Enhancer Cytosine

Carbamoyl phosphate synthetase formation in liver taken from tadpoles treated with thyroxine is enhanced by the addition of orotic acid, uracil or uridine (cytosine and adenosine had no effect). The synthesis of this enzyme is not affected by these pyrimidines in untreated animals. This indicates that there is a relative pyrimidine deficiency during thyroxine-induced metamorphosis [140]. 

Subsequent to the preparation of 8, a number of other sapphyrin-nucleobase conjugated carriers were synthesized in the authors laboratories. These include compound 9 that has two cytosine moieties appended to the sapphyrin macrocycle, as well as two guanine-bearing sapphyrins, 10 and 11. Here, as expected, the ditopic sapphyrin-guanine receptor 10 served to enhance the transport of cytosine-5 -monophosphate (but not GMP or AMP). By contrast, the two tritopic receptors, namely 9 and 11, were designed with the intention of allowing for the formation of the complexation-derived triple-helix-like C-G-C and G-C-G motifs in addition to phosphate chelation by sapphyrin. In other words, it was expected that a centrally... 

Martin, F.L., Cole, K.J., Orme, M.H., Grover, P.L., Phillips, D.H. Venitt, S. (1999) The DNA repair inhibitors hydroxyurea and cytosine arabinoside enhance the sensitivity of the alkaline single-cell gel electrophoresis ( comet ) assay in metabohcally-competent MCL-5 cells. Mutat Res., 445, 21-43... 

Hutter M, Clark T (1996) On the enhanced stability of the guanine-cytosine base-pair radical cation. J Am Chem Soc 118 7574-7577... 

Kawai K, Wata Y, IchinoseN, Majima T (2000b) Selective enhancement of the one-electron oxidation of guanine by base paring with cytosine. AngewChem Int Ed 39 4327-4329... 

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