Open AccessA Comparison on the Coordination Tendency towards Cu 2+ of the Base Moieties in Guanosine, Inosine and Adenosine 5′‐Triphosphates
Author(s) -
SIGEL Helmut,
NAUMANN Christoph F.,
PRUS Bernhard
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03654.x
Subject(s) - chemistry , deprotonation , protonation , moiety , guanosine , gtp' , nucleotide , crystallography , stereochemistry , ligand (biochemistry) , guanine , ternary complex , inorganic chemistry , medicinal chemistry , ion , organic chemistry , receptor , biochemistry , gene , enzyme
The chemical shift of the proton H(8) in the proton magnetic resonance spectrum of GTP was measured in aqueous solution in dependence on pH (2 to 12). Based hereon the acidity constants for protonation at N(7) and deprotonation at N(1) were determined. From the line broadening effects in the presence of Cu 2+ it is concluded that this metal ion interacts with N(7) of the guanine moiety in Cu(GTP) 2− . Hence, the structure of this latter complex corresponds to the one of Cu(ATP) 2− , while in Cu(ITP) 2− only a very minor interaction with N(7) occurs ( cf. Eur. J. Biochem. 41 , [1974] 209–216). There is also evidence that in the complex Cu(GTP‐1H) 3− a 5‐membered chelate involving N(7) and O(6) is formed, while in Cu(ITP‐1H) 3− the interaction with Cu 2+ occurs only with the N(1), O(6)‐site of the base moiety. The decrease in line broadening observed at higher pH indicates that the Cu 2+ ‐nucleic‐base interaction is depressed in CU(ATP)(OH) 3− , Cu(GTP‐1H)(OH) 4− and Cu(ITP‐1H)(OH) 4− , as well. In all the mixed‐ligand systems which consist of Cu 2+ , 2,2′‐bipyridyl (Bipy) and one of the three nucleotides (NTP) the ternary complexes, Cu(Bipy) (NTP) 2− , are formed. Within these ternary complexes a charge‐transfer interaction occurs between the purine part of the nucleotides and 2,2′‐bipyridyl.