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  • Polymer and Materials Science  (273)
  • 1995-1999  (187)
  • 1970-1974  (86)
  • 1
    Electronic Resource
    Electronic Resource
    Proton magnetic resonance studies of the conformational changes of dideoxynucleoside ethyl phosphotriestersPart II of a series entitled Alkyl Phosphotriesters of Dinucleotides and Oligonucleotides. (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2225-2240 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: PMR investigations on the diastereomeric phosphate methyl protons of the dinucleoside ethyl phosphotriesters Tp(C2H5)T, dA, and dIp(C2H5)dI have been used to study the conformational changes of these dimersin solution. In D2O (273°K), the diastereomeric phosphate-methly groups of Tp(C2H5)T appear as a triplet. The methyl resonances of dIp(C2H5)dI and dAp(C2H5)dA appear as two sets of triplets and their chemical shift differences (δ1 - δ2), decrease with increasing temperature, finally becoming zero at 292°K and 333°K, respectively. The same phenomenon is observed for dAp(C2H5)dA in CD3OD; in this detacking solvent, the difference (δ1 - δ2) diminishes to zero at a lower temperature (261°K). At room temperature in D2O, the chemical shift of the phosphate methyl of Tp(C2H5)T appears at lower field than those of dIp(C2H5)dI or dAp(C2H5)dA. The differences between the chemical shifts of these groups (δI - δT or δA - δT) increase with increasing temperature, and reach maximal values at 301°K and 333°K, respectively. The results suggest that at low temperature the largest fraction of the dimer population exists in a stacked state, with the phosphate-ethyl groups outside the stack. Increasing temperature causes an oscillation of the bases and a shift in the dimer population away from the stacked state. Finally at high temperature, the planar bases rorate with respect to one another and in the case of dIp(C2H5)dI and dAp(C2H5)dA, the ethyl groups experience shielding by the anisotropic ring current of the five-membered ring of the bases. Thus, the current pmr studies and those reported earlier from our laboratory support an “oscillation-rotation model” for the unstacking process of the dimers. The relationship of this model and the “two-state model” is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360121004
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  • 2
    Electronic Resource
    Electronic Resource
    Mediated amperometric detection of glucose-6-phosphate dehydrogenase at a poly(vinyl chloride) covered electrode using 1,4-benzoquinone and diaphorase (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 216-220 
    Details
    ISSN: 1040-0397
    Keywords: Glucose-6-phosphate dehydrogenase ; Benzoquinone ; Diaphorase ; NADH ; Redox mediator ; Amperometric detection ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduced nicotinamide adenine dinucleotide (NADH), produced from glucose-6-phosphate dehydrogenase (G6PDH) was catalytically oxidized using diaphorase and 1, 4-benzoquinone to yield 1, 4-hydroquinone. This benzoquinone redox mediator was readily detected at an electrode polarized at +0.5 V (vs. Ag/AgCl) so avoiding the high overpotentials required for a direct electrochemical measurement of NADH. Also, the lipophilic nature of the hydroquinone enabled a novel high selectivity plasticized PVC membrane mounted over the electrode to be exploited. The mediator/PVC combination achieved NADH calibration linear up to at least 100 μM. When used to assay G6PDH activity, a linear calibration from 0.1-1.0 U/mL was produced. The detection system offers the possibility of highly selective measurement of dehydrogenase enzyme activity in biological samples without sample preparation and could provide the basis for simplified homogeneous immunoassays as well as dehydrogenase amperometric enzyme electrodes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140070303
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  • 3
    Electronic Resource
    Electronic Resource
    Lamellar semiconductor-organic nanostructures from self-assembled templatesThis work was supported in part by a grant from the Department of Energy Center of Excellence for the Synthesis and Processing of Advanced Materials. Partial support was also received from the Beckman Institute for Advanced Science and Technology, in particular through the use of its Visualization Facility and a research assistantship for P. V. Braun. Molecular graphics assistance from Milan Keser, of our laboratory, is greatly appreciated. (1996)
    Weinheim : Wiley-Blackwell
    Advanced Materials 8 (1996), S. 1022-1025 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19960081220
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  • 4
    Electronic Resource
    Electronic Resource
    Séparation chromatographique par des gels de polystyrène preparés par réticulation anioniqueHerrn Professor Dr. W. KERN zu seinem 65. Geburtstag mit unseren allerbesten Wünschen gewidmet (1971)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 145 (1971), S. 105-121 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Chromatographische Kolonnen wurden mit anionisch hergestellten Polystyrolgelen verschiedener Porengrößen gefüllt. Lineare Polystyrolproben wurden in diese Kolonnen eingespritzt, und die entsprechenden Elutionsvolumina wurden gemessen. Durch die normalisierten Elutionskurven - die die dynamischen Verteilungskoeffizienten in Abhängigkeit des Logarithmus des Molekulargewichtes des eingespritzten Polystyrols darstellen - wurde veranschaulicht, daß der Molekulargewichtsbereich, in dem chromatographische Trennung stattfinden kann, von den strukturellen Parametern des Gels abhängig ist, und zwar von dem Molekulargewicht des linearen Präpolymeren, von der Konzentration des Polymeren beim Vernetzungsvorgang und vom Anteil des Vernetzungsagens.Es wurde auch festgestellt, daß die chromatographischen Elutionsvolumina von Faktoren abhängig sind, wie der Größe der Gelpartikel und der Fließgeschwindigkeit des Eluenten. Dies zeigt, daß die Bedingungen zur Einstellung des Austauschgleichgewichtes zwischen den Gelporen und der fließenden Zwischenraumflüssigkeit nicht erfüllt sein können. Aber unter Verwendung von Standardbedingungen kann man reproduzierbare Ergebnisse erzielen, die zu gültigen Vergleichen dienen können.Es ist noch hervorzuheben, daß die Makroporosität eines Gels keineswegs als eine notwendige Bedingung für die chromatographische Trennung aufzufassen ist.
    Notes: Chromatographic columns were filled with anionically prepared polystyrene gels of various porosities. Linear polystyrene samples were injected in these columns and the retention volumes were measured. Normalized curves have been compared, the dynamic partition coefficient being plotted versus the logarithm of the molecular weight of the injected polymer. It has been established that the domain of molecular weights in which chromatographic separation may take place depends upon the parameters characterizing the gel: molecular weight of the linear “precursor”, overall concentration at the gel point, proportion of crosslinking agent.It has been found that the chromatographic retention times depend on such factors as size of gel particles, flow-rate of the elution solvent. This shows that the exchange equilibrium between the pores of the gels and the flowing intersticial liquid are far from being fulfilled. However by choosing standard conditions one gets reproducible results which may be adequately compared.It should be emphasized that macroporosity of a gel is not a prerequisit for chromatographic separation.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1971.021450109
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  • 5
    Electronic Resource
    Electronic Resource
    Préparation de gels réticulés par copolymérisation séquencée anionique du styrène avec le divinylbenzène (1970)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 135 (1970), S. 249-261 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch anionische Blockcopolymerisation von Styrol und Divinylbenzol unter Einwirkung eines bifunktionellen Initiators wurden vernetzte Gele hergestellt. Die Reaktion wurde in aprotischen Lösungsmitteln und unter Argon-Atmosphäre durchgeführt. Die Gele wurden durch ihren maximalen Quellungsgrad charakterisiert. Es wurde festgestellt, daß die folgenden drei Parameter die Eigenschaften der Gele beeinflussen: das Molekulargewicht des linearen Polystyrols, aus dem das Gel hergestellt wird, die Konzentration desselben Polystyrols bei der Zugabe von DVB und die Menge des eingesetzten Divinylbenzols pro lebendes Kettenende. Man kann also auf diese Weise homogene Gele verschiedener Porosität synthetisieren. Im Unterschied zu radikalisch hergestellten Gelen ist bei den auf anionischem Wege erhaltenen Proben die Verteilung der Maschengrößen sehr eng, und der Gelpunkt hat hier eine physikalische Bedeutung. Außerdem ist es leicht, hier die Synärese auszuschalten.
    Notes: La préparation de gels réticulés peut être effectuée par copolymérisation séquencée anionique de styrène et de divinylbenzène, sous l'action d'un promoteur bifonctionnel, en milieu aprotique et en atmosphère inerte. Les gels sont caractérisés par leur taux de gonflement maximum. La masse moléculaire moyenne du polystyrène «parent», la concentration globale de la solution, au moment de la réticulation, et la proportion de DVB mise en jeu constituent les trois paramètres qui déterminent la porosité et la structure même du gel. On peut donc préparer à volonté des réticulats homogènes de porosités très différentes.Dans un tel gel la distribution des tailles des mailles est fort étroite; la synérèse peut être aisément évitée; la signification physique du «point de gel» est bien établie. Ces trois propriétés de la réticulation anionique ne se retrouvent pas dans les gels préparés par voie radicalaire et justifient l'étude de ces gels.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1970.021350123
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  • 6
    Electronic Resource
    Electronic Resource
    Etude du gonflement de gels réticulés préparés par copolymérisation séquencée anionique (1971)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 141 (1971), S. 145-159 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The swelling behavior of a series of crosslinked polystyrene gels prepared anionically has been investigated. The degree of swelling of these gels at equilibrium, in a solvent, was found to depend on their structural characteristics which are determined by the conditions of preparation of the gels.The variation of the degree of swelling versus the structural parameters were found in good agreement with the theoretical expectations, for “ideal” networks. Some gels, however, exhibit a non-ideal behavior which can be explained by a decrease of the number ve of elastic chains, owing to free chain ends and to coupling.
    Notes: Das Quellungsverhalten von vernetzten Gelen, die auf anionischem Wege hergestellt wurden, wurde untersucht. Der Quellungsgrad der Gele im Gleichgewicht ist stark strukturabhängig und durch die Bedingungen ihrer Herstellung beeinflußt. Die experimentell erhaltenen Werte des Quellungsgrades stehen in guter Übereinstimmung mit den für ideale Gele aus den strukturellen Parametern berechneten Werten. In einigen Fällen allerdings wurden Abweichungen beobachtet, die durch die Gegenwart von freien Kettenenden oder von Kupplungen (Knoten mit Funktionalitätswert 2) oder von beiden zugleich verursacht werden. In diesen Fällen kann kein Idealmodell die Eigenschaften der Gele erklären.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1971.021410111
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  • 7
    Electronic Resource
    Electronic Resource
    Acid-catalyzed polymerization of 1,6-anhydro-β-D-glucopyranosePresented in part at the 157th National Meeting of the American Chemical Society, Minneapolis, Minnesota, April 1969. (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 9 (1971), S. 2877-2892 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of 1,6-anhydrides were polymerized in the melt at 115°C by use of monochloroacetic acid as catalyst. In the early stages of polymerization (up to 40-50% monomer consumed), each monomer was found to disappear by a first-order rate process. The 1,6-anhydrides investigated and their relative rates of polymerization were: 1,6-anhydro-2-O-methyl-β-D-glucopyranose, 1.0; 1,6-anhydro-3,4-di-O-methyl-β-D-glucopyranose, 1.4; 1,6-anhydro-2-O-methyl-β-D-galactopyranose, 2.3; 1,6-anhydro-3-O-methyl-β-D-glucopyranose, 2.6; 1,6-anhydro-4-O-methyl-β-D-glucopyranose, 6.3; 1,6-anhydro-4-O-(β-D-glucopyranosyl) β-D-glucopyranose, 9.0; 1,6-anhydro-β-D-galactopyranose, 17; 1,6-anhydro-β-D-glucopyranose, 37; 1,6-anhydro-β-D-mannopyranose, 91; and 1,6-anhydro-2-deoxy-β-D-arabino-hexopyranose, 240. The effect of substitution on the rate of polymerization suggests this reaction is mechanistically related to the acid hydrolysis of pyranosides. The results suggest that polymerization proceeds in two stages: (1) an initial build-up of dimer followed by (2) a slower growth to higher molecular weight material.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.150091010
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  • 8
    Electronic Resource
    Electronic Resource
    Celluloseether als Trennschichten hydrophiler Polymermembranen (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 249 (1997), S. 11-32 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: This paper reports on polymer membranes characterized by a surface layer of hydroxyalkyl derivatives of cellulose. Water compatible polymers like hydroxyalkyl derivatives of cellulose are preferably those exhibiting good chemical stability and desired membrane characteristics. Normally, water-compatible polymers used in the coating solutions must be rendered water-insoluble after coating. By adapting crosslinking conditions on separation problems, the membranes are useful for many processes in the fields of biotechnology, food and chemical industry.The membranes presented here possess the advantage of being highly resistant to chemical and biological degradation and, hence, have long lifetimes under many process conditions.
    Notes: Es wird die Entwicklung hydrophiler Polymermembranen diskutiert, die nach Beschichtung mit Celluloseethern und anschließender Vernetzung auf den asymmetrischen Trägermembranen interessante Permeations- und Trenneigenschaften bei hervorragenden chemischen Stabilitäten, vor allem beim Membrantrennverfahren der Nanofiltration, aufzeigen. Weiterhin werden Aussagen zu den Gastrenneigenschaften der Celluloseetherkompositmembranen getroffen.Erläutert werden die Permeations- und Trenndaten der Kompositmembranen in Korrelation zur Vernetzung der Celluloseether anhand verschiedener Einflußgrößen, was qualitative und gegebenenfalls quantitative Aussagen zum Vernetzungsmechanismus der Celluloseetherderivate erlaubt. Dabei stehen die Vernetzungstemperatur, der Einfluß der katalysierenden Wasserstoffionen und bedingt die Vernetzungszeit im Vordergrund. Abgerundet werden die Arbeiten durch Ermittlungen rheologischer Daten, die in Zusammenhang zu den Vernetzungsreaktionen und damit zu membranspezifischen Größen stehen.Infolge der hervorragenden chemischen Stabilität der Celluloseether werden Einsatzmöglichkeiten der Kompositmembranen zur Nanofiltration niedermolekularer Verbindungen aus organisch hochbelasteten Systemen beschrieben.
    Additional Material: 30 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052490102
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  • 9
    Electronic Resource
    Electronic Resource
    Spatial configurations of polynucleotide chains. I. Steric interactions in polyribonucleotides: A virtual bond modelFrom the thesis submitted by Wilma K. Olson in fulfillment of the requirements for the degree of Doctor of Philosophy, Stanford University, 1971. (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1-23 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simplified scheme for treating the spatial configurations of polynucleotide chains is developed using the rotational isomeric state approximation and statistical methods applicable to linear systems of interacting subunits. As a consequence of geometric constraints imposed by the skeletal structure and of the severity of certain steric interactions, it is possible to represent the repeat unit comprising six skeletal bonds by two virtual bonds of fixed length. The configuration of the polynucleotide chain as a whole may be conveniently described by an alternating succession of these two virtual bonds. Moreover, analysis of steric interactions suggests that bond rotations governing the mutual orientation of a given pair of successive virtual bonds should be sensibly independent of the rotations affecting the mutual orientation of other pairs. The statistical mechanical treatment of configuration-dependent properties is much simplified in consequence of this mutual independence. Mean-square dimensions calculated by giving equal weights to all sterically allowed conformations are much smaller than values determined by Felsenfeld and co-workers. The calculated dimensions are markedly increased, however, by placing certain arbitrary restrictions on the rotations about selected pairs of skeletal bonds. It is thus demonstrated that steric interactions alone are insufficient to account for the spatial characteristics of polynucleotide chains. The dimensions are also found to be sensitive to the conformation of the ribose ring of each nucleotide unit, but, insofar as the influences of steric interactions are concerned, the dimensions do not depend on the heterocyclic base attached to the ribose ring.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110102
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  • 10
    Electronic Resource
    Electronic Resource
    Structural comparison between retro-inverso and parent peptides: Molecular basis for the biological activity of a retro-inverso analogue of the immunodominant fragment of VP1 coat protein from foot-and-mouth disease virus (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 569-590 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antibodies induced against intact foot-and-mouth disease Virus (FMDV) particles bind to the retro-inverso analogue of fragment 141-159 of the viral coat protein VP1 of FMDV, variant A, equally well as to the parent peptide. A conformational investigation of this retro-inverso peptide was carried out by nmr spectroscopy and restrained molecular modeling in order to identify the structural basis for the antigenic mimicry between these retro-inverso and parent peptides. In 100% trifluoroethanol a well-defined left-handed α-helical region exists from residue 150 to residue 159, which is consistently present in all conformational families obtained from restrained modelling. A less-defined left-handed helical region is present in the tract 144-148, which is also consistent for all structures. Conformational flexibility exists about Gly149, which leads to two types of structures, either bent or linear. In the bent structures, a three-residue inverse tight turn is found, which can be classified as an inverse γ-turn centered at Gly149. The overall structural features of the retro-inverso peptide are shown to be similar to those of the parent L-peptide. The two molecules, however, are roughly mirror images because they share inherently chiral secondary structure elements. By comparing these conformational conclusions with the x-ray structure of the Fab complex of a corresponding VP1 antigenic fragment, a rationale is proposed to account for the topological requirements of specific recognition that are implied by the equivalent antigenic activity of the natural and retro-inverso compounds. © 1997 John Wiley & Sons, Inc. Biopoly 41: 569-590, 1997.
    Additional Material: 12 Ill.
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