Magic angle spinning and static oriented sample NMR studies of the relaxation in the rotating frame of membrane peptides -: art. no. 194908

To demonstrate the influence of motions with medium-to-slow correlation times (milliseconds to nanoseconds), a systematic study of the spin-lattice relaxation in the rotating frame was conducted for several nuclei (H-1, C-13, and N-15) in small membrane polypeptides, either in oriented or magic angle spinning samples. This study not only assesses the validity of some motional models, but also characterizes the magnetization relaxation rates crucial for the design of polarization transfer experiments. It was found that relaxation time constant (T-1 rho) values on the order of 10(-3)-10(-2) s for backbone nuclei and their dependence on sample orientation are consistent with the model of transmembrane polypeptides undergoing axial diffusion (tau(c) similar to 10(-8)-10(-7) s) and small amplitude off-axis reorientation (tau(c) similar to 10(-6)-10(-5) s). (c) 2005 American Institute of Physics.