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  • Organic Chemistry  (10)
  • Calcium sparks Calcium transients Cardiac pacemaker cells Intracellular calcium Nuclear calcium Spontaneous action potentials
  • Carbon
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  • 1
    Digitale Medien
    Digitale Medien
    Morphologic and morphometric study of patellar resurfacing with woven carbon filamentous pads (2000)
    Springer
    Archives of orthopaedic and trauma surgery 120 (2000), S. 502-507 
    Details
    ISSN: 1434-3916
    Schlagwort(e): Key words Articular resurfacing ; Patella ; Carbon ; filaments ; Foreign body granulomatous reaction ; Interfacial membrane ; Histomorphometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Analysis of retrieved woven carbon filamentous pads, used for resurfacing of the patellar joint surface, disclosed a 4-zonal organizational pattern. Zone 1, facing the articular cavity, was devoid of carbon filaments and consisted of fibrous tissue. Foreign body granulation tissue and fibrous tissue occupied about one-third and ∼50%–60% of the interfilamentous space in zones 2 and 3, respectively. Carbon filaments formed 2%–9% of zone 2 and 14%–16% of zone 3. An interfacial membrane-like zone 4 separated the carbon filamentous pads from a trabecular bony shell. The bone volume within the latter was ∼25%. Given that the purpose of articular resurfacing with implants is repopulation of the defect by chondrocytes producing a cartilaginous matrix, the woven carbon filamentous pads did not fulfill this expectation. In an environment of an ongoing foreign body-induced granulomatous reaction, the stem cells permeating the interstices of the woven carbon filamentous pad are apparently incapable of maturing into highly differentiated cells (chondrocytes) synthesizing a highly complex (cartilaginous) matrix.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004029900123
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  • 2
    Digitale Medien
    Digitale Medien
    The distribution of calcium in toad cardiac pacemaker cells during spontaneous firing (2000)
    Springer
    Pflügers Archiv 441 (2000), S. 219-227 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Calcium sparks Calcium transients Cardiac pacemaker cells Intracellular calcium Nuclear calcium Spontaneous action potentials
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract. Isolated, spontaneously active pacemaker cells from the sinus venosus region of the toad heart were loaded with the calcium indicator fluo-3. The cells were examined with a confocal microscope to investigate the distribution of calcium during spontaneous activity. Three classes of calcium-related signals were present. First, intense, localised, time-invariant signals were detected from structures distributed across the cell interior. Based on the insensitivity to saponin and the distribution in the cell, these signals appear to arise from fluo-3 located in the sarcoplasmic reticulum and the nuclear envelope. Second, spatially uniform signals from the cytoplasm were present at rest and showed spontaneous increases in [Ca2+]i which propagated along the cell. These Ca2+ transients were uniform in intensity across the diameter of the cell and we could detect no significant delay in the middle of the cell compared to the edges. However, within the nucleus the Ca2+ transient showed a clear delay compared to the cytoplasm. Third, localised, transient increases in [Ca2+]i (Ca2+ sparks) which did not propagate were also detectable. These could be detected both near the surface membrane and in the interior of the cell and reduced in magnitude and increased in duration in the presence of ryanodine. The frequency of firing of Ca2+ sparks significantly increased in the 200-ms period preceding a spontaneous Ca2+ transient. These results suggest that pacemaker cells contain sarcoplasmic reticulum which is distributed across the cell. The Ca2+ transient is uniform across the cell indicating that near-synchronous release of Ca2+ from the sarcoplasmic reticulum is achieved. Ca2+ sparks occur in pacemaker cells though their role in pacemaker function remains to be elucidated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004240000418
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  • 3
    Digitale Medien
    Digitale Medien
    Molecular modelling of the inclusion complexes between β-cyclodextrin and (R)/(S)-methylphenobarbitone and its application to HPLC (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 239-244 
    Details
    ISSN: 0899-0042
    Schlagwort(e): HPLC ; reverse-phase additive ; β-cyclodextrin ; methylphenobarbitone ; molecular mechanics ; complex stability ; chiral separation ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Molecular modelling of β-cyclodextrin and optimisation of its potential energy suggests that a favoured conformation is that distorted from a symmetrical torus. The inclusion of water molecules into the torus cavity simulates the increased stability in an aqueous solvent. Complexes of β-cyclodextrin with (R)- and (S)-enantiomers of methylphenobarbitone have been modelled and energetically optimised by the application of molecular mechanics. The simulations suggests that the guest molecules adopt an orientation in which the phenyl ring is projected into the torus cavity, with in each case the plane of the ring parallel to a longer axis of the distorted torus and slightly displaced from the axis through the torus cavity. It is suggested that the asymmetry in the macrocyclic ring contributes to chiral recognition as a result of additional discriminatory binding to the barbiturate ring residue of each enantiomer, which occupy different 3D geometries. The enantiomers form complexes of different minimum potential energies. The resulting difference in complex stability can be related to the behaviour of β-cyclodextrin, as a mobile phase additive in reverse-phase HPLC to effect chiral separation of rac-medthylphenobarbitone during chromatography. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060405
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  • 4
    Digitale Medien
    Digitale Medien
    Calmodulin discriminates between the two enantiomers of the receptor-operated calcium channel blocker sk&f 96365: A study using 1H-NMR and chiral HPLC (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 2 (1990), S. 229-232 
    Details
    ISSN: 0899-0042
    Schlagwort(e): receptor-operated calcium channel antagonist ; 1H NMR ; chiral HPLC ; calmodulin ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1H nuclear magnetic resonance at 360 MHz shows that SK&F 96365 (1-{β-[3-(p-methoxyphenyl)-propyloxy]-p-methoxyphenethyl}-1H- imidazole hydrochloride), an antagonist of mammalian receptor-operated calcium channels, interacts with the calcium-binding regulatory protein calmodulin (CaM). This may be inferred by a number of chemical shift changes in the spectrum of the calcium-saturated protein induced by addition of the compound. Moreover, two well-resolved singlets corresponding to the 2-proton of the SK&F 96365 imidazolium moiety are observed in the spectrum over a wide range of protein:compound ratios. Separation of rac SK&F 96365 into its two enantiomers by high-performance liquid chromatography on a cellulose tris (4-methylbenzoate) column enabled us to show that the doubling of this NMR signal in the presence of CaM is due to a propensity of the protein to distinguish between the two optical isomers of the compound.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530020407
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  • 5
    Digitale Medien
    Digitale Medien
    Application of force field calculations to the prediction of chirally discriminating chromatographic behaviour for β-CDs (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 58-66 
    Details
    ISSN: 0899-0042
    Schlagwort(e): molecular mechanics ; HPLC ; chiral separation ; methylphenobarbitone ; hexobarbitone ; ibuprofen ; mandelic acid ; ephedrine ; pseudoephedrine ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: β-Cyclodextrin and its derivatives have been utilised to effect chiral separation in HPLC and CZE, both as stationary phases and mobile phase additives. The basis of the method is assumed to depend upon the formation of inclusion complexes of differing stabilities between enantiomeric analytes and the cyclodextrin, resulting in a differential dynamic distribution between chromatographic phases. In this study, force field calculations have been employed to model the inclusion complexes of enantiomeric brompheniramine, ephedrine, pseudoephedrine, ibuprofen, mandelic acid, methylphenobarbitone, and hexobarbitone with β-cyclodextrin. The resulting values for Δ(ΔH), the difference in enthalpy of complex formation between enantiomeric pairs has been compared with literature chromatographic data to explain the ability of the systems to achieve enantiomeric separations. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Planar chiral systems, IV. An efficient route for the preparation of 5-formyl-4-hydroxy[2.2]paracyclophane (FHPC) (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 449-451 
    Details
    ISSN: 0947-3440
    Schlagwort(e): Cyclophanes, multifunctionalized ; Auxiliaries, chiral ; Metalation, ortho-directed ; Fries rearrangement ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: For the preparation of the title compound, 4-hydroxy[2.2]paracyclophane (1) is first converted to the carbamate 2. Metalation of 2 with sec-butyllithium yields an ortho-anion which after trapping with dimethylformamide and acidic work-up provides 6 in 64% yield. Further application of the cyclophane anion include its capture by trimethylsilyl chloride to the trimethylsilyl derivative 3 (76%) and its Fries rearrangement to the phenol 4 (78%). The spectroscopic and analytical data of the new compounds are described in full detail.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199519950259
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  • 7
    Digitale Medien
    Digitale Medien
    Carbonyl oxygen as a hydrogen-bond super-base: The amidates (1994)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 705-711 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An infrared spectroscopic study of the 1 : 1 hydrogen-bond association of amidates with both methanol and 4-fluorophenol showed that the site of complexation is the oxygen of the amidate function. However the formamidate HCON2Me3 forms a second 1 : 1 complex on the nitrogen of the amidate. The formation constants of the hydrogen-bond complexes of the amidates with the reference hydrogen-bond donor 4-FC6H4OH indicate that the amidates are stronger hydrogen-bond bases than are amides and amide vinylogues. As such, the amidates constitute the strongest carbonyl bases hitherto investigated on the hydrogen-bond basicity scale.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610071208
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  • 8
    Digitale Medien
    Digitale Medien
    Tributylammonium cyanamidate BU3N+-N--C≡N: A ‘super-basic’ nitrile group more basic, on the hydrogen-bond basicity scale, than any amine or pyridine (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 626-628 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An IR spectroscopic study of the hydrogen bonding of Bu3N+N-C≡N with 4-fluorophenol showed that the site of complexation is the nitrogen of the nitrile function. THe formation constant of the 1:1 complex in CCl4 indicates that this cyanamidate is a stronger hydrogen-bond base than is any nitrile, amine or pyridine. The Bu3N+-N- group increases the basicity of the nitrile group very efficiently because of the conjugation of two lone pairs on the anionic nitrogen with the π systems of the cyano group. This conjugation is also exemplified by the very low ν(C≡N) wavenumber (2104 cm-1).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610080909
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  • 9
    Digitale Medien
    Digitale Medien
    Preparation of 4-(4′-Methyl-2′-oxo-cyclohex-3′-en-1′ -yl) - pentan-1-ol and Derivatives of 3-(4′-Methyl-2′-oxo-cyclohex-3′ -en-1′ -yl)- butan-1-olThe IUPAC-Nomenclature of these compounds is: 6-(4′-hydroxy-1′-methyl-butyl)-3-methyl-cyclohex-2-en-1-one and 6-(3′-hydroxy-1′-methyl-propyl)-3-methyl-cyclohex-2-en-1-one. (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 695-711 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Es wird über eine, bzw. zwei Methoden zur Herstellung von 4-(4′ Methyl-2′-oxo-cyclohex-3′-en-1′-yl)-pentan-1-ol (Schema 1) bzw. 3-(4′-Methyl-2′-oxo-cyclohex-3′-en-1′-yl)-butan-1-olThe IUPAC-Nomenclature of these compounds is: 6-(4′-hydroxy-1′-methyl-butyl)-3-methyl-cyclohex-2-en-1-one and 6-(3′-hydroxy-1′-methyl-propyl)-3-methyl-cyclohex-2-en-1-one.-Derivaten ( Schemata 2 und 3) berichtet. Die Synthesen sind nicht spezifisch bezüglich Diastereoisomerie an den Zentren C(1′) und C(4), bzw. C(1′) und C(3). Als potentielles Terpenoid-Synthon kommt das Produkt der Synthese nach Schema 1 , Schritte (1) bis (3), in Frage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19760590236
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  • 10
    Digitale Medien
    Digitale Medien
    Preparation of Mikanecic EsterThe systematic name of mikanecic acid is 4-vinyl-cyclohex-1-ene-1,4-dicarboxylic acid; it is used in the experimental Part. and its precursor, 1,3-butadiene-2-carboxylic ester (1975)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 2061-2073 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Eine thermische (a) und eine reduktive (b) Methode zur Herstellung von Mikanez-Estern wird beschrieben. Bei der ersten gelang der Nachweis des monomeren Vorläufers, 1,3-Butadien-2-carboxylester. (a)trans/cis-Gemische von Methyl resp. Äthyl 2-Brom-1-methylcyclopropancarboxylat (14/15 resp. 16/17), mit Tri-n-butylzinnhydrid aus den entsprechenden 2,2-Dibrom-1-methylcyclopropancarboxylaten 12 resp. 13 hergestellt, wurden bei 480°/1,7 Torr pyrolysiert. Die bei -78° daraus abgefangenen Kondensate bestanden aus den 1,3-Butadien-2-carboxylaten 5 und 6, im Falle des Äthylesters 6 durch seine 1H-NMR.-Signale charakterisiert und als Addukt (19) mit 4-Phenyl-1,2,4-triazolin-3,5-dion (18) abgefangen (55%). Beim Erwärmen der Kondensate dimerisierten die Dienester 5 resp. 6, so dass sich Dimethyl resp. Diäthyl Mikanezat (9 resp. 10) isolieren liess (67 resp. 100%).(b)Behandlung von Methyl 2(E)-2-Methyl-2-butenoat (20) mit 2 Äquivalenten N-Bromsuccinimid gab (25%) Methyl 2(Z)-4-Brom-2-brommethyl-2-butenoat (21). (Mit 3 Äquivalenten entstand ein Stereomerengemisch 2(Z)- und 2(E)-4,4-Dibrom-2-brommethyl-2-butenoat (22 und 23)). Reduktion des Dibromesters 21 mit Zink in Tetrahydrofuran, Methanol oder Eisessig ergab (50%) Dimethyl Mikanezat (9). Von einer Iodolaktonisierung der aus 9 durch Verseifung hergestellten Mikanezsäure (8) erhielt man 4-Iodo-7-oxo-1-vinyl-6-oxabicyclo[3.2.1]octan-4endo-carbonsäure (24), dessen Bildungsleichtigkeit und IR.-Bande bei 1780 cm eine unabhängige Bestätigung dafür liefert, dass Mikanezsäure (8) durch Kopf-zu-Kopf-Diels-Alder-Dimerisierung von 1,3-Butadien-2-carbonsäure (4) entsteht.Aus Methyl (E)-2-Methyl-2-pentenoat (25) wurde auf gleiche Weise, d.h. über Dibromierung zu 27 und Reduktion mit Zink in Äther, Dimethyl 3,2′-Dimethylmikanezat (29) gewonnen. Die Multiplizität des 1H-NMR.-Signals von H—C(3) in 29 bestätigt, wiederum unabhängig, dass die Dimerisierung des Dienesters (in diesem Fall 28) in Kopf-zu-Kopf-Diels-Alder-Weise stattfindet.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19750580721
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