Photo-CIDNP reveals differences in compaction of non-native states of lysozyme.

Photo-CIDNP effects interpreted for individual residues are used for the structural characterization of non-native ensembles of proteins, which is described in this paper. Two-dimensional photo-CIDNP experiments are compared to conventional HSQC spectra to elucidate the relative solvent exposure of the six tryptophan residues in non-native states of hen egg white lysozyme. The differential solvent accessibility of the tryptophan residues in non-native lysozyme coincides with the dynamical properties of these residues monitored for both backbone and side chain NH sides obtained from analysis of transverse relaxation measurements. These data can be interpreted in the context of the hydrophobic clustering around the tryptophan residues and is supported by the application of this method to the cluster breaking W62G mutant of lysozyme.