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.