Applications of two-dimensional 1H nuclear magnetic resonance methods in photochemically induced dynamic nuclear polarisation spectroscopy

Abstract

Photochemically induced dynamic nuclear polarisation (photo-CIDNP) has been widely used to identify surface residues in proteins and to assign resonances in their ¹H n.m.r. spectra by the spectral simplification that is obtained. Welcome as this simplification may be in many cases, it also presents a limitation to the technique. We have increased the information content of photo-CIDNP spectra using pulse sequences analogous to INEPT (CIDNPT and refocused CIDNPT). Furthermore, we present combinations of photo-CIDNP with two-dimensional (2D)J-correlated spectroscopy (CIDNP-COSY) and with 2D nuclear Overhauser effect spectroscopy (CIDNP-NOESY). In these experiments we insert a saturation pulse sequence and a short laser-irradiation period at the beginning of the preparation period to generate CIDNP, leaving the remainder of the pulse scheme essentially unaltered.

The CIDNPT technique has been applied to N-acetyl tyrosine and to N-acetyl tryptophan. The CIDNP-COSY spectrum of the lac-repressor headpiece is presented. The CIDNP-NOESY spectrum of hen egg-white lysozyme is compared with 1 D cross-polarisation spectra of the same protein.