INFORMATION FROM THE WATER STRIPE IN TOCSY EXPERIMENTS ON SYSTEMS WITH EXCHANGEABLE PROTONS

The water ''stripes'' of the TOCSY maps of aqueous solutions of sucros e, of a 15-aminoacid peptide, and of several of the constituent aminoa cids are shown to contain correlations at the resonance frequencies of protons which are scalar coupled to OH or NH protons which exchange w ith the solvent. Theoretical analysis of chemical exchange during the spin-lock period in TOCSY elucidates the origin of these correlations, and shows that their intensities vary with the duration of the spin-l ock period and with the exchange rate. (C) 1998 Academic Press.