title: Studies of bivalent copper ion binding to poly C.
abstract: Ultraviolet differential spectra of single-stranded poly C, taken in the presence of Cu2+ ions, are studied at various ionic strengths and temperatures. Coordinational and conformational components of these spectra are obtained. The Cu2+ ion coordination site on the polynucleotide bases is found to be N(3) and possibly O(2). The direction of the poly C absorption band shift due to ion binding and conformational transitions is established. At low ionic strengths of the solution Cu2+ ions cause the helical parts of poly C to melt. At high ones the formation of double-stranded parts was observed in addition to the above effect. The calculated concentration dependences of ion-poly C bases association constants show that binding is cooperative at any ionic strength.
mesh_terms: D003300:Copper; D007700:Kinetics; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D011066:Poly C; D011131:Polyribonucleotides; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013816:Thermodynamics
chemical_list: D011131:Polyribonucleotides; D011066:Poly C; D003300:Copper