title: Phosphate-guanosine interactions. A model for the involvement of guanine derivatives in autocatalytic reactions of ribonucleic acids.
abstract: Proton magnetic resonance was used to study the interactions between nucleosides and phosphate monoanion in dimethyl sulfoxide. Ribose was able to form two mutually exclusive 1:1 complexes involving either OH3' and OH5' or OH3' and OH2' as hydrogen bond donor groups. Deoxyribose could form only one of these complexes. A specific interaction of phosphate with the base moiety of nucleosides was observed only with guanosine. A 1:1 complex was formed involving the N(1)H and NH2(2) of guanine. Association constants for both the base and sugar complexes were determined to be in the range 50-60 M-1 at 21 degrees C in dimethyl sulfoxide. This value is more than 1 order of magnitude higher than that measured for guanine-cytosine base pair formation under the same conditions. Water addition to dimethyl sulfoxide led to a decrease of all association constants but the guanine-phosphate "pair" remained more stable than the guanine-cytosine base pair.
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives; D055598:Chemical Phenomena; D002621:Chemistry; D003849:Deoxyguanosine; D006147:Guanine / Q000031:analogs & derivatives; D006151:Guanosine; D006860:Hydrogen Bonding; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008433:Mathematics; D008956:Models, Chemical; D010710:Phosphates; D012313:RNA; D014529:Uridine
chemical_list: D010710:Phosphates; D006151:Guanosine; C001172:9-ethyladenine; D006147:Guanine; D012313:RNA; C014542:9-ethylguanine; D003849:Deoxyguanosine; D000225:Adenine; D014529:Uridine