Stereoselective intramolecular cyclization in irradiated nucleic acids: R- and S-8,5'-cycloadenosine in polyadenylic acid.

The yields of R- and S-8,5'-cycloadenosines have been measured in poly A irradiated with gamma rays in the absence of oxygen. High performance liquid chromatographic analysis of the nucleoside analogues obtained by hydrolysis of the irradiated poly A shows that the R isomer predominates to the extent of 2.5-fold at doses of ionizing radiation in the range of 0-400 Gy.