Inosylyl(3'-->5')inosine (IpI-). Acid-base and metal ion-binding properties of a dinucleoside monophosphate in aqueous solution.
The acidity constants of the (N7)H(+) sites of inosylyl(3'-->5')inosine (IpI(-)) were estimated and those of its (N1)H sites were measured by potentiometric pH titrations in aqueous solution (25 degrees C; I = 0.1 M, NaNO3). The same method was used for the determination of the stability constants of the 1:1 complexes formed between Mg(2+), Co(2+), Ni(2+), Zn(2+), or Cd(2+) (= M(2+)) and (IpI - H)(2-) and, in the case of Mg(2+), also of (IpI - 2H)(3-). The stability constants of the M(IpI)(+) complexes were estimated. The acidity constants of H(inosine)(+) and the stability constants of the M(Ino)(2+) and M(Ino - H)(+) complexes were taken from the literature. The comparison of these and related data allows the conclusion that, in the M(IpI - H) species, chelates are formed; most likely they are preferably of an N7/N7 type. For the metal ions Co(2+), Ni(2+), Zn(2+), or Cd(2+), the formation degrees of the chelates are on the order of 60-80%; no chelates could be detected for the Mg(IpI - H) complexes. It is noteworthy that the (N1)H deprotonation, which leads to the M(IpI - H) species, occurs in all M(IpI)(+) complexes in the physiological pH range of about 7.5 or even below.
Knobloch
Bernd
B
Department of Chemistry, Inorganic Chemistry, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland.
Okruszek
Andrzej
A
Sigel
Helmut
H
D000143:Acids / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry; D015226:Dinucleoside Phosphates / Q000737:chemistry*; D007288:Inosine / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D015394:Molecular Structure; D009711:Nucleotides / Q000737:chemistry*; D012996:Solutions
D000143:Acids; D002614:Chelating Agents; D015226:Dinucleoside Phosphates; D007477:Ions; D008670:Metals; D009711:Nucleotides; D012996:Solutions; D007288:Inosine