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  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared absorption and x-ray diffraction measurements have been made of D,L-copoly-γ-benzylglutamate fibers (cast from dioxane solutions) with various D/L ratios and with various degrees of polymerization. It was found that each chain of these copolymers consists of a random coil portion and an α-helix portion and that the conformation of the latter is similar to the α-helix of pure poly-γ-benzyl-L-glutamate. It was also found that the fraction of the α-helix portion increases with the degree of polymerization of the copolymer. A simplified polymerization mechanism has been proposed for mixtures of D- and L-amino acid N-carboxyanhydrides. A model of the molecular conformation of the D,L-copolypeptide chains derived from this proposed polymerization mechanism is in good agreement with infrared, x-ray, and other measurements. Based on the results of these observations, we discuss the number of L- or D-residues linked in succession that is required for initiating the formation of an α-helix during the course of polymerization.
    Additional Material: 12 Ill.
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  • 2
    ISSN: 0006-3525
    Keywords: Raman tensor ; polarized Raman spectrum ; adenine ; uracil, uridylyl(3′-5′)adenosine ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polarized Raman scattering measurements have been made of a single crystal of uridylyl(3′-5′)adenosine (UpA) by the use of a Raman microscope with 488.0 nm excitation. The UpA crystal belongs to space group P21 (monoclinic), and Raman intensities Iaa, Ibb, and Ic′c′, have been determined for each Raman band. These intensities correspond to the aa, bb, and c′c′ components of the crystal Raman tensor, where c′ is defined as an axis perpendicular to the crystallographic a axis in the ac plane. From these experimental data, and by taking the known crystal structure into account, anisotropic and isotropic molecular Raman tensors have been calculated for the following 11 normal modes: ring stretching modes of the adenine residue (protonated) at 1560, 1516, 1330, and 715 cm-1; ring stretching modes of the uracil residue at 1696, 1657, 1615, 1228, and 790 cm-1; PO-2 symmetric stretching mode at 1080 cm-1; P( - )O single bond stretching mode at 801 cm-1. These pieces of information of the Raman tensors are considered to be useful for estimating the orientations of the DNA and RNA strands in a biological complex from a polarized Raman spectroscopic measurement of such a complex. © 1998 John Wiley & Sons, Inc. Biopoly 45: 135-147, 1998
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 2 (1996), S. 233-242 
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Polarized Raman scattering measurements have been made of a single crystal of AZT (3′-azido-3′-deoxythymidine) by the use of a Raman microscope with the 488.0 nm exciting beam from an argon-ion laser. The AZT crystal belongs to the space group P21 (monoclinic), and Raman scattering intensities, corresponding to the aa, bb, c′c′, and bc′ components of the crystal Raman tensor, have been determined for each prominent Raman band. Here, c′-axis was defined as an axis perpendicular to the a-axis in the ac plane. From these experimental data, and on the basis of the known crystal structure, localized Raman tensors have been determined, which are assignable to azido vibrations at 2088 and 1259 cm-1, to thymine at 1666, 1392, 1238, 771, and 495 cm-1 and deoxyribose vibrations at 870, 849 and 739 cm-1. The knowledge of these localized Raman tensors are considered to be useful for probing the orientation of the AZT molecule in a biological system involving it. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 4 (1998), S. 61-71 
    ISSN: 1075-4261
    Keywords: L-tyrosine ; polarized Raman spectra ; Raman tensor ; ab initio MO calculation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Polarized Raman scattering measurements have been made of a single crystal of L-tyrosine by the use of a Raman microscope with the 488.0-nm exciting beam from an argon ion laser. The L-tyrosine crystal belongs to the space group P212121 (orthorhombic), and Raman scattering intensities corresponding to the aa, bb, cc, ab and ac components of the crystal Raman tensor have been determined for each prominent Raman band. A similar set of measurements has been made of L-tyrosine-d4, in which four hydrogen atoms on the benzene ring are replaced by deuterium atoms. The effects of NH3 → ND3 and OH → OD on the Raman spectrum have also been examined. In addition, depolarization ratios of some bands of L-tyrosine in aqueous solutions of pH 13 and pH 1 were examined. For comparison with these experimental results, on the other hand, ab initio molecular orbital calculations have been made of the normal modes of vibration and their associated polarizability oscillations of the L-tyrosine molecule. On the basis of these experimental data and by referring to the results of the calculations, discussions have been presented on the Raman tensors associated to some Raman bands, including those at 829 cm-1 (benzene ring breathing), 642 cm-1 (benzene ring deformation), and 432 cm-1 (Cα-Cβ-Cγ bending). © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 61-71, 1998
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 1 (1963), S. 47-49 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 1 (1963), S. 531-534 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The adenine residues of nucleic acids give a medium-intensity Raman band around 1580 cm-1 and protonated adenine residue around 1560 cm-1. Each of them shows a peculiarly high degree of depolarization, α = 0.65, in aqueous solutions. A corresponding band, at 1562 cm-1, shows a high anisotropy in the single crystal of uridylyl-(3′-5′)-adenosine (UpA). On the basis of the known structure of this crystal, and on the basis of the polarized Raman data (488.0 nm excitation), the shape and orientation of the Raman tensor associated with this 1562 cm-1 vibration have been determined: one of its principal axes (y-axis) is directed along the long axis of the adenine residue and r1 = αxx/αzz = - 3 and r2 = αyy/αzz = 4. A general relationship has also been derived between the orientation angles (θ and χ) of the adenine residues with a uniaxial arrangement in a biopolymer and the anisotropy of the 1580 cm-1 Raman scattering intensity. This relationship has been used in a discussion of the orientation of the adenine residue in the poly(rA)·poly(rU) duplex fibre.
    Additional Material: 7 Ill.
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