“…The results agree within experimental error with a recent room-temperature redetermination based on diffractometer data (Ward, 1993). Other related crystal structures which have been determined at atomic resolution include ot-cytidine (Post, Birnbaum, Huber & Shugar, 1977), in which the ribose has the ot-anomeric configuration, 1-fl-I:)-arabinosylcytosine (Tougard & Lefebvre-Soubeyran, 1974), cytosine (Barker & Marsh, 1964;McClure & Craven, 1973) and cytosine monohydrate by X-ray diffraction (Jeffrey & Kinoshita, 1963;McClure & Craven, 1973) and neutron diffraction at 82 K (Weber, Craven & McMullan, 1980). Many crystal complexes involving G--C base pairs have been studied, the most notable being sodium guanylyl-3',5'-cytidine nonahydrate (Rosenberg, Seeman, Day & Rich, 1976), because this structure first showed minihelical RNA at atomic resolution.…”