Binding of vancomycin group antibiotics to D-alanine and D-lactate presenting self-assembled monolayers

Peptides terminating in -Lys-D-Ala-D-Ala, -Lys-D-Ala-L-Ala and -Lys-D-Ala-D -Lactate were covalently coupled via an N-terminal aminohexanoic acid linke r to a self-assembled monolayer of HS(CH2)(15)CO2H on a thin gold film. Bin ding of the glycopeptide antibiotics vancomycin and chloroeremomycin to the se surfaces was then measured using a surface plasmon resonance biosensor. Both antibiotics bound with micromolar affinity to the D-Ala-terminating su rface and with millimolar affinity to the D-Lactate-terminating surface. In creasing density of these covalently attached peptides on the surface had n o effect on the resultant affinities of either antibiotic for the surface. In contrast, when the lipid-anchored peptide N-alpha -docosanoyl-epsilon -a cetyl-Lys-D-Ala-D-Ala was inserted into a supported lipid monolayer, the af finity of the strongly dimerizing antibiotic chloroeremomycin for the surfa ce showed a dependence on ligand density. This was not the case with the we akly dimerizing antibiotic vancomycin. The lipid monolayer surface, which i s a more realistic model of the surface of a bacterium, was thus better sui ted for the study of the cooperative binding interactions that occur betwee n dimeric glycopeptide antibiotics and surface-bound ligands. (C) 2000 Else vier Science Ltd. All rights reserved.