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Diffusion-Based Biomolecular Sensing Using Low-Field NMR
Gray, John S
Gray, John S
Abstract
Identification of molecules in complex mixtures is a fundamental problem in analytical chemistry. NMR is widely used for molecular identification in impure samples, but traditionally is an expensive technique that requires a large-scale laboratory setting and extensive training to operate. New relaxometric techniques have been developed for low-cost NMR apparatuses with strong field inhomogeneities, where change in relaxation time T2 of water surrounding the aggregation of paramagnetic nanoparticles around a given analyte is measured. These devices’ strong magnetic field gradients make them suitable for simultaneous measurement of the self-diffusion constant D. In this study, the advantages of a two-dimensional T2-D approach to molecular identification of a protein-specific ligand analyte in complex with its target protein are assessed as a “proof of principle” experiment. Since complexation reduces molecular motion, we expect both T2 and D will decrease, indicating the presence of the ligand by the shape and size of the sensor as a unit rather than its chemical makeup. Per the complex nature of our selected protein-ligand binding interactions (those of bovine serum albumin and naproxen), the detection of a number of unexpected phenomena, including naproxen self-association, non-specific binding interactions, and possibly rapid chemical exchange are reported. A potential method by which low-field, single-sided NMR devices may be used to determine thermodynamic constants is also demonstrated.
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2015-05-01
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Chemistry