Local and global anisotropy - recent re-implementation of 2D ILT diffusion methods

Multidimensional Inverse Laplace Transform (ILT) NMR methods have established themselves over the last two decades in material science, engineering, medical research and industry. Here we report on two variants of the two-dimensional (2D) Diffusion-Diffusion Correlation Spectroscopy (DDCOSY) which allows for the correlation of molecular displacements in different directions, thus sampling local mobility and confinement. The first variant aims to measure Fractional Anisotropy (FA) averaged over the whole sample which can be extracted from the DDCOSY results using a particular gradient orientation scheme. We demonstrate that this method returns averaged FA values which are consistent with DTI measurements. The second variant concerns a shortened version of the DDCOSY (sDDCOSY) experiment for which gradients in the two different directions are applied at the same time. This shortened DDCOSY version may proof indispensable for samples with short T2 relaxation times.