Determination of Na⁺ binding parameters by relaxation analysis of selected ²³Na NMR coherences: RNA, BSA and SDS

Abstract

Nuclear magnetic resonance provides several unique means of investigating the interactions between different inorganic ions and various macromolecules.23 Na is a quadrupolar nucleus, meaning that relaxation analysis of the various coherences allows the measurement of its binding to biological macromolecules. In this study, we analyzed the quadrupolar relaxation of 23 Na + longitudinal magnetization and single-and triple-quantum coherences in aqueous systems containing RNA, bovine serum albumin and sodium dodecyl sulfate micelles. The effectiveness of the James-Noggle method for determining binding constants was evaluated in these systems, and also the applicability of various 23 Na coherences in providing information on the extent and affinity of binding to the three different classes of biomolecules.

NMR Relaxation of Nuclei of Buffer as a Probe for Monitoring Protein Solutions Including Aggregation Processes

“…For the 0.6 mM concentration of RRM2, the R 2 rates for 23 Na and 35 Cl increase by 12% and 60%, respectively. Such a strong protein effect on the relaxation of ions nuclei was observed earlier [26,27,30,48]. It could be seen that in the buffer R 1 = R 2 for both ions but at higher protein concentrations, the difference between R 1 and R 2 increases.…”

“…This promising observation may be used to detect the aggregation of proteins. Torres et al have shown the applicability of this model for RNA, (1) 1∕T 1 = P free ∕T 1,free + P bound ∕ T 1,bound + bound , BSA, and sodium dodecyl sulfate (SDS) micelles that justify it as universal for biomolecules [27]. Similar studies were performed using 14 N, 35 Cl, and 37 Cl nuclei [28][29][30][31][32].…”

Magnetic Resonance Imaging on Sodium Nuclei: Potential Medical Applications of 23Na MRI

“…The studies were carried out at 3 and 7 T fields to obtain 1 H and 23 Na MR images, respectively. 23 Na MRI was performed using the 23 Na/ 1 H transceiver RF head coil and two pulse schemes -single-quantum (SQ) and triple-quantum filtering (TQF) [31][32][33][34][35][36][37][38][39][40][41][42][43][44]. To collect data in the case of SQ 23 Na MRI, the 3D GRE pulse sequence [45]…”

Applications of heteronuclear NMR spectroscopy in biological and medicinal inorganic chemistry

“…These methods yield estimates of the relaxation rate constants, the fraction of bound ions, the binding constants, the rotational correlation time (τ c ), and the quadrupolar coupling constant of the nucleus in its bound state. For example, Torres et al have determined the apparent binding constants (K f ) for Na + and a protein, bovine serum albumin (BSA), a nucleic acid yeast RNA, and a self-associating macroassembly, the detergent sodium dodecyl sulfate (SDS) using the relaxation behavior of selected 23 Na + magnetization coherences [34]. These three macromolecular systems were chosen as representatives of different classes of biomolecules that are likely to have diverse Na + -binding environments.…”