Advances towards resonance assignments for uniformly -: 13C, 15N enriched bacteriorhodopsin at 18.8 T in purple membranes

Solid state NMR spectra from uniformly C-13, N-15 enriched bacteriorhodospin (bR) purified from H. salinarium were acquired at 18.8 T using magic angle spinning methods. Isolated resonances of 2D C-13-C-13 spectra exhibited 0.50-0.55 ppm line-widths. Several amino acid types could be assigned, and at least 12 out of 15 Ile peaks could be resolved clearly and identified based on their characteristic chemical shifts and connectivities. This study confirms that high resolution solid state NMR spectra can be obtained for a 248 amino acid uniformly labeled membrane protein in its native membrane environment and indicates that site-specific assignments are likely to be feasible with heteronuclear multidimensional spectra.