Immunochemistry of rare bases and conformational studies of nucleotides

Antibodies against methylated bases were highly specific. In the case of dimethylated bases, antibodies reacted only with the homologous hapten, slightly with the monomethylated bases at the same position and not at all with the original non-methylated base, or with different methylated bases, Antibodies against monomethylated bases are also very specific. They reacted only with homologous hapten and slightly with the original non-methylated base. Antibodies against inosine distinguished it from 6-mercaptopurine riboside which differs from inosine only in that it has a sulfur atom instead of an oxygen atom. 6-Azauridine, which has a different conformation from uridine, reacted very poorly with anti-uridine antibodies. Antibodies against pseudouridine did not react at all with uridine. Antibodies are very powerful tools to determine conformation of coenzymes containing nucleosides or nuclcotides. Using this approach we were able to suggest that ATP, ADP, CoA, UDP, UTP, CDP and CTP are in a folded configuration.