Figure 3.

(Top) ¹⁵N full-echo NMR spectra of S. aureus grown in media containing [1-¹³C]glycine and L-[ε-¹⁵N]lysine in the presence of varying concentrations of [¹⁹F]oritavancin (low, 3.4 µg/ml; intermediate, 6.7 µg/ml; high, 10.1 µg/ml). The spectra were scaled using the normalization factors of Figure 2 (left). Spectra of S. aureus grown in the presence of [¹⁹F]oritavancin show a reduced ε-¹⁵N lysyl-amide peak at 95 ppm (cell wall) and an increased ε-¹⁵N lysyl-amine peak at 10 ppm (cytoplasmic peptidoglycan precursors), consistent with transglycosylase inhibition. (Bottom) ¹⁵N full-echo NMR spectra of S. aureus grown in media containing [1-¹³C]glycine and L-[ε-¹⁵N]lysine in the presence of varying concentrations of desleucyl-[¹⁹F]oritavancin (low, 3.5 µg/ml; intermediate, 6.9 µg/ml; high, 10.4 µg/ml). The spectra were scaled using the normalization factors of Figure 2 (right). At low drug concentrations, the level of transglycosylase inhibition by desleucyl-[¹⁹F]oritavancin is reduced relative to that by [¹⁹F]oritavancin (lower amine-to-amide ratio). Slowed growths (Figure S2, top right) suggest the possibility of some accumulation of cell-wall debris from dead cells. Chemical shifts are referenced to solid ammonium sulfate.