PEAK ASSIGNMENT IN CROSS CORRELATION NMR RELAXOMETRY

The disclosure of a fast algorithm for bidimensional Laplace inversion [1] has paved the way for the development of new multidimensional time-domain NMR relaxometry experiments [2-4]. While it is now sufficiently easy to obtain many bi- and multidimensional “spectra” cross-correlating the relaxation and water diffusion properties of biological and model systems, interpretation of the results (such as – for example - the assignment of a pool of signals to the originating protons) remains a challenging task. In this work a number of NMR protocols have been developed for overcoming this difficulty and assigning the peaks found in 1H cross-correlation spectra of model sucrose [5] and BSA solutions to the corresponding protons pools. Identification was accomplished by resorting to T1-T2 cross-correlation plots obtained at variable CPMG pulsing rate and spectrometer frequency. Three-dimensional chemical-shift, diffusionand field-cycled-weighted T1-T2 cross correlation spectra were also explored as a further mean for peak assignment. The feasibility of the proposed protocols was also tested on inhomogenous-multicompartment systems such as BSA gels and meat samples.