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  • 1
    ISSN: 0899-0042
    Keywords: aspartame stereoisomers ; chiral separations ; column liquid chromatography ; chymotrypsin on silica ; binding sites ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantioselective and diastereoselective resolutions of the stereoisomers of Nα-aspartyl-phenylalanine 1-methyl ester (APME) have been accomplished on an HPLC chiral stationary phase based upon α-chymotrypsin (the ACHT-CSP) with observed enantioselectivities (α1) for the DL-/LD-enantiomers of as high as 29.17 and for the DD-/LL-enantiomers of as high as 28.97. In addition, the effect on the chromatographic retention of the APME stereoisomers of the activity of the ACHT and the composition of the mobile phase - structure of the anionic component, molarity, and pH - have been studied. The results of this study suggest that the aspartyl moiety and/or the aspartyl-phenylalanine amide linkage play key roles in the observed enantioselectivity; the APME stereoisomers containing L-phenylalanine, i.e., DL- and LL-APME, bind at a different site in the ACHT molecule (the L-Phe site) than the APME stereoisomers containing D-phenylalanine (the D-Phe site); and the observed enantioselectivity is a measure of the difference in the binding affinities at the two sites rather than the consequence of differential affinities at a single site.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: chiral stationary phases ; human serum albumin ; protein binding ; binding sites ; high-performance liquid chromatography ; immobilized proteins ; chemical modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The in situ modification of an immobilized human serum albumin (HSA) high-performance liquid chromatographic chiral stationary phase by p-nitrophenyl acetate is reported. This procedure, which is thought to affect primarily a single reactive tyrosine residue within the protein structure, influenced the chromatographic retention and enantioselectivity factors of a wide range of solutes. For certain solutes, increases in both capacity factor and chiral resolution were observed. Ultrafiltration studies on representative test solutes using free HSA, treated in a similar manner to the immobilized protein, gave similar results as the chromatographic observations, indicating that the latter effects are not artifactual results of immobilization. The effect of the modification of HSA on the binding behavior of drugs reportedly sharing the site predominantly affected by the derivatization, namely, the indole–benzodiazepine binding site, varied greatly. This observation suggests that the affected binding area is not a single, tightly structurally defined site.
    Type of Medium: Electronic Resource
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