Low-field and variable-field NMR relaxation studies of H2O and D2O molecular dynamics in articular cartilage

Abstract

Osteoarthritis (OA) as the main degenerative disease of articular cartilage in joints is accompanied by structural and compositional changes in the tissue. Degeneration is a consequence of a reduction of the amount of macromolecules, the so-called proteoglycans, and of a corresponding increase in water content, both leading to structural weakening of cartilage. NMR investigations of cartilage generally address only the relaxation properties of water. In this study, two-dimensional (T1-T2) measurements of bovine articular cartilage samples were carried out for different stages of hydration, complemented by molecular exchange with D2O and treatment by trypsin which simulates degeneration by OA. Two signal components were identified in all measurements, characterized by very different T2 which suggests liquid-like and solid-like dynamics. These measurements allow the quantification of separate hydrogen components and their assignment to defined physical pools which had been discussed repeatedly in the literature, i.e. bulk-like water and a combination of protein hydrogens and strongly bound water. The first determination of 2H relaxation dispersion in comparison to 1H dispersion suggests intramolecular interactions as the dominating source for the pronounced magnetic field dependence of the longitudinal relaxation time T1.

Modeling Molecular Interactions with Wetting and Non-Wetting Rock Surfaces by Combining Electron Paramagnetic Resonance and NMR Relaxometry

“…In general, small and highly polar molecules meet the requirements for strong adsorption, and relaxation governed by RMTD has first been shown for water and D 2 O; the agreement of the T 1 (ω) dispersion of both 1 H and 2 H nuclei in these molecules can be seen as proof of the dominating intramolecular nature of the relaxation process . Alkanes in porous glass or aluminum oxide, on the other hand, come close to the weak interaction limiting case and have shown very low T 1 (ω) dispersion. ,− It is quite remarkable that in the opposite case of an inorganic surface covered with organic cokeactually, the by-product of a naphtha refining process inside a catalyst and therefore not unlike the bitumen layer deposited on the rock surface in this studythe affinity of alkanes to this coke layer generated very similar T 1 (ω) dispersion as soon as a fraction of the native Al 2 O 3 surface was covered with the organic substance but a flat dispersion with the native surface . In that study, the dispersion of water 1 H nuclei was found to maintain a very pronounced relaxation dispersion irrespective of the coke content, but the surface fractal dimension obtained from the RMTD model changed in full agreement with the surface roughness obtained by independent methods.…”

UTE-T2* versus conventional T2* mapping to assess posterior cruciate ligament ultrastructure and integrity—an in-situ study

“…Conventional T2* mapping has been suggested as an alternative measure of ligament integrity because it may better capture the highly organized collagen structure and low water content (19). By accounting for B 0 inhomogeneity due to paramagnetic and diamagnetic effects, T2* is theorized to reflect the degree of collagen fibre orientation and alignment as well as the spin-to-spin interactions of protons bound to collagen (20,21). Consequently, T2* is widely considered a surrogate marker of ligament integrity and water content, collagen matrix organization, fibre orientation, and fibre alignment (19,20,(22)(23)(24).…”