Use of optimized 1D TOCSY NMR for improved quantitation and metabolomic analysis of biofluids.

One dimensional selective TOCSY experiments have been shown to be advantageous in providing improved data inputs for principle component analysis (PCA) (Sandusky and Raftery 2005a, b). Better subpopulation cluster resolution in the observed scores plots results from the ability to isolate metabolite signals of interest via the TOCSY based filtering approach. This report reexamines the quantitative aspects of this approach, first by optimizing the 1D TOCSY experiment as it relates to the measurement of biofluid constituent concentrations, and second by comparing the integration of 1D TOCSY read peaks to the bucket integration of 1D proton NMR spectra in terms of precision and accuracy.

Biotransformations of (+/-)-geosmin by terpene-degrading bacteria.

Two terpene-degrading bacteria able to transform (+/-)-geosmin have been identified. Pseudomonas sp. SBR3-tpnb, following growth on gamma-terpinene, converts (+/-)-geosmin to several products; the major products are ketogeosmins.

Biotransformations of 2-methylisoborneol by camphor-degrading bacteria.

Many camphor-degrading bacteria that are able to transform 2-methylisoborneol (2-MIB) have been identified. Three of these strains have been examined in detail. Rhodococcus ruber T1 metabolizes camphor through 6-hydroxycamphor but converts 2-MIB to 3-hydroxy-2-MIB.

Limitations in the deduction of carbon NMR spectra from the f1 dimension of standard 2D heteronuclear experiments when applied to natural products.

The structure elucidation of a natural product requires a set of NMR spectra that includes both carbon observe experiments, such as 1D carbon and DEPT, and proton observe experiments, such as HSQC, HMBC, and COSY. Because NMR probes are optimized for either proton or carbon observe experiments, but not both, this often results in some experiments being acquired at a very suboptimal level of efficiency. An alternative is to deduce the carbon spectrum from the indirect, or f 1, dimension of the heteronuclear 2D experiments.

NMR study of the solution structure of curcumin.

Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] is derived from the rhizomes of Curcuma longa. Although early studies concluded that curcumin exists predominantly as a keto-enol tautomer, 1b, in several recent articles the solution structure of curcumin has been represented as a beta-diketone tautomer, 1a. We have investigated the structure of curcumin in solvents ranging in polarity from CDCl3 to mixtures of DMSO-d6 in water, and in buffered aqueous DMSO-d6 solutions with pH values varying from 3 to 9.

Use of semiselective TOCSY and the pearson correlation for the metabonomic analysis of biofluid mixtures: application to urine.

The authors recently proposed an approach to the metabonomic analysis of biofluid mixtures based on the use of the selective TOCSY experiment (Sandusky, P.; Raftery, D. Anal.

Use of selective TOCSY NMR experiments for quantifying minor components in complex mixtures: application to the metabonomics of amino acids in honey.

The application of the traditional methods of multivariate statistics, such as the calculation of principle components, to the analysis of NMR spectra taken on sets of biofluid samples is one of the central approaches in the field of metabonomics. While this approach has proven to be a powerful and widely applicable technique, it has an inherent weakness, in that it tends to be dominated by those chemical species present at relatively higher concentrations. Using a set of commercial honey samples, a comparison of this classical metabonomics approach to one based on the use of the selective TOCSY experiment is presented.