J-modulated 1D directed COSY for precise measurement of proton-proton residual dipolar coupling constants of oligosaccharides

A simple selective 1D experiment for the accurate and precise determination of residual proton–proton dipolar coupling constants of oligosaccharides is proposed. The technique is based on the concept of J-modulated spectroscopy and provides coupling constants by fitting the peak intensities from a series of spectra to known transfer functions with a precision of ±0.02 Hz for splittings >0.3 Hz. This level of precision is possible owing to limiting the number of sites for polarization transfer. Selective pulses and pulsed field gradients are used for selective excitation and coherence selection, yielding clean, artefact-free spectra. The technique is illustrated using trisaccharide samples in Pf1 phage. Copyright © 2002 John Wiley & Sons, Ltd.