Absorbance tritium-labeled

The existence of photoreversible, but not of heat-reversible, absorbance change in irradiated poly dI dC was taken to prove that the photoproducts are entirely dimers (in contrast to those in poly C irradiations where the product is almost entirely the hydrate82a). It was possible to detect dimers of uracil as well as those of cytosine, by means of the much slower photoreversal of uracil dimers. In the acid hydrolysates of irradiated dl-dC, both uracil dimers and uracil could be identified. Enzymatic hydrolysis (snake venom phosphodiesterase) does not split pyrimidine dimers, and the products of such hydrolysis of irradiated tritium-labeled poly dl dC contained trinucleotides shown by radioactivity to contain cytosine dimers. Thymine dimers were formed in the photolysis of the poly dA dT, and were detected and assayed by the same methods. The yield of thymine dimers in irradiated poly... 

Direct feeding of [2- C] or [5- H]hydroxyproline to Avena coleoptiles by Cleland and Olson (1967) demonstrated that 60% of the label absorbed was converted to proline. There was no loss of tritium at C-5 and no [ CJgluta-... 

In case of materials labelled with carbon-14 and/or tritium (Fig.l), after the additicn of a small amount of tungstic oxide to retain phosphoms and promote combustion, the sanple is burnt in a stream of oxygen. Halogens and sulfur are retained by silver wool, vhile the combustion products including HTO and carbon dioxide are led with the oj en stream caito a column of partially dehydrated alumina kept at 20CAi . The water is retained cn the column quantitatively, meamhile the carbon dioxide is transferred into an absorbent suitable for counting. The tritium (HTO) stored ten 5)orarily... 

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