On the Potential of Hyperpolarized Water in Biomolecular NMR Studies

Abstract

A main obstacle arising when using ex situ hyperpolarization to increase the sensitivity of biomolecular NMR is the fast relaxation that macromolecular spins undergo upon being transferred from the polarizer to the spectrometer, where their observation takes place. To cope with this limitation, the present study explores the use of hyperpolarized water as a means to enhance the sensitivity of nuclei in biomolecules. Methods to achieve proton polarizations in excess of 5% in water transferred into the NMR spectrometer were devised, as were methods enabling this polarization to last for up to 30 s. Upon dissolving amino acids and polypeptides sited at the spectrometer into such hyperpolarized water, a substantial enhancement of certain biomolecular amide and amine proton resonances was observed. This exchange-driven (1)H enhancement was further passed on to side-chain and to backbone nitrogens, owing to spontaneous one-bond Overhauser processes. (15)N signal enhancements >500 over 11.7 T thermal counterparts could thus be imparted in a kinetic process that enabled multiscan signal averaging. Besides potential bioanalytical uses, this approach opens interesting possibilities in the monitoring of dynamic biomolecular processes, including solvent accessibility and exchange process.

Renal MR angiography and perfusion in the pig using hyperpolarized water

“…However, the maximum achievable magnetization is limited. with a polarization of 3-5% have been applied to biomolecular NMR studies (24) or MR angiographies in the rat (25). Correcting for the difference in proton concentration, this corresponds to an available signal of two orders of magnitude larger than the Overhauser experiments.…”

Hyperpolarized Water to Study Protein–Ligand Interactions

“…The transfer can either occur directly from the solvent to the ligand or be relayed indirectly via the bound protein. 18 but this could also be achieved by Overhauser liquid-state DNP. 19−22 The hyperpolarization of water is highly reproducible and robust.…”

Rapid-melt Dynamic Nuclear Polarization

“…Other applications include biomolecular NMR [63,64], biological assays [65,66], detection of reaction intermediates having low concentrations [67], protein folding [68], and drug screening [69]. The use of dissolution DNP in a clinical environment is under development [70].…”

“…Other uses of dissolution DNP include biomolecular NMR [63,64], the study of biological assays [65,66] and the detection of low concentration reaction intermediates [67]. Only a few analytical application have been demonstrated [120].…”

“…Details of these methods can be found elsewhere [91,92]. Dissolution DNP is used for metabolic imaging, biomolecular NMR [63,64] and biological assays [65,66] while MAS-DNP has found its applications in surface chemistry, protein structure determination and polymer studies [41,40]. Dissolution DNP is limited to slow relaxing nuclei and only a few number of scans are possible within the T 1 of the nuclei of interest [70].…”