Competition of chrysophaentin A and GTPγS binding to FtsZ by STD NMR. (a) Expanded 1H STD NMR spectrum of chrysophaentin A (1.25 mM) in the presence of FtsZ (12.5 μM). (b-e) STD NMR spectra recorded on the same sample after addition of (b) 0.5, (c) 1.0, (d) 2.0 and (e) 3.0 eq GTPγS. Final concentrations of GTPγS were 625 μM, 1.25 mM, 2.50 mM and 3.75 mM, respectively.