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  • 1
    Digitale Medien
    Digitale Medien
    Vibrational analysis of peptides, polypeptides, and proteins. XXXII. α-Poly(L-glutamic acid) (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1479-1491 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The Raman and ir spectra of α-helical poly(L-glutamic acid) have been assigned on the basis of a normal mode calculation for this structure. The force field was based on our previously refined main-chain force constants for α-poly(L-alanine) and side-chain force constants for β-calcium-poly(L-glutamate). Despite the identical backbone α-helical structures, significantly different frequencies are calculated, and observed, in the amide III and backbone stretch regions of α-poly(L-glutamic acid), as compared with α-poly(L-alanine). This clearly demonstrates the influence of side-chain structure on mainchain vibrational modes.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360240805
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  • 2
    Digitale Medien
    Digitale Medien
    Raman and normal-mode studies of the extended-helix conformation in polypeptide chainsThis is paper number 36 in a series on vibrational analysis of peptides, polypeptides, and proteins, of which Ref. 23 is paper number 35. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S99 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The nature of the local main-chain conformation of polypeptides with charged side chains has been the subject of considerable discussion since Tiffany and Krimm first proposed [(1968) Biopolymers 6, 1379-1381] that, rather than being random, the chain is locally relatively regular, with conformations similar to that of a left-handed threefold helix. Such structures, referred to as “extended-helix” (EH) conformations, have now been studied in a charged poly(L-glutamic acid) system by a combination of Raman spectroscopy and normal-mode analysis. Calculations were done for EH conformations with 3.0 and 2.4 residues/turn, using force fields refined for α-helix, 31-helix, and β-sheet structures. Together with previous results on the α-helix and β-sheet forms, an interesting new correlation emerged: the frequency of the CαC stretch skeletal mode, usually found in the 900-1000 cm-1 region of the Raman spectrum, is essentially linearly correlated with the value of the φ angle. Applying this relationship to the observed frequencies of the α-helix and β-sheet forms of poly(L-glutamic acid), we find that an observed sharp band in the spectrum of crystals of the calcium salt of poly(L-glutamic acid) (which is close to the frequency observed for the charged form in solution) corresponds to an EH conformation very close to that predicted from energy calculations. These studies thus provide very strong support for our proposal that charged polypeptide chains are not random but adopt local conformations of the EH type.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360260011
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  • 3
    Digitale Medien
    Digitale Medien
    7-Amino-actinomycin D complexes with deoxynucleotides as models for the binding of the drug to DNA (1979)
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1749-1762 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorescence, CD, absorption, and 1H-nmr studies are reported for complexes of 7-amino-actinomycin D with deoxydinucleotides, deoxytetranucleotides, and poly(dG-dC)· poly(dG-dC). The optical spectra for the 7-amino-actinomycin D complex with pdG-dC, pdG-dC-dG-dC and pdC-dG-dC-dG are similar in shape to the 7-amino-actinomycin D complex with either DNA or poly(dG-dC). The changes in the 1H chemical shifts of the 7-amino-actinomycin D and the pdG-dC resonances that accompany complex formation show that 7-amino-actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The magnitudes of the induced chemical shifts for the 7-amino-actinomycin D complex formation with pdG-dC are similar to, but slightly different from, the induced chemical shifts which are obtained when actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The pdN-dG dinucleotides (N = C, A, or T) form stacked complexes with 7-amino-actinomycin D. The presence of the 7-amino-group results in a larger dimerization constant (in aqueous solution) for 7-amino-actinomycin D [KD(6°C) = 4.4 × 103M-1], as compared to actinomycin D [KD(6°C) = 1.7 × 103M-1]; the chemical shifts which accompany dimer formation indicate that the chromophores stack in an inverted manner. Intercalation of 7-amino-actinomycin D into minature double helices, as well as into calf thymus DNA, poly(dG-dC)·poly(dG-dC), and poly(dA-dC)·poly(dG-dT), results in an enhancement of the relative fluorescence intensity and a shift in both the absorbance and corrected emission spectra.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1979.360180712
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  • 4
    Digitale Medien
    Digitale Medien
    Über Pterinchemie. 62. Mitteilung. Protonenkatalysierte [1,2]-H-Verschiebung bei der Umlagerung von 6,7-Diphenyl-5,6-dihydropterin zu 6,7-Diphenyl-7,8-dihydropterin (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 922-924 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Proton catalysed [1,2]-H-shift in the rearrangement of 6,7-diphenyl-5,6-dihydropterine (I) to 6,7-diphenyl-7,8-dihydropterine (III)The arrangement from I to the thermodynamically more stable III undergoes through a acid catalysed [1,2]-H-shift (intramolecular 6,7-hydride rearrangement) (see Scheme 1).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19770600322
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  • 5
    Digitale Medien
    Digitale Medien
    Über Pterinchemie. 73. Mitteilung [1]. Zum Verlauf der katalytischen Reduktion von 7-Methylpterin (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 395-401 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: On the Pathway of the Catalytic Reduction of 7-MethylpterinThe catalytic hydrogenation of 7-methylpterin (VII) in a neutral solution occurs first by the reduction of the 7,8-double bond (thermodynamically-controlled reaction) followed by the reduction of the 5,6-double bond. On the contrary, in an acidic medium like CF3COOH, the 5,6-double bond is reduced first (kinetically-controlled reaction). The dihydro-intermediate then undergoes a [1,2]-H-rearrangement leading to the formation of the thermodynamically more stable 7-methyl-7,8-dihydropterin (XV) which on further reduction gives 7-methyl-5,6,7,8-tetrahydropterin (VIII). The catalytic reduction of 7-methyl-7,8-dihydropterin (XV) with deuterium gives stereoselectively a sole product with D at C(6) in the equatorial position.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19800630209
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  • 6
    Digitale Medien
    Digitale Medien
    A study of dynamic quadrupolar and octupolar excitations and calculations on excited d and f states of atom and ions: He-sequence (1970)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 4 (1970), S. 465-486 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The quadrupolar and octupolar distortion of the ions in the He-sequence caused by an external electro-magnetic field has been studied by a variation-perturbation method in the Hartree-Fock scheme. For certain frequencies singularities appear in the response of the system to the perturbation. Approximate representations for the excited d and f states have been obtained from a study of these resonances. Such a perturbation calculation has the advantage that representations of the different excited states are obtained independently. The orthogonality to all the lower lying levels of the same symmetry is not required. The only source of inaccuracy implicit in the procedure lies in the improper consideration of the inter-electronic interaction. This is corrected for by an independent calculation, which is again formulated in terms of a perturbation treatment. The resulting wave functions for the excited states are accurate in the Hartree-Fock model. Expectation values of several operators have been calculated with these corrected wave functions.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560040503
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  • 7
    Digitale Medien
    Digitale Medien
    Coupled Hartree-Fock calculation of the electric dipole hyper-polarizabilities: He sequence (1972)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 6 (1972), S. 337-345 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The variation perturbation method in the coupled Hartree-Fock (HF) scheme has been used to calculate the fourth-order energies of He, Li+ and Be2+ ions subjected to a uniform external electric field. The hyper-polarizabilities γh which are related to the fourthorder energies have been calculated neglecting intra-atomic correlation. For He the observed value is γh = 53.6 ± 4.0 a.u. The present estimate in the coupled and uncoupled HF schemes yield 36.2 and 45.3 a.u. respectively. The other calculations using correlated ground state wave function gave values in the range 42-44 a.u. The discrepancies between our result and those of others have been discussed.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560060212
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  • 8
    Digitale Medien
    Digitale Medien
    Use of coupled-cluster based linear response theory and multireference hermitian MBPT to IP calculations of HF (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 29 (1986), S. 205-210 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We report in this paper the results of outer and inner valence IP calculations for the HF molecule using two different many-body methods for the direct evaluation of energy differences. The first is the nonperturbative coupled-cluster based linear response theory (LRT) and the second is the hermitian open-shell many-body perturbation theory (MBPT). A Huzinaga-Dunning (9s5p→ 5s3p/3s) basis has been used. LRT uses an “ionization operator” S as in the equation of motion method (EOM) to generate the ionized states from a coupled-cluster type of ground state. S is chosen to consist of single ionization and ionization-cum-shake-up operators, thus treating the Koopmans as well as the shake-up states on equal footing. LRT would thus be capable of computing both the outer and the inner valence regions with equal facility. This is borne out by the results. For the open-shell MBPT, the model space is chosen to be spanned by the singly ionized determinants. The convergence of the results for the inner valence region is slow, and the results obtained from the [2, 1] Pade' approximants are presented. Unlike the LRT, the inner valence region is not reproduced with full complexity in MBPT, indicating that it is essential to modify the theory by way of expanding the model space to contain the shake-up determinants also.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560290210
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  • 9
    Digitale Medien
    Digitale Medien
    Self-consistent calculation of 1s2s3S state of helium and heliumlike ions (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 283-291 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this paper we present a simple method within the coupled Hartree-Fock framework to calculate the 1s2s 3S state of helium and heliumlike ions. The results are in very good agreement with those obtained by the use of multiterm correlated wave functions. Some interesting observations associated with the wave function are presented.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560190209
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  • 10
    Digitale Medien
    Digitale Medien
    Self-consistent calculation of 1s2s1S state wave function of helium (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 995-1003 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A simple self consistent variation perturbation method in the coupled Hartree-Fock scheme has been proposed to calculate 1s2s 1S state of the He atom. The present paper deals with an 1s2s 1S wave function in which all the relevant orthogonality conditions are imposed in successive stages. The resulting wave functions together with some interesting features are discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560180407
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