CHOOSING A SPIN-LOCK TRANSMITTER POSITION WHICH MINIMIZES HOHAHA DISTORTIONS OF ROESY SPECTRA - OBSERVATION OF A CORRELATION-TIME DEPENDENCE OF FREQUENCY OFFSET

A technique for reliably selecting a transmitter position for rotating -frame NOE experiments which minimize scalar coupling artifacts is des cribed. The technique makes use of the COSY spectrum of the molecule i n question. The method is illustrated by application to thiostrepton, an antibiotic of molecular weight 1665. For an individual compound, th e range of transmitter settings over which HOHAHA distortions are obse rved is found to depend on the molecular correlation time of the compo und under study. The origin of this effect is discussed in terms of ro tating-frame relaxation during the spin-lock period. (C) 1997 Academic Press.