13 C- and 1 H-detection under fast MAS for the study of poorly available proteins: application to sub-milligram quantities of a 7 trans-membrane protein

We demonstrate that 13 C-detected spectra recorded using fast (60 kHz) magic angle spinning on sub-milligram (<10 μmol) quantities of a protonated 7 trans-membrane helix protein (bacteriorhodopsin) in its native lipid environment are comparable in sensitivity and resolution to those recorded using 15-fold larger sample volumes with conventional solid state NMR methodology. We demonstrate the utility of proton-detected measurements which yield narrow 1 H linewidths under these conditions, and that no structural alterations are observed. We propose that these methods will prove useful to gain structural information on membrane proteins with poor availability, which can be studied in their native lipid environments.