Quantify sodium transmembrane transport in cells via relaxation exchange spectroscopy

Motivation: Transmembrane transport of sodium ions is directly related to the cell functions and metabolisms and could be an indicator of various diseases such as neurodevelopmental disorders, neuropathic pain, etc. There is a lack of non-invasive and clinically-adaptable techniques for quantifying the rate of transmembrane transport of sodium ions. Goal(s): Determine the rate of sodium transmembrane transport using noninvasive nuclear magnetic resonance methods. Approach: 23Na relaxation exchange spectroscopy (REXSY) was applied to the cellular systems for quantitative analysis. Results: The 23Na REXSY method successfully determined the sub-second transmembrane exchange rate of sodium ions in yeast and HeLa cells. Impact: Measuring transmembrane rate of sodium via NMR can assist the pathological studies of diseases related to malfunctions of sodium ion channels and/or sodium metabolism. 23Na REXSY could be coupled to MR imaging to offer novel parameters for clinical diagnosis.