The protonation equilibria of selected glycine dipeptides in ethanol-water mixture: Solvent composition effect

Doǧan A., Özel A., KiIiç E.

Amino Acids, vol.36, no.2, pp.373-379, 2009 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 36 Issue: 2
  • Publication Date: 2009
  • Doi Number: 10.1007/s00726-008-0054-5
  • Journal Name: Amino Acids
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.373-379
  • Keywords: Dipeptides, Ethanol-water mixture, Potentiometry, Protonation constants
  • Ankara University Affiliated: Yes

Abstract

Knowledge of the protonation constants of small dipeptide is important, interesting and necessary for complete understanding of the physiochemical behavior of dipeptide. In this study, the protonation constants of some aliphatic dipeptides (Gly-Gly, Gly-Val, Gly-Leu, Gly-Thr, Gly-Phe and Gly-Met) were studied in water and ethanol-water mixtures [20% ethanol-80% water, 40% ethanol-60% water, 60% ethanol-40% water, (v/v)] at 25 ± 0.1°C under nitrogen atmosphere and ionic strength at 0.10 mol dm-3 by potentiometry. The constants of the systems were calculated by using BEST computer program, and distribution species diagrams were produced using the SPE computer program. The protonation constants were influenced by changes in solvent composition, and their variations were discussed in terms of solvent and structural properties. The concentration distribution of the various species in ethanol-water mixtures was evaluated. © Springer-Verlag 2008.