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  • Articles  (2)
  • 2,3,6-Tri-O-methyl)-β-cyclodextrin  (1)
  • Chemistry  (1)
  • electrostatic interactions  (1)
  • 1
    ISSN: 0935-6304
    Keywords: Chiral discrimination ; 2,3,6-Tri-O-methyl)-β-cyclodextrin ; Capillary Gas Chromatography ; ?-Alkyl-5-methylhydantoin ; Thermodynamic parameters ; Molecular modeing ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Permethylated β-cyclodextrin (hereafter designated perMe-β-CD), dililuted or not in polysiloxane, is an efficient chiral discriminant for native, 3-methylated, and 1,3-dimethylated series of 5-methyl-5-(CnH2n + 1)hydantoins. From thermodynamic data obtained with pure perMe-β-CD and with the aid of molecular modeling, it is concluded that: (i) For native hydantoin derivatives having a carbon chain at the 5-position varying from ethyl to nonyl (2≤n≤9), the retention time is related to their H-bonding capability. The resolution is poor for derivatives with n≤4. For n≤5, the resolution is considerably improved and this increase in resolution is attributed to the long alkyl chain being capable of being buried inside the cyclodextrin cavity. (ii) For 1,3-dimethylhydantion derivatives having a carbon chain at the 5-position varying from ethyl to hexyl(2≤n≤6), the retention time is mainly determined by a steric fit between the solute and the inner volume of the macrocyclic cavity. For n = 2, a particular behavior is observed, consistent with a total inclusion of the solutes inside the cavity. By contrast with the native hydantoins, the selectively is high for light derivatives. Thus, the selectivity does not correlate with a strong docking energy (such as the presence of H-bonds postulated with native derivatives). (iii) For 3-methylhydantoin derivatives having a carbon chain at the 5-position varying from ethyl to octyl (2≤n≤8), as expected, retension time and selectivity are intermediate between that of native hydantoins and 1,3-dimethylhydantoins. For all three series, where n≤5, the increase in chain length (n) does not bring about substantial changes in the chromatographic results. Therefore, for these long alkyl chain derivatives, similar dominant interactions with perMe-β-CD are postulated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4951
    Keywords: anti-(H2A-H2B) autoantibodies ; antigen binding mechanism ; comparative molecular modeling ; electrostatic interactions ; nucleosome ; systemic lupus erythematosus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The value of comparative molecular modeling for elucidating structure-function relationships was demonstrated by analyzing six anti-nucleosome autoantibody variable fragments. Structural models were built using the automated procedure developed in the COMPOSER software, subsequently minimized with the AMBER force field, and validated according to several standard geometric and chemical criteria. Canonical class assignment from Chothia and Lesk's [Chottin and Lesk, J. Mol. Biol., 196 (1987) 901; Chothia et al., Nature, 342 (1989) 877] work was used as a supplementary validation tool for five of the six hypervariable loops. The analysis, based on the hypothesis that antigen binding could occur through electrostatic interactions, reveals a diversity of possible binding mechanisms of anti-nucleosome or anti-histone antibodies to their cognate antigen. These results lead us to postulate that anti-nucleosome autoantibodies could have different origins. Since both anti-DNA and anti-nculeosome autoantibodies are produced during the course of systemic lupus erythematosus, a non-organ specific autoimmune disease, a comparative structural and electrostatic analysis of the two populations of autoantibodies may constitute a way to elucidate their origin and the role of the antigen in tolerance breakdown. The present study illustrates some interests, advantages and limits of a methodology based on the use of comparative modeling and analysis of molecular surface properties.
    Type of Medium: Electronic Resource
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