Application of nonlinear sampling schemes to COSY-type spectra

Summary Nonlinear sampling along the t₁ dimension is applied to COSY-type spectra. The sine dependence of the time domain signals for the cross peaks is matched by a nonlinear sampling scheme that samples most densely around the maximum of the sine function. Data are processed by maximum entropy reconstruction, using a modified implementation of the Cambridge algorithm of Skilling and Bryan. The procedure is demonstrated for P.E.COSY spectra recorded on a cyclic hexapeptide and on a 126-residue domain of the protein villin. The number of t₁ values in the nonlinearly sampled experiments was reduced by a factor of four compared to linear sampling. The sensitivity and resolution of the resulting spectra are comparable to those achieved by conventional methods. The method described can thus significantly reduce the measuring time for COSY-type spectra.Abbreviations COSY two-dimensional correlation spectroscopy - E.COSY exclusive COSY - P.E.COSY primitive E.COSY - TPPI time proportional phase incrementation - FID free induction decay To whom correspondence should be addressed.