MUSIC in triple-resonance experiments: Amino acid type-selective H-1-N-15 correlations

Amino acid type-selective triple-resonance experiments can be of great help for the assignment of protein spectra, since they help to remove ambiguiti es in either manual or automated assignment procedures. Here, modified trip le-resonance experiments that yield amino acid type-selective H-1-N-15 corr elations are presented. They are based on novel coherence transfer schemes, the MUSIC pulse sequence elements, that replace the initial INEPT transfer and are selective for XH2 or XH3 (X can be N-15 or C-13). The desired amin o acid type is thereby selected based on the topology of the side chain. Ex periments for Gly (G-HSQC); Ala (A-HSQC); Thr, Val, Ile, and Ala (TAVI-HSQC ); Thr and Ala (TA-HSQC), as well as Asn and Gin (N-HSQC and QN-HSQC), are described, The new experiments are recorded as two-dimensional experiments and therefore need only small amounts of spectrometer time. The performance of the experiments is demonstrated with the application to two protein dom ains, (C) 1999 Academic Press.