High resolution in the indirectly detected dimension exploiting the processing of folded spectra

Multi-dimensional experiments using proton detection such as HSQC are often used to study organic and bioorganic molecules. Whereas the resolution in the directly detected dimension is normally high, the resolution in the ind irectly detected dimension is often much lower, limiting the unambiguous as signment to carbon or nitrogen atoms. The principle exploited here consists in taking advantage of the fact that spectral resolution increases when sp ectral widths are reduced. The price to pay for such resolution enhancement is that signals fold into the smaller window, making their chemical shift ambiguous. The software presented here efficiently assists spectroscopists to choose the correct chemical shift out of a large number of possibilities . It checks for their compatibility with signals in reference spectra. When the indirectly detected dimension is not too crowded, such processing is s traightforward and unambiguous. It thereby permits one to attain the natura l linewidth in the indirectly detected dimension. In the case of HSQC spect ra it reaches the resolution available in proton decoupled one-dimensional spectra. A program for processing folded two-dimensional spectra is availab le. It was applied to the H-1-C-13 HSQC of cholesterol. Copyright (C) 2000 John Wiley & Sons, Ltd.