its synthesis. The latter hypothesis would seem to be supported by our failure to demonstrate in vitro erythropoietin production by the two established kidney tubule cell lines, LLC-PK1 and PK-15.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00320362
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  • 4
    Digitale Medien
    Digitale Medien
    Kidney tissue somatomedin C and initial renal growth in diabetic and uninephrectomised rats (1988)
    Springer
    Diabetologia 31 (1988), S. 310-314 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Kidney ; hypertrophy ; nephrectomy ; rat ; somatomedin C ; streptozotocin ; diabetes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Kidney growth after induction of experimental diabetes in rats was compared to compensatory renal growth in response to unilateral nephrectomy. After 4 days of diabetes, kidney weight had increased from 816±21 mg (SEM) to 940±42 mg (15%). In insulin-treated diabetic rats kidney weight was unchanged at the end of the study, namely 828±15 mg. In unilaterally nephrectomised rats kidney weight increased from 840±20 mg (SEM) to 1050±60 mg during 4 days (24%). We observed increased kidney content of somatomedin C in both diabetic and uninephrectomised rats. In untreated diabetic rats it was maximal after 48 h, with an increase of 77% (3469±312 ng/g (SEM) versus 1961±173 ng/g). After 4 days the somatomedin C content had returned to initial levels. In insulin-treated rats somatomedin C content did not increase during the observation period. The somatomedin C content of the remaining kidney after unilateral nephrectomy was maximal after 24 h with an increase of 58% (from 1340±203 ng/g (SEM) to 2122±214 ng/g). The somatomedin C content returned to normal at day 4. Serum somatomedin C declined insignificantly in diabetic animals during the experimental period, but a significant decrease (p〈0.02) was found in uninephrectomised rats. This study demonstrates that kidney somatomedin C peaks during the first or second day after uninephrectomy or induction of diabetes, respectively, and that insulin treatment sufficient to prevent kidney growth abolishes the increase. These similar rapid initial hypertrophies/hyperplasies may thus be dependent on local somatomedin C formation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00277413
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  • 5
    Digitale Medien
    Digitale Medien
    Enzymuria in workers exposed to inorganic mercury (1988)
    Springer
    International archives of occupational and environmental health 61 (1988), S. 65-69 
    Details
    ISSN: 1432-1246
    Schlagwort(e): Inorganic mercury ; Occupational exposure ; Biological monitoring ; Kidney ; Enzymuria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Urinary excretion of beta-hexosaminidase (NAG = N-acetyl-beta-glucosaminidase) and albumin was examined in 41 chlor-alkali workers exposed to inorganic mercury and 41 age-matched controls. Either U-HG or B-Hg levels for these workers were available dating from the 1960s to the present. Increased U-NAG was seen in workers with a U-Hg today of more than 4μg/mmol creat (about 50μg/l; 35 μg/g creat). Multiple linear regression analysis showed that U-NAG was correlated to U-Hg and integrated dose but not to the present B-Hg level. No albuminuria (detection limit 12.5 mg/1) was found in any of the subjects. In a longitudinal study, no decrease in UNAG levels was seen in 15 chlor-alkali workers after their vacation (x = 20 d). In five workers followed for ten months after a short exposure period, no definite time trend could be seen. The results show that there is a slight effect on renal tubules even at rather low levels of exposure to mercury vapour. The clinical significance of the enzymuria levels found here is, however, debatable.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00381609
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  • 6
    Digitale Medien
    Digitale Medien
    The relationship between renal metabolism and proximal tubule transport during ontogeny (1988)
    Springer
    Pediatric nephrology 2 (1988), S. 356-367 
    Details
    ISSN: 1432-198X
    Schlagwort(e): Kidney ; Development ; Tubular ; Energy ; Glycolysis ; Sodium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The proximal tubules of newborn and adult animals reabsorb a similar fraction of the filtered load of Na+ and H2O (65%–70%). In tubules from adult animals, transcellular, active Na+ reabsorption accounts for one-third of the total, while two-thirds occur passively through the paracellular pathway, driven by hydrostatic and oncotic forces (one-third) and by cell-generated effective osmotic and ionic gradients (one-third). Since two-thirds of the Na+ is reabsorbed passively and does not require energy, the mature proximal tubule has a high Na+/O2 molar ratio (48 Eq of Na+/mol of O2). Measurements of ouabain-sensitive oxygen consumption in suspensions of proximal tubules indicate that in newborn, aerobic metabolism can support about 50% of the net Na+ transport rate compared with the 33% in tubules from adult animals. Independent confirmation of the direct and proportional relationship between active Na+ transport and ouabain-sensitive O2 consumption exists for the adult but not for the newborn. However, measurements of epithelial conductances and of transepithelial hydrostatic and oncotic pressure differences indicate that passive paracellular fluxes can account for the remaining 50% of the proximal Na+ reabsorption in newborn. The high permeability of the proximal tubules of newborn animals to small molecular weight solutes suggests that cell-generated osmotic and ionic transepithelial gradients are minimal in the tubules of newborn animals. Yet in the newborn, the osmolality of the end proximal tubule fluid was found to exceed that in plasma. This indicates that osmotic gradients due to differences in reflection coefficients for preferentially reabsorbed solutes and Cl− do exist across the proximal tubules of the newborn and suggests that these gradients may contribute to Na+ and H2O reabsorption. If this is indeed the case, then the contribution of active and of hydrostatic and oncotic pressure-driven flows to the overall reabsorption of Na+ and fluid has been overestimated. Resolution of this discrepancy requires measurements of the reflection coefficients for HCO 3 − and Cl− in the proximal tubule of the newborn. The metabolic processes by which energy is supplied to renal proximal cells during development are also incompletely characterized. There is evidence that maturation of aerobic metabolism, Krebs cycle enzymes activity, and of the mitochondrial membrane surface area precede the development of net reabsorptive transport (Na+, H2O, HCO3, glucose). By contrast, maturation of Na+−K+-ATPase activity at the basolateral cell membrane follows that in reabsorptive transport and does not limit its development. The extent to which age-related changes in reabsorptive fluxes are due to the development of luminal membrane transport systems, to the decrease in paracellular permeability, or both remains to be determined. The high activity of enzymes in the hexosemonophosphate pathway and the high NADH/NAD ratio present during the first few weeks of extrauterine life poise the proximal tubules for high rates of biosynthesis of membrane lipids, glycoproteins, nucleic acids, and transporter proteins necessary for final differentiation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00858693
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  • 7
    Digitale Medien
    Digitale Medien
    Epidermal growth factor in the mouse kidney: developmental changes and intranephron localizations (1988)
    Springer
    Pediatric nephrology 2 (1988), S. 124-128 
    Details
    ISSN: 1432-198X
    Schlagwort(e): Epidermal growth factor ; Mouse ; Kidney ; Submaxillary gland ; Ontogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The developmental changes in epidermal growth factor (EGF) have been studied in tissue homogenates, kidney slices, and microdissected nephron segments of the mouse. Immunoreactive EGF concentration per milligram of protein increased in the kidney by about 20-fold from 1 week to 3 weeks of life, reaching the highest levels between 5 and 7 weeks, and decreasing by 10 weeks of life. The time course of the changes was different from those of submaxillary and urinary EGF. Above 7 weeks of age, kidney EGF was higher in female than in male mice. Among various zones of the kidney (outer cortex, inner cortex, outer medulla I, II and papilla), the outer medulla I and II contained the highest quantities of EGF per gram of wet tissue. The highest EGF content per millimeter length was observed in the medullary and cortical thick ascending limbs of Henle's loop. The amounts exceeded by about 4.5-fold those found in glomeruli and in proximal convoluted and proximal straight tubules, and by about 3-fold those present in distal and collecting tubules. Unilateral nephrectomy resulted in no significant changes in EGF levels in the contralateral kidney. The results suggest that the ontogeny of kidney EGF is different from that of the EGF found in the submaxillary gland, and that there is nephron heterogeneity in EGF content.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00870392
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  • 8
    Digitale Medien
    Digitale Medien
    Dopamine receptors in the developing sheep kidney (1988)
    Springer
    Pediatric nephrology 2 (1988), S. 156-162 
    Details
    ISSN: 1432-198X
    Schlagwort(e): Dopamine ; Receptors ; Kidney ; Sheep ; Ontogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract These studies were designed to characterize dopamine receptor density and affinity in kidneys removed from sheep of varying ages (fetal, newborn, and adult) using radioligand binding methods. Three different radioligands were used: the specific dopamine-1 antagonist3H-SCH 23390, the dopamine-1/dopamine-2 antagonist3H-haloperidol, and the dopamine-2 antagonist3H-spiroperidol. The specific binding of3H-haloperidol and3H-spiroperidol was saturable with time and ligand concentration, being indicative of dopamine receptors. The specific binding of the dopamine-1 selective radioligand3H-SCH 23390 was also saturable with time but displayed several points of saturation with increasing ligand concentration. The specific binding of3H-haloperidol, which had a low affinity and is indicative of dopamine-1 receptors, showed no age-related changes in maximum receptor density or affinity. On the other hand, the maximum receptor density of dopamine-2 receptors measured by3H-spiroperidol decreased with age. The observations that renal dopamine-1 receptor density or affinity do not change with maturation are in agreement with our pervious studies that showed no age-related changes in dopamine-receptor-mediated renal vasodilatation in sheep. The significance of the decrease in renal dopamine-2 receptor density with age remains to be determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00870397
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  • 9
    Digitale Medien
    Digitale Medien
    The effect of chronic adriamycin treatment on heart kidney and liver tissue of male and female rat (1988)
    Springer
    Archives of toxicology 61 (1988), S. 275-281 
    Details
    ISSN: 1432-0738
    Schlagwort(e): Adriamycin ; Heart ; Kidney ; Liver ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The influence of chronic adriamycin treatment on cellular defence mechanisms against free radicals has been determined in rats. To that end, the changes in vitamin E content, activity of superoxide dismutase, catalase and factors of the glutathione system were measured in heart, kidneys and liver after 24 and 52 days of treatment. Moreover, damage was assessed by measuring the activity of NADPH- and NADH-cytochrome c reductase. The results concerning the components of the oxidative defence systems in male rats showed reductions in the activity of superoxide dismutase and catalase in renal tissue and in factors of the glutathione system in liver tissue. In cardiac tissue an increased activity of catalase and elevated content of total glutathione were found. Vitamin E content was increased in liver and to a lesser extent, in kidneys. The activity of Se-dependent glutathione peroxidase sharply decreased only in liver. Major differences between male and female rats were not observed in renal and cardiac tissue, as far as protective factors were concerned. However, a decrease in catalase activity was detectable earlier in male kidneys. The protective factors in liver of female rats were far less susceptible to in vivo treatment with adriamycin, as compared to liver of male rats. Decreased activity of the cytochrome reductases was found in liver of male rats. In male renal tissue only cytochrome c reductase activity was significantly reduced. Male cardiac tissue showed no signs of biochemical damage, although from histological examination in a parallel study [J Natl Cancer Inst 76: 299–307 (1986)] lesions were evident. In female rats no damage was found in liver, kidneys and heart.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00364850
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  • 10
    Digitale Medien
    Digitale Medien
    Cardiomyopathy associated with carnitine loss in kidneys and small intestine (1988)
    Springer
    European journal of pediatrics 148 (1988), S. 193-197 
    Details
    ISSN: 1432-1076
    Schlagwort(e): Cardiomyopathy ; Carnitine ; Carnitine deficiency ; Carnitine transport defect ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A boy was first seen at the age of 1 year on account of congestive cardiomyopathy. Growth and development had been normal. Total plasma carnitine was extremely low (1.8 μmol/l; normal range: 25–64 μmol/l). No hypoglycaemia, lactic acidaemia or dicarboxylic aciduria were found. Other laboratory findings were unremarkable except for a slight deficiency in iron, vitamin D and vitamin E. Total muscle carnitine was 1.5% of normal; however, no signs or symptoms of myopathy could be detected. After carnitine loading, liver carnitine increased to 24% of normal. Isolated muscle mitochondria showed decreased oxidative capacity with all substrates tested. Stimulation of O2 uptake by adenosine diphosphate (ADP) was decreased. After loading with both intravenous and oral carnitine, there was a rise in plasma carnitine and a rapid loss in the urine and the faeces. These findings suggest a defect in the brush border carnitine transport system of the kidneys and of the small intestine. Renal clearance of carnitine was abnormally high. Therapy with 1 g oral l-carnitine/kg per day was instituted without any problems and the cardiac disease resolved within 3 months. The parents and the patient's five sibs also had low plasma carnitine but displayed no cardiomyopathy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00441399
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  • 11
    Digitale Medien
    Digitale Medien
    Biosynthesis of pyrimidine nucleotides and level of cytochrome P-450 in rat liver and kidney after clofibrate administration (an in vivo study) (1988)
    Springer
    Journal of cancer research and clinical oncology 114 (1988), S. 59-63 
    Details
    ISSN: 1432-1335
    Schlagwort(e): Biosynthesis ; Pyrimidine nucleotides ; Cytochrome P-450 ; Clofibrate ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Like other lipid-soluble xenobiotics, clofibrate (ethyl-2-(4-chlorophenoxy)-2-methylpropanoate) increased the level of microsomal cytochrome P-450 in liver and decreased the utilization of 14C-orotic acid for the synthesis of hepatic cytidine nucleotides. This phenomenon was associated with the increased (a) uptake of 14C-cytidine, (b) total content of cytidine components of the acid-soluble extract and (c) utilization of this nucleoside for the synthesis of RNA. No changes were observed in uridine components. Clofibrate also increased the level of cytochrome P-450 in kidney microsomes; the degree of induction was almost the same as in the liver. The variations of renal pyrimidine metabolism after administration of the drug were analogous to those observed in the liver.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00390486
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  • 12
    Digitale Medien
    Digitale Medien
    Pyruvate carboxylation in glutamine synthesis from alanine by isolated guinea-pig renal cortical tubules (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 7-11 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Kidney ; Guinea-pig ; Alanine ; Glutamine ; Carboxylation ; Pyruvate carboxylase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Isolated guinea-pig kidney cortex tubules were incubated in Krebs-Henseleit buffer containing NaH14CO3 (25 mM) andl-alanine (5 mM). A high rate of alanine metabolism was found to be accompanied by a high rate of both14CO2 fixation and glutamine synthesis. The fixation of14CO2 was virtually abolished in the presence of oxalate, a known inhibitor of pyruvate carboxylase, indicating that, in guinea-pig renal cortex, this enzyme is responsible for the synthesis of oxaloacetate in the conversion of alanine into glutamine. More than 90% of the label fixed was found in carbon 1 mainly of glutamine and to a lesser extent of glutamate. In the presence of alanine+NaH14CO3+MSO, an inhibitor of glutamine synthetase, most of the14CO2 fixed by pyruvate carboxylase was subsequently released and carbon 1 of glutamate was the only site of labelling. In the presence of alanine+NaH14CO3, the fact that not all the glutamine found was labelled in carbon 1 could be explained by glutamine synthesis from endogenous substrates as well as by glutamine synthesis from alanine after prior equilibration of [4-14C]-oxaloacetate with fumarate; that such equilibration occurred was demonstrated by the observation that [1-14C]-glutamine and [1-14C]-glutamate were synthesized from [1-14C]-alanine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00583724
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  • 13
    Digitale Medien
    Digitale Medien
    Comparison of transcellular and transepithelial water osmotic permeabilities (P os) in the isolated proximal straight tubule (PST) of the rabbit kidney (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 66-74 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Osmotic permeability ; Paracellular water flow ; Proximal tubule ; PST ; Transcellular permeability ; Epithelia ; Water transport ; Leaky epithelia ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Measurements of the water osmotic permeabilities of apical and basolateral membranes of PST cells and of the transepithelial permeability have been carried out using a very fast method with high temporal and spatial resolution. At 25°C the values obtained are: 80.8±11.9×10−4 cm3/s osmol cm2 of apical (luminal) surface area and 90.1 ±13.0×10−4 cm3/s osmol cm2 of basement membrane area (no membrane invaginations taken in account). These values are higher than previously published values due to the use of a faster and more accurate volume measuring and recording system. The transepithelial water osmotic permeability at 25°C is 77±11 in units of 10−4 cm3/s osmol cm2 basement membrane area. The transcellular water osmotic permeability is 32±7 (same units), leaving a paracellular contribution of 45±10 (same units). In the presence of 2.5 mM parachloromercuribenzenesulfonate (pCMBS) the apical permeability is reduced with an incubation of 10–15 min to 23% of its control value and the basolateral permeability to 8% of its control value (after 25 min) but the transepithelial permeability is only reduced to about 1/2 of the control value. This leaves a transcellular permeability of 6×10−4 cm3/s osmol cm2 of basement membrane area and a paracellular contribution of 33±6 (same units). These results indicate a significant contribution of the paracellular pathway to the transepithelial water osmotic permeabilities in PST.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00583732
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  • 14
    Digitale Medien
    Digitale Medien
    A comparison of the effects of renal artery constriction and anemia on the production of erythropoietin (1988)
    Springer
    Pflügers Archiv 413 (1988), S. 62-66 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Erythropoiesis ; Erythropoietin ; Renal artery constriction ; Hypoxia ; Kidney ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract It is generally assumed that the O2 supply to the kidneys is the major determinant of the synthesis of erythropoietin (Ep). In the present study, the O2 supply of the kidneys of rats was lowered by the reduction of renal blood flow (rbf). Plasma Ep was determined after about 18 h of bilateral application of Goldblatt clips with graded inner diameters. The results were compared to findings in anemic rats, in which the systemic O2 supply was lowered by exchange transfusion of blood with plasma. We found a linear correlation between Ep levels in plasma and the degree of reduction of rbf. However, there was an exponential relationship between Ep levels and the concentration of hemoglobin in blood. In addition, the elevation of plasma Ep was only moderate, when rbf was reduced (maximum 0.07 IU Ep/ml plasma). The increase in Ep concentration was much more pronounced in anemia (up to about 7 IU Ep/ml plasma). From these results it may be concluded that decreasing oxygen supply to the kidney through reduction in renal blood flow (ischemic hypoxia) is less effective in increasing erythropoictin production than reducing the hemoglobin concentration (anemic hypoxia). The possibility must be considered that the increase in renal production of erythropoietin due to anemic hypoxia is triggered by one or more extrarenal signals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00581229
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  • 15
    Digitale Medien
    Digitale Medien
    Successful transplantation of kidneys bearing previously mismatched HLA A and B locus antigens (1988)
    Springer
    Transplant international 1 (1988), S. 190-195 
    Details
    ISSN: 1432-2277
    Schlagwort(e): HLA ; Kidney ; Transplantation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Transplantation of kidneys bearing HLA antigens to which recipients have previously been exposed is generally avoided, and such prudence is a well-documented means of preventing early graft loss. Prior exposure and subsequent reactions can, however, take a wide variety of forms, and blanket avoidance may prevent many deserving patients from being transplanted. In our region, operating through a single tissue-typing laboratory, we follow a consistent policy of allowing retransplantation with kidneys bearing previous mismatches, provided no relevant antibody response has been detected. Twenty-one of 34 such transplants remain functioning at time periods ranging from 7 months to 7 years. Four were lost due to rejection within the 1st month, and the remaining 9 functioned for periods ranging from 2 months to 8 years. Three were lost for reasons other than rejection. Our antibody screening policy and our criteria for a negative crossmatch results in the exclusion of two-thirds of all repeat mismatch transplantations. The results indicate that in the remaining third, transplantation can be performed across a repeat mismatch with excellent long-term results, provided our defined crossmatch policy is adhered to strictly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00346783
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  • 16
    Digitale Medien
    Digitale Medien
    Short-term stimulation of cellular autophagy by furosemide in the thick ascending limb of Henle's loop in the rat kidney (1988)
    Springer
    Cell & tissue research 253 (1988), S. 625-629 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Furosemide ; Kidney ; Thick ascending limb, Henle's loop ; Cellular autophagy ; Ultrastructural morphometry ; Intracellular degradation ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In an effort to investigate the functional relationship between cell-specific work and intracellular degradative processes, the effect of furosemide on cellular autophagy was investigated in two different portions of the nephron, namely, the thick ascending limb of Henle's loop (TAL), which is a main target of this drug, and the proximal convoluted tubule (PCT) as a reference structure. Eight male adult rats were treated with furosemide (60 mg/kg body weight, s.c.). Eight control animals received physiological saline. 1 to 4 h after the injections the animals were killed by perfusion fixation. Small specimens of kidney tissue from the inner stripe of the outer medulla and from the outer cortex were processed for electron microscopy; they were investigated morphometrically for volume fraction and numerical density of autophagic vacuoles (AVs). A significant increase of both parameters (volume fraction: 0.42 × 10-4 to 1.09 × 10-4; numerical density: 4.2 × 105/mm3 to 15.5 × 105/mm3) was seen under the influence of furosemide in TAL cells, whereas PCT cells did not show a significant increase in volume fraction or any increase in numerical density of AVs. These data suggest that the functional unloading of TAL, via blocking of the Na+- 2Cl- — K+ co-transport by furosemide, results in adaptative “structural unloading”, i.e., an increased sequestration of cytoplasmic components into AVs, within a short-time interval.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00219753
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  • 17
    Digitale Medien
    Digitale Medien
    44-kDal bone phosphoprotein (osteopontin) antigenicity at ectopic sites in newborn rats: kidney and nervous tissues (1988)
    Springer
    Cell & tissue research 251 (1988), S. 23-30 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Bone phosphoprotein ; Osteopontin ; Kidney ; Inner ear ; Trigeminal nerve ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Previous immunohistochemical data have shown that the 44-kDal bone phosphoprotein (44K BPP, also called sialoprotein I or oestopontin) recently isolated in our laboratory was synthesized by osteoblasts and osteocytes and was expressed early during differentiation of boneforming cells. We report here the presence of 44K BPP antigenicity at certain ectopic sites, namely, the proximal-convoluted tubule of the kidney, neurons, sensory and secretory cells in the internal ear. To insure specificity and reproducibility, different immunohistochemical methods were used and affinity-purified antibodies against two separate preparations of pure 44K BPP were tested. In the cells of the proximal-convoluted tubule, 44K BPP immunoreactivity was observed within apical endocytotic vacuoles and within lysosomes. This staining thus correlates with the degradation of the 44K BPP epitope which we previously demonstrated to occur in serum. On the other hand, in the neurons of the acoustic ganglion and the sensory cells of the macula, 44K BPP immunoreactivity was associated with the Golgi apparatus indicating synthesis and secretion by these cells. The finding that the 44K BPP (or a structurally related molecule) is synthesized by neurons and neuroepithelial cells deserves further investigation with respect to a possible embryologie relationship between neuroectodermal cells and the precursors of some bone forming-cells of the skull.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215443
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  • 18
    Digitale Medien
    Digitale Medien
    The innervation of the renal cortex in the dog (1988)
    Springer
    Cell & tissue research 253 (1988), S. 539-546 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Kidney ; Renal innervation ; Catecholamine-synthesizing enzymes ; Dopamine ; Immunohistochemistry ; Dog
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Two cytochemical techniques were used at the ultrastructural level to study the distribution of specific axon types to different intrarenal structures in the dog. Using the chromaffin reaction to distinguish catecholaminergic fibres from other axon populations, it was found that the renal cortex of the dog is supplied only by catecholaminergic nerves. Immunostaining for tyrosine hydroxylase (TH) labelled all of the intracortical nerves, and 20% to 25% of these profiles also contained dopa decarboxylase (DDC)-immunoreactivity, indicating they were dopaminergic rather than noradrenergic. Both DDC-positive and DDC-negative axons were seen in close association (∼80 nm) with blood vessels and juxtaglomerular cells as well as tubular epithelial cells. The distribution of TH- and DDC-immunoreactive nerves in the renal cortex is compatible with existing functional evidence indicating that both dopaminergic and noradrenergic nerves are involved in the regulation of renal blood flow, tubular reabsorption and renin release.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00219744
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  • 19
    Digitale Medien
    Digitale Medien
    Microfibrils are a major component of the mesangial matrix in the glomerulus of the rat kidney (1988)
    Springer
    Cell & tissue research 254 (1988), S. 183-187 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Glomerular mesangium ; Kidney ; Tannic acid ; Microfibrils ; Basement membrane ; Rat (Wistar)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The mesangial matrix of the rat glomerulus was studied by transmission electron microscopy in specimens preserved by a modified technique, which avoids osmium tetroxide but uses tannic acid as a contrasting agent. It can be demonstrated that microfibrils are a major component of the normal glomerular mesangial matrix. They are non-branching tubular structures with a hollow centre, an undefined length and a thickness of ∼15 nm. Microfibrils make up a dense fibrillar network interconnecting mesangial cells and glomerular basement membrane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00220032
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  • 20
    Digitale Medien
    Digitale Medien
    A new stable epithelial cell line (RK-L) from normal rat kidney (1988)
    Springer
    Cell & tissue research 252 (1988), S. 429-434 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Kidney ; Cell line ; Tissue culture ; Epithelium ; Biological transport ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary A stable epithelial cell line has been established from the kidneys of a normal Sprague-Dawley rat. This line, termed RK-L, has a high proliferative capacity (minimal doubling time 12.3 h) and can be grown in medium containing 1% fetal bovine serum. Thus far, the line has been carried through more than 60 serial passages. The RK-L cells were found to display similarities with kidney tubule cells. Using light microscopy, confluent cultures were seen as pavement-like monolayers forming domes, which are thought to result from transepithelial fluid transport. Electron microscopy revealed polarized cells that had microvilli on the apical surface, junction complexes in the apical part of the lateral cell membrane, and a basal lamina-like layer. Pinocytotic activity was indicated by infoldings of the apical plasma membrane and the formation of vesicles. The RK-L line should prove useful for investigations of kidney tubule transport mechanisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00214386
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  • 21
    Digitale Medien
    Digitale Medien
    Macroautophagic phenomena in renin granules (1988)
    Springer
    Cell & tissue research 251 (1988), S. 229-231 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Kidney ; Juxtaglomerular apparatus ; Renin granules ; Lysosomes ; Autophagy ; Mouse
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The secretory granules of marine epithelioid cells take up and probably degrade mitochondria; they thus appear to have macroautophagic properties. As renin granules also have other properties uncommon for secretory granules, they are suggested to fulfill functions in these cells otherwise reserved for lysosomes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215470
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  • 22
    Digitale Medien
    Digitale Medien
    Exercise versus immersion: antagonistic effects on water and electrolyte metabolism during swimming (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 248-253 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Aldosterone ; Antidiuretic hormone ; Blood volume ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Changes in blood composition, renal function, aldosterone and antidiuretic hormone (ADH) concentrations were investigated in 10 untrained male subjects when swimming (60 min at a heart rate of about 155 beats·min−1, water temperature 28° C) and during the subsequent 3 h in a sitting position. Many specific effects of either exercise or immersion were abolished or attenuated; no significant changes in plasma aldosterone, [ADH], [K+], [Cl−], or of urinary volume, glomerular filtration rate, free water or osmolar clearance were observed. The urine was diluted resulting in lowered [Na+]. In blood some quantities which are only slightly influenced by immersion increased during swimming ([Na+], [Lac−], [H+], osmolality, [creatinine]). Exercise induced plasma volume loss, calculated from increasing [Hb], was small (110 ml), probably because interstitial fluid enters the vascular space during the initial phase of immersion. One might anticipate that the training effects on fluid and electrolyte metabolism and circulation are different when swimming and when performing endurance sports on land.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00640671
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  • 23
    Digitale Medien
    Digitale Medien
    A contribution to the UV degradation of polyurethanesPaper presented at the 18th Colloquium of Danubian Countries for “Natural and artificial ageing of plastics” in Villach June 24-26, 1987. (Austria) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 247-263 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effects of the nature of the polyols used in polyurethane (PUR) synthesis on the structural transformations after ageing by UV irradiation has been studied. The investigations were performed on PUR prepared from polyester and polyether diol oligomers.The characterization of the samples before and after ageing in view of the structural changes, which influence the course of the photooxidative degradation and photocrosslinking as well as in view of changes of mechanical properties has been done. Comparative investigations were performed by spectroscopic and viscometric measurements.The results show pronounced heterogeneity of the degradative reactions, including the existence of crosslinking processes and producing thus very inhomogeneous polymeric material. The course and the intensity of photooxidative degradation of PUR differ together with changes of mechanical properties depending whether polyester or polyether polyol have been used. The processes of photooxidative degradation is less expressed in polyesterurethane then in polyurethane based on polyether, under the same conditions of experiments. Different structures of polyester diols caused the various ageing behaviour of PUR too.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580114
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  • 24
    Digitale Medien
    Digitale Medien
    Beurteilung von hals-verbindungenVortrag anlä-sslich des 18. Donäulandergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich), vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 283-300 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: QUALIFICATION OF HALS COMPOUNDSA complex method of examination has been developed suitable for the qualification of light stabilizers; by this method, according to experience, the efficacy of HALS compounds can be extensively and expediently characterized.Several light stabilizers of the HALS-type were examined and qualified, used alone or together with a UV-absorber.It has been found that, when selecting the appropriate structure for a given polymer, the weatherability of polyolefine foils is effectively increase to six-eightfold; the increase is even tenfold when the stabilizer is combined with a benzophenone-type compound.As a utilization of these experiences, a contract with the industry, led to the production of an LDPE based agricultural foil with a life-time of several years.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580116
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  • 25
    Digitale Medien
    Digitale Medien
    Simulation des natürlichen hagelschlags an transparenten kunststoffplattenVortrag anläßlich des 18. Donäulandergesprächs über “Nattürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 301-311 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Natural hail impact tests are scarcely available because hailstorms are limited to a small area and cannot be predicted regarding time, place and intensity. Therefore we relied on laboratory tests simulating natural hailstones by polyamide balls (5-50 mm dia.) whose final velocity could be varied according to meteorological data. So the influence of diameter (weight) and velocity of the artificial hailstones could be taken into consideration independently.The energy of damage or equivalent natural hailstone diameter were determined for 16 mm double skin sheet from PMMA as 0.2 J (14 mm dia.) for star shaped cracks and 2 J (26 mm dia.) for holes. These values do not significantly decrease after 10 years weathering. 10 mm double skin sheets from PC show an extremly high energy of damage of abt. 10 J (38 mm dia.) which decreases to a medium level of 2 J (26 mm dia.) after several years weathering. This decrease is remarkably reduced by weather resistant protective coating.As hailstorms consist to more than 80% of hailstones below 10 mm dia. (0.04 J) the mentioned sheet materials are quite hail resistant also after long weathering periods, but they cannot withstand an extreme hail catastrophe as in Munich July 12, 1984.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580117
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  • 26
    Digitale Medien
    Digitale Medien
    Specimen temperature as a constant marginal condition and as a variable test parameter during accelerated weatheringVortrag anläßlich des 18. Donauländergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24.-26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 313-320 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The influence of the specimen temperature on many ageing processes is well known. Two aspects is dealt with: -Measurements of the specimen temperature on several positions of a specimen in commercial weathering devices at different exposure conditions. Technical measures to achieve to uniform ageing at all positions of a planar and homogeneous specimen. Examples from practical use.-Changing specimen temperatures (+60°C to -20°C) during the course of accelerated weathering, i.e. a combination of conventional accelerated weathering with a temperature cycle test.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580118
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  • 27
    Digitale Medien
    Digitale Medien
    Some special aspects of thermal ageing of isotactic polypropylene (measuring method: Isothermal long-term DTA)Vortrag anläßlich des 18. Donauländergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24.-26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 321-334 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: An Folien (Dicke 100 pm) aus isotaktischem Polypropylen mit verschiedenen Antioxidansgehalten (0,0% bis 0,1%) wird die thermooxidative Alterunq mit der isothermen Langzeit-Differential-Thermo-Analyse (ILDTA) bis zu Temperaturen weit unter dem Kristallitschmelzbereich verfolqt und die Messwerte mit Ergebnissen aus dem Zeitstand-Zugversuch korreliert. Dabei zeigt sich, daß aus Messunqen mit der ILDTA bereits vor Einsetzen der autokatalytischen Zersetzunq sreaktion Ruckschlüsse auf die thermische Vorqeschichte der Proben und Aussagen auf das rnit einem Abfall der mechanischen Eigenschaften verbundene Ende der thermo-oxidativen Stabilität des Polymeren getroffen werden können.Weiters bietet die ILDTA die Moglichkeit, durch den direkten Zusamenhang zwischen Oxidationszeit und Antioxidansögehalt die örtliche Stabilisatorverteilung in Platten und in Folien zu bestimmen und damit Diffusionsvorqange zu verfolgen.
    Notizen: Thermo-oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long-term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo-oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties.In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580119
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  • 28
    Digitale Medien
    Digitale Medien
    Coupling particle size distribution technique. A new ultracentrifuge technique for determination of the particle size distribution of extremely broad distributed dispersionsDedicated to Prof. Dr. H.-J. Cantow on the occasion of his 65th birthday (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 162 (1988), S. 35-52 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Größenverteilungsfunktion von Dispersionen mit extrem breiter Verteilung (Durchmesserbereich 20 〈 D 〈 2000 nm) kann in der analytischen Ultrazentrifuge (AUC) nicht durch eine Standardmethode, z. B. durch Messung der Trübung τ bei einer einzigen Konzentration, bestimmt werden, weil sich die spezifische Trübung τ/c von sehr kleinen und sehr großen Teilchen zu stark unterscheidet. Um dieses Problem zu lösen, haben wir eine neue AUC-Technik, die sogenannte Coupling-PSD-Technik entwickelt. Dabei werden zwei unterschiedliche Konzentrationen derselben Dispersion gleichzeitig in einem einzigen AUC-Lauf vermessen und zwei korrespondierende Lichtintensitiit-Zeit-Kurven aufgezeichnet. Bei einer niedrigen Standardkonzentration cs werden hauptsachlich die größeren Teilchen erfaßt während bei einer 5 bis 30 mal heheren Konzentration ch vor allem die kleineren Teilchen registriert werden. Die beiden I(t)-Kurven werden mathematisch verkniipft und unter Verwendung des Stokeschen Gesetzes und der Streutheorie von Mie für homogene isotrope Kugeln in die gesuchte breite Verteilungsfunktion umgerechnet. Wir benutzen eine mit einem 8-Zellen-Rotor und einem Multiplexer ausgestattete AUC. Da sehr groBe und sehr kleine Teilchen gleichzeitig in einem einzigen Zentrifugenlauf bestimmt werden, kennen wir nicht mehr wie zuvor eine konstante Rotorgeschwindigkeit N anwenden, sondern miissen diese mit Hilfe eines Geschwindigkeitsprogramms N(t) innerhalb einer Stunde von 0 auf 40000 U/min erhehen.
    Notizen: The particle size distribution (PSD) of extremely broad distributed dispersions (diameter range 20 〈 D 〈 2000 nm) is not possible to be measured by analytical ultracentrifuge (AUC) using the standard technique, i.e. measuring turbidity τ at a single concentration c, because the specific turbidity τ/c varies too much between very small and very large particles. To solve this problem we have developed a new AUC technique, the so-called Coupling-PSD-Technique. Here two different concentrations of the same dispersion are measured simultaneously by one single AUC run with two corresponding curves of light intensity I vs. time t being registered. At a low standard concentration cs, mainly the larger particles are detected, while at a concentration ch 5 to 30 times higher mainly the smaller particles are registered. Both I(t)-curves are coupled mathematically and transformed into the requested broad distribution curve employing Stokes' law and Mie's light scattering theory for homogeneous isotropic spheres.We use an AUC together with an 8-cells-rotor and a multiplexer. Because very large and very small particles are to be measured simultaneously in one single run, we can no more apply a constant rotor speed N as before, but by means of a time program N(t) we always have to increase the rotor speed from 0 to 40000 rpm within one hour.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051620103
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  • 29
    Digitale Medien
    Digitale Medien
    Graft copolymerization of methyl methacrylate on poly(vinyl chloride) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 162 (1988), S. 135-148 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die chemische Modifizierung von Polyvinylchlorid (PVC) durch ein Amin verleiht dem Polymeren höhere Reaktivität gegenüber der Pfropfcopolymerisation mit einem Vinylmonomeren. Die Pfropfcopolymerisation von Methylmethacrylat auf mit n-Butylamin modifiziertes PVC wurde thermisch mit Benzoylperoxid (Bz2O2) als Initiator oder photoaktiviert mit Benzophenon (BP) als Photosensibilisator gestartet. Das aus bestimmten Experimenten erhaltene rohe Polymerprodukt wurde durch fraktionierte Fällung in die verschiedenen Bestandteile wie Polymethylmethacrylat (PMMA, Homopolymeres), PVC-g-PMMA (Pfropfcopolymeres) und unverändertes (aminiertes) PVC aufgespalten. Die getrennten Fraktionen wurden mit Hilfe der IR-Spektroskopie und der Thermogravimetrie charakterisiert. Der Mechanismus der Pfropfcopolymerisation von den beiden verschiedenen Systemen wurde erörtert. In beiden Fällen wurden Pfropfausbeuten um 30 - 70%* und Pfropfcopolymerzusammensetzungen, PMMA/PVC (w/w) zwischen 2 und 3 erhalten.
    Notizen: Chemical modification of poly(vinyl chloride), PVC, by an amine renders the polymer more reactive towards graft copolymerization with a vinyl monomer. The graft copolymerization of methyl methacrylate (MMA) on PVC modified by treatment with n-butylamine (n-BA) was started thermally at 30° using benzoyl peroxide (Bz2O2) as initiator and under photoactivation at 40° using benzophenone (BP) as photo sensitizer. The gross polymer products from selected experiments were fractionally separated into the constituent polymeric entities viz., poly(methyl methacrylate), PMMA (homopolymer), PVC-g-PMMA (graft copolymer), and unreacted (aminated) PVC following a method of fractional precipitation. The separated fractions were characterized by IR spectroscopy and thermogravimetry. The mechanisms of graft copolymerization for the two different systems have been discussed. In each case, grafting efficiencies of the order of 30-70% and graft copolymers having compositions given as PMMA/PVC (w/w) equal to 2-3 were readily obtained.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051620109
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  • 30
    Digitale Medien
    Digitale Medien
    Surface sulphonated highly crosslinked styrene-divinylbenzene copolymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 162 (1988), S. 193-201 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Eine Reihe oberflächensulfonierter, makroporöser Styrol-Divinylbenzol-Copolymerer mit unterschiedlichen Gehalten an SO3H-Gruppen wurden hergestellt. Sowohl von diesen Copolymeren als auch vom nichtsulfonierten Copolymeren wurden Porenstruktur, Oberflächenhydrophilie und -polarität sowie das Sorptionsverhalten gegenüber einigen in Blut vorkommenden Substanzen bestimmt. Der Sorptionsgrad wird umso kleiner, je größer die Oberflächenpolarität ist. Die teilsulfonierten Polymeren könnten eine Anwendung in der Hämoperfusion finden.
    Notizen: A series of surface sulphonated macroporous styrene-divinylbenzene (S-DVB) copolymers containing various amounts of  - SO3H groups was obtained. Porous structure, surface hydrophilicity and polarity, and sorption properties of these copolymers as well as those of starting S-DVB resin towards some substances which are present in blood were determined. The sorption degree becomes the smaller the higher is the surface polarity. The partially sulphonated copolymers may find an application in hemoperfusion.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051620113
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  • 31
    Digitale Medien
    Digitale Medien
    Studies on the enhancement of separation characteristics of sulfonated poly(phenylene oxide)/polysulfone thin film composite membranes for reverse osmosis applications. I. Effect of chemical treatment (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 1-13 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der Einfluß einer chemischen Behandlung von dünnen Filmen einer Composit-Membran aus sulfoniertem Polyphenylenoxid wurde untersucht. Über den Einfluß der Konzentration von wáßrigen Lösungen von Formaldehyd, Schwefelsäure, Salzsäure, Phosporsäure, Natriumhydroxid sowie der Behandlungsdauer auf die Trenncharakteristik der inversen Osmose der Composit-Membranen mit einer Ionenaus-tauschkapazität von 2,14 und 2,50 meq/g in verschiedenen Kombinationen wird ausführlich berichtet. Die Ergebnisse zeigen, daß unter den besten chemischen Behandlungsbedingungen eine Erhöhung der Trenncharakteristik der inversen Osmose der sulfonierten Polyphenylenoxid/Polysulfon-Composit-Membran erreicht wird.
    Notizen: The effect of chemical treatment on the reverse osmosis (RO) separation characteristics of sulfonated poly(phenylene oxide) (SPPO) thin film composite membranes was investigated. The effects of the concentrations of aqueous solutions of formaldehyde, sulfuric acid, hydrochloric acid, phosphoric acid, sodium hydroxide, and treatment time on the RO separation characteristics of the composite membranes with ion exchange capacity (IEC) of 2.14 and 2.50 meq/g in various combinations are reported in detail. The results indicate some enhancement in RO separation characteristics of the SPPO/polysulfone (PS) composite membrane under the best conditions of the chemical treatment.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630101
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  • 32
    Digitale Medien
    Digitale Medien
    Studies on the enhancement of separation characteristics of sulfonated poly(phenylene oxide)/polysulfone thin film composite membranes for reverse osmosis applications. II. Effects of nitromethane and the chemical treatment combined with gamma-ray irradiationPart I cf. lit.3. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 15-21 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Bei der Herstellung dünner Filme von sulfonierten Polyphenylenoxid/Polysulfon (SPPO/PS)-Composit-Membranen wurde untersucht, daß ein Zusatz von Nitromethan zu einer Lösung von sulfoniertem Polyphenylenoxidnatrium erhöhte Wirkung auf die Trenncharakteristik der inversen Osmose besitzt. Der Einfluß von gamma-Strahlung auf dünne Filme der Composit-Membran unter nassen und trockenen Bedingungen wurde ebenfalls untersucht. Um die maximal mögliche Verbesserung zu erreichen, wurden die Composit-Membranen einer kombinierten chemischen und Gammastrahlen-Behandlung unter nassen und trockenen Bedingungen unterworfen.Die experimentellen Ergebnisse dieser kombinierten Behandlung zeigen, dalß die SPPO/PS Composit-Membran dabei abgebaut wird.
    Notizen: The enhancement effect of the addition of nitromethane into the coating solution of sulfonated sodium poly(phenylene oxide) (SPPONa) polymer for the synthesis of sulfonated poly(phenylene oxide)/polysulfone (SPPO/PS) thin film composite membranes on reverse osmosis (RO) separation characteristic was studied. The effect of gamma-ray irradiation on the SPPO/PS thin film composite membranes was also evaluated when the membrane samples were in the wet and dry conditions. The composite membranes were also subjected to a chemical treatment combined with gamma-ray irradiation in both wet and dry conditions in the hope of obtaining the maximum possible enhancement under each treatment. However, the experimental data of this combined treatment indicated the possibility of some degradation of the SPPO/PS composite membranes.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630102
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  • 33
    Digitale Medien
    Digitale Medien
    Effect of blending techniques on the curing of elastomer blends (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 37-45 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Mischungen aus Poly(styrol-co-butadien)/Polybutadien, Naturkautschuk/Poly-(ethylen-co-propylen-co-dien und Naturkautschuk/Poly(butadien-co-acrylnitril)) wurden nach drei unterschiedlichen Verfahren compoundiert und Härtungsverhalten sowie Zugfestigkeit und Bruchdehnung der Vulkanisate wurden verglichen.
    Notizen: Compounding of styrene-butadiene copolymer/polybutadiene, natural rubber/ethylene-propylene-diene terpolymer and natural rubber/butadiene-acrylonitrile copolymer blends was done in three different ways and their curing behaviour and the tensile properties of the vulcanizates are compared.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630104
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  • 34
    Digitale Medien
    Digitale Medien
    Modification of starch by graft copolymerisation with methyl methacrylatePresented at 12th National Conference of the Chemical Society of Nigeria, Calabar, Nigeria, Sept. 23-25, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 93-99 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Methylmethacrylat (MMA) wurde mit Hilfe von Cerammoniumnitrat als Initiator auf Stärke gepfropft. Die Pfropfcopolymeren wurden durch selektive Lösungsextraktion in einem Soxhlet-Extraktor isoliert. Der Einfluß von Reaktionszeit, Initiatorkonzentration, Temperatur sowie der Monomer- und Särekonzentration auf die Pfropfausbeute wurde untersucht. Eine erste Studie der Kinetik dieser Pfropfcopolymerisationsreaktion zeigt, daß sie dem üblichen kinetischen Verhalten einer Radikalpolymerisation folgt.
    Notizen: Methyl methacrylate (MMA) was grafted onto starch using ceric ammonium nitrate as initiator. The graft copolymers were isolated by selective solvent extraction in a Soxhlet apparatus. The effects of reaction time, initiator concentration, temperature, monomer, and acid concentrations on the graft yields were investigated. A preliminary kinetic study of the graft copolymerisation reactions shows that they follow the conventional kinetic behaviour of free radical polymerisation.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630108
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  • 35
    Digitale Medien
    Digitale Medien
    Adsorption of phenols on carbonaceous adsorbents produced from phenol-formaldehyde-resin mixed with olive stones (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 47-61 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Durch Verwendung von Phenol-Formaldehyd-Harz mit gepreßten Olivenkenen im Gewichtsverháltnis 20/80 wurden kleine zylindrische Formkörper durch Härtung hergestellt. Diese wurden pyrolysiert und einige Proben mit Wasserdampf aktiviert. Für diese Formkörper und für zwei kommerzielle Aktivkohlen für Laboratoriumsbzw. Industrie-Anwendungen wurden folgende Eigenschaften bestimmt: die spezifische Oberfláche, die Struktur, die Adsorptionseigenschaften sowie die Adsorptionskapazität. Die Ergebnisse zeigen, daß die hergestellten kohlenstoffhaltigen Materialien durch Aktivierung höhere Werte für die untersuchten Eigenschaften ergeben als die nur pyrolysierten Proben und die zwei kommerziellen Aktivkohlen. Es wurde festgestellt, daß die Adsorption des 4-Nitrophenols für alle untersuchten kohlenstoffhaltigen Materialien gemäß der Freundlich-Gleichung stattfindet. Die Raster-Elektronenmikroskopie zeigt, daß die hergestellten kohlenstoffhaltigen Materialien andere Porenarten aufweisen als die kommerziellen Aktivkohlen. Die experimentellen Ergebnisse werden durch die molekularen Dimensionen der zur Adsorption verwendeten Substanzen und den Polarisationseffekt der Substituenten am Benzolring erklärt.
    Notizen: Mixtures of phenol-formaldehyde-resin and pressed olive stones in a weight ratio of 20/80 were cured as small cylinders and then pyrolyzed. Some samples were also activated by steam. For these specimens and for two commercial activated carbons of laboratory or industrial uses the specific surface area, the structure, the adsorption properties, and the adsorption capacity were determined. The results indicate that the carbonaceous material produced by activation has greater values for the examined properties in comparison to the only pyrolyzed and the two commercial activated carbons, respectively. It was found that the Freundlich-equation is valid for the adsorption of 4-nitrophenol on all carbonaceous materials examined. The produced carbonaceous materials have different kinds of pores than the commercial activated carbons. The experimental results are explained with regard to the molecular dimensions of the adsorptive substances and the polarization effect of the substituents of the benzene ring.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630105
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  • 36
    Digitale Medien
    Digitale Medien
    Nonlinear programming methods to determine surface free energy components of polymers using harmonic mean approximation (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 101-114 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Durch Anwendung der nichtlinearen Programmiermethode basierend auf der mittleren harmonischen Näherung wurden aus den Kontaktwinkeldaten die freie Dispersions- und polare, freie Oberflächenenergie, γSVd und γSVp, sowie die kritische, freie Oberflächenenergie, γc, von Polymeren bestimmt. Die Komponenten der freien Oberflächenergie der zu untersuchenden Flüssigkeiten, γLVd und γLVp, die die Bedingungen für den maximalen Wechselwirkungsparameter, Φ, wiedergeben, wurden ebenfalls mit Hilfe dieser Methode bestimmt.
    Notizen: The dispersion and polar surface free energy components, γSVd and γSVp, and the critical surface free energy, γc, of polymers were determined from contact angle data by the application of a nonlinear programming method using harmonic mean approximation.The surface free energy components of the probe liquids, γLVd and γLVp, which reflect the conditions of the maximized interaction parameter, Φ, were also simultaneously determined by this method.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630109
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  • 37
    Digitale Medien
    Digitale Medien
    Gemeinsame kondensation von bisphenol A, melamin und formaldehyd (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 169-193 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The condensation reaction of bisphenol A, melamine, and formaldehyde was investigated by gel permeation chromatography, 13C-NMR-spectroscopy, IR-spectroscopy and elemental analysis. Because of the high reaction rates the condensation could be investigated only in the range of pH 6-10. At pH 6 and 7 the reaction of melamine with formaldehyde is dominating.With increasing pH-value the condensation of bisphenol A with formaldehyde is observed preferably. At pH 10 the condensation results in high molecular products. Cocondensation of melamine and bisphenol A through methylene bridges does not take place. But as a separation of the bisphenol A-formaldehyde condensates from the other condensation products was not possible, the three components may be connected through methylene-ether groups and/or intermolecular hydrogen bridges.
    Notizen: Die gemeinsame Kondensation von Bisphenol A, Melamin und Formaldehyd wurde mit Hilfe der Gelpermeationschromatographie, der 13C-NMR-Spektroskopie, IR-Spektroskopie und Elementaranalyse untersucht. Wegen der hohen Kondensationsgeschwindigkeit verläuft die Reaktion in Gegenwart der drei Komponenten nur im Bereich von pH 6-10 kontrollierbar. Bei pH 6 und 7 überwigt die Kondensation zwischen Melamin und Formaldehyd. Mit steigendem pH-Wert tritt die Reaktion von Bisphenol A mit Formaldehyd in den Vordergrund und führt bei pH 10 zu hochmolekularen Kondensationsprodukten.Auf direkte Cokondensation hinweisende Methylenverknüpfungen zwischen der phenolischen Komponente und Melamin konnten nicht nachgewiesen werden. Die Kondensationsprodukte des Melamins bzw. des Bisphenol A mit Formaldehyd lassen sich aber nicht mehr vollständig aus den Reaktionsgemischen der Vorkondensation abtrennen, was dafür spricht, daß die Komponenten über Methylenetherbrücken und/oder intermolekularen Wasserstoffbrücken miteinander verknüpft sind.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630115
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  • 38
    Digitale Medien
    Digitale Medien
    Preparation of cyclodextrin membrane-modified electrodes as sensor materials (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 205-207 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Cyclodextrin membrane-modified electrodes as sensor materials have been prepared by dipping platinum electrodes in the water suspensions of an oriented cyclodextrin polymer, followed by drying the polymer layers on the electrodes. The polymer is obtained by the solid-liquid reaction between the crystal of cyclodextrin inclusion complex and hexamethylene diisocyanate in anisole. The thickness (2 - 80 μm) of the cyclodextrin membrane is satisfactorily controlled by changing the concentration of the water suspension of the polymer. The cyclodextrin membranemodified electrodes show a significant response to p-nitrophenolate in water which is highly in contrast with no measurable response to o- and m-nitrophenolates.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630118
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  • 39
    Digitale Medien
    Digitale Medien
    Antioxidants and stabilizers, 107Part 106 cf. Polym. Degr. Stabil. 17 (1987) 287.. Reaction of N-phenyl-1,4-benzoquinoneimine with the 1-cyano-1-methylethyl-radical (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 91-104 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Im Zusammenhang mit dem Studium des Wirkungsmechanismus von industriell hergestellten Antidegradantien vom Typus der N-Phenyl-N′-sek-alkyl-1,Cphenylendiamine wurde die Reaktion von N-Phenyl-1,4-benzochinonimin (I) und 4-Hydroxydiphenylamin (II) mit dem Kohlenstoff-Radikal 1-Cyano-l-methylethyl (R·) studiert. Das Gemisch von I und II reagiert mit R· sehr leicht unter Bildung der Verbindungen III, VI und VIII. I allein reagiert wesentlich langsamer, und das Reaktionsgemisch enthält mehrere Produkte. Neben der Verbindung III wurden auch die Verbindungen IV und VII identifiziert. II allein reagiert bei denselben Bedingungen nicht. Die Verbindung IV bildet die zwei isomeren Strukturen syn und anti. Die Verbindung VIII ist ziemlich unbeständig; aus ihren Umwandlungsprodukten wurde XI isoliert. Bei der Reduktion von IV entsteht die Verbindung V, die ähnlich wie VIII unbeständig ist.
    Notizen: The reaction of N-phenyl-1,4-benzoquinoneimine (I)Decoding of abbreviations see p. 103/104. and 4-hydroxydiphenylamine (II) with the carbon centred 1-cyano-1-methylethyl radical (R·) was studied in connection with an investigation of the action mechanism of industrial antidegradants, such as N-phenyl-N′-sec-alkyl-1,4-phenylenediamines. The mixture of I and II reacts very readily with R·, giving rise to III, VI, and VIII. I alone reacts much slowlier, and the reaction mixture contains more products. IV and VII were identified along with III. Under the conditions used, II alone does not react at all. IV exists in two isomeric forms, syn and anti. VIII is very labile; XI was isolated from its transformation products. Reduction of IV gives V, which is labile, similarly to VIII.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051560109
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  • 40
    Digitale Medien
    Digitale Medien
    Ozoninduzierter Abbau von Polyoxymethylen (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 123-137 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Samples of polyoxymethylene (unstabilized and stabilized with the antiozonants N-isopropyl-N′-phenyl-p-phenylenediamin (IPPD) and bis-(1,2,3,6-tetrahydrobenzaldehyd)pentaerithritylacetal (Vulkazon AFS)) were ozonized under mechanical load in a special climate chamber. Surface damages were determined by IR-spectroscopy and scanning electron microscopy. During the ozonolysis a damaged layer is formed, the thickness of which increases with increasing time of ozonization. During this damaging reaction acetal groups are attacked and oligomers are formed.
    Notizen: Proben von unstabilisiertem und mit den Antiozonantien N-Isopropyl-N′-phenyl-p-phenylendiamin (IPPD) und Bis-(1,2,3,6-tetrahydrobenzaldehyd)-pentaerithrityl-acetal (Vulkazon AFS) stabilisiertem Polyoxymethylen wurden unter mechanischer Belastung in einer Klimakammer ozonisiert. Die Schädigungen auf der Oberfläche wurden IR-spektroskopisch und rasterelektronenmikroskopisch untersucht. Während der Ozonisierung von POM bildet sich eine geschädigte Schicht, deren Dicke mit zunehmender Ozonisierungszeit wächst. Hierbei wird das Polymere an den Acetalbindungen angegriffen, wodurch Ketten gespalten werden und Oligomere entstehen.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051560111
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  • 41
    Digitale Medien
    Digitale Medien
    On the structure of macroreticular styrene-divinylbenzene copolymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 105-121 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Mit Hilfe verschiedener Methoden wurde der Einfluß der Entfernung unterschiedlicher porenbildender Verdünner aus porösen Styrol-Ethylstyrol-Acrylnitril-Divinylbenzol-Copolymeren auf die Netzwerkstruktur untersucht. Der günstigste Weg, den ursprünglichen strukturellen Bau des porösen Netzwerkes zu bewahren, welches in Gegenwart von solvatisierenden Verdünnern erhalten wurde, ist das Entfernen des inerten Mediums mit Methanol. Wenn die Wasserdampfmethode angewendet wird, fin det der sog. Kollapseffekt statt, und die aus solchen Harzen hergestellten Anionenaustauscher adsorbieren weniger Farbstoff im Vergleich zu jenen, die aus Perlen hergestellt worden sind, die mit Methanol behandelt wurden; Grund hierfür ist die durch den Kollaps veränderte Porengröße. Es wurde ebenfalls festgestellt, daß die in Anwesenheit von solvatisierenden Verdünnern (Mischungen aus Quellungs- und Fällmitteln) hergestellten Copolymeren in Methanol sehr gut quellen, obwohl dieses ein Fällungsmittel für Polystyrol ist.
    Notizen: The influence of the removal of various diluents, pore forming agents from the porous styrene-ethylstyrene-acrylonitrile-divinylbenzene copolymers on the structure of the matrix was investigated by several methods. The most advantageous pathway to preserve the initial structural edifice of the porous networks performed in the presence of solvating diluents consisted in the removal of the inert media with methanol as it was noticed from the experimental data. If the steam treatment is applied, the collapse effect takes place and the anion exchangers prepared from such matrices exchange/adsorb less dye stuff by comparison with ones formed from beads treated with methanol, because the pore size was changed. It was also noticed that the porous copolymers performed in the presence of the solvating diluents (mixtures of solvatings and precipitants) swell very well in methanol though it is a precipitating medium for the polystyrenic macromolecular chains.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051560110
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  • 42
    Digitale Medien
    Digitale Medien
    Heat stability of styrene-zinc acrylate copolymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 139-149 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: An Styrol-Zinkacrylat-Copolymeren wurde die Abhängigkeit der Glasübergangstemperatur von der Aufheizgeschwindigkeit und der Zusammensetzung mit Hilfe der Differential-Scanning-Calorimetrie untersucht. Die Thermogravimetrie wurde benutzt, um die Pyrolyse dieser Copolymeren an Luft bei drei verschiedenen Aufheizge-schwindigkeiten zu untersuchen. Die thermische Zersetzung von Ionomeren ist ein 3-Stufen-Prozeß. Die Reaktionsordnung und Aktivierungsenergie wurde für jede Stufe der Zersetzung bestimmt unter Verwendung eines Computerprogramms, das auf den Methoden von Kissinger, Freeman-Carrol und Ozawa basiert. Es zeigte sich, daß die thermische Stabilität durch die ionischen Gruppen abnimmt.
    Notizen: The dependence of glass temperature on the heating rate and the composition for styrene-zinc acrylate copolymers has been investigated by differential scanning calorimetry. Thermogravimetry was used in order to examine these copolymers undergoing pyrolysis in an atmosphere of air at three different heating rates. Thermal decomposition of ionomers is a three-stage process. The orders and activation energies have been determined for each stage of decomposition using the computer programs based on the methods of Kissinger, Freeman-Carrol, and Ozawa. It was found that the heat stability is lowered by the ionic groups.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051560112
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  • 43
    Digitale Medien
    Digitale Medien
    Free radical grafting of some hydrophilic monomers onto unsaturated segmented polyurethanes  -  a kinetic study (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 151-162 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Pfropfung der hydrophilen Monomeren N-Vinylpyrrolidon, 2-Hydroxyethyl-methacrylat und Acrylamid auf ungesättigte segmentierte Polyurethane in N,N-Dimethylformamid mit 2,2′-Azobisisobutyronitril als Initiator wurde untersucht. Die Pfropfcopolymeren wurden von den Homopolymeren durch selektive Extraktion in Soxhlet-Apparaturen abgetrennt. Die kinetische Untersuchung der Pfropfcopolymerisation zeigte, daß die Reaktionen dem gewöhnlichen kinetischen Verhalten radikalischer Polymerisationen folgen. Die Abhängigkeiten der Pfropfungsgeschwindigkeit von der Initiator- und N-Vinylpyrrolidonkonzentration waren von 0,5 bzw. 1,0 Ordnung. Für 2-Hydroxyethylmethacrylat wurden sie zu jeweils 0,5 und 2,0 gefunden. Die Gesamtaktivierungsenergie der Pfropfcopolymerisation des 2-Hydroxyethylmethacrylats und des N-Vinylpyrrolidons betragen jeweilig 21,81 und 16,28 kJ/mol.
    Notizen: Grafting of unsaturated segmented polyurethanes with some hydrophilic monomers such as N-vinyl pyrrolidone, 2-hydroxyethylmethacrylate and acrylamide in N,N-dimethylformamide have been studied using 2,2′-azobisisobutyronitrile (AIBN) as initiator. Graft copolymers were isolated from homopolymers by selected solvent extraction using a Soxhlet apparatus. A kinetic study of graft copolymerization reactions showed that the reactions follow the conventional kinetic behaviour of free radical polymerization. The dependencies of the grafting rate on initiator and N-vinyl pyrrolidone concentrations were of 0.5 and 1.00 order, respectively. However, for the 2-hydroxyethylmethacrylate, the dependencies of the grafting rate on initiator and monomer concentrations were found to be of 0.5 and 2.00 order, respectively. The overall activation energy for the graft copolymerization of the 2-hydroxyethylmethacrylate and N-vinyl pyrrolidone were 21.81 kJ/mol and 16.28 kJ/mol, respectively.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051560113
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  • 44
    Digitale Medien
    Digitale Medien
    Highly dispersed Ni catalysts on carbon from thermal decomposition of cellulose-hydrous nickel gel membrane (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 156 (1988), S. 179-185 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Ultra fine particles were impregnated by using a finely porous cellulose gel membrane. The impregnated gel membrane is a green transparent one and looks like a solid solution. Highly dispersed Ni catalysts on carbon were obtained from thermal decomposition of these gel membranes. The particle size is in the range of several nm to a few ten nm. They show interesting catalytic properties for hydrogenation of olefins such as cyclooctadiene.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051560115
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  • 45
    Digitale Medien
    Digitale Medien
    Ageing of polyethylene filled with a mineral fillerPaper presented at the 18th Colloquium of Danubian Countries for “Natural and artificial ageing of plastics” in Villach (Austria) June 24-26, 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 351-362 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The thermo-oxidation resistance and weatherability of LDPE and HDPE compositions, containing up to 45 wt.% calcium carbonate, are investigated. The thermo-oxidation resistance is investigated by dynamic DTA and natural ageing is carried out in an exposure station in a seaside climate. The change in strength and colour after ageing is determined. The behaviours of filled and unfilled polymers are compared. Empirical equations are given, describing the change in the investigated parameters during natural ageing.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580121
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  • 46
    Digitale Medien
    Digitale Medien
    Influence of production parameters on ageing processes of thermoplasticsVortrag anläßlich des 18. Donauländergespächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 335-349 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: An Proben aus Polypropylen, die bei sehr unterschiedlichen Einstellungen von Spritzgußmaschinen und Extrudern hergestellt wurden, stellten sich deutliche Abhängigkeiten des Alterungsverhaltens von den thermischen und mechanischen Produktionsparametern ein, die nicht durch unterschiedliche Schmelzetemperaturen bedingt sind. Insbesondere kann ausgesagt werden, daß bei Spritzguß eine hähere Scherbelastung und damit stärkere Orientierungen -eine stärkere Veränderung der Eigenspannungen hervorrufen-einen früheren Glanzabfall und-eine geringere Initialzeit bis zur Rißbildung bewirken.Bei Extrusion fiihrt eine geringere Abkühlgeschwindigkeit und damit ein gröberes Gefüge zu -einer stärkeren Veränderung der Eigenspannungen-einem friiheren und ausgeprägteren Glanzverlust-sowie zu einem früheren Abfall der Reißdehnungen.Unbekannt ist, -ob diese Wirkungen auch bei anderen Thermoplasten als PP auftreten-ob sie auch bei stabilisierten Systemen in relativ gleichem Umfange auftreten-und ob es sich lohnt, die beobachteten Effekte ggf. durch ge zielte Maschineneinstellungen auszunutzen.Auf jeden Fall sollten auf diesem Gebiet weitere Arbeiten durchge-führt werden.
    Notizen: Specimens of unmodified polypropylene have been manufactured using extreme adjustings of injection moulding machines and extruders. After artificial weathering, distinct relations of ageing processes to thermal and mechanical production parameters were found, which are not influenced by different melting temperatures. It can be started in particular, that during injection moulding a larger shear stress (resulting in more distinct orientation) results in -a greater change in residual stresses-an earlier gloss reduction-a shorter initial period before cracking.During extrusion a lower cooling rate (resulting in a coarser structure) leads to -a greater change in residual stresses-an earlier and more distinct gloss reduction-an earlier loss of ultimate strain.It remains unknown, whether -these relationships will be similar with other thermoplastic materials than PP-these relationships appear to the same relative extend with stabilized systems-it may be advantageous, to use the observed effects by adjusting the injection moulding and extrusion machines in a special way.It seems to be significant to do more research work in this field.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580120
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  • 47
    Digitale Medien
    Digitale Medien
    Solvolytic degradation of aliphatic polyesteroligomers: Poly(tetramethylene adipate) diol (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 1-15 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Poly(tetramethylenadipat)diol mit einer Molmasse von 2000 wurde bei Temperaturen von 60 und 80°C in Gegenwart von Wasser bzw. 1,4-Butandiol sowie den gebräuchlichsten PUR-Katalysatoren (Dabco und Dibutylzinndilaurat) gelagert und die Solvolyse untersucht. Die Geschwindigkeit der Solvolyse nimmt mit steigender Temperatur deutlich zu. Die Alkoholyse wird durch Dibutylzinndilaurat weitaus stärker katalysiert als durch 1,4-Diazabicyclo[2.2.2]oktan. Die Hydrolyse verläuft langsamer, da vermutlich die Katalysatoren bei diesem Prozeß desaktiviert werden. Die mechanischen Eigenschaften von Polyurethanen, die mit den partiell abgebauten Diolen hergestellt wurden, korrelieren gut mit der Abnahme der Molmasse.
    Notizen: Poly(tetramethylene adipate)diol having a molar mass of 2000 was stored at temperatures of 60 and 80°C in the presence of water or 1,4-butanediol and a common PUR-catalyst like 1,4-diazabicyclo [2.2.2]octane (DABCO) or dibutyltindilaurate (DBTL) and the solvolysis was investigated. The rate of solvolysis is low at 60°C except for DBTL and shows a drastic increase at 80°C. In the alcoholysis reaction DBTL is a much more active catalyst than DABCO. The rate of hydrolysis is slower probably because the catalysts are deactivated by the acidic products formed in this process. The mechanical properties of polyurethanes made from the degraded polyols are in good correlation with the decrease in molar mass.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600101
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  • 48
    Digitale Medien
    Digitale Medien
    Carbon fibre reinforced bismaleimide composites, I (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 17-28 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der Einfluß der Zugabe von Bis(allylphenyl) Typ (TM 120)-Monomeren auf die Eigenschaften von unidirektional mit Carbonfasern verstärkten 4,4′-Bismaleimidodiphenylmethan (BM) - 2,4-Tolylendiamin (A) (1:0,3 Molverhältnis) (BM-A)-Verbundkörpern wird vorgestellt. Das Aushärteverhalten sowie das thermische Verhalten in Luft wurde mit Hilfe der Differentialkalorimetrie (DSC) und der Thermogravimetrie (TGA) untersucht. Die thermische Stabilität nimmt mit ansteigenden Konzentrationen von TM 120 deutlich zu. Demgegenüber steht ein Anstieg der Biegefesigkeit, der interlaminaren Scherfestigkeit sowie der Schlagzähigkeit mit zunehmender Monomerkonzentration. Optimale mechanische Eigenschaften wurden bei etwa 20 Tle./100 Tle. TM 120 erreicht.
    Notizen: The paper deals with the effect of addition of bis(allylphenyl) type (TM 120) monomer on the properties of unidirectionally carbon fibre reinforced 4,4′ bismaleimidodi-phenyl methane (BM) - 2,4-tolylene diamine (A) (1:0.3 molar ratio) (BM-A) composites. The curing and thermal behaviour of the blends was investigated by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) in air atmosphere. A marginal decrease in thermal stability was observed with increasing concentration of TM 120. Flexural, interlaminar, and impact strength of the laminates increased in the presence of this monomer. Optimum mechanical properties were observed at ∼ 20 phr of TM 120.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600102
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  • 49
    Digitale Medien
    Digitale Medien
    Structure and aging in the welded bonds of PP- homopolymer with PP- copolymer (PP-R)Vortrag anläßlich des 18. Donauländergesprächs über “Natürliche und künstliche Alterung von Kunststoffen” in Villach (Österreich) vom 24. bis 26. Juni 1987. (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 158 (1988), S. 363-378 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: In dieser Arbeit wurden Veränderungen des verschweisßten Rohr- und Fittingmaterials (isotaktisches Polypropylen Homo- bzw. Copolymer PP-R grau pigmentiert) wührend der für die Praxis relevanten Innendruckversuche untersucht.Bei der technischen Verschweißung von Polyolefinen entstehen charakteristische Gefüigezonen im Schweißnahtbereich, welche vom Fßgematerial und den Fngebedingungen beeinflußt werden. In der vorliegenden Untersuchung wurden sowohl die Materialcbergange im Fiigebereich (mit den Methoden - schichtenweise Differentialkalorimetrie, Polarisations- bzw. Elektronenmikroskopie sowie Fluoreszenzspektroskopie mit extrem hoher Ortsauflösung) als auch die Eigenspannungen hinsichtlich ihrer Verlnderung bei Langzeitpriifung im Innendruckzeitstandversuch bei 95°C bis zu einer Prüfzeit von 18.100h untersucht.Die Abbauvorgänge der Makromoleküle bei der Langzeitprüfung der 364 untersuchten Schweißmuster werden in einer gesonderten Arbeit behandelt (1).Durch die Innendruckversuche bei 950 C findet eine Nachkristallisation und eine Gefügevergrijberung sowohl in der Schweißnaht als auch im Gefüge der Schweißpartner statt. Dabei werden die beim Schweißvorgang eingebrachten Orientierungen und Eigenspannungen unter dem Einfluß von Wärme beim Innendruckversuch weitgehend abgebaut. Durch die unter Druckeinwirkung einsetzenden Flieävorgange jedoch werden neue Eigenspannungen eingebracht.Es konnte gezeigt werden, daß bei guter Verschweißung von PP mit PPCO ein kontinuierlicher Übergang (Mischungsbereich) vom Homopolymeren zum Copolymeren auftritt, der auch beim Langzeiteinsatz im Innendruckversuch erhalten bleibt.
    Notizen: The present study deals with changes of welded material of pipes and fittings (isotactic polypropylene homo and copolymer PP-R grey pigmented) during the standardized internal pressure tests, which are commonly used for these products.Technical welding of polyolefines causes characteristic structures, which depend on the natural of the welded material and the welding conditions.In this investigation both the transition of material in the welding seam and the changes of internal stresses during internal pressure tests at 95°C until 18.100h test time were examined. The methods we used were Differential calorimetry of think layers, Polarization- and Electron microscopy, Fluorescence spectroscopy with extreme high local resolution.The effects of decomposition of the macromolecules in the welded samples during the internal pressure tests will be described in a separate paper (1).The internal pressure tests at 95O C cause a recrystallization and an increase of the particle size in the structure of the welding seam and in the structure of the welded parts themselves. Under the above described testing conditions the orientations and internal stresses initiated by the welding procedure will relaxe influenced by heat. However the creep effects that occur in the material when exposed to pressure introduce new internal stresses. It could be shown that in perfectly welded parts a continuous transition from PP to PPCO occurs, which did not change after long time application of internal pressure tests.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051580122
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  • 50
    Digitale Medien
    Digitale Medien
    Coordination polymers, 1. Magnetic, spectral, and thermal properties of coordination polymers derived from terephthalaldehyde bis(S-benzyldithiocarbazate) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 67-81 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurden neue Coordinationspolymere mit Schiffschen Basen aus Terephthalal dehyd und S-Benzyldithiocarbazol als Liganden in DMF-Lösung hergestellt. Die erhaltenen Coordinationspolymeren wurden durch Elementaranalyse, magnetische Suszeptibilität, elektronische und IR-Spektroskopie charakterisiert. Die durch Thermogravimetrie bestimmte thermische Stabilität der Coordinationspolymeren nahm in der folgenden Reihenfolge ab: \documentclass{article}\pagestyle{empty}\begin{document}${\rm Zn} \simeq {\rm Fe} 〉 {\rm Co} 〉 {\rm Ni} 〉 {\rm Min} \simeq {\rm Cu}$\end{document} Mn(II)-, Fe(II)-, Co(II)- und Ni(II)-Coordinationspolymere haben eine Oktaederstruktur mit der Koordinationszahl6, während bei den Cu(II)- und Zn(II)-Coordinationspolymeren eine 4-fach koordinierte quadratisch-planare bzw. eine tetraedrische Struktur gefunden wurde. Ligandenfeld- und nephelawetische Parameter wurden aus den Spektren errechnet. Dam wurde die Ligandenfeldtheorie spin-erlaubter Übergänge angewandt, die sich als konsistent mit einer 6-fach koordinierten Struktur für Mn(II)-, Fe(II)-, Co(II)- und Ni(II)-Coordinationspolymere erwies. Die Elementaranalysen ergaben bei allen Coordinationspolymeren ein Ligand: Metall-Verhältnis von 1 : 1 und deuteten bei den Mn(II)-, Fe(II)-, Co(II)- und Ni(II)-Coordinationspolymeren auf am Zentralatom assoziierte Wassermoleküle hin.
    Notizen: New Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) coordination polymers of Schiff base ligand derived from terephthalaldehyde and S-benzyldithiocarbazate have been synthesized in DMF media. The coordination polymers have been characterized by their elemental analysis, magnetic susceptibility, and by electronic and infrared spectral measurements.The thermal stability of each polymer was found out by thermogravimetric analysis. The thermal stability of coordination polymers obtained from thermograms has the following order: \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Zn} \simeq {\rm Fe} 〉 {\rm Co} 〉 {\rm Ni} 〉 {\rm Min} \simeq {\rm Cu}$\end{document} Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers are of a six-coordinated octahedral structure while Cu(II) and Zn(II) coordination polymers are found to be four-coordinated square planar and tetrahedral structure, respectively. The ligand-field and nephelauxetic parameters have been determined from the spectra, using ligand-field theory of spin-allowed transitions which are found consistent with six-coordinate structure for Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers. Elemental analyses indicates a ligand: metal ratio of 1 : 1 in all the coordination polymers and the association of water molecules with central metal atom in case of Mn(II), Fe(II), Co(II), and Ni(II) coordination polymers.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600105
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  • 51
    Digitale Medien
    Digitale Medien
    Studies on the electrodeposition of polyimides (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 91-106 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Emulsionen von aromatischen Polyamidsären (PMPE and PBPPM) in DMF und Methanol wurden benutzt, um gleichmäßige Filme auf Leiteroberflächen durch Elektrophorese abzuscheiden. Die Ausbeute und Qualität der abgeschiedenen Filme hängen von der Art der Polyamidsäre, dem Lösemittel, dem Fällungsmittel, dem oberflächenaktiven Mittel, dem pH-Wert und dem Polymergehalt ab. Die Bedingungen zum Erreichen der höchsten Abscheidungsausbeuten wurden bestimmt.
    Notizen: The emulsions of aromatic polyamic acids (PMPE and PBPPM) in DMF and methanol were used to coat uniform films on conductor surfaces by electrodeposition. The deposition yield and quality of the deposited films are dependent on sort of polyamic acid, solvent (DMF), precipitant (MeOH), surfactant (TEA), pH value and solid content. To get maximum deposition yields from PMPE and PBPPM, the best conditions of electrodeposition were required as follows: pH value 5.7 and 5.58, MeOH/DMF weight ratio 3.0 and 2.8, solid content 3.5 and 2.4 wt.-%. Deposition yield was found to obey Faraday's law of electrolysis, and the higher the equivalent weight of the polyamic acid, the higher the coulombic yield.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600107
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  • 52
    Digitale Medien
    Digitale Medien
    Model of double associates for sorption of binary gas mixtures on polymers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 107-115 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Ein einfaches Modell von Doppelassoziaten wurde verwendet, um die Doppelschichtsorption von binären Gasgemischen an flexiblen linearen Polymerketten zu beschreiben. Die Isothermengleichung nach diesem Modell ist ein einfaches Produkt der isothermen Gleichung, die die Doppelschichtadsorption von binären Gasgemischen an einer homogenen festen Oberfläche beschreibt und einer Funktion, die die spezifischen Merkmale der Sorption an Polymeren widerspiegelt.
    Notizen: A simple model of double associates is used to represent bilayer sorption of binary gas mixtures on a flexible linear chain of a polymer. The isotherm equation derived in terms of this model is a simple product of the isotherm equation describing bilayer adsorption of binary gas mixtures on a homogeneous solid surface and a function reflecting specific features of sorption on polymers.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600108
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  • 53
    Digitale Medien
    Digitale Medien
    Einfluß der polymerisationsbedingungen auf die morphologie von schwefel-styrol-polymerisaten (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 131-140 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: For a polymer system sulfur-styrene containing 10 wt.-% styrene the morphologie depending on the polymerization temperature and time is described. Besides the characteristical orthorhombic phase a monoclinic and a pseudoorthorhombic phase were detected. Moreover amorphous material exists, depending on the polymerisation parameters.
    Notizen: Für ein Polymersystem Schwefel-Styrol mit 10% Styrol wird die Abhängigkeit der Morphologie von der Polymerisationstemperatur und -zeit beschrieben. Neben der charakteristischen orthorhombischen Phase wurden röntgenographisch eine monokline und eine pseudoorthorhombische Phase nachgewiesen. Außerdem liegt, abhängig von den Polymerisationsparametern, ein amorpher Anteil vor.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600110
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  • 54
    Digitale Medien
    Digitale Medien
    Molecular weight distribution of living polymers in a semi-batch reactor (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 117-129 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Für eine anionische Polymerisation mit langsamer Start- und schneller Wachstumsreaktion wurde ein analytischer Ausdruck entwickelt, der es erlaubt, mittlere Molekulargewichte und Molekulargewichtsverteilungen von Polymeren vorauszuberechnen, die in einem halbkontinuierlichen Polymerisationsverfahren bei Zulauf einer verunreinigten Monomerlösung zu einer vorgelegten Initiatolösung entstehen. Die Gültig keit des Modells wurde an der Polymerisation von Isopren mit n-Butyllithium in n-Heptan überprüft. Die beobachteten Unterschiede zwischen theoretischen und experimentellen Werten werden auf die Änderungen in den Geschwindigkeitskonstanten von Start- und Wachstumsreaktion zurückgeführt, die dadurch hervorgerufen werden, daß sich die Polarität der Lösung durch die Anreicherung mit polaren Verbindungen ändert. Weiterhin wird gezeigt, daß bimodale Molekulargewichtsverteilungen entstehen, wenn sich an die halbkontinuierliche Verfahrensweise eine diskontinuierliche zur Erhöhung des Monomerumsatzes anschließt.
    Notizen: For anionic polymerization with slow initiation and rapid propagation step analytical expressions are presented to calculate average molecular weights and molecular weight distributions for a semi-batch process, in which a monomer solution contaminated by impurities is fed to an initiator solution in the reactor. The validity of the model was checked for the case of the polymerization of isoprene by n-butyllithium in n-heptane. The differences observed between theoretical and experimental values are explained by the changes in the rate constants of the initiation and the propagation step caused by the change in the polarity of the reaction solution by the continuously fed impurities. Furthermore it is shown that polymers with bimodal molecular weight distributions are formed if the semi-batch procedure is followed by a batch one to increase the monomer conversion.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600109
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  • 55
    Digitale Medien
    Digitale Medien
    Thermosetting mechanism of polyethersulfone (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 141-154 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der Wärmehärtungsmechanismus von zu Anstrichen verwendeten Polyethersulfonen wurde unter Verwendung von FTIR/PAS und ESCA untersucht. Als Ergebnis wurde bestätigt, daß der Luftsauerstoff Einfluß auf den Wärmehärtungsmechanismus hat. Das heißt, die Härtung des Polyethersulfonfilms beginnt an der Oberfläche und verläuft entsprechend Reaktion (4) weiter.
    Notizen: Thermosetting mechanism of paint-use polyethersulfones was studied by utilizing FTIR/PAS and ESCA. As a result, it was confirmed that the oxygen in the air has an effect on the thermosetting mechanism. That is, the polyethersulfone film were baked from the surface, and proceeded according to reaction (4).
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600111
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  • 56
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of resins from 4-ethylphenol and cinnamaldehyde (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 155-162 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Es wurde der Mechanismus der Reaktion von 4-Ethylphenol mit Zimtaldehyd mittels HET 2DJ 13C-NMR Spektroskopie, 1H-NMR Spektroskopie und GPC untersucht. In der ersten Stufe findet die Addition des 4-Ethylphenols an die Carbonylgruppe und an die Doppelbindung des Zimtaldehyds statt. In der zweiten Stufe reagiert die —CH(OH)-Gruppe mit 4-Ethylphenol und bildet verzweigte Produkte in rötlich gefärbten Harzen mit einem Durchschnittsmolekulargewicht on 600. Die Reaktion verläuft bei Temperaturen über 100°C in stark saurem Medium.
    Notizen: The mechanisms of the reaction between 4-ethylphenol and cinnamaldehyde were studied by means of HET 2DJ 13C-NMR spectroscopy, 1H-NMR spectroscopy and GPC. In the first step of the reaction the addition of 4-ethylphenol to carbonyl group and to double bond of cinnamaldehyde takes place. In the second step of the reaction the —CH(OH)-group reacts with 4-ethylphenol to form branched products of red coloured resins with an average molecular weight of 600. The reaction takes place at temperatures above 100°C in strong acid medium.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600112
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  • 57
    Digitale Medien
    Digitale Medien
    Studies on electrical and paramagnetic properties of poly(phenylene sulphide) (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 163-173 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die elektrischen und paramagnetischen Eigenschaften des durch eine direkte Methode aus Benzol und Schwefel synthetisierten Poly(phenylensulfid)s wurden untersucht. Die Geichstromdunkelleitfähigkeit dieses Polymeren im nativen Zustand ist 10-10 S/m. Sie nimmt während des Dotierens mit Jod um 8 Größenordnungen zu. Es wurde für undotierte Proben n-Typ- und für die mit Jod dotierten Proben p-Typ-Leitfähigketi beobachtet. Anhand der ESR-Messungen wurden die Zahl der paramagnetischen Zentren und der g-Faktor bestimmt, die entsprechend gleich 0.80 · 1017 Spins/g und 2.0037 für das undotierte Polymere bei Raumtemperatur betragen. Änderungen der Spinkonzentration sowohl für die mit Jod dotierten als auch für die im Temperaturbereich von 513 - 903 K getemperten Proben werden dargestellt. Es wird versucht, die Form der ESR-Linien auf eine quantitative Weise zu diskutieren.
    Notizen: Electrical and paramagnetic properties of poly(phenylene sulphide) synthesized by a direct method from benzene and sulphur were investigated. In darkness dc conductivity of the polymer in its pristine state is of the order 10-10 S/m. Upon doping with iodine it increases by 8 orders of magnitude. For undoped samples the n-type conductivity and for those doped with iodine the p-type conductivity was observed. On the basis of ESR experiments the number of spins and g-value were determined, which for undoped polymer at room temperature are equal to 0.80 · 1017 spins/g and 2.0037, respectively. Next, the changes in spin concentration both for the iodine doped samples and these annealed within the temperature range 513 - 903 K were described. An attempt to discuss the ESR lineshape in a quantitative way was also made.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600113
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  • 58
    Digitale Medien
    Digitale Medien
    Synthesis and study of the chelating properties of 3-carboxy-4-hydroxyacetophenone-formaldehyde resins (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 175-186 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: 3-Carboxy-4-hydroxyacetophenon (CHAP) wurde in verschiedenen Mengenverhältnissen mit Formaldehyd unter Verwendung von Alkali als Katalysator polykondensiert. Die erhaltenen Polykondensate (CHAP-F) wurden durch Elementaranalyse, IR-Spektroskopie, Bestimmung des Zahlenmittels der Molmasse (M̄n), Thermogravimetrie und Bestimmung der Grenzviskosität charakterisiert. Es wurden polymere Metallchelate mit Cu2+ -, Fe3+ -, Co2+ -, Ni2+ - und UO2+2 -Ionen hergestellt und charakterisiert. Mit Hilfe der Batch-Austauschmethode wurden Ionenaustauschereigenschaften eines CHAP-F Harzes gegen Fe3+ - Cu2+ - und Ni2+ -Ionen bestimmt.
    Notizen: 3-Carboxy-4-hydroxyacetophenone (CHAP) was polycondensed with various proportions of formaldehyde using alcoholic alkali as catalyst. The resin samples, designated as CHAP-F, have been characterized by elemental analyses and IR spectroscopy, by estimation of their number average molecular weights (M̄n), by measurement of intrinsic viscosity, and by TGA. Polymeric metal chelates of one CHAP-F sample with Cu2+, Fe3+, Co2+, Ni2+, and UO22+ ions have been prepared and characterized.Ion-exchanging properties of one CHAP-F resin sample for Fe3+, Cu2+, and Ni2+ metal ions are studied by the application of the batch-equilibration method.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600114
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  • 59
    Digitale Medien
    Digitale Medien
    Nucleophilic addition to phenylisocyanates: A theoretical study (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 187-192 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Reaktionsenthalpien für die Addition von Hydroxidanion an substituierte Phenylisocyanate wurden mit MNDO berechnet. Die erhaltenen Werte stimmen sehr gut mit den Reaktionsgeschwindigkeiten der Addition von 2-Ethylhexanol an Phenylisocyanate überein. Dies ermöglicht eine Abschätzung der Reaktionsgeschwindigkeiten für nucleophile Additionen innerhalb vernünftiger Grenzen, ohne daß experimentelle Arbeiten durchgeführt werden müssen.
    Notizen: The enthalpies for the addition of hydroxide anion to substituted phenylisocyanates have been calculated with MNDO. The results obtained correlate well with the rates of addition of 2-ethylhexanol to phenylisocyanates. This allows us to estimate the rates for nucleophilic addition within reasonable limits without the need for experiments.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600115
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  • 60
    Digitale Medien
    Digitale Medien
    Mitteilungen (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 160 (1988), S. 211-211 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051600118
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  • 61
    Digitale Medien
    Digitale Medien
    Modification of epoxy resins with acrylic rubbers containing a pendant epoxy group (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 63-76 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Durch Copolymerisation von Butylacrylat (BA) mit Vinylbenzylglycidylether (VBGE) wurden neue Acrylkautschuke mit Epoxyseitengruppen hergestellt. Um die Zähigkeit eines gehärteten Epoxidharzes (Bisphenol A/Diglycidylether/p,p′-Diaminodiphenylsulfon) zu erhöhen, wurde dieses mit den erhaltenen Acrylkautschuken modifiziert. Eine Zugabe von 20 Gew.-% eines Copolymeren mit 74% BA und 26% VBGE-Einheiten führte zu einer 30proz. Zunahme der Bruchzähigkeit (KIC) des gehärteten Harzes bei einer minimalen Einbuße an Festigkeit und Steifigkeit. Die modifizierten Harze wiesen eine Zwei-Phasen-Morphologie auf, bei der Kautschukteilchen mit einer mittleren Größe von 2 μm in eine Epoxymatrix eingebettet sind. Das Copolymere ohne Epoxyseitengruppen, das aus BA und Vinylbenzylmethoxyethylether hergestellt wurde, war als Modifier unwirksam, was darauf hindeutet, daß die seitenstándigen Epoxidgruppen zu einer guten Zwischenphasenadhäsion zwischen Kautschukteilchen und Matrix, und damit zu erhöhter Zähigkeit führen. Kautschuke, die 55 oder 86% BA-Einheiten enthielten, waren ebenfalls ungenügende Modifier. Zugabe des ersteren ergab Harze mit einer homogenen Phasenstruktur, während die Zugabe des letzteren zu einer Phasentrennung zwischen Kautschuk und Epoxidharz führte.
    Notizen: New acrylic rubbers with a pendant epoxy group were prepared by copolymerization of butyl acrylate (BA) with vinylbenzyl glycidyl ether (VBGE). The modification of an epoxy system (bisphenol-A diglycidyl ether/p,p′-diaminodiphenyl sulfone) with the acrylic rubbers was carried out in order to increase the toughness of the cured epoxy resin. The addition of 20 wt.-% of the copolymer containing 74% of BA and 26% of VBGE units resulted in a 30% increase in the fracture toughness (KIC) of the cured resin at minimal expenses of strength and modulus of the resin. The modified epoxy resin had two-phase morphology in which the rubber particles with average diameter of 2 μm are dispersed in the epoxy matrix. The copolymer without the pendant epoxy group, prepared from BA and vinylbenzyl methoxyethyl ether, was ineffective as a modifier, indicating that the reaction of the pendant epoxide with the epoxy matrix resulted in good interfacial adhesion between the rubber particles and the matrix, and in the increased toughness. The epoxide-containing copolymers with 55 or 86% of BA units were also insufficient modifiers. The addition of the former yielded cured resins with homogeneous structure, whereas that of the latter resulted in macroscopic phase separation between the rubber and the epoxy resin.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630106
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  • 62
    Digitale Medien
    Digitale Medien
    Polyurethane ionomers: Effects of emulsification on properties of toluene diisocyanate based polyether polyurethane cationomers (1988)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 163 (1988), S. 77-91 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Lösungen von Polyether/Polyurethan-Kationomeren, die auf Toluoldiisocyanaten basieren, wurden hergestellt und durch Zugabe von Wasser emulgiert. Die Eigenschaften von aus diesen Lösungen und Emulsionen gegossenen Filmen werden mit Hilfe der Infrarot-Spektroskopie, dynamisch-mechanischer Messungen, der Differentialkalorimetrie, der Weitwinkel-Röntgendiffraktometrie und von Zug-Dehnungsmessungen untersucht. Der Einbau eines asymmetrischen, kettenverlängernden Bausteins, wie N-Methyldiethanolamin, führt zu einem Polyurethan (PU), das, ßhnlich wie das mit symmetrischem, kettenverlängerndem 1,4-Butandiol aufgebaute Polyurethan, eine meßbare Ordnung innerhalb der Hartsegmente aufweist. Nach der Quarternisierung mit Glykolsaure haben die PU-Kationomeren erhöhte Werte für Reißdehnung, Zugmodul und -festigkeit. Dies kann auf die Coulomb-Wechselwirkung zwischen benachbarten Hartsegmenten zurückgefiihrt werden. Das Emulgieren der PU-Ionomer-Lösung führt zu einer verstärkten Mischung der Weich-und Hartsegmente, wodurch die ursprünglichen Hartsegmentbereiche mit asymmetrischen 2,4-Urethanisomeren eine höhere Konzentration an 2,6-Isomeren enthalten. Die Hartsegmentbereiche erreichen dadurch höhere Ordnung. Diese erhähte Ordnung und Phasenmischung führt zu einer Verbesserung der mechanischen Eigenschaften. Die Veränderung der Leitfähigkeit und Viskosität wahrend dem Emulgieren zeigt, daß das Wasser zuerst auf der Oberfäche des Mikroionengitters der Hartsegmente adsorbiert wird und dann in die ungeordneten und geordneten Hartsegmentbereiche eindringt.
    Notizen: Toluene diisocyanate based polyether polyurethane cationomer solutions are prepared and then emulsified by adding water. Properties of films cast from the solutions and emulsions are studied using infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry, wide-angle X-ray diffraction, and tensileelongation testing. It is found that the use of the asymmetric chain extender, N-methyl-diethanolamine, also leads to a polyurethane (PU) with detectable order in the hard domains as in the PU with symmetric chain extender such as 1,4-butandiol. After quaternization with glycolic acid, the PU cationomers have increased elongation and tensile strength and modulus. These can be attributed to the proper Coulomb interaction between two neighboring hard segments. The emulsification of the PU ionomer solution results in an increased mixing between the soft segments and the hard segments with asymmetric 2,4-urethane isomers originally located in the hard domains, and therefore make the hard domains containing a higher concentration of symmetric 2,6-isomer. The hard domains then become more ordered. Such increased order and phase mixing leads to an increase of the three tensile properties. During the emulsification conductivity and viscosity variations show that water is firstly adsorbed on the surface of the hard segment microionic lattices and then enters into the disordered and ordered hard domains successively.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1988.051630107
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  • 63
    Digitale Medien
    Digitale Medien
    Conformational studies of nucleic acids. V. Sequence specificities in the conformational energetics of oligonucleotides: The homo-tetramers (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 59-77 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformational energetics of the tetranucleoside triphosphates d(ApApApA), d(GpGpGpG), d(CpCpCpC), d(TpTpTpT), ApApApA, GpGpGpG, CpCpCpC, and UpUpUpU are thoroughly examined using a classical potential energy function. The sugar modeling method and multiple correlation functions derived in previous papers of this series are utilized in these examinations. The data are analyzed and compared in terms of the energy profiles for rotation about the conformation-determining torsion angles in the tetramers. Overall, the predictions are in reasonable qualitative agreement with the existing experimental data. It is found that the base type does not greatly affect the locations of the important minima in these profiles, but rather exerts a large influence on the relative depths of the minima and the barriers to conversion between them. Conformational sequence dependence is manifest to a greater extent by the DNA tetramers than the RNA tetramers. Of the DNA tetramers, d(CpCpCpC) appears, from the results presented herein, to have the greatest potential for polymorphism. This and other findings are analyzed in terms of the preferences of particular DNA sequences for either the A-, B-, or Z-conformation.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270105
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  • 64
    Digitale Medien
    Digitale Medien
    A simplified analysis of scatchard plots for systems with two interacting binding sites (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 79-86 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A simple graphical method for calculating stoichiometric and site binding constants for systems with two initially equivalent interacting sites is derived from a modified Scatchard equation. The binding constants can be calculated from Scatchard plots (r/[A] as a function of r) using the values of r/[A] (r is the molar ratio of bound ligands to total protein and [A] is the equilibrium concentration of free ligand) when r = 0 and r = 1 (half-saturation). The applicability of the method to the adsorption of bilirubin by peptide pendants immobilized on a polyacrylamide support is demonstrated.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270106
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  • 65
    Digitale Medien
    Digitale Medien
    Application of the augmented theory of α-helix-to-random-coil transitions of two-chain, coiled coils to extant data on synthetic, tropomyosin-analog peptides (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 87-96 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The statistical mechanical theory for the helix-to-random-coil transition in two-chain coiled coils is applied to extant data for two synthetic coiled-coil polypeptides. These peptides have the primary structure K(LEALEGK)n, in which n = 4, 5. This repeating heptet sequence mimics the pattern of hydrophobic, acidic, and basic residues characteristic of the 284-residue tropomyosin molecule, the prototypical coiled-coil protein. Theoretical calculations for single chains show that such model peptides cannot be directly compared to proteins like tropomyosin because of differences in chain length (29 and 36 residues vs 284) and in intrachain interactions, the latter caused by the differences in amino acid composition and seqeunce between protein and model. Application of the theory to extant data on the two synthetic peptides provides a semiquantitative fit and results in an assessment of the interhelix interaction in the model peptides. The value obtained, ∼ 2000 cal · (mol of turn pairs)-1, is four to five times larger than has been obtained for tropomyosin. This probably is a result of greater regularity in the structure of the synthetics and of the exclusive presence of leucine in the hydrophobic interface. The theory employed here insists that this powerful interhelix interaction in the synthetic is the principal reason that such short chains can be so highly helical at moderate and low temperatures. Theory predicts, indeed, that a tropomyosin-length chain with a sequence homologous to these synthetics would be completely thermally stable in the entire temperature range accessible in aqueous solutions. Theory also predicts a much more pronounced effect of concentration on the 29- and 36-residue synthetic polymers than is predicted or observed in the case of tropomyosin, and it also predicts a pronounced stabilizing effect of pH-reduction on the thermal curves. On the last two points, sufficient data are not yet available with which to test the theory.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270107
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  • 66
    Digitale Medien
    Digitale Medien
    The source of energy for bacteriophage dna packaging: An osmotic pump explains the data (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 165-169 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270113
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  • 67
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270201
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  • 68
    Digitale Medien
    Digitale Medien
    The combined use of NMR, distance geometry, and restrained molecular dynamics for the conformational study of a cyclic somatostatin analogue (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 323-338 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A cyclic peptide analogue of somatostatin, including the o-aminomethylphenylacetic acid spacer, was studied by the combined use of two-dimensional nmr spectroscopy, distance geometry, and restrained molecular dynamics. Analysis of distances determined from nuclear Overhauser effect (NOE) buildup rates revealed that these were inconsistent with a unique backbone conformation near the spacer. Assuming that the conformational heterogeneity is localized to the spacer, the NOE distances measured for the remaining part of the molecule were used to generate a large number of structures with the distance geometry algorithm, which were then refined by restrained energy minimization. Four classes of structures emerged, which together account for all observed NOEs. A representative structure of each class was further refined with the restrained molecular dynamics technique, and shown to be stable on a 20-ps time scale. The flexibility of the spacer was examined by simulating interconversions induced by an appropriate restraining potential. As a result, the explanation for the lack of somatostatin activity of the analogue studied was reconsidered.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270211
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  • 69
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270301
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  • 70
    Digitale Medien
    Digitale Medien
    Optical activity of saccharides - the vacuum-uv origin of sodium-D rotation (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 415-421 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A semiempirical theory of saccharide optical activity indicates that the dominant source of NaD rotation is a vacuum-uv CD band near 150 nm, a band observed experimentally in polysaccharide film CD spectra. The model is a modification of polarizability theory in which high-energy electronic excitations are coupled by degenerate perturbation theory, giving rise to “molecular excitons.” The existence of an excitation mode well separated in energy from even higher energy modes arises from the local symmetry of tetrahedral carbon atoms in a puckered ring structure. Calculated NaD rotations correlate well with experimental values.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270305
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  • 71
    Digitale Medien
    Digitale Medien
    Prediction of protein helix content from an autocorrelation analysis of sequence hydrophobicities (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 451-477 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It is demonstrated that protein α-helix content can be predicted from an autocorrelation analysis of the protein hydrophobicity sequence. The Fourier transform of the autocorrelation function yields the spectral densities or weights of the various frequencies contributing to the autocorrelation function. Using sequence and secondary structure data from more than 160 proteins and domains, a linear relationship was found between spectral density at periodicity 3.7 and protein α-helix content (r = 0.83). This relation permits prediction of the helix content (x) of proteins of known sequence to within ± 15%, i.e., as (x ± 15)%. Predictions based on the autocorrelation procedure are compared with values obtained by other methods.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270308
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  • 72
    Digitale Medien
    Digitale Medien
    Induced CD provides evidence for helical solution conformation in cellulosic chains (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 479-491 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Evidence for a helical contribution to the conformation of methylcellulose in dilute solution is given by CD measurements. Congo red binds to methylcellulose in dilute aqueous solution and becomes optically active. The shape of the induced CD spectra is as predicted by exciton coupling for a helical arrangement of chromophores. The magnitude of the induced CD changes reversibly with temperature, decreasing upon heating. The dimer analogue of the polymer, prepared by acid methanolysis, does not show this effect. These observations suggest that the induced optical activity reflects the conformational dissymmetry of the polymer. Analogous experiments with the cellulose oligomers (cellotriose through cellohexaose) show that five anhydroglucose units are necessary before asymmetry is induced upon dye binding.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270309
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  • 73
    Digitale Medien
    Digitale Medien
    Polarized raman scattering from oriented single microcrystals of d(A5T5)2 and d(pTpT) (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 493-507 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polarized Raman spectra have been obtained from single microcrystals of the duplex of the decamer d(A5T5)2 using a Raman microscope. This is the first report of Raman spectra from a crystal of a deoxyoligomer that contains only long, nonalternating sequences of adenine and thymine. Sequences containing d(A)n and d(T)n are of interest in view of recent suggestions that they induce bends in DNA and that they might exist in a nonstandard B-conformation. Polarized Raman spectra of a crystal of d(pTpT) have also been obtained. Both crystals display Raman bands whose intensities are very sensitive to the orientation of the crystal with respect to the direction of polarization of the incident laser beam. These spectra indicate that the helical axes of the oligonucleotides are parallel to the long axes of the crystals and that the d(A5T5)2 is not appreciably bent in the crystal. The Raman spectrum from the d(pTpT) crystal indicates that all of the furanose ring puckers are in a C2′-endo configuration since only the C2′-endo marker band at 835 ± 5 cm-1 is present. Crystals of d(A5T5)2 show measurable Raman intensities in both the 838- and 816-cm-1 bands. This indicates the presence of both the C2′-endo and C3′-endo, or possibly other non-C2′-endo, furanose conformations. The 816-cm-1 band is weak so that only a small fraction of the residues are estimated to be in the non-C2′-endo conformation. In both the d(pTpT) and d(A5T5)2 crystals the intensity of the bands due to vibrations of the backbone show only a small dependence on orientation of the crystals. This result is explained by the low symmetry of the puckered sugar rings. It is concluded that Raman spectra obtained from oligonucleotide crystals in which the orientation of the crystal axes to the laser polarization is not carefully controlled may contain intensity artifacts that are due to polarization effects.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270310
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  • 74
    Digitale Medien
    Digitale Medien
    A critical review of the nucleosidic vibration modes appearing in the 800-500-cm-1 spectral region, based on new harmonic dynamics calculations (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 605-616 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: On the basis of a harmonic dynamics calculation, it is shown that in the 800-500-cm-1 spectral region of DNA vibrational spectra, the characteristic Raman peaks and ir bands do not arise from the same nucleosidic motions. The Raman spectra involve mainly the ring-breathing modes of nucleic bases while the ir spectra reveal essentially their out-of-plane vibrations. Moreover, the calculated results show the splitting of the guanine- and adenine-residue breathing modes upon their coupling with the sugar-pucker motions. This fact is in agreement with the poly[d(G-C)] and poly[d(A-T)] Raman spectra.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270405
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  • 75
    Digitale Medien
    Digitale Medien
    A type II β-turn in a flexible peptide: Proton assignment and conformational analysis of the α-factor from saccharomyces cerevisiae in solution (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 431-449 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two-dimensional 1H-nmr spectra of the α-mating factor [in dimethyl sulfoxide-d6 (DMSO) and in water] and several dodecapeptide analogues (in DMSO) were obtained. Homonuclear correlated spectroscopy resulted in the complete and unequivocal assignment of all backbone and side-chain resonances of the peptides. The solution conformation of the pheromones was probed using two-dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY) and rotating frame nuclear Overhauer effect spectroscopy (ROESY). The 2D NOE results, and results of complementary one-dimensional experiments, suggest that a type II β-turn is assumed by the central portion of active pheromones in both DMSO and water. Inactive analogues of the α-factor do not exhibit this structural feature. Except for this one β-turn, the nmr parameters for α-factor are indicative of a conformationally flexible molecule in both solvents. This conclusion is in contrast to that of other researchers who have proposed a highly structured conformation of α-factor in aqueous solution.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270307
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  • 76
    Digitale Medien
    Digitale Medien
    Quantitative analysis of the three regimes of DNA electrophoresis in agarose gels (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 509-524 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An extensive series of experiments has been performed to study the mobility of DNA fragments ranging in size from 2.0 to 48.5 kilobose pairs. By varying the agarose concentration in the gels and the electric field strength, three DNA electrophoresis regimes were clearly identified: the Ogston regime (small DNA fragments in large pores of agarose), the reptation regime without DNA chain stretching (small pores of agarose and weak electric fields), and the reptation regime with DNA chain stretching (small pores of agarose, strong electric fields, and large DNA fragments). Here we report on the experimental identification of these regimes and on the conditions governing the transition between each of them. The onset of reptation and of stretching of DNA chains in gel electrophoresis are described quantitatively for the first time, and a phase diagram for the dynamics of DNA during electrophoresis is presented.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270311
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  • 77
    Digitale Medien
    Digitale Medien
    Conformations and mitochondrial uncoupling activity of synthetic emerimicin fragments (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 683-701 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Several amino terminal fragments of the emerimicins (Ac-Phe1-Aib2-Aib3-Aib4-Val5-Gly6-Leu7-Aib8-Aib9-Hyp10-Gln11-D-Iva12-Hyp13-Ala/Aib14-Phol15) ranging in length from five to ten residues have been synthesized. Nuclear magnetic resonance studies have been carried out on the 1-5, 6-10, 1-6, 1-7, 1-8, 1-9, and 1-10 fragments. The number of solvent-shielded NH groups in CDCl3 solutions for 1-5, 1-6, 1-7, 1-8, 1-9, and 1-10 indicate that 310-helical structures are favored in this solvent. In (CD3)2SO, an additional NH group, assigned to Aib(3) NH is solvent exposed in the fragments longer than six residues, suggesting partial unfolding of the N-terminal β-turn or transition to an α-helical conformation. The data for fragment 6-10 are consistent with a conformation having a single Leu-Aib β-turn. Infrared studies suggest an increase in the number of intramolecular hydrogen bonds with increasing peptide chain length. Appreciable mitochondrial uncoupling activity is observed for peptides with a chain length of at least seven residues. The order of efficiencies of the fragments is 1-7 〈 1-8 ∼ 1-10 〈 1-9, with the decapeptide exhibiting anomalously low uncoupling activity.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270411
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  • 78
    Digitale Medien
    Digitale Medien
    Molecular and crystal structures of three monothiated analogues of the terminally blocked ala-aib-ala sequence of peptaibol antibiotics (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 747-761 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The molecular and crystal structures of three monothiated analogues of the blocked L-Ala-Aib-L-Ala sequence of peptaibol antibiotics, t-Boc-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe, Ac-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe, and Ac-ψ(CSNH)-L-Ala-Aib-L-Ala-OMe, determined by x-ray diffraction analyses, are reported. In all cases the peptide chain is folded with ϕ,ψ angles close to or slightly distorted from those expected for a type II β-bend conformation. However, the 4 → 1 H-bond distance falls within the accepted limits only for Ac-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe. The structures are compared with those already published for their two oxygenated analogues.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270504
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  • 79
    Digitale Medien
    Digitale Medien
    Collapse of a polypeptide chain as a result of the intramolecular formation of antiparallel β-sheets (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 805-819 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The folded nature of an intramolecular antiparallel β-sheet suggests that the introduction of this structure into a statistical coil might be accompanied by a contraction of the chain. The magnitude of the contraction, and the conditions that produce the maximum contraction, have been assessed by the combination of generator matrices with an earlier formulation for the configuration partition function. The results show that the mean square dimensions do indeed pass through a minimum upon the transition from a statistical coil to an antiparallel β-sheet. The depth of the minimum is relatively insensitive to the values of δ and τ, provided the assignments are within the physically sensible range. (The borders of the ordered region are assumed to be of higher energy than the interior.) In contrast with the depth of the minimum, the β-sheet content that produces the minimum is quite sensitive to plausible variation in δ and τ. A much greater collapse of the chain can be produced by antiparallel β-sheet formation than that found in the course of the helix-coil transition. The collapse may cause the volume pervaded by the chain to come within an order of magnitude of the volume characteristic of the globular state.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270508
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  • 80
    Digitale Medien
    Digitale Medien
    The crystal and molecular structure of the anticancer drug actinomycin D - some explanations for its unusual properties (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 843-864 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The crystal structure of the antitumor antibiotic actinomycin D has been determined by the methods of x-ray crystallography. There are three independent molecules in the asymmetric unit. Two of the molecules form a hydrogen-bonded dimer. The peptides within all three molecules have very similar conformations. The greatest conformational variability in the drug molecules occurs in the torsion angles of the bonds connecting the phenoxazone ring to the peptide rings. The results of this analysis has allowed us to explain the unusual physical properties of ActD as well as to provide an explanation for the thermodynamics of its interactions with DNA.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270511
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  • 81
    Digitale Medien
    Digitale Medien
    Sedimentation coefficients of DNA topoisomers: The helical wormlike chain (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 675-682 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The sedimentation coefficient sN of the DNA topoisomer with the linking number N is evaluated as a function of N and chain length on the basis of a (circular) twisted wormlike chain, i.e., a special case of the helical wormlike chain. Evaluation is carried out by an application of the Oseen-Burgers procedure of hydrodynamics to the cylinder model with the preaveraged Oseen tensor. The necessary mean reciprocal distance between two contour points is obtained by a Monte Carlo method. It is shown that sN increases as |ΔN| is increased from 0 in the range of small |ΔN|, where ΔN = N - N, with N the number of helix turns in the linear DNA chain in the undeformed state. It is found that there is semiquantitative agreement between the Monte Carlo values and the experimental data obtained by Wang for sN.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270410
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  • 82
    Digitale Medien
    Digitale Medien
    Masthead (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270501
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  • 83
    Digitale Medien
    Digitale Medien
    A 2H-nmr study of the DNA hydration water in solid li-DNA assemblies (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 717-732 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: High-resolution 2H-nmr is employed to monitor the D2O in hydrated solids of Li-DNA prepared from solution by three different methods: lyophilization, slow evaporation of the water, and wet spinning in alcohol. From the spectral shapes and spin-spin relaxation measurements, the DNA in the lyophilized samples is found to be locally ordered with a domain size of ∼ 0.4 μm. Much longer range macrosopic ordering is found in samples prepared by slow evaporation of the water. Here the DNA spontaneously assembles into a structure that is probably cholesteric, in which the pitch axis is perpendicular to the plane on which the DNA dried. The wet-spinning method produces macroscopically, uniaxially oriented DNA molecules with a maximum helix axis disorder of 12°. To aid in the comparison between calculated and experimental line shapes, a two-dimensional technique is employed to separate the contributions to the line width arising from DNA static disorder, magnetic inhomogeneities, and spin-spin relaxation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270502
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  • 84
    Digitale Medien
    Digitale Medien
    Mechanism of fibrin coagulation based on selective, cation-driven, protofibril association (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 763-774 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The cation sensitivity of linear and lateral assembly processes of thrombin- and reptilase-activated fibrinogen was examined. Analytic ultracentrifugation shows that the linear assembly of fibrin oligomers (protofibrils) is neither cation dependent nor sensitive to chelating agents. Protofibrils generated with thrombin-hirudin gelate with either 1-2 mM Ca(II) or 15-100 μM Zn(II). By contrast, protofibril B, generated with reptilase-diisopropylfluorophosphonate, gelates only with Ca(II) but is insensitive to Zn(II). These results indicate that the release of fibrinopeptides A and B (FPA and FPB) expose two types of lateral binding sites that are sensitive to Ca(II) and Zn(II) respectively. Transmission electron (TEM) micrographs of negatively stained gels indicate that the linear packing of the monomers within the fibrin- and cation-induced protofibrin fibers is essentially identical. Scanning electron (SEM) micrographs show that the Ca(II)-induced protofibrin B gel is similar to fibrin. In all, it seems that branching and gelation derive from two types of cation-sensitive, lateral associative processes. Based on these findings, a new paradigm for fibrin coagulation is proposed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270505
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  • 85
    Digitale Medien
    Digitale Medien
    Distance distributions in native and random-coil troponin I from frequency-domain measurements of fluorescence energy transfer (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 821-830 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We used time-dependent fluorescence energy transfer to determine the distribution of donor-to-acceptor distances in native and denatured troponin I(TnI). The single tryptophan residue (Trp 158) of TnI served as the donor (D), and the acceptor (A) was a labeled cysteine residue (Cys 133). The time-dependent intensity decays of the donor were measured by the frequency-domain method from 10 to 320 MHz. The frequency response of the donor emission, in the absence and presence of acceptor, was used to recover the distribution of D to A distances, using an algorithm that accounts for the intrinsic multiexponential decay of the donor. In the native state the D-A distribution is characterized by an average distance of 23 Å and a half-width of 12 Å. Denaturation results in a modest increase in the average distance to 27 Å, and a dramatic increase in half-width to 47 Å. We believe the ability to recover distance distributions will have numerous applications in the characterization of biological macromolecules.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270509
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  • 86
    Digitale Medien
    Digitale Medien
    The association behavior of β-lactamases in polyethylene glycol solution (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 865-881 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The β-lactamases (EC 3.5.2.6) from Bacillus licheniformis 749/C, Enterobacter cloacae P99, and TEM plasmid RP4 are studied in 10-14% (w/v) polyethyleneglycol (PEG) 8000 solutions at pH 6.5 by x-ray scattering and in 18% PEG by equilibrium sedimentation. Although all three enzymes crystallize with twofold crystal symmetry from PEG 8000, it is not possible in this study to prove that dimerization occurs; however, both techniques give evidence for association above 1% (w/v) protein concentration. For the B. lichen., P99, and TEM enzymes, a dimerization of at most 0, 5, and 10% (v/v), respectively, account for the variation of radii of gyration Rg with concentration, after accounting for the effects of nonideality. Apparent Rg were 3-5% smaller in PEG solution than in PEG-free solution. Enhanced ordering of the molecules in PEG solution or the presence of a PEG-depleted hydration shell around the enzymes can account for the observation of reduced Rg values. Accordingly, values of the partial specific volume (defined at constant chemical potential of PEG) indicate considerable PEG exclusion and are consistent with the ability of high Mr PEGs to induce crystallization of these enzymes.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270512
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  • 87
    Digitale Medien
    Digitale Medien
    Conformation of the second disulfide loop in human transforming growth factor-α studied by two-dimensional nmr spectroscopy (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 923-937 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The determination of the conformation of a cyclic heptadecapeptide derived from the second loop of human transforming growth factor-α, [Ala21]-hTGF-α-(16-32), is described. Two-dimensional homonuclear Hartmann-Hahn and rotating-frame cross-relaxation spectroscopy in H2O were used to obtain the complete proton resonance assignments and the necessary distance constraints between nonbonded hydrogen atoms to derive a conformation without involving any energy minimization. The result is an ellipsoidal-shaped structure with a turn at Gly19 and a bend formed by residues 26-29, Gln-Glu-Asp-Lys. Comparison is made with the second loop of human epidermal growth factor and the results are discussed in terms of receptor binding and biological activity.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270604
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  • 88
    Digitale Medien
    Digitale Medien
    Study of the bisintercalation of the antitumor drug ditercalinium by 31P-nmr (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 957-968 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Bisintercalation of ditercalinium, a potent antitumoral 7H-pyriodo[4,3-c]carbazole rigid dimer, into the self-complementary tetranucleotides d(CpGpCpG)2, d(m5CpGpm5CpG) and the self-complementary hexanucleotide d(CpGpApTpCpG)2 was investigated by 162-MHz 31P-nmr. The slow exchange, on the nmr time scale, observed between the free and complexed nucleotides allows identification of the phosphorus signals in the complexes through two-dimensional chemical exchange spectroscopy. Differences in 31P chemical shifts upon intercalation are discussed in relation to the complex geometry and nature of the drug.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270606
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  • 89
    Digitale Medien
    Digitale Medien
    Small angle neutron and x-ray scattering studies of concentrated protein solutions II. Cytochrome C (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1065-1083 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) techniques were used to study two series of concentrated protein solutions containing horse heart cytochrome C (a spherical protein molecule with hydrated diameter σH = 32.6 Å and pI = 10.2) at pD = 2.9 and 11.9, respectively. The concentration of the protein ranges from 1.2 to 24 g/dL. A titration experiment was made to determine the protein charge (Zt) for each sample. Since the form factor of the protein was already determined from a previous experiment [C. F. Wu and S. H. Chen (1987) J. Chem. Phys. 87, 6199-6205] at pD = 6.8, the present series of experiments was used to test the effect of protein charge on the interparticle structure factor. It is demonstrated that the absolute values of both SANS and SAXS cross sections can be calculated with a theory (called the generalized one-component macroion theory) of the interparticle structure factor, which contains a single unknown parameter, the effective protein charge Zp. Comparison of Zt and Zp thus obtained shows that when the bare surface charge density of the protein calculated by using Zt exceeds about 3 μC/cm2, Zp becomes much smaller than Zt. This is interpreted as a charge renormalization phenomenon similar to that known to occur for highly charged polystyrene latex particles in aqueous solution [S. Alexander, P. M. Chaikin, P. Grant, G. J. Morales, and P. Pincus (1984) J. Chem. Phys. 80, 5776-5781].
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270703
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  • 90
    Digitale Medien
    Digitale Medien
    Effects of pH and temperature on cardioactive polypeptides from sea anemones: A 1H-nmr study (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1143-1157 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effects of pH and temperature on the 300-MHz 1H-nmr spectra of three cardioactive polypeptides from sea anemones, anthopleurin-A from Anthopleura xanthogrammica (AP-A) and Anemonia sulcata toxins I and II (ATX I and II), are described. AP-A and ATX II exhibit major spectral heterogeneity. Evidence from the pH and temperature studies and from high performance liquid chromatography indicates that this heterogeneity is conformational rather than chemical in origin. By contrast, purified isotoxins of ATX I show no evidence of conformational heterogeneity. The pKa values of most of the ionizable groups in these polypeptides are not strongly perturbed by interactions in the tertiary structure, with the exception of one of the Asp carboxylates, which has a pKa of ≲ 2 in AP-A and ATX II and 3.0 in ATX I. Protonation of this carboxylate, suggested to be Asp-9, leads to a conformational change in all three molecules. All three polypeptides are thermally stable, showing some conformational changes but not major unfolding at elevated temperatures.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270708
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  • 91
    Digitale Medien
    Digitale Medien
    Terbium(III) induced Z to A transition in poly(dG-m5dC) (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1183-1186 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270711
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  • 92
    Digitale Medien
    Digitale Medien
    Evidence for similar function of transmembrane segments in receptor and membrane-anchored proteins (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1171-1182 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transmembrane (TM) regions of receptor proteins should have unique structural and/or chemical characteristics if these regions contain residues functional in TM signal transduction. However, in a survey of the membrane-occurring residues in 37 integral membrane proteins, we found that amino acid compositions of TM regions of receptor proteins (n = 11) could not be distinguished statistically from corresponding regions of membrane-anchored proteins (e.g., recognition molecules) with a functional external domain attached to a single hydrophobic membrane-spanning anchor segment (n = 16). TM regions in both categories of proteins differed from the compositions of TM regions in membrane-transport proteins (n = 10). The analysis implies that TM regions in receptor proteins may function mainly to anchor (and position) receptors in their cellular membranes, and therefore residues in receptors that participate in signal transduction need not be restricted to these regions. In addition to mechanisms involving receptor aggregation, ligand-activated conformational perturbation of a receptor external aqueous domain, resulting in membrane penetration of hydrophobic segment(s) of this domain to produce intramembranous contact with its cytoplasmic domain, is hypothesized as a further possible mode of signal transduction.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270710
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  • 93
    Digitale Medien
    Digitale Medien
    Molecular dynamics of structural transitions and intercalation in DNA (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1239-1248 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The large-scale flexibility of DNA and the intercalation of actinomycin D have been studied by computer simulation using molecular dynamics. The stretching and unwinding of B and Z forms of DNA and intercalation in B-DNA were examined through molecular dynamics simulations, and the energetics of transitions were calculated by the conformational energy minimization method. The principal results of this research are as follows: (1) A dynamic conformational pathway is presented for longitudinal stretching and unwinding of the double helix to open an intercalation site. (2) Large-scale transitions are possible in both B and Z forms of DNA through a conformationally allowed kinetic pathway. (3) The stretching and untwisting of a 5′(CG)3′ step is energetically more favorable than for a GC step in B-DNA. (4) The formation of an adjacent second cavity in B-DNA requires larger energy than the formation of the first cavity, affirming the neighbor-exclusion principle of intercalation. (5) Docking an intercalated actinomycin D in the stretched structure is shown to be geometrically and energetically feasible.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270805
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  • 94
    Digitale Medien
    Digitale Medien
    Microcalorimetric studies of solvent-induced conformational change of sodium and cesium salts of poly(L-glutamic acid) in aqueous media (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1267-1281 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Organic solvent-induced coil → helix conformational change of poly(sodium) L-glutamate (NaPLG) and poly(cesium L-glutamate) (CsPLG) in solution in aqueous mixed solvents have been studied at 25°C. Heats of dilution of NaPLG in the water-dioxane pair have been measured as a function of polymer concentration and solvent composition. The results indicate that the overall chain conformation in the disordered form is not too different from that in the α-helical form. Heat capacity measurements by flow microcalorimetry have also been done. The apparent monomolar heat capacity at constant pressure of the polymer, Cp, φ, decreases with dilution similarly to other strong polyelectrolytes in aqueous media. In the water-dioxane pair, Cp, φ increases with the dioxane content due to partial desolvation of ionic species resulting from increasing ionic association. In the case of the water-2-chloroethanol (CE) pair, the transition takes place at low CE content and results show a fast decrease in Cp, φ when the α-helical conformation predominates. It is believed carboxylate groups and CE molecules associate themselves into a complex formation responsible for the transition. The size of the cation plays a significant role in the thermodynamic properties of these polyelectrolytes in solution since sodium ions are more strongly bound to the chain than cesium ions.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270807
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  • 95
    Digitale Medien
    Digitale Medien
    Excluded-volume effect on the bidimensional conformation of DNA molecules adsorbed to protein films (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1329-1331 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270811
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  • 96
    Digitale Medien
    Digitale Medien
    Helix-coil dynamics of a Z-helix hairpin (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1319-1327 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The helix-coil transition of a Z-helix hairpin formed from d(C-G)5T4(C-G)5 has been characterized by equilibrium melting and temperature jump experiments in 5M NaClO4 and 10 mM Na2HPO4, pH 7.0. The melting curve can be represented by a simple all-or-none transition with a midpoint at 81.6 ± 0.4°C and an enthalpy change of 287 ± 15 kJ/mole. The temperature jump relaxation can be described by single exponentials at a reasonable accuracy. Amplitudes measured as a function of temperature provide equilibrium parameters consistent with those derived from equilibrium melting curves. The rate constants of Z-helix formation are found in the range from 1800 s-1 at 70°C to 800 s-1 at 90°C and are associated with an activation enthalpy of -(50 ± 10) kJ/mole, whereas the rate constants of helix dissociation are found in the range from 200 s-1 at 70°C to 4500 s-1 at 90°C with an activation enthalpy +235 kJ/mole. These parameters are consistent with a requirement of 3-4 base pairs for helix nucleation. Apparently nucleation occurs in the Z-helix conformation, because a separate slow step corresponding to a B to Z transition has not been observed. In summary, the dynamics of the Z-helix-coil transition is very similar to that of previously investigated right-handed double helices.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360270810
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  • 97
    Digitale Medien
    Digitale Medien
    Crystal structure and molecular conformation of N-boc-L-pro-dehydro-leu-OCH3 (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1595-1606 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The peptide N-Boc-L-Pro-dehydro-Leu-OCH3 was synthesized by coupling dehydroleucine methyl ester with Boc-Pro-OH. It was crystallized from its solution in a methanol-water mixture at 4°C and the crystals belong to the orthorhombic space group P212121 with a = 10.239(1) Å, b = 19.276(4) Å, c = 20.319(3) Å, V = 4010(1) Å3, and Z = 8. The structure was solved by direct methods using MULTAN 80. The structure was refined to an R value of 0.095 for 1871 observed reflections. There are two crystallographically independent molecules in the unit cell. The molecular dimensions of the two molecules are very similar. The backbone conformation angles of these molecules are as follows: θ1 = -176(1)°, ω0 = -2(2)°, φ1 = -72(1)°, ψ1 = 141(1)°, ω1 = 169(1)°, φ2 = -98(1)°, ψ2 = -179(1)°, θT = 179(1)°, θ11 = 174(1)°, ω10 = -3cm-1, φ11 = -64(1)°, ψ11 = 148(1)°, ω11 = 167(1)°, φ12 = -67(1)°, ψ12 = 175(1)°, and θ1T = 172(1)°, respectively. Other torsion angles such as θ′2 = 86(1)°, χ2 = -5(2)°, ′12 = 131(1)°, and χ12 = -16(2)° are interesting to define the backbone conformation together with the dehydro-Leu side chain as a conformation similar to that of the β-bend type II. The central amide bond of Pro-dehydro-Leu segment is deviated from the planarity. The Boc group adopts a trans-cis conformation. The side-chain torsion angles χ1, χ2, χ3, χ4, and χ0 for Pro-residue in the two molecules are 11(2)°, -11(2)°, 6(2)°, 2(1)°, -9(1)° and -18(1)°, 31(1)°, -31(1)°, 21(1)°, and -1(1)° respectively. The side chain of the Pro residue of molecule A is in the flattened Cγ-endo conformation while the pyrrolidine ring in miolecule B adopts the well-known Cγ-exo conformation. The side-chain torsion angles χ, χ2,1, and χ2,2 in the leucyl residues of molecules A and B are -5(2)°, -111(2)°, 126(2)° and -16(2)°, -110(2)°, and 133(2)°, respectively. The molecular packing is stabilized by intermolecular hydrogen bonds and van der Waals interactions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360271005
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  • 98
    Digitale Medien
    Digitale Medien
    Formation and stability of helical poly (N∊, N∊, N∊-trimethyl-L-lysine) in sodium perchlorate solution (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1627-1640 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly(trimethyl-L-lysine), [Lys(Me3)]n, is converted from random coil to α-helix at about 1/30 of the NaClO4 concentration required by poly(L-lysine), (Lys)n. NaClO4 generates turbidity in [Lys(Me)3]n at concentrations above that required for helix formation, and decreases turbidity above lM NaClO4. The turbidity runs parallel to enhanced, and then decreased, fluorescence of a dansyl label. Helix formation per se does not induce enhanced fluorescence. Increasing NaClO4 concentration increases Tm linearly with log[NaClO4] for both (Lys)n and [Lys(Me3)]n until the denaturing effect of high NaClO4 sets in. Increasing NaClO4 also increases the breadth of the transition. Heating helical [Lys(Me3)]n or (Lys)n does not produce a CD spectrum resembling that of “random-coil” (Lys)n, except for [Lys(Me3)]n at relatively low NaClO4 concentration.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360271008
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  • 99
    Digitale Medien
    Digitale Medien
    Conformational behavior of α,α-dialkylated peptides: Ab initio and empirical results for cyclopropylglycine (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1673-1685 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The preferred conformations of model cyclopropylglycine peptides have been investigated by means of ab initio and empirical methods. Empirical computations performed with fixed bond lengths and valence angles using two well-known force fields show that only values of φ in the ranges ±70° ± 20° are sterically allowed, and that the C7-conformation corresponds to the absolute energy minimum irrespective of the terminal groups used. Also, ab initio computations give similar results, but suggest greater stabilities for bridge and, especially, extended structures. These discrepancies can be removed, adding to the empirical force field a twofold torsional potential on ψ and using softer steric repulsive potentials. Complete geometry optimization using both ab initio and empirical methods does not affect the relative stabilities of folded conformations, but leads to a further significant stabilization of the fully extended structure via large modifications of some valence angles.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360271011
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  • 100
    Digitale Medien
    Digitale Medien
    Images of DNA fragments in an aqueous environment by scanning tunneling microscopy (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1691-1696 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360271013
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