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  • 1
    ISSN: 1432-1017
    Keywords: Resonance Raman spectroscopy ; Vibrational analysis ; Hypoxanthine ; Nucleic acids ; Molecular force field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Ultraviolet resonance Raman scattering spectra from aqueous solutions of hypoxanthine and its deuterated species (C8-deuterated, N-deuterated and C8-, N-deuterated derivatives) have been collected and reported in the spectral region between 400 and 1800 cm−1. The laser excitation wavelengths at 281 nm and 257 nm correspond to preresonance and pure resonance conditions, respectively, with the purine strongly allowed π → π* electronic transition: thus the observed experimental Raman features mainly correspond to inplane vibrational modes. The latter were then assigned according to the Wilson GF method by using an empirical harmonic valence force field. Normal mode calculations are based on a non-redundant set of internal coordinates. The calculated vibrational mode wavenumbers and their isotopic shifts upon selective deuterations are in good agreement with the experimental data. The present normal mode analysis rests on the transferability of the guanine and adenine force constants proposed in recent works based on resonance Raman spectroscopy and neutron inelastic scattering data from these major purine bases.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 2523-2532 
    ISSN: 0021-8995
    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
    Notes: The shrinkage of a series of epoxy adhesives diluted with either phenyl glycidyl ether (PGE) or 1,4-butanediol diglycidyl ether (BDE) and cured with either diethylenetriamine (DTA) or diethylaminopropylamine (DPA) was measured and compared with the steel-to-steel lap shear strength obtained with these adhesives. It was found that the adhesives with the highest level of shrinkage also gave the highest strengths. Samples cured initially at room temperature with DPA underwent a significant expansion when postcured at elevated temperatures. The amount of shrinkage was found not to be dependent on sample size.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 3 (1997), S. 61-71 
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A new approach to the empirical force field determination by the adaptive optimization method is studied. The problem is conceived as a multiparameter optimization task and solved by the genetic algorithms (GA). The principles of the approach and the most efficient GA strategies are presented. With regard to the computational demands, the GA parameters were looked for in the test series in the force field refinement of the CHCl3 molecule. The most efficient ones were applied to the force field refinement of the bigger molecule of purine. The results show that the GA approach is powerful enough to provide a plausible force field of purine. The perspectives of the approach to bigger systems are outlined. © 1997 John Wiley & Sons, Inc. Biospect 3: 61-71, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 507-514 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultraviolet resonance Raman spectra of inosine and its deuterated species (C8-d, Nl-d and C8-, Nl-deuterated derivatives) in aqueous solution have been collected (λexc = 257 and 281 nm) and reported in the spectral region between 400 and 1800 cm-1. The observed vibrational modes have been assigned using the Wilson GF method with an empirical harmonic valence force field and a non-redundant set of internal co-ordinates. This normal mode analysis is based on previous work on the vibrational assignments of the hypoxanthine nucleic base and the furanose ring with various geometries. Here the analysis has been carried out by using three different nucleoside conformations as determined from x-ray studies of molecular crystals. The most striking features of the present work are: (i) the assignments of inosine vibrational modes are very different from those of the hypoxanthine base; (ii) the best fit between measured and calculated vibrational wavenumbers and their isotopic shifts upon selective deuteration has been obtained from inosine structures containing an N-type sugar (C3′-endo) associated with a low-anti base. In addition, we have tested the reliability of the force field in the case of inosine residues involved in a canonical A-RNA helical structure by comparing the calculated wavenumbers of the most characteristic vibrational modes with those observed in off- and on-resonance Raman spectra of poly(rI).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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