Studies in rhodopsin. VI. Regeneration of rhodopsin.

reducing power of steroids. The low pH of the reagent, which is responsible for hydrolysis of the cellulose, cannot be raised materially without seriously affecting the sensitivity. The latter depends on the formation of the yellow arsenomolybdate complex which requires a large excess of acid. In the experience of the author, variations of the blank value and serious disagreement between duplicate determinations are largely due to contamination of the chromatogram strips with extraneous reducing matter. It is therefore apparent that a minimum of handling of the paper strips and scrupulous cleanliness on the bench and in the laboratory atmosphere are essential for satisfactory operation. In spite of its inherent weaknesses, the arsenomolybdate method is capable of furnishing valuable information on the composition of adrenal extracts. It is hoped eventually to correlate the results obtained by quantitative chromatography with those of biological assays, thus enabling an estimate to be made of the potency, as well as the steroid distribution, of a particular extract. SUMMARY