The assignment of magic-angle-spinning NMR spectra of large membrane proteins such as the 281-residue outer membrane protein G (OmpG) is difficult because of substantial signal overlap and line-broadening effects. To obtain sequence specific assignments, a new labeling strategy was applied to OmpG in which alanine and glycine were uniformly [
15N,
13C]-labeled and phenylalanine and tyrosine were [
15N, C
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,C
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-
13C]-labeled. This labeling pattern resulted in many long-range inter-residue cross-peaks being observed in spectra recorded with long mixing times. In addition, a reduction in the number of C' labels resulted in NCO-type spectra with little overlap and provided the basis for unambiguous sequential assignments. In conjunction with spectra from [1,3-
13C]- and [2-
13C]-glycerol samples, a total of 45 reliable sequence specific assignments could be made for OmpG on the basis of this sample.