Molecular dynamics monitored by crosshyphen;correlated cross relaxation of spins quantized along orthogonal axes

摘要

A new approach is proposed for the analysis of molecular dynamics on a wide range of time scales by the measurement of specific crosshyphen;correlated nuclear magnetic resonance crosshyphen;relaxation pathways of spins quantized along orthogonal spinhyphen;lock axes. Crosshyphen;correlated time modulation of (i) chemical shifts andJcouplings, and of (ii) dipolar coupling and chemical shielding anisotropy, respectively, are determined using a sensitive technique, calledorthohyphen;ROESY(orthogonal rotating frames Overhauser effect spectroscopy). The two processes (i) and (ii) can be separated experimentally by their distinct dependence on the spinhyphen;lock radio frequency amplitude. The relaxation rate constant depends on the power spectral density sampled at a frequency close to zero. This renders the experiment attractive for investigations of slowly tumbling (bio)molecules.