Multivariate Curve Resolution for 2D Solid-State NMR spectra

Abstract

We present a processing method, based on the multivariate curve resolution approach (MCR), to denoise 2D solid-state NMR spectra, yielding a substantial S/N ratio increase while preserving the lineshapes and relative signal intensities. These spectral features are particularly important in the quantification of silicon species, where sensitivity is limited by the low natural abundance of the 29 Si nuclei and by the dilution of the intrinsic protons of silica, but can be of interest also when dealing with other intermediate-to-low receptivity nuclei. This method also offers the possibility of coprocessing multiple 2D spectra that have the signals at the same frequencies but with different intensities (e.g.: as a result of a variation in the mixing time). The processing can be carried out on the time-domain data, thus preserving the possibility of applying further processing to the data. As a demonstration, we have applied Cadzow denoising on the MCR-processed FIDs, achieving a further increase in the S/N ratio and more effective denoising also on the transients at longer indirect evolution times. We have applied the combined denoising on a set of experimental data from a lysozyme–silica composite.

In-Cell Structural Biology by NMR: The Benefits of the Atomic Scale

“…One-dimensional spectra can yield equivalent information using amino acid-type specific 15 N-labeling at about twice lower concentrations. A number of strategies shall be combined to improve sensitivity: better isotope-labeling schemes, notably when introducing deuteration, better pulse sequences adapted to the cellular viscosity, paramagnetic T1 relaxation enhancement, − continuous readout using time-resolved nonuniform sampling, ,− deep-learning assisted spectral reconstruction, − denoising procedures, ,− deep-learning assisted peak picking, etc. Using all these advanced techniques, it might be possible to record exploitable in-cell 2D NMR spectra of proteins/nucleic acids at intracellular concentrations of a few μmol/L.…”

Study and application of graphene oxide in the synthesis of 2,3-disubstituted quinolinesviaa Povarov multicomponent reaction and subsequent oxidation

“…The {1H}- 13 C HETCOR spectra were coprocessed for denoising as recently proposed by some of us, 88 and processed applying a square-sine window function on both time dimensions. The presence of paramagnetic impurities originating from Mn ions is particularly critical for the spectrum acquisition of pristine GO produced by Graphenea as they present a relatively high Mn residual, in accordance with the results published by Panich.…”

Real-Time Quantitative In-Cell NMR: Ligand Binding and Protein Oxidation Monitored in Human Cells Using Multivariate Curve Resolution

“… 23 − 26 Recently, MCR-ALS has been applied to deconvolute NMR spectra of complex metabolic mixtures 27 and to improve the S/N of 2D Solid-State NMR spectra. 28 To evaluate the applicability of MCR-ALS to real-time in-cell NMR data, the improved bioreactor setup was employed to monitor conformational and chemical modifications of proteins directly in human cells, in response to cell treatment with exogenous molecules.…”

“…Quantification of the relative concentrations of protein species was performed using the Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) algorithm . MCR-ALS is a mathematical approach that has been applied to various analytical and spectroscopic techniques to recover pure response profiles of different chemical species contained in the sample (here, the NMR spectra and the relative concentration profiles of each state of the protein) with minimal prior information on the composition and the spectral features of the analyzed mixture (here, the cell sample). − Recently, MCR-ALS has been applied to deconvolute NMR spectra of complex metabolic mixtures and to improve the S/N of 2D Solid-State NMR spectra . To evaluate the applicability of MCR-ALS to real-time in-cell NMR data, the improved bioreactor setup was employed to monitor conformational and chemical modifications of proteins directly in human cells, in response to cell treatment with exogenous molecules.…”