Use of capillary electrophoresis to measure dimerization of glycopeptide antibiotics

Capillary electrophoretic methods were used to examine dimerization and estimate dimerization constants (Kdim) for the glycopeptide antibiotics vancomycin, ristocetin A, and LY264826 (A82846B). The Kdim for LY264826 was 60- and 200-fold higher than the Kdim for ristocetin A and vancomycin, respectively. Dimerization of vancomycin measured in the presence of the cell wall analog N, N'-diacetyl-L-Lys-D-Ala-D-Ala was enhanced 200-fold; however, dimerization of ristocetin A was antagonized by the presence of N, N'-diacetyl-L-Lys-D-Ala-D-Ala. The relative differences in Kdim determined by capillary electrophoresis in general follow the same trend as those observed using nuclear magnetic resonance spectroscopy and sedimentation equilibrium.