CRAFT (complete reduction to amplitude frequency table) – robust and time‐efficient Bayesian approach for quantitative mixture analysis by NMR

Abstract

The intrinsic quantitative nature of NMR is increasingly exploited in areas ranging from complex mixture analysis (as in metabolomics and reaction monitoring) to quality assurance/control. Complex NMR spectra are more common than not, and therefore, extraction of quantitative information generally involves significant prior knowledge and/or operator interaction to characterize resonances of interest. Moreover, in most NMR-based metabolomic experiments, the signals from metabolites are normally present as a mixture of overlapping resonances, making quantification difficult. Time-domain Bayesian approaches have been reported to be better than conventional frequency-domain analysis at identifying subtle changes in signal amplitude. We discuss an approach that exploits Bayesian analysis to achieve a complete reduction to amplitude frequency table (CRAFT) in an automated and time-efficient fashion - thus converting the time-domain FID to a frequency-amplitude table. CRAFT uses a two-step approach to FID analysis. First, the FID is digitally filtered and downsampled to several sub FIDs, and secondly, these sub FIDs are then modeled as sums of decaying sinusoids using the Bayesian approach. CRAFT tables can be used for further data mining of quantitative information using fingerprint chemical shifts of compounds of interest and/or statistical analysis of modulation of chemical quantity in a biological study (metabolomics) or process study (reaction monitoring) or quality assurance/control. The basic principles behind this approach as well as results to evaluate the effectiveness of this approach in mixture analysis are presented.

A subband Steiglitz‐McBride algorithm for automatic analysis of FID data

“…Finally, performance of the proposed algorithm is compared with CRAFT, a Bayesian algorithm for quantitative NMR mixture analysis . The CRAFT analysis for 28 regions of interest of 1 H NMR spectrum of a representative fermentation broth in 90 % H 2 O took approximately 3.5 min.…”

“…Parametric time‐domain methods, due to their superior resolution, have been shown to surpass their nonparametric counterparts . Several parametric estimators for multiple‐damped exponentials—such as filter diagonalization method, Hankel singular value decomposition, Hankel total least squares, complete reduction to amplitude frequency table (CRAFT), and matrix pencil—have been shown to accurately quantitate and extract the parameters of the FID signal . However, many of these methods (though not CRAFT) require the number of cisoids in the signal model to be known a priori, and this can introduce a systematic bias into their estimates.…”

Sparse multidimensional iterative lineshape-enhanced (SMILE) reconstruction of both non-uniformly sampled and conventional NMR data

“…Furthermore, this can be achieved using just the three most intense points of the observed line shapes in each dimension. Note that even though SMILE makes use of a very basic peak picking algorithm during its iterative signal reconstruction procedure, it is distinctly different from sophisticated peak analysis programs such as CRAFT, which relies on a Bayesian engine to analyze one-dimensional line shapes in an optimal manner (Krishnamurthy 2013). …”

Mate as Dietary Supplement for Broiler Chickens: Effect on the Metabolic Profile and Redox Chemistry of Meat

“…CRAFT corresponds to a Bayesian approach for NMR spectral analysis provided as a toolbox included in the packages of the VnmrJ 4.0 software (Agilent Technologies). 26 Multivariate data analyses were performed on Weka software 27,28 using the information gain (IG) method 29 on the data taken from the table of frequency, amplitude and linewidth as extracted from CRAFT software. The IG method provided a ranking of peaks in the NMR spectra that are of importance to discriminate the samples (FIDs), allowing the selection of the most suitable variables.…”