FIG. 1a. (A) High frequency region of the 1H NMR spectrum of Lys-vasopressin, 20 mM, solvent 90% H2O-10% D2O, T = 273 K, pH ~3.2, 1H frequency 600 MHz on a Bruker AMX-600 instrument equipped with a 5 mm Z-gradient probe, 32 scans (B) Cross-section through the 2D- WATERGATE-NOESY spectrum along w2 at the w1 frequency of t he water line, time domain data size 512 x 4096 points and 96 scans per free induction decay, mixing time tm = 100 ms. (C) Cross-section through the 2D-WATERGATE ROESY spectrum along w2 at the w1 frequency of the water line, spin-locking mixing time tm = 100 ms (processed and plotted with iden tical parameters as in (B). Resonance assignments for selected peaks are indicated.