Intraresidual HNCA: An experiment for correlating only intraresidual backbone resonances

摘要

Resonance overlap in C-13(alpha)-dimension can seriously deteriorate sequential assignment of proteins, especially in the case of highly alpha helical or partially unfolded structures. In this paper, two novel triple-resonance experiments, for obtaining solely intraresidual H-N, N, C-alpha correlations, are introduced. The proposed experiments are complementary to the conventional HN(CO)CA experiment, and can be utilized for the sequential assignment of N-15/C-13/(H-2)-labeled proteins. Coherence transfer efficiency of the new experiment is comparable to the conventional HNCA experiment on proteins with sufficiently long N-15 transverse relaxation time. These new coherence transfer schemes are also very useful building blocks for experiments gathering structural information, such as J-couplings, exclusively on the intraresidual alpha carbon. Experimental assessment is demonstrated on ubiquitin at 600 H-1 MHz. [References: 32]