FREE RADICAL FORMATION IN RIBOFLAVIN COMPLEXES

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Abstract
The red color which results when solutions of tryptophan and riboflavin-5[image]-phosphate are mixed in appropriate concentrations at suitable temperature is caused by the formation of a tryptophan-riboflavin complex in which a riboflavin molecule has taken up one electron from the tryptophan. Riboflavin is then in a semiquinoid form and exists as a free radical. Qualitative and quantitative observations are reported concerning the reaction and absorption spectra of the tryptophan-riboflavin complex in the presence of a number of amino acids, tryptophan derivatives and several tryptophan-containing proteins.