DNP Enhanced Frequency-Selective TEDOR Experiments in Bacteriorhodopsin

Abstract

We describe a new approach to multiple [superscript 13]C–[superscript 15]N distance measurements in uniformly labeled solids, frequency-selective (FS) TEDOR. The method shares features with FS-REDOR and ZF- and BASE-TEDOR, which also provide quantitative [superscript 15]N–[superscript 13]C spectral assignments and distance measurements in U-[[superscript 13]C,[superscript 15]N] samples. To demonstrate the validity of the FS-TEDOR sequence, we measured distances in [U-[superscript 13]C,15N]-asparagine which are in good agreement with other methods. In addition, we integrate high frequency dynamic nuclear polarization (DNP) into the experimental protocol and use FS-TEDOR to record a resolved correlation spectrum of the Arg-[superscript 13]Cγ–[superscript 15]Nε region in [U-[superscript 13]C,15N]-bacteriorhodopsin. We resolve six of the seven cross-peaks expected based on the primary sequence of this membrane protein.