Selective proton labelling of amino acids in deuterated bovine calbindin D9K. A way to simplify 1H-NMR spectra

A technique for proton labelling of selected amino acids in deuterated calbindin D9K, heterologously expressed in E. coli, was developed in order to simplify and obtain higher resolution in 1H-NMR spectra. The spectra from two double-labelling experiments, Val plus Ser and Val plus Leu, when compared to the uniformly protonated protein showed a dramatically simpler pattern with low background signals and gave considerably sharper resonances due to reduced relaxation rates in the deuterated proteins. The selective proton labelling technique will enable detailed and rapid analysis of interesting domains of proteins and will also make the analysis of larger proteins feasible.