Optimising selective deuteration of proteins for 2D ¹H NMR detection and assignment studies Application to the Phe residues of <i>Lactobacillus casei</i> dihydrofolate reductase

Abstract

A selectively deuterated dihydrofolate reductase from L. casei has been prepared containing partially deuterated aromatic amino acids. This provides simplified 2D NMR spectra and allows signals from all 8 Phe residues to be identified. The pattern of deuteration is such that (i) the only cross‐peaks detected in the aromatic region of the 2D COSY spectrum are those between the Phe 2′,6′ and 3′,5′ protons and (ii) chemical shift degeneracy in the aromatic region is removed thus allowing unambiguous assignment of cross‐peaks in 2D NOESY spectra required for specific assignment purposes.