“…Valuable contributions towards our understanding of polymer structure are obtained from X-ray studies of the crystal and molecular structures of the component mononucleosides and mononucleotides (1)(2)(3)(4)(5). Recently, highresolution X-ray analyses of several ribose dinucleoside monophosphates, adenylyl-(2',5')-uridine (6), uridylyl-(3',5')-adenosine (UpA) (7,8), guanylyl-(3',5')-cytidine (GpC) (9), and adenylyl-(3',5')-uridine (ApU) (10) as well as of the deoxydinucleotide 5'-phosphoryl thymidylyl-(3',5')-thymidine (d(pTpT1) (1 I), have appeared in the literature.…”