Determining the internal orientation, degree of ordering, and volume of elongated nanocavities by NMR: Application to studies of plant stem

Abstract

This study investigates the fibril nanostructure of fresh celery samples by modeling the anisotropic behavior of the transverse relaxation time (T₂) in nuclear magnetic resonance (NMR). Experimental results are interpreted within the framework of a previously developed theory, which was successfully used to model the nanostructures of several biological tissues as a set of water filled nanocavities, hence explaining the anisotropy the T₂ relaxation time in vivo. An important feature of this theory is to determine the degree of orientational ordering of the nanocavities, their characteristic volume, and their average direction with respect to the macroscopic sample. Results exhibit good agreement between theory and experimental data, which are, moreover, supported by optical microscopic resolution. The quantitative NMR approach presented herein can be potentially used to determine the internal ordering of biological tissues noninvasively.

Keywords: Dipole–dipole interactions; NMR; Nanocavity; Nanostructure; Ordering degree; Quantitative MRI; Relaxation anisotropy; T(2); Transverse relaxation time.