Sensitivity gains, linearity, and spectral reproducibility in nonuniformly sampled multidimensional MAS NMR spectra of high dynamic range

Abstract

Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear 13C–13C correlation spectra. We demonstrate on model compounds and on 1–73-(U-13C, 15N)/74–108-(U-15N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7–2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear 13C–13C MAS correlation experiments that yield high-quality artifact-free datasets.

Magic angle spinning NMR of viruses

“…However, in the case of sensitivity-limited MAS NMR experiments on complex biological systems, NUS can be exploited to attain bona fide sensitivity gains in the time domain, provided appropriate sampling schedules, as was derived analytically by Rovnyak [131]. More recently, Rovnyak and colleagues demonstrated experimentally and analytically that 2-fold sensitivity enhancements can be achieved in each indirect dimension using random, exponentially-weighted nonuniform sampling schedules [131, 132]. Processing NUS data requires specialized, typically nonlinear, reconstruction algorithms.…”

“…To date, in addition to the authors’ work on thioredoxin and LC8, [132, 136, 151], NUS and variations of the technique have been applied to several other biological systems in the context of MAS NMR, including GB1 [145, 152] ubiquitin [118], SH3 [44], Aβ fibril [153], proteorhodopsin [152], a truncated MerF construct [154], and magnetically-aligned, phospholipid-embedded Pf1 [144, 154]. It is anticipated that the application of nonuniform sampling to complex viral systems will be a widely used approach for gaining sensitivity or reducing the experiment time in multidimensional MAS NMR experiments.…”

Towards automatic protein backbone assignment using proton-detected 4D solid-state NMR data

“…NUS schemes have been widely applied in solution NMR studies (Coggins et al 2010;Hyberts et al 2012;Orekhov et al 2003). More recently, the usefulness of NUS in ssNMR has also been explored and validated (Huber et al 2011;Jones and Opella 2006;Lin and Opella 2013;Linser 2014;Suiter et al 2014;Sun et al 2012;Trent Franks et al 2010).…”

Fast magic angle spinning NMR with heteronucleus detection for resonance assignments and structural characterization of fully protonated proteins

“…200 ppm, and covering the entire chemical shift range with adequate digital resolution is time consuming if 13 C is sampled in an indirect dimension when full spectral widths need to be covered. The use of nonuniform sampling may alleviate this challenge to some extent; however, in the case of 13 C experiments, the number of points that need to be sampled to retain the intensity information is still rather large (Suiter et al 2014). Therefore, 13 C detected experiments may be preferred for the acquisition of high-resolution spectra in the above situations.…”