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August 5, 1939, Vol 113, No. 6 >
Other Articles | August 5, 1939

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JAMA. 1939;113(6):504. doi:10.1001/jama.1939.02800310042015.
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APPLICATION OF AN ENZYMIC REACTION IN CHEMICAL METHODS FOR THE DETERMINATION OF VITAMIN B1  The development of chemical methods for the determination of vitamins is of practical importance since such methods make assays easily possible. The assay by chemical means of vitamin B1 is complicated; this factor exists in many biologic materials both as thiamin and as cocarboxylase, the pyrophosphate of thiamin. Indeed it has been found that thiamin pyrophosphate is the predominant form of vitamin B1 in many yeasts and animal tissues. When applied directly to such materials, chemical methods depending on the reaction between thiamin and diazotized p-aminoacetophenone or on the formation of thiochrome from thiamin yield values decidedly lower than those obtained by biologic assay. The method involving the use of p-aminoacetophenone is specific for thiamin and does not permit the determination of the vitamin in the phosphorylated form. Similarly it has been

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Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

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