Protonation Constants of ۵'-IM P in Diffe rent Aqueous Solutions of Methanol

Inosin e ۵'-monophosphate (I MP) is a nu cleotide (Sc heme ۱). The acid-base behavior of nucleotides, nucleosides, and polynucleotide s is essential to deduce the speciation and the possible conformational changes with pH or the amount of organic solvent in s olution. But in determination of aci dity constans of these molecules we are faced with several drawbacks, such as lo w solubility in aqueous s olutions an d the low values of acidity constants. Therefore, we forc ed to choo se mixed solvents [۱]. T wo solvents mixed t ogether produce a solve nt with quite different properties, both, physically (dielectric, density an d viscosit y) and chem ically (acid-base and d onor-acceptor propertie s). By mixing solvents of different polarity in proper ratio, dielectric constant of the me dium can be varied an d, at the sa me time, the strength of dissolved acids and bases. It should also be emphasized that solvent mixtures can be more convenient than individual solvents owing to enhance d solubilising efficiency, increased sharpness of color change of indicators during titration and more manageable shape of acid-base titration curves [۲]. Howeve r, chemists have usuall y attempted to understan d solvent effects in ter ms of polarity, de¿ned as the ove rall solution capabilities that depend on all possible (speci¿c and non speci¿c) intermolecular interactions betwee n solute and solvent molecules [۱]. In this study the protonation constants of Inosi n ۵'-monophosphate (IMP) have been determined in diffe rent aqueou s methanol mixtures to examine the dependence of acid-base equilibria on solvent composition

کلیدواژه ها:

Dissociation Const ants ، Inosine ۵'-monoph osphate ، Methanol ، spectroscopic st udy