Figure 2.
(Top) 13C{15N} REDOR spectra after 8-Tr evolution for whole cells enriched with D-[1-13C]alanine and D-[15N]aspartic acid, grown in the presence of alaphosphin and no vancomycin (left) or 25 μg/ml vancomycin (right). The REDOR difference spectra (ΔS) represent only D-Ala cross-linked to D-Asp. (Bottom) 13C{15N} REDOR dephasing (ΔS/S0) of the 175 ppm-peak as a function of dipolar evolution time. The maximum one-bond dephasing decreases from 24% to 12% after treatment with vancomycin as a result of the accumulation of uncross-linked peptidoglycan precursors in the cytoplasm. Uncross-linked peptidoglycan subunits in mature cell wall are cleaved into tripeptides by a carboxypeptidase in E. faecium and therefore are not detected in the 13C{15N} REDOR experiment.