Binding constant determination of glycopeptide antibiotics to D-Ala D-Ala terminus peptides using affinity capillary electrophoresis

ORGN 383

Dinora B. Chinchilla, Catherine Silverio, Jose Zavaleta, and Frank Gomez. Department of Chemistry and Biochemistry, California State University, Los Angeles, 5151 State University Dr, Los Angeles, CA 90032
Binding constants between the glycopeptide antibiotics ristocetin A (Rist A), teicoplanin (Teic), vancomycin (Van), and oritavancin (Orit) and D-Ala-D-Ala terminus peptides were determined using affinity capillary electrophoresis (ACE). In these experiments two techniques are used to obtain binding constants. In the first, a plug of antibiotic and non-interacting standards are injected and electrophoresed. Analysis of the change in the relative migration time ratio (RMTR) of the antibiotic, relative to the non-interacting standards, as a function of the concentration of peptide, yields a value for the binding constant (Kb). In the second, samples of peptide and standards are injected and electrophoresed in increasing concentrations of antibiotic in the running buffer. Analysis using the RMTR yields a Kb. The findings described here demonstrate the advantage of using ACE for estimating binding parameters between antibiotics and ligands. The values for binding constants agree well with those estimated using traditional forms of analysis.