Double helix formed by the dinucleoside phosphate thymidylyl-3′,5′ -deoxyadenosine

Abstract

IN our conformational studies of nucleic acid components we have obtained X-ray diffraction photographs from specimens of the dinucleoside phosphate thymidylyl-3′,5′-deoxyadenosine (TpdA) which are similar to those obtained from certain synthetic DNA copolymers. The dinucleoside phosphate was obtained from International Enzymes Ltd as the triethylammonium salt. Some of it was dissolved in a small quantity of water between a glass slide and a coverslip resting on two thin glass fibres. Some of the material which dried out under the coverslip showed evidence of orientation when viewed between crossed polaroids. X-ray diffraction photographs were taken on a microcamera using a Hilger and Watts semi-microfocus X-ray generator and one of these is shown in Fig. 1.