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  • Polymer and Materials Science  (86)
  • 2020-2022
  • 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
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Interaction of nucleic acids. VI. Interaction of purine with nucleic acids (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 765-782 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of purine with DNA, tRNA, poly A, poly C, and poly A. poly U complex was investigated. In the presence of purine, the nucleic acids in coil form (such as denatured DNA, poly A and poly C in neutral solutions, or tRNA) have lower optical rotations. In addition, hydrodynamic studies indicate that in purine solutions the denatured DNA has a higher viscosity and a decreased sedimentation coefficient. These findings indicate that through interaction with purine, the bases along the poly-nucleotide chain are unstacked and are separated farther from each other, resulting in increased assymmetry (and possibly volume) of the whole polymer. Thus, the de-naturation effect of purine reported previously can be explained by this preferential interaction of purine with the bases of nucleic acids in coil form through a hydrophobic-costacking mechanism. Results from studies on optical rotation and helix-coil transition show that the interaction of purine is greater with poly A than with poly C. The influence of temperature, Mg++ concentration, ionic strength, and purine concentration on the effect of purine on nucleic acid conformation has also been investigated. In all these situations the unraveling of nucleic acid conformation occurs at much lower temperatures (20-40°C lower) in the presence of purine (0.2-0.6M).
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1970.360090703
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  • 8
    Electronic Resource
    Electronic Resource
    Spatial configuration of polynucleotide chains. II. Conformational energies and the average dimensions of polyribonucleotidesFrom 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. 25-56 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energies are calculated for pairs of successive bond rotations within an internal residue of a polyribonucleotide chain. Contributions to these energies include bond torsional strain, van der Waals repulsions, London attractions, electrostatic interactions, and inductive interactions between nonbonded atoms in the nucleotide repeat unit. The average dimensions of unperturbed random-coil polyribonucleotide chains are then evaluated on the basis of energies thus estimated, using for this purpose the previously developed virtual bond treatment. The characteristic ratio \documentclass{article}\pagestyle{empty}\begin{document}$ C_\infty = \mathop {{\rm lim}}\limits_{n \to \infty } (\langle r^2 \rangle_0/nl^2) $\end{document} of the mean-square end-to-end distance calculated for polyribonucleotide chains in which all pentose rings are fixed in a C3′-endo conformation is ≈9; for chains consisting exclusively of C2′-endo units it is ≈25. These values are considerably greater than those obtained by giving equal weight to all conformations judged to be sterically allowed. Satisfactory agreement between the calculations here and experimental values from viscosity and light-scattering studies is achieved by treating the chain as a random copolymer of C3′-endo and C2′-endo conformational isomers. The critical dependence of the characteristic ratio on the rotation about bond C3′-O3′ in the C2′-endo chain, however, obscures the interpretation of chain dimensions. The chain is also treated in higher approximation as a sequence of independent repeat units, each of which consists of six chemical bonds. The characteristic ratio obtained in this manner is 6.5 for the C3′-endo chain and 18.5 for the C2′-endo chain. Finally, the effects of partially stacked conformations in polyribonucleotides are investigated using the virtual bond treatment. Chain dimensions are calculated for random coil poly rA chains in which stacking is introduced by both noncooperative and cooperative processes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110103
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  • 9
    Electronic Resource
    Electronic Resource
    Ultracentrifugal field relaxation behavior of fd-DNA (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1931-1935 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120819
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  • 10
    Electronic Resource
    Electronic Resource
    Spatial configurations of polynucleotide chains. III. PolydeoxyribonucleotidesFrom 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. 57-66 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The virtual bond scheme set forth in preceding papers for treating the average properties of polyriboadenylic acid (poly rA) is here applied to the calculation of the unperturbed mean-square end-to-end distance of polydeoxyriboadenylic acid (poly dA). The modifications in structure and in charge distribution resulting from the replacement of the hydroxyl group at C2′ in the ribose residue by hydrogen in deoxyribose produce only minor modifications in the conformational energies associated with the poly dA chain as compared to those found for poly rA. The main difference is manifested in the energy associated with rotations about the C3′-O3′ bond of the deoxyribose residue in the C2′-endo conformation; accessible rotations are confined to the range between 0° and 30° relative to the trans conformation, whereas in the ribose unit the accessible regions comprise two ranges centered at approximately 35° and 85°. The characteristic ratio 〈r2〉0/nl2 calculated on the basis of the conformational energy estimates is ≈9 for the poly dA chain with all deoxyribose residues in the C3′-endo conformation and ≈21 with all residues in the C2′-endo form. Satisfactory agreement is achieved between the theoretical values and experimental results on apurinic acid by treating the poly dA chain as a random copolymer of C3′-endo and C2′-endo conformational isomers present in a ratio of ∼1 to 9.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110104
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