Simultaneous determination of vitamin E homologs in chicken meat by liquid chromatography with fluorescence detection.

A simple and reliable method for the simultaneous determination of all eight homologs of Vitamin E in chicken meat is described. All analytes, including the internal standard (alpha-tocopherol acetate), were eluted within 35 min and detected using their native fluorescence (295 nm excitation and 330 nm emission). Chromatography using hexane based eluent on a normal phase silica column included an initial column conditioning step to prevent irreversible adsorption of tocopherols and tocotrienols on silica. Lowest detectable levels of alpha-tocopherol, gamma-tocopherol, alpha-tocotrienol, beta-tocotrienol, gamma-tocotrienol and delta-tocotrienol were 0.73, 0.86, 1.0, 1.2, 1.7 and 1.3 ng, respectively.

Effect of dietary tocopherols and tocotrienols on the antioxidant status and lipid stability of chicken.

We determined the effect of dietary tocopherols and tocotrienols on the lipid stability of pre-cooked chicken breast and thigh. The birds were supplemented with one of two doses of a commercial mixture of tocopherols and tocotrienols (Oryza1, Oryza2) or one of two doses of all-rac α-tocopherol acetate (Toc1, Toc2). Diets were formulated so that Oryza1 and Toc1 and Oryza2 and Toc2 contained similar tocopherol concentrations. No quantifiable amounts of tocotrienols were found in either breast or thigh muscles. Tocotrienols present in the diet reduced muscle α-tocopherol concentration. The effect of Oryza1 on the tocopherol content in muscle and on its lipid stability was not significant. The Oryza2, Toc1 and Toc2 diets increased the α- and γ-tocopherol in breast and thigh muscles and enhanced their lipid stability. This improvement was only due to the antioxidant action of the tocopherols. Lipid stability of pre-cooked chicken was not enhanced by adding tocotrienols to a tocopherol supplement.

Considerations concerning interaction characterization of oligopeptide mixtures with vancomycin using affinity capillary electrophoresis-electrospray mass spectrometry.

In the past few years affinity capillary electrophoresis (ACE) has proven to be a powerful tool to study molecular interactions. In ACE the change in electrophoretic mobility between a free and a complexed ligand with a receptor dissolved in the background electrolyte is observed. It provides an accurate way to calculate binding or dissociation constants and, when coupled to mass spectrometry, it forms a promising method to analyze solution-based combinatorial libraries. We report a model study on the macrocyclic antibiotic vancomycin using a 36-component library of tetrapeptides of the type 9-fluorenylmethoxycarbonyl (Fmoc)-L-Asp-L-Asp-D-Xaa-D-Xaa. The mass spectrometry conditions were optimized by fine-tuning the background electrolyte and sheath flow composition to achieve optimal sensitivity in the negative ionization mode. Different types of capillaries were also evaluated on their potential to screen combinatorial libraries. The library components that show the strongest interaction were identified. The dissociation constants of a mixture of six compounds with a broad affinity range were simultaneously established by Scatchard analysis on ACE-MS.

Preparation of racemic 2r-carboxy-trans, trans-3,4-dideutero-pyrrolidine (DL-trans, trans-3,4-dideutero-proline) and unambiguous assignment of protons in the 1H n.m.r. spectrum of proline.

Racemic trans-3,4-dideutero proline has been prepared by catalytic deuteration of 3-pyrroline-2-carboxylic acid. The stereospecificity of the reduction (i.e. trans to the carboxylic group) was ascertained after transformation of the dideutero compound into the diketopiperazide c/Pro, Aib/, for which unambiguous proton assignments in the 1H n.m.r. spectrum had been obtained previously. The identification of the configuration of the dideuteroproline allows for the affirmation of the correctness of proton assignments as previously proposed in literature.