An analysis of NMR sensitivity enhancements obtained using non-uniform weighted sampling, and the application to protein NMR
Publication year: 2012
Source:Journal of Magnetic Resonance
Christopher A. Waudby, John Christodoulou
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
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.
Source:
Journal of Magnetic Resonance