a, Chemical structures of disaccharide-modified glycopeptide antibiotics with increasing aliphatic side chain lengths (from left to right): vancomycin (no modification), LY309687 (trifluoromethoxybenzyl side chain), oritavancin (chlorophenyl-benzyl side chain), FNCE (N-9-fluorononyl side chain), and FBBCE (N-9-fluorobiphenylbenzyl side chain). b, ATP leakage was attempted in S. aureus harvested at OD660nm 1.5 by addition of glycopeptide antibiotics to final concentrations of 0, 1, 2, 5, 10, 50, and 100 μg/mL, and daptomycin (D) at 100 μg/mL. All glycopeptide antibiotics did not induce appreciable ATP leakage attributable to membrane depolarization at the concentrations tested. In comparison, daptomycin induced ATP leakage consistent with the membrane disruption. All error bars represent 95% confidence interval.