Microbiological analysis of 5-formyltetrahydrofolic acid and other folates using an automatic 96-well plate reader

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Abstract

The growth of auxotrophic bacteria remains the method of choice for the determination of biologically active folate metabolites in plasma. This report describes a microbiological assay for folates adapted to use disposable 96-well plates and an automatic plate reader. The modifications in the assay decreased reagent costs and made the analysis of hundreds of samples per day possible with a sensitivity limit of 10 fmol of (6S)-5-formyltetrahydrofolic acid. This limit compares favorably with that of previously reported, more laborious methods. The unnatural 6R diastereomer of 5-formyltetrahydrofolic acid did not interfere with the microbiological assay of the natural 6S diastereomer.

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This work was supported in part by Grant NIH BRSG S07RR-05471 to the City of Hope National Medical Center. E. M. Newman was supported in part by the Sam Revel Research Fellowship. J. F. Tsai was a student under the Committee for Advanced Science Training program of the California State Museum of Science and Industry.

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