Analysis of biological NMR relaxation data with continuous distributions of relaxation times

Abstract

NMR relaxation time measurements of protons in biological samples have historically been analyzed in terms of one- and two-component exponential models. Single-component analyses often give inadequate fits to biological data. Two components usually give statistically satisfactory fits but the relaxation time and size of the two compartments derived from the fit are excessively sensitive to noise and the range and baseline of the experimental data. This paper presents a method of analyzing relaxation decay curves in terms of continuous distributions of relaxation times. Rather than depending on a priori assumptions, the experimental data determine the number and character of the components. The method has been well validated using simulated data and experimental data from aqueous solutions. When applied to biological relaxation data, the continuum analysis gives broad distributions of relaxation times with structure that has never been described before.