An analysis of NMR sensitivity enhancements obtained using non-uniform weighted sampling, and the application to protein NMR
June 2012
Publication year: 2012
Source:Journal of Magnetic Resonance, Volume 219
Non-uniform weighted sampling (NUWS) is a sampling strategy, related to non-uniform sampling (NUS) in the limit of long acquisition times, in which each indirect increment of a multidimensional spectrum is sampled multiple times according to some weighting function. As the spectrum is fully sampled it can be processed in a conventional manner by the discrete Fourier transform, making the analysis of sensitivity much more straightforward than for NUS data. Previously, 2–3 fold increases in signal-to-noise ratio (SNR) have been reported using NUWS. However, as the sampling schedule acts as a window function, the observed SNR must be compared with uniformly sampled data apodized using the same weighting function. On doing this, we calculate more modest improvements of 10–20% in SNR, and these are verified experimentally for spectra of ?-synuclein and YFP. Nevertheless, we prove that NUWS always improves the sensitivity compared with identically processed uniformly sampled data, and when combined with rapid recycling experiments such as the SOFAST–HMQC, NUWS methods have the potential to make a useful and practical contribution to sensitivity-limited measurements.
Graphical abstract
Highlights
? Sensitivity of non-uniform weighted sampling compared with uniform sampling. ? Theoretical expressions derived for NMR sensitivity with variable number of scans. ? ‘Real-world’ improvements in sensitivity calculated and verified experimentally. ? Easily applicable to sensitivity-limited samples.
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