Amino acid type-selective backbone 1H-15N-correlations for Arg and Lys

Four novel amino acid type-selective triple resonance experiments to identify the backbone amino proton and nitrogen resonances of Arg and Lys and of their sequential neighbors in (13C,15N)-labeled proteins are presented: the R(i+1)-HSQC and R(i,i+1)-HSQC select signals originating from Arg side chains, the K(i+1)-HSQC and K(i,i+1)-HSQC select signals originating from Lys side chains. The selection is based on exploiting the characteristic chemical shifts of a pair of carbon atoms in Arg and Lys side chains using selective 90 degree pulses. The new experiments are recorded as two-dimensional 1H-15N-correlations and their performance is demonstrated with the application to a protein domain of 83 amino acids.