In isotopically labeled macromols., it is possible to excite the signal of a selected proton by shuttling magnetization back and forth between the chosen proton and a heteronucleus such as 13C or 15N, using two-way doubly selective heteronuclear cross-polarization. Selective excitation of a chosen proton can be followed by homonuclear coherence transfer to identify side-chain resonances of the corresponding amino acid in proteins. The resulting one-dimensional expts. yield information that can usually only be obtained from three-dimensional HSQC-TOCSY spectra. The method also provides efficient suppression of solvent signals without affecting resonances close to the solvent peak. (c) 1999 Academic Press. [on SciFinder (R)]