Sub-second 2D NMR Spectroscopy at Sub-millimolar Concentrations

Abstract

A recently proposed protocol enables the acquisition of two-dimensional nuclear magnetic resonance (2D NMR) spectra within a single scan. A promising application opened up by this new data acquisition mode concerns its combination with active nuclear polarization methods, whereby spectroscopy is carried out on analytes whose spin magnetizations have been significantly enhanced over their Boltzmann thermal values. The present paper explores the potential of such combination, with the acquisition of peptide and protein 2D NMR 1H correlation spectra recorded after the samples had been subject to laser-driven chemically induced dynamic nuclear polarization (CIDNP). It is demonstrated that the speed and sensitivity enhancement afforded by these combined processes enables the acquisition of quality 2D NMR data sets within a fraction of a second, at analyte concentrations that are under 1 mM.

1H Photo-CIDNP Enhancements in Heteronuclear Correlation NMR Spectroscopy

“…The absence of t1 noise illustrates the fact that laser stability, shutter timing response and sample photodegradation are not an issue, under the data collection conditions adopted here. These results are entirely consistent with the feasibility of 2D photo-CIDNP shown by others for a variety of homonuclear 13,15,48,49 and heteronuclear 16,17 pulse sequences. While photodegradation and photobleaching set an upper limit to the number of increments that may be obtained in multidimensional photo-CIDNP, this limit can be stretched by a number of approaches, including sample spinning between increments to optimize dye mixing 15,48 and addition of hydrogen peroxide to reoxidize reduced flavin 16…”

“…Given that in the presence of an applied magnetic field the difference in the number of 1 H α and β nuclear spin states is very small at equilibrium (of the order of 1 in 10 5 ), even small variations in the reactivity of molecules carrying α and β spins may in principle lead to large signal enhancements 10. To date, however, there are only few reports testifying on the effectiveness of photo-CIDNP to enhance NMR sensitivity in the context of biomolecular systems 13.…”

Ultrafast Two‐Dimensional NMR Relaxometry for Investigating Molecular Processes in Real Time

“…This finding has been widely considered as one of the brightest recent innovations in NMR spectroscopy. [11,12] In addition, the principles of continuous spatial encoding [13] of ultrafast NMR have also been applied to magnetic resonance imaging (MRI) [7,14] and to measure so-called Z-spectra in chemical exchange saturation transfer experiments. It has been used, for example, for real-time identification of analytes undergoing chromatographic separation, [8] chemical transformations, [9] and H/D exchange processes in proteins, [10] as well as recording NMR spectra of hyperpolarized substances.…”

Communication: Ultrafast homonuclear correlation spectroscopy with diagonal suppression

“…[3][4][5][6] Frydman and co-workers proposed single scan or ultrafast (UF) nD NMR, which replaces parametric evolution time incrementation with spatial encoding and Echo Planar Imaging (EPI) type of acquisition. [7][8][9][10] Practical applications of the UF method have been demonstrated in several recent studies [11][12][13] including magnetic resonance imaging. 14 The UF implementation of 2D COSY has been employed to study dynamic processes, 15 as also for quantification of metabolites.…”