A nuclear magnetic resonance study of water in aggrecan solutions

Abstract

Aggrecan, a highly charged macromolecule found in articular cartilage, was investigated in aqueous salt solutions with proton nuclear magnetic resonance. The longitudinal and transverse relaxation rates were determined at two different field strengths, 9.4 T and 0.5 T, for a range of temperatures and aggrecan concentrations. The diffusion coefficients of the water molecules were also measured as a function of temperature and aggrecan concentration, using a pulsed field gradient technique at 9.4 T. Assuming an Arrhenius relationship, the activation energies for the various relaxation processes and the translational motion of the water molecules were determined from temperature dependencies as a function of aggrecan concentration in the range 0–5.3% w/w. The longitudinal relaxation rate and inverse diffusion coefficient were approximately equally dependent on concentration and only increased by upto 20% from that of the salt solution. The transverse relaxation rate at high field demonstrated greatest concentration dependence, changing by an order of magnitude across the concentration range examined. We attribute this primarily to chemical exchange. Activation energies appeared to be approximately independent of aggrecan concentration, except for that of the low-field transverse relaxation rate, which decreased with concentration.

Effect of long‐term heat exposure on rheological and intrinsic water characteristics of bone‐derived beef stocks

“…A vast amount of relaxation studies elucidating temperature effects have attempted to interpret or fit T 2 relaxation rates to Arrhenius equation. [28][29][30] We found the T 2 relaxation time increased with increasing temperature, which is agreement with the Arrhenius equation. Intriguingly, the present study also demonstrated that the heat-induced variations in the concentrated beef stocks' attributes became more evident at higher measurement temperature, as the relaxation times generally were dispersed over a larger span with increasing temperature.…”

“…In the present study, T 2 relaxation measurements were conducted at three different measurement temperature; 5°C, 22°C, and 50°C. A vast amount of relaxation studies elucidating temperature effects have attempted to interpret or fit T 2 relaxation rates to Arrhenius equation . We found the T 2 relaxation time increased with increasing temperature, which is agreement with the Arrhenius equation.…”

NMR techniques in studying water in biotechnological systems

“…Many properties of biomaterials depend significantly on waterbiopolymer interactions. The interactions between water and biomolecules were investigated by NMR methods for a long period of time (Kuntz et al 1969;Wüthrich et al 1996;Krishman 1996;Wider 1998;Szuminska et al 2001;Van-Quynh et al 2003;Cosgrove et al 2007;Rodin et al 2014Rodin et al , 2017Belton 2011;Foster et al 2016;Mandala et al 2018;Yazawa et al 2016;Zubow et al 2016;Kerch 2018;Callaghan and Lelievre 1986). The data obtained discovered hydration features and resulted in the development of the hydration models (Kuntz et al 1969;Kuntz and Kauzmann 1974;Mathur-De Vre 1979;Wüthrich et al 1996;Otting 1997;Halle 2004;Cosgrove et al 2007;Belton 2011;Xie et al 2019).…”

“…Nowadays, NMR gives various tools for successful studying of different molecules and macromolecules of biotechnological systems. Using some nuclei-isotopes as the labels in proteins, it is possible to carry out effective multidimensional experiments to detail the protein structure and interactions (Foster et al 2007;Martini et al 2013;Foster et al 2016;Mandala et al 2018). The proton and deuterium relaxations are used to study the hydration exchange and dynamics of globular proteins resulting in information about the internal motion of proton groups in protein chains (Denisov and Halle 1995;Krishman 1996;Otting 1997;Ishima and Torchia 2000;Mittermaier and Kay 2006;Foster et al 2007;Zhang et al 2015;Rodin 2017;Mandala et al 2018).…”

“…This work considers NMR approaches and basic techniques which were used quite frequently in studying watermacromolecule interactions, discovering the details of hydration and macromolecule dynamics with the factors responsible for biological functions in complex biomaterials (Rodin 1997;Mittermaier et al 2006;Belton 2011;Foster et al 2016;Rodin 2018c;Tarannum et al 2018). The review highlights those tools that enable the studies of functional properties of materials in drug delivery (Rodin and Izmailova 1995;Huang and Melacini 2006;Baldwin and Kay 2009;Zhang et al 2013Zhang et al , 2015Bernini et al 2011).…”