Low-frequency localized spin-dynaimical coupling in proteins

摘要

We show that magnetic field dependence of the proton spin-lattice relaxation rates 1/T_1=A#omega#_0~(-b) in non-crystalline proteins may be quantitatively related to structural flucturations localized along the backbone that modulate proton-proton dipolar couplings.The parameter A is related tothe temperature,the dipolar coupling strength and the energy for the highest vibrational frequency in the polymer backbone.The parameter b is related to the fractal dimensionality of the spatial distribution of protons and to the spectral dimensionality that characterizes the anolalous diffusion.Extension of the theory is presented to treat the case of hydrated proteins.This theory is satisfactorily compared with field cycling experiments realized on lysozyme protein.