Thiobarbituric acid acceptors

Although other natural sugars were tested as possible alternate substrates the specificity for KDO was absolute. However, the nucleotide CTP could be replaced by deoxy-CTP as a nucleotide acceptor when the reaction was carried out at both pH 8.0 and pH 9.5. Also, UTP was an effective nucleotide acceptor when the reaction was carried out at pH 9.5 but much less so when tested at pH 8.0. No other nucleotide tested acted as a substrate or inhibited the formation of the NaBH,-resistant thiobarbituric acid positive reaction. The apparent K values.determined at.pH 9.5 for CTPdeoxy-CTP and UTP were fto x 10 4 M, 3.4 x 10 M, and 8.8 x 10 M, respectively. Th apparent V values for CTP,... 

Many different acceptor groups have been investigated. Very large nonlinearities have been achieved using, for instance, nitro, cyanovinyl, thiobarbituric acid moieties [49], or strong multicyano-containing heterocyclic electron acceptors [35,50-52]. 

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