A METHOD FOR THE ESTIMATION OF CHI-1 TORSION ANGLES IN PROTEINS

A method for estimating alphaCH-betaCH coupling constants from the sha pe and fine structure of NH-alphaCH fingerprint-region cross peaks of COSY spectra is presented. Spectral simulations have been used to anal yse the effect of variations in 3J(NH-alphaCH), 3J(alphaCH-betaCH), li newidths and digital resolution on the appearance of NH-alphaCH COSY c ross peaks. On the basis of these simulations a set of rules for broad ly categorising experimental NH-alphaCH cross peaks according to alpha CH-betaCH coupling constants has been devised. The method has been app lied to the analysis of NH-alphaCH cross peaks of hen lysozyme. The re sults are compared to previous measurements of alphaCH-betaCH coupling constants using E.COSY techniques.