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  • 1990-1994  (82)
  • 1975-1979  (594)
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  • 1976  (594)
  • Physics  (492)
  • Life Sciences  (184)
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  • 1990-1994  (82)
  • 1975-1979  (594)
  • 1890-1899
  • 1810-1819
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  • 101
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 591-600 
    ISSN: 0091-7419
    Keywords: Pyruvate ; hepatoma cells ; cell shape ; macromollecular synthesis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cells maintained in basal growth medium with 0.2-1.0% serum often require citric acid cycle intermediates for optimal viability. We have found that pyruvate added to minimal growth medium causes cellular flattening and formation of external processes accompanied by increaded DNA synthesis in cultured hepatoma cells (HTC cells).Cells were cultured in plalstic T-flasks (0.5, 1.0, or 2.0 × 106 cells/flask) containing 5 ml medium (90% Eagle's Basal Medium (BME) and 10% Swim's S-77) with various concentrations of fetal calf serum (0.2,0.25, 0.5, 1.0, 2.0, 10%) and either pyruvate (50, 100, 250,500, 1,000μg/ml), or one of: dibutyryl cAMP (DBcAMP) or dibutyryl cGMP (DBcGMP) at 10-3, 10-4, or 10-5 M. At 44-48 hr cultures were pulsed with tritiated thymidine, uridine, or lecucine. Cells became attached to the plastic surface within 24hr. Cells in medium with 0.25 to 2.0% serum had a rounded appearance. With added pyruvate, cellular flattening, process formation, and an increased adherence to the substratum was absorbed. By 48 hr, culture without pyruvate grew in rounded clusters; with pyruvate, cells formed extensive interconnecting processes that appeared loosely attached to the monolayer surface. At the cell densities tested, process formation was maximal with 250 to 500 μg/ml pyruvate. Cytochalasin B blocked flattening and process formation; EDTA (1 mg/ml) caused retraction of processes within 3 min, and a slow dissolution of these structures within cells was observed. DBcAMP or DBcGMP did not induce process formation. Flattening and process foormation in pyruvate-enriched cultures were accompanied by marked stimulation of DNA synthesis and smaller increases in RNA and protein synthesis. Cell number was not affected.These pyruvate-induced changes suggest that alterations in energy metabolism, or precursors that enhance viability and macromolecular synthesis in mammalian cell cultures, may exert marked effects on cellular morphology without corresponding changes in growth of neoplastic liver cells.
    Additional Material: 7 Ill.
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  • 102
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 1-14 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Virally transformed fibroblasts have on their surfaces zero or reduced amounts of a large external transformation-sensitive (LETS) glycoprotein. This protein is extremely sensitive to proteolysis. When prelabeled normal fibroblasts are cocultivated with transformed cells, the LETS glycoprotein of the normal cells shows an increased rate of turnover. Experiments are described which investigate the possibility that this phenomenon and the absence of LETS glycoprotein are due to proteolysis by the transformed cells. In particular, the role of plasminogen activation is examined by the use of protease inhibitors and plasminogen-depleted serum. It is concluded that activation of plasminogen is not required for the disappearance of the LETS glycoprotein although the involvement of other proteases cannot be ruled out. The role of proteases in affecting cell growth and behavior is discussed.
    Additional Material: 5 Ill.
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  • 103
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 15-26 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The binding, mobility, and mode of cell entry of the plant toxin ricin (or RCAII) were investigated on susceptible and partially resistant murine cell lines. When susceptible cells (SV40-transformed 3T3 fibroblast cells and BW5147 lymphoma cells) were examined, ricin bound rapidly, induced endocytosis, and entered the cell cytoplasm via broken endocytotic vesicles to inhibit cell protein synthesis, as found previously (1). Addition of lactose within 15 min after initial ricin binding prevented toxicity. After this time lactose addition no longer blocked the inhibition of protein synthesis.In a partially resistant lymphoma (BW5147/RCA3) that shows only a slight reduction in the total number of ricin-binding sites, ricin bound rapidly to the cell surface, but was endocytosed significantly less at low ricin doses compared to its parental line, indicating a possible difference in cell surface behavior. The exposed surface proteins on the BW5147 parental and BW5147/RCA3 resistant lines were examined by 125I-labeling utilizing lactoperoxidase-catalyzed iodination. The radiolabeled components were solubilized and separated by slab gel electrophoresis in sodium dodecyl sulfate. Autoradiograms of the slab gels indicated that two surface components of approximately 80,000 and 35,000 mol wt were much less exposed or were missing on the resistant line.
    Additional Material: 7 Ill.
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  • 104
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A chromosomally stable mouse-Chinese hamster hybrid cell line was subjected to five rounds of selection with cytotoxic antisera raised in rabbits against either the parental mouse 3T3 cells or the parental Chinese hamster Wg-1 cells. Routine karyological analysis of clones isolated at each stage of serum selection revealed that treatment with either serum resulted in a limited loss of chromosomes (compared to the untreated hybrid cell cultured in parallel) and that the pattern of chromosome loss could not be correlated with the particular antiserum used for selection. However, more detailed analysis with the SSC-formamide C-banding technique, which identifies chromosomes containing a mouse centromere region, demonstrated that while large-scale chromosome loss was not achieved as a result of antiserum selection, the limited loss of chromosomes did, in fact, reflect a specific depletion of chromosomes in response to treatment with cytotoxic antiserum. Specific chromosomal elimination was shown to occur as early as the first round of antiserum treatment. Antigenic analysis of the serum-selected clones revealed a quantitative decrease in the expression of the species-specific surface antigens selected against, but no qualitative loss of antigens was detected. The results suggest that treatment with cytotoxic antiserum may select for clones that have lost specific chromosomes bearing genes regulating the expression of species-specific surface antigens, rather than for those demonstrating large-scale depletion of chromosomes bearing the corresponding structural genes. Some of these chromosomally depleted hybrid cell clones have been used (along with pseudotype viruses containing the genome of vesicular stomatitis virus within the envelope of murine leukemia virus, VSV [MuLV]), to study the mechanisms regulating MuLV replication in Chinese hamster cells. The results indicate that the restriction of MuLV replication in Chinese hamster cells operates at two levels: (a) an inability to adsorb to or penetrate Chinese hamster cells; and (b) an additional intracellular block which is dominant in the mouse-Chinese hamster hybrid cell clones examined. This latter block is presently under study.
    Additional Material: 5 Ill.
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  • 105
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 161-168 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have isolated 5 families of proteins from human red blood cell membranes and characterized their secondary structure by ultraviolet circular dichroism measurements. The protein families were prepared by selective solubilization from ghosts under nondenaturing conditions. We find that the intact ghost has a mean α-helix fraction of 0.37, whereas a low-ionic-strength extract (bands 1, 2, 5, “spectrin”) has a substantially higher helix fraction, 0.55. Further extraction of the ghosts with para-chloromercuribenzoate yields bands 2.1, 4.1, 4.2, and 6; their helix content is only 0.17. Finally, the major intrinsic protein, band 3, was solubilized by a nonionic detergent. Its helix fraction is 0.38.
    Additional Material: 2 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 169-180 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Intact rat or human erythrocytes and their isolated (ghost) membranes were incubated with the high speed supernatant fraction of homogenates derived from 32P-labeled rat livers. Phospholipid molecules were transferred between the red cell membranes and the liver extracts, as reflected by the convergence of their specific radioactivities with time. Whereas ghosts usually approached isotopic equilibrium with the liver supernatant fraction during a few hours of incubation at 37° C, the exchange of phospholipids by intact cells was no more than one-half, even after 18 hr. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and sphingomyelin were all exchanged in both intact cells and ghosts, albeit to different extents. (A control experiment, incubating 32P-labeled rat erythrocytes or ghosts with unlabeled rat liver extracts, also demonstrated the exchange of all four major phospholipids.) These data may signify that the phospholipids on the cytoplasmic side of the membrane of intact erythrocytes do not exchange with the phospholipids in exogenous liver extracts. If so, all four major phospholipid classes would appear to be present to some extent at both membrane surfaces. The first inference is in agreement with several other studies on this membrane, while the second inference is not.
    Additional Material: 3 Ill.
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  • 107
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 199-204 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The addition of serum to density-inhibited human fibroblast cultures induced a wave of DNA synthesis, measured as [3H] thymidine incorporation into acid-precipitable material, beginning after 8-12 hr and reaching maximum levels at 16-24 hr. Addition of dibutyryl-3′ : 5′-cyclic AMP (DBcAMP) together with serum inhibited [3H] thymidine incorporation by 75-95%. When DBcAMP was added for the first 4 hr of serum stimulation and then removed, the wave of DNA synthesis was not delayed. This suggested that serum could induce DNA synthesis even though cyclic AMP concentrations were maintained at high levels by DBcAMP during this initial period. These results are inconsistent with the hypothesis that it is the immediate transient reduction in 3′ : 5′-cyclic AMP concentration following the addition of serum that triggers DNA synthesis. By contrast, DBcAMP added 8 hr after serum inhibited [3H] thymidine incorporation to the same extent as DBcAMP added at the same time as serum. This indicated that a step essential for DNA synthesis and occurring late in G1 was inhibited by high concentrations of 3′ : 5′-cyclic AMP.
    Additional Material: 3 Ill.
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  • 108
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 343-353 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The bacterial sensing system has been studied on three levels. First, a quantitative method has been devised for measuring the “action spectrum” of the bacterium in response to a sudden addition of attractant. Second, a technique has been developed for the rapid isolation of mutants defective in the transmission part of the sensing system. Third, a study of the effects of light on the transmission system reveals two components, one which generates tumbling and another which inhibits it.
    Additional Material: 5 Ill.
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  • 109
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 467-473 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The mechanism of interferon action in human fibroblasts has been studied by use of both antisera to human fibroblast interferon and the antisera to the surface of human fibroblast cell. The anti-interferon serum completely neutralized the antiviral effect of human fibroblast interferon. Interferon antiserum prevented the intracellular antiviral state from developing when added to the medium of the cells in which interferon synthesis had already been induced by poly (I · C). This suggests that development of the antiviral state involves interferon interaction with the external part of the producing cell. Treatment with the serum directed against the surface of human fibroblast cells failed to inhibit the antiviral activity of human interferon in these cells.In addition, the effect of gangliosides on the antiviral activity of human interferon was studied and it was found that human interferon binds to gangliosides and that this interaction leads to inactivation of the antiviral effect of interferon. Pretreatment of human fibroblasts with gangliosides had no effect on the sensitivity of these cells to exogenous interferon.
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  • 110
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 515-520 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Light has been used as a primary energy source in studies of tetracycline transport by Rhodopseudomonas sphaeroides. Accumulation of the antibiotic occurs in light, while efflux occurs in dark. Both fluorescence enhancement and radioisotopic tracing have been used to monitor transport. Km's obtained from both techniques are similar. Light-induced accumulation of tetracyclines is inhibited by a variety of inhibitors, including antimycin A, N-ethylmaleimide, carbonylcyanide m-chloro-phenylhydrazone, and 2,4-dinitrophenol. A rapid efflux is observed after loading when cells are placed in the dark or treated with inhibitors.
    Additional Material: 5 Ill.
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  • 111
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976) 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 112
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 549-557 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Con A-methacrylate microsphere conjugates prepared by a two-step glutaraldehyde reaction were used to label Con A-binding sites on bovine rod photoreceptor cells for visualization by scanning electron microscopy. A dense distribution of markers was observed on the surface of the rod outer segment, the inner segment, and the synaptic region. Disk membranes also appear to be heavily labeled with the Con A-microsphere conjugates. The Con A inhibitor, α-methyl mannoside, inhibited the binding of the conjugate to the surface of these visual cells.
    Additional Material: 6 Ill.
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  • 113
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 527-548 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Proteins are selectively sequestered by a number of cell types. However, only in oocytes is the process sufficiently aggravated and specific to be readily studied. In these cells certain serum proteins are taken up in proportions different from those found in the serum.In vitro incubations of hormonally stimulated and synchronous mosquito oocytes show that the only protein capable of initiating the transport process is the female specific yolk protein. Heterologous proteins such as IgG, bovine serum albumin, cytochrome C, and ferritin are inactive. The female specific protein is a phosphoglycolipoprotein. It is synthesized in the fat body, a liver analog in the insect, and passed into the serum before being transported into the oocytes. Preliminary kinetic analysis shows the uptake process to be specific with an apparent Km of about 10-7 M. Glycolytic inhibitors stop protein uptake.The receptor-mediated binding steps in the transport process are most easily studied in the chicken because of the enormous amount of oocyte membrane available from a given oocyte and because up to 1 gm of protein is normally transported per day per oocyte. IgG and the hen specific phosvitin lipovitellin are two of the physiologically important proteins that are transported intact into the chicken oocytes. The uptake appears selective as shown by studies with iodinated proteins. Ferritin conjugated to IgG is shown by electron microscopy to bind to isolated plasma membranes only where coated pits have formed, whereas ferritin alone is not seen localized on any membrane surface. These very specialized regions of the membrane are similar to micropinocytotic pits but, in addition, possess on their cytoplasmic side dense ridges that form the coat. Transport involves binding to the coated pits, the pinching off of the pits, and the subsequent movement of the coated vesicles in the cytoplasm.
    Additional Material: 16 Ill.
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  • 114
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 103-108 
    ISSN: 0091-7419
    Keywords: outer membrane ; lipopolysaccharide ; bacteriophage ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The topography of lipopolysaccharide insertion into the outer membrane of Salmonella is discussed in context with a review of recent findings pertaining to general properties of the outer membrane, such as asymmetry and lateral mobility of surface components.
    Additional Material: 3 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 131-137 
    ISSN: 0091-7419
    Keywords: actin filament bundles ; LETS protein ; cytoskeleton ; chick embryo fibroblasts ; triton cytoskeleton ; nonmuscle actin ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The Balb/3T3 and C3H/10T1/2 lines, noted for their marked postconfluence inhibition of proliferation and anchorage dependence, and frequently studied as nontumorigenic lines that are compared with tumorigenic sublines transformed with various agents, produced tumors within two to four months at low-cell dosage (3 × 104 cells) when implanted subcutaneously attached to 1 × 5 × 10 mm polycarbonate platelets. Platelets alone did not produce tumors. The cultured Balb/3T3 tumor cells showed loss of both postconfluence inhibition of proliferation and anchorage dependence. Tumors arising form attached Balb/3T3 cells in (BALB/c × C57B1/6)F1 hybrids were shown to be transplantable to BALB/c but not to C57B1/6 mice, proving that the tumors were derived form Balb/3T3 and not from host cells. The tumors exhibited unique transplantation rejection antigens that did not cross-react with each other. Scanning electronmicroscopy of Balb/3T3 cells and derive tumor cells on TeflonTeflon: Registered trademark of DuPont Plastics. substrates (on which only the tumor cells and not the parent Balb/3T3 cells could grow) revealed that the two cell types were remarkably similar in appearance, except that the tumor cells were larger and showed many more microvilli that tended to concentrate over the nucleus. We conclude that Balb/3T3 cells and C3H/10T1/2 cells are preneoplastic and give rise to spontaneously transformed clones when implanted in vivo attached to a solid substrate.
    Additional Material: 1 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 185-198 
    ISSN: 0091-7419
    Keywords: hamster spermatozoa ; Concanavalin A ; cell surface ; acrosome ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The plasma membrane of epididymal spermatozoa of the golden hamster (Mesocricetus auratus) exhibits morphological differences over various parts of the head and tail as detected by air-dried replicas and freeze-etching techniques. In an attempt to ascertain whether any topographical differences exist in the number or distribution of carbohydrate moieties associated with the cell surface, cells were labeled with Concanavalin A and marked with hemocyanin.It was found that while the plasma membrane over the acrosomal region differed from that of the postacrosomal region in membrane components revealed by freeze fracturing, there was no apparent difference in the distribution or density of Con A binding sites detectable by hemocyanin localization. The tail regions exhibited differences in both fracture face appearance and the distribution of detectable carbohydrate moieties.It was also found that binding sites for Concanavalin A exist on the inner and outer acrosomal membranes in addition to those on the plasma membrane.
    Additional Material: 21 Ill.
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  • 117
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 239-255 
    ISSN: 0091-7419
    Keywords: substrate ; adhesion ; footpad ; microfilaments ; protoglycans ; glycoprotein ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The proteins and polysaccharides which are left adherent to the tissue culture substrate after EGTA-mediated removal of normal, virus-transformed, and revertant mouse cells (so-called SAM, or substrate-attached material), and which have been implicated in the cell-substrate adhesion process, have been characterized by SDS-PAGE and other types of analyses under various conditions of cell growth and attachment. The following components have been identified in SAM: 3 size classes of hyaluronate proteoglycans; glycoprotein Co (the LETS glycoprotein); protein Ca (a myosin-like protein); protein Cb (MW 85,000); protein C1 (MW 56,000, which is apparently not tubulin); protein C2 (actin); proteins C3-C5 (histones) which are artifactually bound to the substrate as a result of EGTA-mediated leaching from the cell; and proteins Cc, Cd, Ce, and Cf. The LETS glycoprotein (Co) and Cd appear in newly-synthesized SAM (which is probably enriched in “footpad” material - “footpads” being focal areas of subsurface membranous contact with the substrate) in greater relative quantities than in the SAM accumulated over a long period of time (which is probably enriched in “footprint” material - remnants of footpads left behind as cells move across the substrate). Co and Cd turn over very rapidly following short radiolabeling periods during chase analysis. The SAM's deposited during a wide variety of cellular attachment and growth conditions contained the same components in similar relative proportions. This may indicate well-controlled and coordinate deposition of a cell “surface” complex involving the hyaluronate proteoglycans, the LETS glycoprotein, actin-containing microfilaments with associated proteins, and a limited number of additional proteins in the substrate adhesion site. Evidence indicates that SAM is the remnant of “footpad” vesicles by which the cell adheres to the substrate and that EGTA treatment weakens the subsurface cytoskeleton, allowing these footpad vesicles to be pinched off from the rest of the cell. Three different models of cell-substrate adhesion are presented and discussed.
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  • 118
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 417-429 
    ISSN: 0091-7419
    Keywords: nervous system - cell surface antigen(s) ; rat CNS clonal cell lines ; preimplantation embryos ; indirect immunofluorescence staining ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: An antiserum raised by immunization of C3H.SW/Sn mice with cerebellum from 4-day-old C57BL/6J mice recognizes a cell surface component(s) [NS-5] present in different degrees on various parts of the mouse central nervous system. When analyzed by an antiserum-and complement-mediated cell cytotoxicity test and by the ability of various tissues to absorb anti-NS-5 antiserum activity, the antigen(s) was detectable on cerebellum, retina, olfactory bulb, cortex, basal ganglia, and medulla, but not on nonneural tissues with the exception of mature spermatozoa and 4-day-old kidney. The antigen(s) detected by the anti-NS-5 antiserum was found in similar quantities on young and adult rat and mouse cerebellum; however, it was not detectable on any of 16 clonal cell lines derived from the rat central nervous system. During preimplantation stages of murine development, the antigen could be detected on all cells of (2-4)-cell and (8-16)-cell stages and on the trophoblastic cells of blastocysts by indirect immunoflourescence. Embryos on day 9 of gestation, the earliest stage tested after implantation, expressed the antigen(s), but expression was restricted to the nervous system.
    Additional Material: 6 Ill.
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  • 119
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 475-495 
    ISSN: 0091-7419
    Keywords: T4 giant phage ; morphogenesis ; optical/computer image processing ; protein composition ; phage capsid structure ; phage head length determination ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A study has been made of the structure of the capsids of T4D giant phage produced from mutants in gene 23 and temperature-sensitive mutants in gene 24, and T4D and T2L giant phage formed by the addition of L-canavanine followed by an L-arginine chase in the growth medium.All the giant phage capsids have been shown to be built according to the same geometrical architecture. This consists of a near-hexsagonal surface net, lattice constant 129.5 Å, folded into a left-hand T = 13 prolate icosahedron elongated along one of its fivefold symmetry axes. Their only apparent difference from wild-type T-even phage capsids is their abnormally elongated tubular part.A comparison of the capsomere morphologies and protein compositions of the giant phage capsids showed that all T4D giants are indentical but differ from T2L: The T4D capsomere has a complex (6+6+1)-type morphology, whereas the T2L has a simple 6-type. T2L phage, however, lack two capsid proteins, “soc” and “hoc”, present in T4D. The difference in capsomere morphology can therefore be related to the difference in the protein compositions of these two phage.Possible differences between the initiation and means of length regulation of giant phage heads and the aberrant polyheads are discussed.
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  • 120
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 521-530 
    ISSN: 0091-7419
    Keywords: cyclic AMP ; permeability ; renal medulla ; vasopressin ; microtubules ; microfilaments ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vasopressin-stimulated cyclic AMP content and the uptake of 3H2O and 22Na into canine renal medullary slices were measured. Cyclic AMP was increased threefold by 9 × 10-9M vasopressin in isotonic (290 mOsm/kg H2O) Krebs-Ringers bicarbonate. A significant increase in vasopressin-stimulated 3H2O uptake began at 2.75 min after hormone addition and lasted until 5.00 min. Colchicine (1 × 10-5 M) inhibited the vasopressin- stimulated 3H2O uptake. This effect required a minimum preincubation period of 30-40 min in colchicine-containing medium. Colchicine had no effect on basal or vasopressin-stimulated cyclic AMP (10 mM). Lumicolchicine (10-5M) had no effect on either vasopression- or dibutyryl cyclic AMP-stimulated 3H2O uptake. 14 C-colchicine bound predominantly to the cytosol fraction enriched in microtubules, while virtually no binding was observed on plasma membranes. Loght-microscopic examinations of cross sections of tissue slices showed that a majority of vasopressin-treated collecting tybulels and some control tubules had occluded lumens. Colchicine-treated cells, in the presence of vasopressin, had open lumens indicating a blockage of the vasopressin-induced water transport. Cells treated with cytochalasin B (1 μgm/ml) also had open lumens in the presence of vasopressin. Cytochalasin B also blocked vasopressin and dibutyryl cyclic AMP-stimulated 3H2O uptake into collecting duct cells but had no effect on vasopressin stimulated cyclic AMP levels. It was concluded that microtubules and possibley microfilaments are involved in the subcellular mechanism by which vasopresssin increases the permeability of the collecting duct to water.
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  • 121
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    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 565-576 
    ISSN: 0091-7419
    Keywords: FRAP ; lectins ; wheat germ agglutinin ; concanavalin A ; lateral mobility ; cell surface ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The use of fluorescence recovery after photobleaching (FRAP) techniques to monitor the lateral mobility of plant lectin-receptor complexes on the surface of single, living mammalian cells is described in detail. FRAP measurements indicate that over 75% of the wheat germ agglutinin receptor (WGA-receptor) complexes on the surface of human embryo fibroblasts are mobile. These WGA-receptor complexes diffuse laterally (as opposed to flow) on the cell surface with a diffusion coefficient in the range of 2 × 10-11 to 2 × 10-10 cm2/sec. Both the percentage of mobile WGA-receptor complexes and the mean diffusion coefficient of these complexes are higher than that obtained from earlier FRAP measurements of the mobility of concanavalin A-receptor (Con A-receptor) complexes in a variety of cell types. The possible reasons for the differing mobilities of WGA and Con A receptors are discussed.
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  • 122
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    Journal of Supramolecular Structure 5 (1976), S. 601-601 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 123
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    Journal of Supramolecular Structure 5 (1976), S. 531-563 
    ISSN: 0091-7419
    Keywords: α-actinin ; microtunules ; membrane ruffles ; cell spreading ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In the assembly of actin filaments that takes place during the spreading of a polulation of human lung cells, after trypsin detachment off the substratum and replating, tropomyosin exhibits a considrable lag in its association with the newly forming filament bundles; it begins to associate with them during the later stages of cell spreading as the actin filament bundles normally seen in interphase cells begin to organize. This lag is evident in a number of cell types that are spreading onto a substratum; it does not appear to be due to a selective degradation of this molecule during rounding up of the cells, since tropmyosin associates with the actin filament bundles after this lag even under conditions where the protein synthetic activity of the cell is inhibited to more than 95% by cycloheximide. The preferential binding of tropomyosin to fully assembled filament bundles but not to newly formed bundles of actin filaments suggests therefore the existence of two classes of action filaments: those that bind tropomyosin and those that do not. This selective localization of tropomyosin and those that do not. This selective localization of tropomyosin on actin filaments was further pursued by examining the localization of this molecule in membrane ruffles. The immunofluorescent results indicate that ruffling is an actin-filament-dependent, microtubule-independent phenomenon. Tropomyosin is absent from membrane ruffles under a variety of circumstances where ruffling is expressed and, more generally, from any other cellular activity where actin filaments are expected to be in a dynamic state of reorganization or are required to be in a flexible configuraion. It is concluded that in tissue culture cells tropomyosin binds preferentially to actin filaments involved in structural support to confer rigidity upon them as well as aid them in maintaining a stretched phenotype. The absence of tropomyosin from certain motile phenomena where actin filaments are involved indicates that these classes of actin filaments are regulated by cytoplasmic mechanisms distinct from that by which tropomyosin (and troponin) mediates contractility in skeletal mulscle; it opens the possibility that different types of actin filaments enagaged in different cellular motile phenomenon in tissue culture cells may be regulated by a host of coexisting regulatory mechanisms, some as yet undetermined.
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  • 124
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    Journal of Supramolecular Structure 5 (1976), S. 577-589 
    ISSN: 0091-7419
    Keywords: centrioles ; microtubule assembly ; microtubule organizing centers ; mitotic spindle ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: RNase alters the in vitro assembly of spindle asters in homogenates of meiotically dividing surf clam (Spisula solidissima) oocytes. Some effects of RNase, such as reduced astral fiber length, appear nonenzymatic and probably result from RNase binding to tubulin. However, RNase-induced changes in the microtubule organizing center are also observed. Since other polycations can mimic RNase effects, the existence of an RNA component of the spindle organizing center remains uncertain. Effects of RNase and other polycations on astral fiber length can be prevented and reversed by the RNase inhibitor, polyguanylic acid. Polyguanylic acid can also augment astral fiber length in the absence of added RNase or other polycations. Augmentation by polyguanylic acid is favored by high ionic strength, and can be duplicated by polyuridylic acid and, with less efficiency, by polyadenylic acid. Polucytidylic acid and unfractionated yeast RNA, however, are unable to augment aster assembly. Polyguanylic acid can also augment the length of astral fibers on complete spindles isolated under polymerizing condition. These results demonstrate that specfic polyribonucleotides can alter spindle assembly in vitro. The presence of an inhibitor of microtubule assembly in Spisula oocytes, which can be inactivated by specific RNAs, is suggested.
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  • 125
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 11-27 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fluorescence anisotropy decay experiments are described for polystyrene in various ethylacetate-tripropionin mixtures. Decay curve trends agree with the proposed theoretical autocorrelation function. Study of the effects of viscosity shows that the mean relaxation time varies according to a nonlinear law for low viscosities and that the relaxation time θ, reflecting the effects of the possible departures from the motions permitted by an ideal tetrahedral lattice, obeys a law of the type: θ = α + bη. Furthermore, the effects of the direction of the fluorophore transition moment are examined.
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  • 126
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1-10 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The scattering law S(k,w) for dilute polymer solutions is obtained from Kirkwood's diffusion equation via the projection operator technique. The width Ω(k) of S(k,w) is obtained for all k without replacing the Oseen tensor by its average (as is done in the Rouse-Zimm model) using the “spring-bead” model ignoring memory effects. For small (ka\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt N $ \end{document} ≪ 1) and large (ka ≫ 1) values of k we find Ω = 0.195 k2/β α η0 \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt N $ \end{document} and Ω = k2/βξ, respectively, indicating that the width is governed mainly by the viscosity η0 for small k values and by the friction coefficient ξ for large k values. For intermediate k values which are of importance in neutron scattering we find that in the Rouse limit Ω = k4a2/12βξ. When the hydrodynamic effects are included, Ω(k) becomes 0.055 k3/βη0. Using the Rouse-Zimm model, it is seen that the effect of pre-averaging the Oseen tensor is to underestimate the half-width Ω(k). The implications of the theoretical predictions for scattering experiments are discussed.
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  • 127
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 437-449 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The luminescence of 1,2-polybutadiene was measured during and following irradiation with 1.4-MeV electrons at 90 °K. Measured under isothermal conditions, the light intensity at first increases sharply on start-up of irradiation, and then reaches a plateau after several seconds. The equilibrium value was found to be linearly dependent on the dose rate employed. The postirradiation luminescence decay measured at 90°K follows second-order kinetics.The light emitted by the irradiated sample during warm-up to room temperature is characterized by the appearance of four intensity maxima at 118, 168, 223, and 261 °K. The first three peaks are attributable to the onset of local motion, whereas the peak at 223 °K is caused by the long-range motion occurring at the glass-to-rubber transition. A preirradiation of the polymer in vacuo causes an increase in these four peaks as well as the formation of a new maximum at 143 °K.Intermittent exposure of the irradiated sample to light of wavelengths λ 〉 450 nm causes the isothermal luminescence decay to be interrupted by a burst of light emitted by the sample during and shortly following the light exposure. This treatment also results in considerably reduced intensity maxima during warm-up to room temperature. An interpretation of the findings reported is given on the basis of reactions involving primary and secondary transient species produced during irradiation and on the molecular parameters of the polybutadiene.
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  • 128
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 401-414 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic piezoelectric stress constant e*25 of drawn films of poly(γ-methyl D-glutamate) (PMDG) cast from solutions in α-helix-promoting solvents 1,2-dichloroethane (DCE) and chloroform and from the nonhelicogenic solvent dichloroacetic acid (DCA) was measured from -180°C to 200°C at 110 Hz. The drawn and annealed films cast from chloroform show a small peak for the real part of piezoelectric stress constant -e′25 in the temperature range of the mechanical α2-crystalline relaxation, which is caused by the distortion motion of the backbone chain of the α-helix. On the other hand, drawn films cast from DCE show the peak of the real part of the piezoelectric stress constant, whose magnitude decreases in the range of the mechanical α1-crystalline relaxation or the β-relaxation processes, which were previously ascribed, respectively, to mutual slipping of α-helices and to the micro-Brownian motion of disordered regions. Also, -e′25 becomes virtually zero near 180°C where the α2-relaxation is located. These results suggest that the polarization change induced by applied strain is caused by distortion of the backbone chains in the α-helix. Near 0°C, the temperature range of the side-chain mechanical relaxation, -e′25 exhibits a marked peak both for films cast from chloroform and from DCE. The maximum value of -e′25 and the orientation function of the α-helix axis are linearly related and extrapolation of -e′25,max to unit orientation function gives 1.3 × 104 cgs esu which corresponds to 2.4 Debye per residue. This value corresponds reasonably to the value of 3.71 Debye for the permanent dipole moment of NHCO bond if the correction for crystallinity is made. This result also indicates the piezoelectric properties of PMDG arise from distortion of the backbone chain of the α-helix induced by applied strain.
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  • 129
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 955-957 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 130
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 941-954 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A mathematical model developed in an earlier paper describes the experimental x-ray profiles of equatorial nylon-6 reflections in terms of Pearson VII functions. The present paper deals with the physical aspects and interpretations of the interrelations of the parameters obtained and the relation between these parameters and the results of other types of measurements. It was found that the growth of the crystallites perpendicular to the chain axis is not isotropic, the strongest growth being in the direction of the hydrogen bonds. Growth and perfection of the crystallites are found to be highly correlated. Large crystals are related to short distances between the planes containing the hydrogen bonds and so to densely packed, i.e., perfect unit cells. This correlation forms the basis for the observed similarity between our quantification technique and the method of the crystal perfection index introduced by Statton. Curve resolution, however, makes the method better applicable for poorly crystallized samples. Comparison of the results with those of small-angle x-ray scattering gave a high degree of consistency with respect to the determined crystal size. In the literature mention is made of a relation between the dimensions and the melting point of the crystals; this relation is confirmed by comparing the appropriate x-ray parameters with DTA results of methoxymethylated nylon 6-yarns.Information about the γ-phase can be obtained from equatorial and meridional reflections. The expected relationship between the relevant peak areas was established. This reported evidence shows the physical validity of the parameters obtained using the Pearson VII model for the analytical description of x-ray reflections of nylon-6 yarns.
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  • 131
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1201-1209 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass-transition temperatures of a series of copolymers of ethyl acrylate and acrylic acid neutralized with various cations were investigated. It was found that a plot of Tg as a function of ion content, for every type of ion investigated here, gives an unusual sigmoidal curve, which can be correlated with the onset of the failure of time-temperature superposition in viscoelastic studies, as will be shown in a future publication. Also, all of the Tg versus concentration curves for the various counterions can be superposed if the plots are made against cq/a, where c is the metal acrylate content, q the cation charge, and a the distance between centers of charge. Furthermore, in one region of water content, a linear relation is obtained between the glass transition and the water content (in weight-%) independent of the ion concentration over wide ranges of ion content. Finally, above an ion concentration of 12 mole-%, the rate of change in Tg per water molecule per ion pair at constant ion content, (∂Tg/∂n)c is linear but with different slopes above and below two water molecules per ion pair.
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  • 132
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1087-1095 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The changes which take place on annealing rigid PVC in the vicinity of the glass transition have been followed by differential scanning calorimetry. The changes appear as an increase in the glass-transition temperature and a decrease in the enthalpy with time of annealing. For annealing at 75°C, the enthalpy after 50-100 hr approaches the value characteristic of the equilibrium liquid state. The results obtained for annealing at 65°C and 75°C are in accord with those expected for the relaxation of an amorphous material, and are at variance with those expected on the basis of crystallization taking place on annealing. The enthalpy relaxation process is characterized by a distribution of activation energies centered about 18.8 kcal mole-1, and seems to reflect a multiplicity of molecular processes.
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  • 133
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1149-1156 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melt rheological behavior of an anionically polymerized styrene-butadiene-styrene (SBS) block copolymer sample (S: 7 × 103 and B: 43 × 103) was studied using a Weissenberg rheogoniometer. Highly non-Newtonian behavior, high viscosity and high elasticity, which are characteristics of ABA type block copolymers, were observed at 125°C, 140°C, and 150°C. The data at these temperatures superimposed well onto a master curve giving a constant flow activation energy. However, the data at 175°C indicated a marked change in the flow mechanism between 150°C and 175°C. At 175°C, the sample showed Newtonian behavior, negligible elasticity, and deviation from the master curve. These findings may be considered as an indication that the SBS block copolymer sample undergoes a structural change from a multiphase structure at low temperatures into a homogeneous structure at some temperature between 150°C and 175°C.
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  • 134
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1161-1167 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new crystalline form of isotactic poly(pentene-1) was obtained from dilute solution in amyl acetate. We have designated it as form III. The morphology and structure of isothermally crystallized samples were investigated by electron microscopy and electron and x-ray diffraction. This crystalline modification can be indexed on an orthorhombic unit cell (cell dimensions: a = 21.20 ± 0.05 Å, b = 11.48 ± 0.05 Å, c = 14.39 ± 0.05 Å (fiber axis) and probable space group P212121).
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  • 135
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1187-1199 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Glass-transition temperatures and phase separation have been studied in amorphous bisphenol-A polycarbonate plasticized with pentaerythritol tetranonanoate (PETN), trimellitic acid, tridecyloctyl ester (TMDO), and tritolyl phosphate. (TTP). Phase separations occur with partially compatible plasticizers like PETN or TMDO. With PETN, for compositions situated in the miscibility gap, the system is composed of a pure plasticizer phase and of a plasticized polymeric phase characterized by a transition temperature of 110°C. In the case of TMDO and additional phase separation occurs below 55°C and two plasticized polycarbonate phases are observed. In compositions falling in the region where the could point curve crosses the glass-transition diagram the phase separation may be delayed by quick cooling. TTP is completely compatible with polycarbonate and the variation of the glass-transition temperature follows a Gordon and Taylor equation.
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  • 136
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1235-1240 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An x-ray back-reflection rotating camera has been used to measure the lattice constant, thermal expansion, and compressibility in the polymer chain direction of a polydiacetylene, poly[bis(p-toluene sulfonate) of 2,4-hexadiyne 1,6-diol]. The thermal expansion coefficient of the polymer chain is small and positive (0.9 ± 0.2 × 10-6 °K-) at 300°K, but negative below about 70°K. Application of 3.43 kbar hydrostatic pressure at 299°K changed the unit cell dimension in the polymer chain direction by less than 10 ppm.
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  • 137
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1425-1431 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Persistence vectors a ≡ 〈r〉 are calculated for polypropylene, polystyrene, and poly(methyl methacrylate) chains as functions of chain length and stereochemical constitution. Differences between the progressions of a with chain length for these vinyl polymers are related to their conformational characteristics. The preferences of the syndiotactic chains for the tt dyad conformation are manifested most strikingly in the behavior of this vector.
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  • 138
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solvent-cast films of blends of poly(∊-caprolactone) (PCL) with poly(vinyl chloride) (PVC) were examined by low-angle x-ray scattering and by small-angle light scattering. X-ray scattering from crystalline compositions were analyzed using the Tsvankin-Buchanan technique and led to values of the repeat period of the lamellar structure and the thickness of the crystalline and amorphous layers. With increasing content of PVC, the amorphous layer thickness increased sufficiently to accommodate the PVC, leading to values of the linear crystallinity consistent with macroscopic measurements by density and DSC techniques up to about 50% PVC by weight. Above this concentration, the lamellar structure no longer appeared to be volume filling. At high concentration of PCL, the polymer consisted of volume-filling spherulites containing the lamellar substructure. Spherulite sizes were measured by light scattering and absolute light scattering intensities were consistent with calculations based upon the degree of crystallinity and anisotropy of the spherulites. Compositions containing more than 60% PVC were amorphous. Low-angle x-ray scattering was interpreted in terms of the Debye-Bueche theory which leads to values for a correlation distance lc and the mean-square electron density fluctuation 〈η2〉 (which was also obtained from the invariant). By the method of Porod, the correlation distances were resolved into persistence lengths within the two phases, which were determined as a function of composition. The fluctuation 〈η2〉 was analyzed in terms of a two-phase model to show that its value was somewhat larger than would be obtained if the phases were composed of the pure components. It was not possible to uniquely determine their compositions. The data were consistent with the existence of a transition zone of the order of 30 Å thick between phases.
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  • 139
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1485-1493 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The universal calibration for gel permeation chromatography (GPC) has been applied to amylose and dextrans. The molecular weight distribution of amylose has been measured starting from known data on dextrans. The agreement found between the molecular weight averages resulting from GPC and those obtained by other methods justifies the procedure followed. The GPC measurements were performed with dimethylsulfoxide as the elution solvent and deactivated silica gel (Porasil) as the column-filling material.
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  • 140
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1495-1512 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Unoriented T-die flat films of nylon 6 and PET films annealed at 90°C were stretched in water at 80°C. Amorphous PET films were stretched in water at 65-75°C. Changes in the light scattering patterns from these samples upon stretching were investigated. One of the observed LS patterns from the stretched samples is the Hv eight-leaf pattern consisting of four lobes and streaks. In the nylon 6 and heat-treated PET showing this pattern, spherulitic patterns can be seen in polarization microscopy. The microscopic spherulitic superstructure may possibly be the factor responsible for producing the lobe-and-streak pattern. On the other hand, many microscopic eight-leaf patterns can be observed in amorphous unannealed PET showing the lobe-and-streak pattern. These microscopic patterns are due to retardation at stress concentrations around impurities and nuclei. The superstructure giving these microscopic patterns must be the origin of the lobe-and-streak pattern from unannealed PET. Another scattering pattern, the Vv cruciform pattern, was observed in both stretched nylon 6 and unannealed PET. This pattern is due to an orientation change across the slip lines observed under a polarizing microscope. It is noted (1) that the appearance of the slip lines in PET coincides with the occurrence of oriented crystallization on stretching, (2) that the lobe-and-streak pattern from PET in which orientation crystallization has taken place is fairly stable to heat treatment and does not disappear until just before melting, and (3) that the superstructures produced at low stretching seem to be deformed on further stretching, in accordance with affine deformation theory.
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  • 141
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1567-1573 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An Interesting kinetic effect in the environmental stress cracking (E.S.C.) of polyethylene has been observed, in which the liquid viscosity plays an important role. E.S.C. of a low density, high melt index polyethylene due to silicone oils has been studied using constant load creep experiments. For relatively low stresses, it has been found that the time to fracture is independent of the viscosity of the silicone oil, all other factors being approximately equal. However, at high stresses, the time to fracture increases with increasing viscosity for a given stress. This effect has been shown to be due to the relative ease with which the liquid penetrates a growing crack and thus always be at the crack front. Times to fracture for viscous liquids at high stresses are longer since crack propagation continues partially with and partially without liquid contact, fracture rate being much slower when not in the presence of the liquid.
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  • 142
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1591-1599 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric β-relaxation in oriented poly(ethylene terephthalate) was investigated over wide ranges of frequency and temperature, with the electric field applied at inclinations of 0°, 45°, and 90° to the draw direction. Pronounced directional anisotropy is observed over the entire range of temperature and frequency. With the external field parallel to the draw direction the dielectric loss is considerably smaller than the value obtained with the field normal to the draw direction. The value obtained with the electric field at 45° to the draw direction is intermediate between the other two. On the other hand, the activation energy is largest for 0° inclination and smallest for 90° inclination. It is suggested that motions of the dipoles involve localized rocking of the molecular chain backbone, particularly when the external electric field is parallel to the chain direction.
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  • 143
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1659-1669 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic mechanical properties of cold-compacted films of polyethylene prepared by γ-ray-induced polymerization in bulk at 30°C are discussed in connection with the fine structure. The cold-compacted films show a broad α-relaxation at a lower temperature than do single-crystal mats or melt-crystallized polymer. From the effects of annealing and swelling by carbon tetrachloride on the relaxation, it is concluded that the α-relaxation, like the α-relaxation in the single-crystal mats, originates from molecular motions within lamellar crystals. This is consistent with the finding that these films are composed of stacked small irregular lamellar crystals. The γ-relaxation is also similar to that in crystal mats.
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  • 144
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1641-1658 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The drawing behavior of a series of linear polyethylene homopolymers with weight-average molecular weight (M̄w) ranging from 67,800 to ∼3,500,000 and variable distribution (M̄w/M̄n = 5.1-20.9) has been studied. Sheets were prepared by two distinct routes: either by quenching the molten polymer into cold water or by slow cooling below the crystallization temperature (∼120°C) followed by quenching into cold water.When the samples (2 cm long) were drawn in air at 75°C using a crosshead speed of 10 cm/min it was found that for low M̄w polymers the initial thermal treatment has a dramatic effect on the rate at which the local deformation proceeds in the necked region. At high M̄w such effects are negligible. An important result was that comparatively high draw ratios (λ 〉 17) and correspondingly high Young's moduli could be obtained for a polymer with M̄w as high as 312,000. It is shown how some of the structural features of the initial materials (mainly studied by optical microscopy, small-angle x-ray scattering and low-frequency laser Raman spectroscopy) can be interpreted in terms of the molecular weight and molecular weight distribution of the polymers. Although crystallization and morphology can be important at low M̄w, it suggested that the concept of a molecular network which embraces both crystalline and noncrystalline material is more helpful in understanding the drawing behavior over the whole range of molecular weights.
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  • 145
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1693-1700 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Spin-lattice relaxation times (T1) for methyl, methylene, and methine carbons in an amorphous polypropylene have been measured as a function of temperature from 46 to 138°C. The carbons from isotactic sequences characteristically exhibited the longest T1's of those observed. The T1 differences increased with temperature with the largest difference occuring for methine carbons where a 32% difference was observed. Activation energies were determined for the motional processes affecting T1's for isotactic and syndiotactic sequences with essentially no dependence upon configuration noted.
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  • 146
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1903-1907 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
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  • 147
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1913-1916 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 148
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1921-1929 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In evaluating molecular orientation by dynamic infrared techniques, it is shown, subject to certain restrictions, that an extensional mechanism plays an important role in the measured orientation. Dichroic measurements can indicate a change in segmental orientation without any change occurring in the chain axis orientation. Extensional orientation was evaluated for a general helical molecule in terms of singular and coupled vibrational modes. Significant orientation changes can occur by the extensional mechanism, the sign and magnitude of which depend on the components of the transition moment vector.
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  • 149
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1801-1812 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A method is proposed for calculating the activation energy over the entire temperature range from relaxation measurements at two frequencies as a function of temperature by taking into account the entire experimental curve. The method is independent of the distribution of relaxation times, but assumes the validity of the time-temperature superposition principle.
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  • 150
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1871-1875 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The γ and δ relaxations of polystyrene (PS) are rendered more active dielectrically by sorbed oxygen. This effect, coupled with comparative work on molecularly similar systems has led to the assignment of the γ relaxation to a rotational libration of the phenyl ring in PS. Specific interactions of the pendant phenyl ring with molecular oxygen to induce off-axis dipole moments in the phenyl moiety is proposed. It is concluded that this interaction is strong enough to influence the dielectric relaxation strength of other relaxations in PS. It is further concluded that because of the interactions occuring in aromatic polymers containing sorbed oxygen, care must be taken to exclude oxygen or to vary its content, in order that intrinsic motions in the polymer system can be studied.
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  • 151
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1909-1912 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
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  • 152
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1917-1919 
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    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 153
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2105-2108 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 154
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2109-2112 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
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  • 155
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2119-2128 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polystyrene networks prepared by anionic polymerization have been characterized by small-angle neutron scattering. Two kinds of systems have been examined:(A) networks with labelled branch points allowing characterization of the spatial distribution of crosslinking points; (B) networks containing a low proportion of chains labelled with perdeuterated polystyrene in order to characterize the conformation of individual elastic chains of the polymeric network. The dependence of the results on swelling and uniaxial extension is discussed.
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  • 156
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2129-2136 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Relaxation of birefringence and stress in simple extension has been studied for polyisobutylene at -26.0°C and 25.0°C for extension ratios ranging from about 1.2 to 2.0. The dependence of both the stress and birefringence on the extension ratio, for a given time, is well described by equations of the Mooney-Rivlin form. The Mooney-Rivlin treatment of the birefringence experiments was found to reinforce but not add to information available from the stress-relaxation experiments alone. At 25.0°C, the stress-optical coefficient is found to be stress dependent. Possible explanations of this behavior are discussed. An experiment is also reported in which the birefringence is observed under zero stress immediately after cutting a strained sample. The zero stress birefringence is believed to be due to regions of stress-induced crystallization taking a finite time to melt after the stress is removed.
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  • 157
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2195-2209 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The lateral swelling, changes in length and tensile stress-strain curve of reconstituted collagen hollow fibers, crosslinked with uv irradiation, were measured as a function of the pH and ionic strength of their aqueous environment. From pH 5 to pH 10 the lateral swelling and length are constant; at lower and higher pH the lateral swelling increases rapidly while the fiber shrinks in length. Corresponding to these changes, a pronounced toe develops in the stress-strain curve and extends to a higher strain in more acid (or basic) media. This toe is attributed to the straightening of a microcrimp in the collagen fibrils; the microcrimp is accentuated by the repulsion between the charged fibrils in acid or basic media. Direct small-angle x-ray evidence of these microcrimp structure changes at low pH is presented. Increasing the ionic strength of an acid solution by adding NaCl decreases the lateral swelling, increases the length, and decreases the extent of the toe on the stress-strain curve. These changes result from an increased screening of the charge on neighboring fibrils at higher ionic strengths thus decreasing the repulsion between fibrils and the resulting microcrimp. Although the zigzag elastica model of the crimp developed by Diamant et al. [Proc. Roy. Soc., Ser. B, 180, 293 (1972)] provides a good empirical fit to the stress-strain data, it is shown to be inappropriate where the crimp results from repulsive forces between fibrils. A new model taking these forces into account is developed and is shown to be in reasonable agreement with the experimental results.
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  • 158
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2231-2240 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mean-square dipole moments of poly(ethylene oxide) and poly(hexamethylene oxide) chains have been determined from dielectric constant measurements on dilute solutions of the polymers in benzene. The values obtained are in good agreement with those predccted using the rotational isomeric state models for these chains. In addition, the unperturbed dimensions of poly(hexamethylene oxide) have been calculated as a function of molecular weight, using the isomeric state theory.
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  • 159
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2253-2257 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of phase transformation are treated for heterogeneous nucleation, where all nuclei are simultaneously initiated, and where initiation follows first-order kinetcs. The phase transformation curves are sigmoid. For simultaneous initiation in two dimensions, a(t)/(1 - a(t)) ∝ t2. For first-order initiation, we have, approximately, a(t)/(1 - a(t)) ∝ t2.85, and v(t)/(1 - v(t)) ∝ t3.74.
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  • 160
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2241-2251 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cloud-point curves have been determined for aqueous solutions of poly(ethylene oxide) (PEO) at several concentrations for a variety of inorganic salts (sulfates, carbonates, nitrates, and chlorides). From these, theta conditions have been determined. The resulting dependences of the critical temperature θ (mostly between 300 and 360°K) on the molar concentrations (or ionic strengths) of the salts in solution cannot wholly be summarized in sequences of ion effects. The major findings are that sulfates and carbonates are much more effective in reducing θ than the chlorides and nitrates at the same concentrations. The trends found depend on salt concentration, i.e., certain plots of the data cross over, but they broadly agree with those found for comparable systems by other workers. Exceptional are the chlorides of Group II and LiCl which show minima when θ is plotted against molar salt concentration. While interpretations based on solvent structure-breaking are not adequate, there are similarities in behavior with the structure-breaking attributes of the ions based on independent studies (infrared). The results are briefly discussed in terms of current postulates: a more detailed discussion will accompany further experimental studies on these systems.
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  • 161
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2273-2284 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Six 6,10-ionenes with different counterions were prepared by ion exchange reactions in aqueous solutions. The counterions were Br, I, CIO4, BF4, SCN, and B(C6H5)4. The dynamic mechanical properties of these polymers were investigated by use of a torsional braid analyser. Three relaxations α (25-140°C), β (-30-0°C), and γ (-140-120°C) were observed at the frequencies of 0.3-0.8 Hz. The temperature of the α and β relaxations were largely dependent on the size of counterions, but those of the γ relaxations had little variation. The effects of electrostatic forces in the polymers on each relaxation was discussed. The influence of absorbed water on the α, β, and γ relaxations was examined. The absorbed water in the polymers greatly depressed the temperature of the α relaxations and this phenomenon was interpreted to be the result of the specific hydration on ionic portions.
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  • 162
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2291-2311 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small-angle and wide-angle x-ray scattering measurements, using a position-sensitive detector, were made during melt-crystallization of linear polyethylenes and PEO-PS-PEO triblock copolymer. The scattering measurements indicated that the triblock copolymer grew by the enlargement of regions in which lamellae are regularly stacked. During primary crystallization at higher temperatures similar behavior is observed in two linear polyethylenes. At lower temperatures, changes in the shape of small-angle scattering curves during the primary stage of crystallization indicate that amorphous gaps within the lamellar stacking become filled in. During secondary crystallization at higher temperatures new crystallites appear to grow between those formed in the primary stage. Concurrent decrease of the overall scattered intensity leads to the conclusion that secondary crystallization has two components: crystallization of new lamellae behind the spherulite growth front and the thickening of existing lamellae.
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  • 163
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1241-1255 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fibers were drawn from polymers of octadecyl acrylate, octadecyl methacrylate, N-octadecylacrylamide, and a series of N-substituted acrylamides with a second amide group in the side chain as well as from copolymers of octadecyl and methyl esters of acrylic and methacrylic acid. Wide-angle and small-angle x-ray diffraction patterns were recorded for these materials. The interpretation of the characteristic difference between the behavior of the polycrylates and polymethacrylates, as proposed by Platé and his collaborators, is found to be inconsistent with a number of features of the experimental evidence. In the case of poly(octadecyl methacrylate) the data allow the estimation of two parameters of the electron density distribution in the side-chain crystallites. With polyacrylamide derivatives, a second amide group in the side chain is found to destabilize the side chain crystallites. The bahavior of the copolymers is very complex and exhibits, in one case, evidence for a long periodicity parallel to the fiber axis.
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  • 164
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1287-1295 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrophobic-hydrophilic block copolymers were prepared by “living” anionic polymerization. They consist of polystyrene and poly(ethylene oxide) blocks, and are soluble in water. Their interfacial properties were investigated, employing aqueous solutions. The block copolymers lowered the surface tension of water in analogy with the low molecular weight surfactants such as sodium lauryl sulfate and heptaethylene oxide n-dodecyl ether. Their aqueous solutions exhibited solubilization properties differing from those of polyethylene glycol. Therefore, it is thought that the polystyrene blocks produce solubilization phenomena. In samples of the same styrene content, the precipitation temperature of a high molecular weight copolymer in water was lower than that of a low molecular weight copolymer at the same concentration in the same solvent. The surface tension and precipitation temperature of aqueous solutions seem to be influenced by molecular weight and composition.
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  • 165
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1317-1324 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A weak acid gel (carboxylmethyldextran) was titrated with sodium hydroxide while equilibrated with a solution sodium poly(vinyl sulfate), a salt of a strong acid polyelectrolyte.It was found that the quantity \documentclass{article}\pagestyle{empty}\begin{document}$$ S = {\rm pH} - {\rm pNa} + \log (V/V_0) $$\end{document} in which V/V0 is the volume of gel relative to its volume in acid form in pure water, is independent of the concentration Cp of the polyelectrolyte solution and of the relative volume of gel.The relation \documentclass{article}\pagestyle{empty}\begin{document}$$ S - \log \left({\frac{{\alpha ^2}}{{1 - \alpha}}} \right) = {\rm pK'} + \log \gamma _{{\rm Na}}^{\rm g} + \log (v/V_0) $$\end{document} where α is the degree of ionization, pK′ is the apparent pK of the gel, γnAG is the activity coefficient of the counterion in the gel phase, and v is the number of ionizable groups, is found to be constant for all values of Cp and for 0.1 〈 α 〈 0.9. These results can be extended to highly crosslinked ionexchange resins.
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  • 166
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1891-1901 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A nonisothermal creep experiment has been analyzed to ascertain its suitability for determining the temperature dependence of low activation energy viscoelastic processes in elastomers far above Tg. The nonisothermal method was employed to determine the activation energy for creep near 35°C in a lightly crosslinked cis-1,4 polybutadiene elastomer at small strains within the linear viscoelastic region, and at various large deformations up to rupture. The observed activation energy was essentially independent of the level of strain, and the value of ΔHa (∼11 kcal/mole) determined via the nonisothermal creep method was in good agreement with the result (∼12 kcal/mole) obtained via time-temperature superposition of isothermal linear viscoelastic creep data. The nonisothermal data allowed for an estimate of the volume of the “flow unit” associated with the controlling viscoelastic creep mechanism, attributed here to slippage of entanglements within the lightly crosslinked network.
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  • 167
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1877-1890 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dielectric relaxation and Brillouin scattering are jointly used in studying molecular relaxation in poly(propylene oxide) (PPO) and its solutions in methylcyclohexane. The dielectric method was applied to the more concentrated (100%, 80%, 60%, by volume) solutions over a wide temperature and frequency range (30 Hz to 8 GHz) in order that the variation in activation energy characteristic of a glass-forming substance could be delineated. The present work extends previous work on the undiluted polymer to higher frequencies so that range of 12 decades in the dielectric loss maximum fmax as a function of temperature is now available. The “Antoine” equation is found to represent the behavior of log fmax, of the bulk concentrated solutions very well. The more dilute (40%, 20%) solutions were studied only in the high-frequency (GHz) region since phase separation occurred at low temperatures. Both the temperature and dilution effects were interpreted in terms of free-volume theory. Brillouin scattering spectra were obtained at several scattering angles and a wide range of temperatures. A maximum in the curve of hypersonic attenuation versus temperature was observed in each polymer solution. The attenuation maximum shifts toward lower temperature upon dilution, in agreement with the dielectric relaxation result. The Brillouin scattering follows different activation parameters and evidences a more rapid process than does the dielectric relaxation. It is speculated that it monitors a secondary or subglass relaxation, due perhaps, to damped torsional oscillations.
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  • 168
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    Journal of Supramolecular Structure 4 (1976), S. 141-159 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The specificity of lactoperoxidase-catalyzed iodination for the proteins of the hepatoma tissue culture cell plasma membrane was examined by histochemical, biochemical, and cell fractionation techniques. Light microscope autoradiography of sectioned cells shows the incorporated label to be localized primarily at the periphery of the cell. Most of this label can be released from the cell by trypsin but not by collagenase or hyaluronidase. The label is recovered from the cells as either monoiodotyrosine or diiodotyrosine after hydrolysis of cell extracts with a mixture of proteolytic enzymes. The label co-purifies during cell fractionation with an authentic liver cell plasma membrane marker enzyme, 5′-nucleotidase. Thus, the incorporated iodide is itself a valid marker for those membrane polypeptides having tyrosine residues accessible to the lactoperoxidase. The polypeptide complexity of the purified plasma membrane was examined by high resolution dodecyl sulfate-polyacrylamide gel electrophoresis. At least 50 polypeptides in the membrane are accessible to iodination. These polypeptides probably represent the bulk of the protein mass of the membrane and iodinating them does not affect cell viability, growth rate, or cell function. Labeling experiments with fucose and glucosamine show that at least nine of the iodinated peptides may be glycoproteins.
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  • 169
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    Journal of Supramolecular Structure 4 (1976), S. 181-184 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: ATP stimulates chromaffin granules from the bovine adrenal medulla to release epinephrine and specific soluble proteins. ATP analogs substituted in the β-γ-position with either nitrogen or carbon were also found to be effective at inducing release from isolated chromaffin granules. However, an ATP analog substituted at the α-β position with carbon was strongly inhibitory. Cyclic AMP was also found to be synthesized by isolated chromaffin granules under release conditions. ATP analogs were effective as substrates for adenylate cyclase in the same order as their efficiency for inducing release from vesicles. Hydrolysis at the β-γ linkage of ATP therefore is probably not necessary for release; however, hydrolysis at the α-β position may be important in the release process. Cyclic AMP may be produced and play a regulatory role in this event.
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  • 170
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    Journal of Supramolecular Structure 4 (1976), S. 185-197 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The present study was undertaken to localize adenylate cyclase activity in salivary glands by cytochemical means. For the study, serous parotid glands and mixed sublingual glands of the rat were used. Pieces of the fixed glands were incubated with adenosine triphosphate (ATP) or adenylyl-imidodi-phosphate (AMP-PNP) as substrate: inorganic pyrophosphate or PNP liberated upon the action of adenylate cyclase on the substrates is precipitated by lead ions at their sites of production.In both glands, the reaction product was detected along the myoepithelial cell membranes in contact with secretory cells, indicating that a high level of adenylate cyclase activity occurs in association with these cell membranes. The association with a high level of the enzyme activity might be related to the contractile nature of myoepithelial cells which are supposed to aid secretory cells in discharging secretion products.A high level of adenylate cyclase activity was also detected associated with serous secretory cells (acinar cells of the parotid gland and demilune cells of the sublingual gland), but not with mucous secretory cells. In serous cells, deposits of reaction product were localized along the extracellular space of the apical cell membrane bordering the lumen. This is the portion of the cell membrane which fuses with the granule membranes during secretion. Since the granule membranes are not associated with a detectable level of adenylate cyclase activity, it appears that the enzyme activity becomes activated or associated with the granule membranes as they become part of the cell membrane by fusion. The association with a high level of adenylate cyclase activity appears to be related to the ability of the membrane to fuse with other membranes. It is likely, since the luminal membrane of mucous cells which does not fuse with mucous granule membranes during secretion is not associated with a detectable enzyme activity.
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    Journal of Supramolecular Structure 4 (1976), S. 221-231 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The HLB dependency for the solubilization of membrane proteins and adenylate cyclase activity from a plasma membrane-enriched fraction from rat liver has been determined. The HLB (hydrophilic/lipophilic/balance) number of a detergent is an empirical measure of its relative hydrophobicity. Detergent HLB numbers vary systematically with the length of the ethylene oxide chain for a homologous series of detergents such as the Triton X series. These detergents have a constant hydrophobic moiety, octylphenyl, and a variable polar portion, polyethoxyethanol. Basal-NaF-epine-phrine-, and glucagon-stimulated adenylate cyclase activities were solubilized in the HLB range of 16.8-17.4. Solubilization was most effective in 0.01 M Tris buffers at pH 7.5 containing 1-5 mM mercaptoethanol, 1 mM MgCl2, and 0.1% Triton X-305. The detergent to membrane protein ratio used in these studies was 3:1.Criteria for solubilization included lack of sedimentation at 100,000 × g, the absence of particulate material in the supernatant when examined by electron microscopy, and inclusion of hormonally sensitive adenylate cylcase activity in Sephadex G-200 gels. The apparent molecular weight of the solubilized enzyme was approximately 200,000 in the presence of Triton X-305. The solubilized enzyme was stimulated 5-fold by NaF, 7-fold by glucagon, and 20-fold by epinephrine compared to the particulate enzyme used in this study which was stimulated 10-fold, 3,4-fold, and 4-fold by NaF, epinephrine, and glucagon, respectively. The solubilized enzyme is stable for several weeks when stored at -60° C.
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  • 172
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    Journal of Supramolecular Structure 4 (1976), S. 241-258 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The binding of many polypeptide hormones to cell surface receptors does not appear to follow the law of mass action. While steady-state binding data are consistent in many cases with either heterogeneous populations of binding sites or interactions of the type known as negative cooperativity, study of the kinetics of dissociation of the hormone receptor complex allows an unambiguous demonstration of cooperative interactions. Negative cooperativity, which seems to be wide-spread among hormone receptors, provides exquisite sensitivity of the cell at low hormone concentrations while buffering against acutely elevated hormone levels. The molecular mechanisms underlying the cooperativity are still largely unknown. Cooperativity may stem from a conformational transition in individual receptors or involve receptor aggregation in the fluid membrane (clustering) or more extensive membrane phenomena. Thus, new models of hormone action must be considered which integrate the progress in our knowledge of both the complex mechanisms regulating hormone binding to their surface receptors, and the dynamic properties of the cell membrane.
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  • 173
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Simian virus 40 (SV40) induces cell division in microcultures of sparsely plated nongrowing mouse BALB/3T3 cells during acute infection at moderate multiplicities of infection (MOI = 10-100). The infected cells are killed when a MOI of 1,000 is used. SV40 tumor (T) antigen is synthesized in the infected cells, but viral DNA, virion antigen, and progeny virions are not synthesized (abortive infection). The addition of exogenous dibutyryl adenosine 3′-5′-monophosphate (dbcAMP) at the time of infection stimulates the SV40-induced cell division at all MOI and inhibits SV40-induced cell death at high MOI. The percentage of T antigen-positive cells, as monitored by immunofluorescence, is also increased by the addition of dbcAMP at the time of infection. This regulation of SV40-induced cell division and T antigen formation by exogenous dbcAMP occurs within the first 6 hr after infection at 37° C and is dependent upon both the MOI and the concentration of added dbcAMP. The addition of dbcAMP to productively infected TC7 monkey cells has little effect on the SV40-induced cell death or T antigen formation.
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  • 174
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    Journal of Supramolecular Structure 4 (1976), S. 289-303 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vasopressin-sensitive pig kidney adenylate cyclase is sensitive to several effectors, such as Mg2+, other divalent cations, and guanyl nucleotides. The purpose of the present study was to compare the main characteristics of adenylate cyclase activation by vasopressin, Mg2+, and GMPPNP, respectively. Mg2+·ions were shown to exert at least three different effects on adenylate cyclase. The substrate of the adenylate cyclase reaction is the Mg-ATP complex. Mg2+ interacts with an enzyme regulatory site. Finally, Mg2+ can modulate the hormonal response, with Mg2+ions affecting the coupling function-that is, the quantitative relationship between receptor occupancy and adenylate cyclase activation. At all the magnesium concentrations tested, from 0.25 mM to 16 mM, adenylate cyclase activation was not a direct function of receptor occupancy. At low Mg2+ concentrations, adenylate cyclase activation dose-response curve to the hormone tended to be superimposable to the hormone dose-binding curve. These results suggest a role of magnesium at the coupling step between the hormone-receptor complex and adenylate cyclase response. Cobalt, but not calcium, ions could exert the same effects as Mg2+ ions on this coupling step.GMPPNP induced considerable adenylate cyclase activation (15 to 35 times the basal value). Activation by GMPPNP was highly time and temperature dependent. At 30° C, a 20 to 60 min preincubation period in the presence of GMPPNP was needed to obtain maximal activation. The higher the dose of GMPPNP in the medium, the longer it took to reach equilibrium. At 15° C, activation was still increasing with time after 3 hr preincubation in the presence of the nucleotide. GMPPNP was active in a 10-8 M to 10-5 M concentration range. Unlike the results obtained with lysine vasopressin, the kinetic characteristics of dose-dependent adenylate cyclase activation curves by GMPPNP were unaffected by varying Mg2+ concentrations except for the increase in velocity when raising Mg2+ concentration. It was not clear whether or not the activation processes by the hormone and by GMPPNP had common mechanisms.
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  • 175
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    Journal of Supramolecular Structure 5 (1976), S. 317-334 
    ISSN: 0091-7419
    Keywords: actin ; cytoskeleton ; filament ; gel ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: This is a review of the evidence that the cytoplasmic contractile proteins function as a cytoskeletal system inthe cytoplasmic matrix. Biochemical experiments show that cycoplasmic actin filaments can form a solid gel under conditions likely to exist in living cells. The actin filaments are associated with other proteins which may stabilize the gel and which are involved with motile force generation like myosin. Ultrastructural studies show that actin filaments are difficult to preserve, but that under stabilizing conditions networks of actin filaments are found throughout the cytoplasmic matrix.
    Additional Material: 11 Ill.
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  • 176
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    Journal of Supramolecular Structure 5 (1976), S. 457-473 
    ISSN: 0091-7419
    Keywords: sporulation ; membranes ; Bacillus subtilis ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Membrane protein alterations during the early stages of sporuloation were examined by polyacrylamide gel electrophoresis. Solubilized samples of the vegetative cell membrane (VCM), sporulation membrane fraction (SMF), and inner forespore membranes (IFM) were compared with respect to their protein compositions. The VCM contained 39 protein components, distinguishable as separate bands on gel electrophoresis, and these ranged in molecular weight from 16,000 to greater than 100,000. During the first 5 hr of sporulation, 6 of these 39 protein bands disappeared, 8 increased and 12 decreased in concentration, and 13 showed no discernible change. In addition, 15 new protein components were identified in the SMF during the fireist 5 hr. The new components consisted of 7 protein bands that were transiently associated with the SMF, and 8 proteins that persisted in the SMF from their time of appearance until at least T5 of sporulation. Comparison of the protein composition of the IFM with those of the VCM and SMF revealed that membrane protein alterations occur during sporulation.The turnover of H3-tryptophan-labeleld membrane protein was followed during growth and sporulation. During the 30 min of growth following a simple chase with excess unlabeled tryptophan, membrane protein appeared stable, whereas 5-10% of the nonmembrane protein turned over to acid-soluble material. However, manipulation of the cells by dilution ito fresh medium, or centrifugation, as part of the chase procedure, resulted in elution of membrane protein to the cytoplasm. In contrast, proteins labeled during vegetative growth were always eluted to the cytoplasm during the first 2 hr of sporulation, and this was followed by a period of reassociation with the membrane fraction. The results are discussed with respect to membrane differentiation as it relates to spore development.
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  • 177
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    Journal of Supramolecular Structure 5 (1976), S. 515-520 
    ISSN: 0091-7419
    Keywords: mutant RCAII ; ricin ; toxin ; protein synthesis ; variant cell line ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Ricinus communis agglutinin II (RCAII, ricin, toxin) at low concentrations inhibits protein synthesis in cell-free extracts, but not in intact cells, of an RCAII-resistant mouse lymphoma variant cell line. The concentration dependence of the inhibition by RCAII was the same in cell-free extracts of both RCAII-resistant variant and RCAII-sensitive parental cells, while intact parental cells are 250 times more sensitive to RCAII toxicity. The onset of RCAII inhibition of cell-free protein synthesis was extremely rapid in both cases, being complete in a few minutes. Under these condidtions RCAII inhibits protein synthesis in intact RCAII-sensitive parental cells, but maximal inhibition requires several hours to occur. These results support our previous electron microscopic observations that the variant cells are defective in the uptake of RCAII by endocytosis at low toxin concentrations.
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  • 178
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    Journal of Supramolecular Structure 4 (1976), S. 89-97 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Specific binding sites for the serum complex of phosvitin and lipovitellin have been shown to exist on the outer surface of rapidly growing chicken oocytes. The existence and specificity of these sites were demonstrated by competition for binding to unfixed oocyte membrane fragments and by displacement of already bound and labeled phosvitin-lipovitellin from formaldehyde-fixed membranes. Only unlabeled phosvitin-lipovitellin competed with the 125I-labeled complex for binding to the fragments or displacement of bound label; IgG isolated from egg yolks and bovine serum albumin were ineffective.
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  • 179
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    Journal of Supramolecular Structure 4 (1976), S. 259-269 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: [3 H]-Catecholamine binding to intact cells, isolated cell membranes, and to several isolated macromolecules has been shown by several laboratories to be neither stereospecific nor inhibited by known β-antagonists. Since additional evidence indicates that this binding is not an artifact (i.e. due neither to the binding of a catecholamine oxidation product nor hormone binding to a catabolic enzyme such as COMT), the question remains as to whether this represents binding to a bona fide membrane receptor. Because all ligands which bind strongly or compete for this binding possess a catechol group, one possible explanation is that the binding affinity is primarily determined by the catechol moiety, whereas the correct stereoisomer of the side chain is necessary to activate the receptor. Thus, although binding is a necessary condition for hormone action, the necessary and sufficient condition for activation of adenyl cyclase is both the catechol group and the correct stereoisomer of the side chain.A theoretical model is developed here to provide a quantitative basis for this hypothesis. This model extends the current concept of distinct subunits in the adenyl cyclase system by separating the receptors from the catalytic sites and placing them at separate locations within the membrane. Utilizing the spare receptor model of Furchgott, and the mobility of macromolecules within a “lipid sea,” the appropriate equations to predict both hormone binding and enzyme activation are derived. Using the observed affinity constants from catecholamine binding studies, it is then shown that this model can predict the experimental observations and hence explain the apparent dichotomy arising from binding and enzyme activation studies.
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  • 180
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    Journal of Supramolecular Structure 4 (1976), S. 205-219 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Studies on the reaction kinetics and chromatographic properties of detergent-dispersed adenylate cyclase are described. Detergent-dispersed enzyme was prepared from whole rat cerebellum and from partially purified plasma membranes from rat liver.Data were simulated to fit kinetic models for which an inhibitor is added in constant proportion to the variable substrate. Models were chosen to distinguish whether the adenylate cyclase reaction may be controlled by an inhibitory action of free ATP-4 (or HATP-3) or by a stimulatory action of free divalent cations. The various kinetic models were then tested with the dispersed brain adenylate cyclase with both Mg++ and Mn++ and in two different buffer systems. The experimental data indicate that this enzyme has a distinct cation binding site, but exhibits no significant inhibition by HATP-3 or ATP-4.The detergent-dispersed adenylate cyclase both from liver plasma membranes and from brain have been chromatographed on anion exchange material and have been chromatographed on anion exchange material and have been subjected to gel filtration. The presence of detergent was required for elution of cyclase activity from DEAE-Sephadex but was not required when DEAE-agarose was used. Dispersed brain cyclase was also chromatographed on agarose-NH(CH2)3 NH(CH2)3-NH2 which exhibits both ionic and hydrophobic properties. Fifty percent of the applied activity was recovered with a fivefold increase in specific activity. The data suggest that the relative effectiveness of a given chromatographic procedure for detergent-dispersed adenylate cyclase may reflect the in fluence of both hydrophobic and ionic factors.
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  • 181
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    Journal of Supramolecular Structure 4 (1976), S. 233-240 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cells dissociated from the R3230AC mammary adenocarcinoma from intact and diabetic rats were examined for insulin binding and glucose transport. The Kd for insulin binding, ∼ 10-10 M, was similar in all tumors studied. However, the apparent number of receptor sites per cell increased in cells from diabetic rats. Kinetic analysis of 3-0-methyl glucose (3-OMG) entry showed both diffusional and passive carrier characteristics. Insulin (4 × 10-9 M) in vitro did not affect diffusional entry, whereas the hormone altered the passive carrier system, as reflected by an increase in Km and Vmax. Insulin decreased initial velocity of glucose transport at 4-6 mM glucose levels but increased initial velocity of glucose transport at 20 mM glucose. An explanation of the role of insulin on tumor growth in vivo from effects on glucose transport in vitro is proposed.
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  • 182
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    Journal of Supramolecular Structure 4 (1976), S. 305-317 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Additional Material: 3 Ill.
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  • 183
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    Journal of Supramolecular Structure 5 (1976), S. 199-219 
    ISSN: 0091-7419
    Keywords: cyclic nucleotides ; protein sulfhydryls ; tubulin ; glutathione ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: It is shown that cyclic nucleotides can have a variety of effects on cell division, cell shape, cell adhesion, and cell movement, depending on the cells selected and the conditions under which they are used. For example, while CHO cells elongate under the influence of exogenous dibutyryl CAMP, Y-1 adrenal tumor cells round up and polyoma-transformed 3T3 cells show no change in shape. The totality of experience with cyclic nucleotides suggests that where they have been used by cells as control elements involving the four processes listed above, they are superimposed on basic cellular processes that progress in their absence - that is, they must be acting indirectly. In attempting to understand the inhibitory action of methyl xanthines on egg development, we were forced to abandon the idea that they acted through cyclic nucleotides. We found that methyl xanthines inhibited the activation of glutathione reductase and that glutathione oxidizing agents act as mitotic inhibitors. Further, we found that tubulin polymerizability, NAD-kinase activity, and a mitotic apparatus associated Ca+2-ATP-ase were all inhibited by oxidation of some of their sulfhydryls and were activated by reduction of the resulting disulfides. These results are discussed in terms of reported cycles and activations of glutathione reductase (GR) in cells and reports that mixed disulfides of glutathione and proteins can act as substrates for GR. Using the fact that a CAMP-dependent protein kinase has been reported to be activated by glutathione, we have suggested potential sites where sulfhydryl control processes and cyclic nucleotide control processes may interact in certain restricted cases.
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  • 184
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    Journal of Supramolecular Structure 5 (1976), S. 291-308 
    ISSN: 0091-7419
    Keywords: colicin E1 ; membrane deenergization ; cell envelope structural change ; fluorescence probe ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: It is of interest to inquire whether agents that uncouple or deenergize membranes cause concomitant structural changes. The agents considered here are the uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone and the bacteriocidal protein colicin E1, agents for which there is some precedent for believing that they interact with membranes.In intact E. coli ML 308-225 cells the inhibition of [14C]-proline active transport by FCCP increases with uncoupler concentration from ∼ 20% at 2 μM to ∼100% at 5 μM. The increase in the rotational relaxation time (ρ) of the cell-bound fluorescent probe N-phenyl-1-naphthylamine (PhNap)Abbreviations: FCCP - carbonyl cyanide p-trifluoromethoxyphenylhydrazone; ANS - 8-anilino-1-naphthalenesulfonate; PhNap, N-phenyl-1-naphthylamine; EDTA - ethylenediaminetetraacetate. and 8-anilino-1-naphthalene-sulfonate (ANS) under these conditions shows the same dependence on FCCP concentration. For cells treated with EDTA to remove part of the outer lipopolysaccharide layer, inhibition of proline transport and the increase in ρ value of ANS show the same dependence on FCCP concentration with saturation at 0.3 μM. EDTA treatment causes a large increase in the binding and rotational relaxation time of PhNap, the latter quantity approaching a value obtained with purified inner membrane. Similar effects are produced in untreated cells by 5 μM FCCP. It is concluded that (a) EDTA treatment removes a permeability barrier t o FCCP and PhNap in the outer membrane; (b) uncoupling by FCCP removes a similar permeability barrier to PhNap; (c) binding of amphiphilic ANS, assumed to be located in the outer membrane, is hardly changed by these treatments; (d) deenergization of the inner membrane by FCCP thus causes a structural change in the outer membrane as measured by the permeability change to hydrophobic PhNap and the increase in ρ values of the amphiphilic ANS; (e) The binding sites reached by PhNap within the permeability barrier at or near the inner membrane are changed by FCCP from their initial state. This is inferred from an increase in PhNap quantum yield extrapolated to infinite cell concentration, and from removal by FCCP of an apparent phase transition sensed by the PhNap rotational relaxation time. Thus, uncoupling and deenergization by FCCP appears to cause structural change both in the outer membrane and inside the permeability barrier of the outer membrane.Transmission of the colicin E1 response in the envelope of intact and EDTA-treated cells can also be monitored by an increase in ANS and PhNap fluorescence intensity, a smaller fractional increase in dye binding, and a large increase in probe rotational relaxation time. The fluorescence changes of ANS again imply structural effects in the outer membrane caused by colicin. The binding and fluorescence changes of PhNap caused by colicin E1 acting on intact cells again imply an effect of deenergization on the permeability barrier of the outer membrane. Fluorescence changes with PhNap in intact and EDTA-treated cells show that the dye binding sites are altered in the presence of colicin E1. It is also shown that the PhNap intensity change can be blocked by low concentrations of vitamin B12, which competes for the colicin E1 receptor.Some properties are presented of the probe chlorotetracycline, which has been proposed by others to be an indicator of magnesium. The probe appears to reside in an environment somewhat similar to that of ANS, but the colicin-induced changes in its fluorescence parameters appear to be small under our conditions.
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  • 185
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    Journal of Supramolecular Structure 5 (1976), S. 371-380 
    ISSN: 0091-7419
    Keywords: cell shape ; pattern ; neural plate shaping ; simulation ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Spatial patterns of the future elongation of cells exist in the early embroyo. In the newt, such a pattern of changers of cell shape contributes to the formation of the neural plate. Regardless of where neural plate. Regardless of where neural plte cells are transplanted, they change shape as prescribed by tge pattern. Embryonic induction has a role in establishing this pattern.
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  • 186
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    Journal of Supramolecular Structure 5 (1976), S. 381-389 
    ISSN: 0091-7419
    Keywords: fusion rosette ; membrane fusion ; ciliated-protozoa ; secretory mutants ; particle partition coefficient ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The mosaic and dynamic character of cellular membranes is illustrated by the specific intramembrane particle array, the fusion rosette, found to be essential for memberane fusion and secretion in the ciliated protozoa, Tetrahymena and Paramecium. The rosette is not a permanent site within the membrane. When secretion of mucocysts is synchronized by treating cells with the local anesthetic dibucaine, all rosettes disappear, only to reassemble as new mucocysts mature. Assembly of the functional rosette is under genetic control. A series of secretory mutants of Paramecium, blocked in various stages of the secretory cycle, has been studied (11). Mutants that do not secrete lack the fusion rosette, although other intramembrane particle components of the fusion site are present. Certain properties of the rosett, in particular its particle partition coefficient, are temperature-dependent, which may affect the ability of the rosette particles to assemble. A temperature-sensitive mutant, nd9, secretes normally, and has rosettes at 18°C, but fails to secrete attached trichocysts at 27°C.
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  • 187
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    Journal of Supramolecular Structure 5 (1976), S. 397-407 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Four neurotoxins that activate the action potential Na+ ionophore of electrically excitable neuroblastoma cells interact with two distinct classes of sites, one specific for the alkaloids veratridine, batrachotoxin, and aconitine, and the second specific for scorpion toxin. Positive heterotropic cooperativity is observed between toxins bound at these two classes of sites. Tetrodotoxin, a specific inhibitor of the action potential Na+ current, inhibits activation by each of these toxins in a noncompetitive manner (KI = 4-8 nM). These results suggest the existence of three functionally separable components of the action potential Na+ ionophore: two regulatory components, which bind activating neurotoxins and interact allosterically in controlling the activity of a third ion-transport component, which binds tetrodotoxin. The dissociation constant for scorpion toxin binding is increased 10-fold by depolarization of the cells with K+, suggesting that the scorpion toxin binding site is located on a voltage-sensitive regulatory component of the ionophore.
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  • 188
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    Journal of Supramolecular Structure 5 (1976), S. 409-416 
    ISSN: 0091-7419
    Keywords: antibiotics ; bilayer lipid membranes ; surface charfe ; phospholipid vesicles ; fusion ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A technique has been developed for monitoring the interaction of charged phospholipid vesicles with planar bilayer lipid membranes (BLM) by use of the antibiotics Valinomycin, Nonactin, and Monazomycin as surface-charge probes. Anionic phosphatidylserine vesicles, when added to one aqueous compartment of a BLM, are shown to impart negative surface charge to zwitterionic phosphatidylocholine and phosphatidylethanolamine bilayers. The surface charge is distributed asymmertically, mainly on the vesicular side of the BLM, and is not removed by exchange of the vesicular aqueous solution. Possible mechanisms for the vesicle-BLM interactions are discussed.
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  • 189
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    Journal of Supramolecular Structure 5 (1976), S. 431-451 
    ISSN: 0091-7419
    Keywords: gramicidin A ; channel ; fluorescence energy transfer ; membrane fluorimeter ; antibiotic ; hybrid channels ; grarnicidin C derivatives ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Gramicidin A is a linear polypeptide antibiotic that facilitates the diffusion of monovalent cations across lipid bilayer membranes by forming channels. It has been proposed that the conducting channel is a dimer which is in equilibrium with nonconducting monomers in the membrane. To directly test this model in several independent ways, we have prepared and purified a series of gramicidin C derivatives. All of these derivatives are fully active analogs of gramicidin A, and each derivative has a useful chromophore esterified to the phenolic hydroxyl of tyrosine #11.Simultaneous conductance and fluorescence measurements on planar lipid bi-layer membranes containing dansyl gramicidin C yielded four conclusions: (1) A plot of the logarithm of the membrane conductance versus the logarithm of the membrane fluorescence had a slope of 2.0 ± 0.3, over a concentration range for which nearly all the gramicidin was monomeric. Hence, the active channel is a dimer of the nonconducting species. (2) In a membrane in which nearly all of the gramicidin was dimeric, the number of channels was approximately equal to the number of dimers. Thus, most dimers are active channels and so it should be feasible to carry out spectroscopic studies of the conformation of the transmembrane channel. (3) The association constant for dimerization is more than 1,000-fold larger in a glycerolester membrane with 26 Å-hydrocarbon thickness than in a 47 Å-glycerolester membrane. The dimerization constant in a 48 Å-phosphatidyl choline membrane was 200 times larger than in a 47 Å-glycerolester membrane, showing that it depends on the type of lipid as well as on the thickness of the hydrocarbon core. (4) We were readily able to detect 10-14 mole cm-2 of dansyl gramicidin C in a bilayer membrane, which corresponds to 60 fluorescent molecules per square μm. The fluorescent techniques described here should be sufficiently sensitive for fluorescence studies of reconstituted gates and receptors in planar bilayer membranes.An alternative method of determining the number of molecules of gramicidin in the channel is to measure the fraction of hybrid channels present in a mixture of 2 chemically different gramicidins. The single-channel conductance of p-phenylazo-benzene-sulfonyl ester gramicidin C (PABS gramicidin C) was found to be 0.68 that of gramicidin A. In membranes containing a mixture of these 2 gramicidins, a hybrid channel was evident in addition to 2 pure channels. The hybrid channel conductance was 0.82 that of gramicidin A. Fluorescence energy transfer from dansyl gramicidin C to diethylamino-phenylazobenzene-sulfonyl ester gramicidin C (DPBS gramicidin C), provided an independent way to measure the fraction of hybrid channels on liposomes. For both techniques the fraction of hybrid channels was found to be 2ad where a2 and d2 were the fractions of the 2 kinds of pure channels. This result strongly supports a dimer channel and the hybrid data excludes the possibility of a tetramer channel. The study of hybrid species by conductance and fluorescence techniques should be generally useful in elucidating the subunit structure of oligomeric assemblies in membranes.The various models which have been proposed for the conformation of the gramicidin transmembrane channel are briefly discussed.
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  • 190
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    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 165-171 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The preparation of chloroprene-methyl methacrylate copolymers in the presence of Lewis acids (Et1.5AlCl1.5) in hydrocarbon solvent and the effect of Lewis acids concentration on copolymer composition are described. 13C NMR spectra were obtained on these copolymers. In samples of high MMA content, tactic placements of MMA were observed as well as several different kinds of sequences for chloroprene and MMA. In samples of low MMA content, no tactic placements of MMA were found but several different kinds of chloroprene sequences were observed. From the analysis of the 13C NMR spectra of the different copolymers examined, it is apparent that all the various kinds of chloroprene sequences in these copolymers can be determined.
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  • 191
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 187-210 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study has been made of the crosslinking of linear polyethylene in solution. Networks containing a low number of trapped entanglements and elastically ineffective chain ends were prepared by crosslinking high molecular weight linear polyethylene in 1,2,4-trichlorobenzene solutions with dicumyl peroxide at 120°C. No syneresis was observed during crosslinking except at high peroxide concentrations. The networks were characterized by swelling measurements, infrared spectroscopy, and differential scanning calorimetry. The crosslinking efficiency, calculated from swelling, was found to be proportional to the square of the polymer volume fraction. The proportionality constant was 0.8, indicating close to unit efficiency for undiluted polymer.Chemical modification of the polyethylene chains by attachment of peroxide and solvent fragments was of the order of one foreign unit per elastically active network chain, depending on peroxide and polymer concentration. Sol-gel analysis indicated that no chain scission occurred. These results are shown to be consistent with a “cage” mechanism for crosslinking. The possible topological consequence of this mechanism, preferential crosslinking of entanglements, is discussed. The concentration of trapped entanglements was also found to be proportional to the square of the polymer volume fraction. The proportionality constant corresponds to a molecular weight between entanglements of 4000 for the undiluted polymer, which is close to the value of 4200 found for networks prepared from the undiluted polymer. Since the results obtained are based mainly on the use of the swelling equation, different aspects of the applicability of this equation for the evaluation of the crosslinking process are discussed. As regards the reference dimensions, which should be known for a quantitative application of the elastic theory, the results strongly support the use of the dimensions of the network chains after completion of crosslinking.
    Additional Material: 12 Ill.
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  • 192
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    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 251-262 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isolated spherulites of poly(methyl D-glutamate) (PMDG) were nucleated in bromoform. The morphology of these spherulites was investigated by SEM and photographic small-angle light scattering (SALS). From the SALS patterns, the development and growth of the spherulites could be noted. Films of PMDG cast from bromoform solution were found to be partially spherulitic. The mechanical properties of these films, prepared by different procedures, were compared with the general behavior of PMDG films cast from chloroform, the latter of which does not contain spherulitic texture.
    Additional Material: 13 Ill.
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  • 193
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 299-308 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Data are presented to show that two correlations of viscosity-concentration data are useful representations for data over wide ranges of molecular weight and up to at least moderately high concentrations for both good and fair solvents. Low molecular weight polymer solutions (below the critical entanglement molecular weight Mc) generally have higher viscosities than predicted by the correlations.One correlation is ηsp/c[η] versus k′[η], where ηsp is specific viscosity, c is polymer concentration, [η] is intrinsic viscosity, and k′ is the Huggins constant. A standard curve for good solvent systems has been defined up to k′[η]c ≍ 3. It can also be used for fair solvents up to k′[η]c ≍ 1.25· low estimates are obtained at higher values.A simpler and more useful correlation is ηR versus c[η], where ηR is relative viscosity. Fair solvent viscosities can be predicted from the good solvent curve up to c[η] ≍ 3, above which estimates are low. Poor solvent data can also be correlated as ηR versus c[η] for molecular weights below 1 to 2 × 105.
    Additional Material: 4 Ill.
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  • 194
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    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 317-322 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: X-ray line broadening measurements were used to determine the apparent “mosaic block” sizes of randomly oriented polyethylene and polyoxymethylene single crystals. Both dried-down and uncollapsed crystals were examined. PE lamellae were grown at 80, 85, and 90°C by isothermal crystallization from a 0.1% solution in xylene. POM crystals were grown at 125°C by self seeding from an 0.05% solution of the polymer in o-dichlorobenzene. A given preparation was split into two parts. One part was dried down in the usual manner, the other was exchanged to paraffin oil and the crystals never permitted to dry down. Previously reported studies used dried-down crystals and gave crystallite sizes of approximately 300 Å. More recently, using electron microscopy, it has been postulated that PE single crystals are free of “mosaic block” over regions of several thousand angstroms. It is evident from this present study that crystallite sizes in uncollapsed lamellae are significantly larger than those observed for the same crystals dried down. In the case of uncollapsed lamellae, one can explain the observed crystallite sizes solely on the basis of chain obliquity rather than by invoking the “mosaic block” model. It has also been determined that there is an upper limit to the crystallite sizes that can be observed in PE and POM crystals using wide-angle x-ray techniques. This limit may account for discrepancies between x-ray and electron diffraction.
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  • 195
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    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 323-342 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The morphology and thermal behavior of trans-1,4-polybutadiene single crystals prepared from dilute solutions in n-heptane have been investigated by electron microscopy, wide-angle and low-angle x-ray diffraction, and differential scanning calorimetry. The thickness of the single crystals of trans-1,4-PBD is much greater, for the same undercooling, than that of other linear polymers. From the calorimetric study, convincing evidence of the presence, in the single crystals, of crystalline blocks of form 1 with two different thermodynamic stabilities is obtained and the relative amounts are calculated. From thermodynamic considerations we find a value of 75°C for the equilibrium transition temperature between forms 1 and 2, 139°C for the equilibrium melting temperature of form 2, and 31.2 erg/cm2 for the fold-surface free energy of modification 2.
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  • 196
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 343-352 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Complete and partial alcoholyses of ethylene-vinyl acetate (E-VA) copolymers yield ethylene-vinyl alcohol (E-VOH) copolymers and ethylene-vinyl acetate-vinyl alcohol (E-VA-VOH) terpolymers, respectively. From the 220-MHz proton NMR spectra of E-VOH copolymers the stereoregular and chemical sequence distributions of the comonomers can be readily determined. Partially hydrolyzed E-VA polymers were acetylated with perdeuterated acetic anhydride. The monomer distributions in the terpolymers were then quantitatively determined by examining the proton spectra of the derived products. It was found that alcoholysis of E-VA polymers occurs preferentially at VA units which have neighboring VA groups.
    Additional Material: 5 Ill.
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  • 197
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 353-365 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The small-angle x-ray scattering (SAXS) from quenched and annealed rigid polyvinyl chloride (PVC) has been measured using a Bonse-Hart system. After correcting for absorption, background, and beam divergence, the scattering has been placed on an absolute basis using a standard silica suspension as a reference. The scattering from annealed (6 days at 75°C) and unannealed PVC was identical within experimental error, varying with scattering angle in a manner similar to the SAXS from other amorphous polymers. The intensity decreases rapidly with increasing scattering angle over the ranges from 20 sec to 20 min. Beyond 20 min the intensity is fairly constant, decreasing only slightly with increasing angle. At the largest angles of measurement (in the range of 120 min), the measured intensity is close to the value calculated for thermal density fluctuations frozen-in at the glass transition.The angular variation of intensity is well described by the scattering from heterogeneities of various sizes and concentrations superimposed on the scattering from thermal density fluctuations. These heterogeneities range in radius from 50 to 4500 Å and, assuming the crystalline excess density, the total concentration of heterogeneities is less than 0.5%. The mean-square fluctuation in density, determined from the measured intensity invariant, is also consistent with such a distribution of heterogeneities.The present SAXS results on rigid PVC are inconsistent with the presence of nodular features as representative of the bulk polymer. Rather, it is suggested that they are associated with surface effects. It is further suggested that previously indicated volume fractions of crystallinity in rigid PVC (generally in the range of 5-12%) are incorrect, and that the model of a three-dimensional network of crystallites used to explain the rheological behavior of this material should be re-examined.
    Additional Material: 4 Ill.
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  • 198
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 427-435 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal structure of poly(m-phenyulene isophthalamide) was determined by x-ray analysis. The triclinic cell, with a = 5.27 Å, b = 5.25 Å, c (fiber axis) = 11.3 Å, α = 111.5°, β = 111.4° and γ = 88.0° and space group P1, contains one monomeric unit. The crystal density is 1.47 g/cc. The molecules in the crystal are contracted by 1 Å per monomeric unit from the fully extended conformation, and the planes of the benzene rings and adjacent amide groups make angles of about 30°. The crystal is composed of molecular chains connected by N—H···O hydrogen bonds along the a and b axes forming a “jungle gym” network structure. The low tensile modulus of this polymer as compared with that of poly(p-phenylene terephthalamide) is attributed to the contracted molecular conformation.
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  • 199
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    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 521-529 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectroscopy has been used to analyze the characteristics of the crystal-crystal phase transition of trans-1,4-polybutadiene. The low- and high-temperature structures were found to coexist at the transition. The Raman spectra obtained at high temperature can be understood on the basis of the change in chain conformation associated with the phase transition.
    Additional Material: 6 Ill.
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  • 200
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Relaxation of stress and birefringence in simple extension has been studied for two samples of 1,2-polybutadiene with 95% and 88% vinyl content and weight-average molecular weight 1.9 and 2.9 × 105, respectively. The extension ratio, λ, ranged from 1.14 to 2.08, temperatures from 0 to 15°C, and times, reduced to 0°C, up to 3 × 105 sec. The stress-optical coefficient C was negative and positive, respectively, for the two samples, the difference being attributable to opposite signs and very different magnitudes of the contributions of the 1,2 and 1,4 moieties to the birefringence. For each polymer, C was independent of time but increased (algebraically) with temperature. For one polymer a very minor dependence of C on λ was observed. At any instant of time, the dependence of both stress and birefringence on λ could be described by equations of the Mooney-Rivlin form with coefficients C1,C2 and B1,B2, respectively. At short times the contributions of the C1 and C2 terms to the stress and of the B1 and B2 terms to the birefringence are roughly equal. With increasing time, C1 and B1 decrease gradually while C2 and B2 remain constant over several decades in time. Finally, C2 and B2 decrease rather rapidly. A tentative interpretation of these phenomena in terms of motions of entanglements is given.
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