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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Journal of computer aided molecular design 10 (1996), S. 23-30 
    ISSN: 1573-4951
    Keywords: AMBER ; HIV-1 protease inhibitor ; N,N-dialkyl benzene sulfonamides ; Force field ; Hydrogen bonding ; Structure-based drug design ; Continuum solvation methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary VX-478 belongs to a novel class of HIV-1 protease inhibitors that are based on N,N-disubstituted benzene sulfonamides. Force field parameters for the N,N-dialkyl benzene sulfonamide moiety have been assembled from the literature and from our own ab initio calculations. These parameters were employed to calculate solvation and binding free energy differences between VX-478 and two analogs. The free energy perturbation method has been used to determine these differences using two approaches. In the first approach, intergroup interaction terms only were included in the calculation of free energies (as in most reports of free energy calculations using AMBER). In the second approach, both the inter- and intragroup interaction terms were included. The results obtained with the two approaches are in excellent agreement with each other and are also in close agreement with the experimental results. The solvation free energies of N,N-dimethyl benzene sulfonamide derivatives (truncated models of the inhibitors), calculated using continuum solvation (AMSOL) methods, are found to be in qualitative agreement with the experimental and free energy perturbation results. The binding and solvation free energy results are discussed in the context of structure-based drug design to show how physicochemical properties (for example aqueous solubilities and bioavailabilities) of these HIV-1 protease inhibitors were improved, while maintaining their inhibitory potency.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 67 (1984), S. 419-426 
    ISSN: 1432-2242
    Keywords: Spinous Solanums ; Crossability relationships ; Interspecific hybrids ; Chromosome repatterning ; S. melongena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytogenetic studies involving six species of spinous Solanums have been made using the parameters of crossability/fertility relationships and chromosome pairing in parental and derived hybrid genomes. These studies have made it possible to integrate hybrid reproductive performance with observed cytological phenomena and draw inferences on concerned intergenomic homeologies. It has been found that species' differences, as they exist, are ascribable to chromosome repatterning, in their divergence and maintenance as distinct taxa. In the light of these studies, the grouping of these species has to be reconsidered.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 59 (1981), S. 303-306 
    ISSN: 1432-2242
    Keywords: Solanum indicum ; Solanum torvum ; F1 Solanum hybrid ; Meiosis ; Sterility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The F1 hybrid Solanum indicum x S. torvum could be maintained only under special conditions. Meiosis was highly irregular: about 45% of chromosomes remained as univalents and wherever pairing was observed, it appeared to be loose. A maximum number of three higher chromosome associations other than bivalents, including ‘Y’ and ‘spoon’ type associations, indicate extensive chromosome repatterning. Occasional occurrence of twelve bivalents per PMC suggests that, notwithstanding the extreme divergence, the species have retained sufficient ancestral chromosome homoeologies. Chromosome distribution at anaphase-I was highly irregular and precocious division of chromosomes was observed frequently. This hybrid was 100% sterile and the dropping off of immature flower buds was observed.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract S. integrifolium (2n = 24) can easily be crossed as the pistillate parent with S. melongena (2n = 24) and S. melongena var. insanum (2n = 24). However, crosses in the other direction do not succeed. Both hybrids are vigorous. Chromosome association at diakinesis and metaphase I was studied. Chromosome associations higher than bivalents were observed in the hybrids indicating structural repatterning of chromosomes. The modal chromosome association in hybrids was twelve bivalents per PMC. This is suggestive of the retention of ancestral chromosome homeologies by the taxa concerned. Despite regular meiosis both hybrids were highly pollen-sterile (about 95%), which was attributed to segregational events of the recombined chromosomes.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 5 (1986), S. 141-143 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 305 (1981), S. 415-416 
    ISSN: 1618-2650
    Keywords: Best. von Metol ; Spektralphotometrie ; Phenol, Sauerstoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 1241-1253 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ro 31-8959 is a highly potent inhibitor of HIV-1 proteinase in phase III clinical trials for treatment of AIDS. It is also the first subnanomolar inhibitor that demonstrated reversed stereochemical preference at the central hydroxyl group. Free energy perturbation calculations have been carried out to rationalize the preference for the R-diastereomer by consideration of two models of the (weaker) S-diastereomer. In the first model, the central hydroxyl group makes only one hydrogen bond with the active site aspartates, whereas the hydroxyl group in the second model makes at least three strong hydrogen bonds. Using the first model, the free energy difference in binding of Ro 31-8959 and its S-diastereomer is calculated to be 3.4 kcal/mol, which is in close agreement with the experimental value. Although the second model has a more favorable interaction with the active site aspartates compared to the first model, it has a higher energy N-axial conformation at the decahydroisoquinoline group in P1′. We show here that the two contributions cancel each other and the two models of S-diastereomer are predicted to have equivalent binding. The stereochemical preference in a hydroxyethylamine series of inhibitors appears to be affected by both intermolecular and intramolecular (conformational) energies. The binding data on the proline containing inhibitors are rationalized based on these results. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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