Dissociation constants of protonated oxidized glutathione in seawater media at different salinities

Pasquale Crea, Concetta De Stefano, Frank J. Millero, Silvio Sammartano, Virender K. Sharma

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Oxidized glutathione (GSSG), which has four carboxylic and two amino groups, interacts with metal ions and may affect the bioavailability and geochemistry of metals in natural waters. In the present paper, six stepwise protonation constants KiH for GSSG were measured as a function of salinity, S = 5-35‰ at t = 25°C (and in NaCl/MgCl2 mixtures at different ionic strengths), in order to provide thermodynamic data for their acid base properties, which are useful for studying the interaction with metals in these media. The protonation enthalpies (ΔHi/kJ mol-1) were also determined at t = 25°C. The results were interpreted using the SIT model and Pitzer equations. The seawater model with the interaction parameters accounts for the differences between the values in NaCl and seawater. The results suggest that it is important to consider all of the ionic interactions in natural waters in examining the proton dissociation of GSSG.

Original languageEnglish (US)
Pages (from-to)447-466
Number of pages20
JournalAquatic Geochemistry
Issue number3
StatePublished - Jun 2010


  • Medium effects
  • Oxidized glutathione
  • Pitzer coefficients
  • Protonation constants
  • SIT model
  • Synthetic seawater

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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