Figure 2.
Contour plots of 15N,1H correlation spectra showing the indole 15N–1H spin system of Trp-48 recorded in a 2 mM solution of uniformly 15N-labeled ftz homeodomain complexed with an unlabeled 14-bp DNA duplex in 95% H2O/5% 2H2O at 4°C, pH = 6.0, measured at the 1H frequency of 750 MHz. (a) Conventional broad-band decoupled [15N,1H]COSY spectrum (22, 23). The evolution caused by the 1J(1H,15N) scalar coupling was refocused in the ω1 and ω2 dimensions by a 180° proton pulse in the middle of the 15N evolution time t1, and by waltz composite pulse decoupling of 15N during data acquisition, respectively. (b) Conventional [15N,1H]COSY spectrum recorded without decoupling during t1 and t2. (c) TROSY-type 15N,1H correlation spectrum recorded with the pulse scheme of Fig. 1. Chemical shifts relative to DSS in ppm and shifts in Hz relative to the center of the multiplet are indicated in both dimensions. The arrows identify the locations of the cross-sections shown in Fig. 3.