Suppression or differentiation of solvent resonance by a combination of DEFT with a two-dimensional sequence

Abstract

A new pulse sequence is described which combines the driven equilibrium Fourier transform (DEFT) and 2D pulse scheme, and allows simultaneous suppression of the solvent peak (H 2O/D 2O) in 1D and 2D experiments without perturbing the nearby solute signals. To overcome the sensitivity problem, and to allow for 2D experiments in a reasonably short time, a steady-state condition was set up by adjusting τ 1 (pulse delay) and D (recycle delay) to be 2–4 times the longest spin-lattice relaxation time T 1 (peptide) such that M z (solvent) was nulled prior to the 2D pulse sequence. Longitudinal and transverse relaxation rates of the solvent were analyzed in the steady state, and a direct calculation of T 1 (solvent) was performed using an equation derived in the present work. This novel pulse sequence is also extended to 2D NOE experiments with effective solvent suppression. The method is demonstrated in a variety of 1D and 2D experiments on the cyclic delta opioid receptor selective peptide ▪.