Modeling the acid–base properties of glutathione in different ionic media, with particular reference to natural waters and biological fluids

Cigala, Rosalia Maria; Crea, Francesco; Stefano, Concetta De; Lando, Gabriele; Milea, Demetrio; Sammartano, Silvio

doi:10.1007/s00726-011-1110-0

Cited by 41 publications

(29 citation statements)

References 53 publications

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“…50,51 GSH is featured by four functional groups involved in acid−base equilibria. Starting from the fully deprotonated form (GSH 3− ), the first group that protonates is the amino group, the second is the thiolate, and, finally, the two carboxylates.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

et al. 2014

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This contribution reports the results of an investigation on the speciation of various lanthanoid(III) cations (Ln 3+ ), namely, La 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Dy 3+ , and Yb 3+ , in the presence of reduced glutathione (or simply glutathione, GSH), in NaCl (aq) at I = 0.15 mol·dm −3 and T = 298.15 K. GSH forms in all cases the same four species, namely, Ln(GSH)H 3 , Ln(GSH)H 2 , Ln(GSH)H, and Ln(GSH)OH, whose stability depends on the type of lanthanoid, although it is also possible to consider an average stability for a generic lanthanoid, at least for the protonated species. Measurements at different temperatures and ionic strengths for the La 3+ /GSH and Gd 3+ /GSH systems have also been performed, to evaluate their effect on the speciation of both GSH and the Ln 3+ cations. The dependence of the determined stability constants on I and T has been modeled by an extended Debye−Huckel type and by the van't Hoff equations. In this last case, the formation enthalpy changes of La 3+ /GSH species have also been determined. The stability constants obtained have been therefore used to quantify the sequestering ability of GSH toward the investigated cations, in different pH, ionic strength, and temperature conditions, by the calculation of several pL 0.5 parameters. Their analysis showed that, generally, the sequestering ability of GSH increases with increasing pH and decreases with increasing temperature, while the ionic strength has only a small effect. Finally, results obtained may be exploited for the evaluation of the speciation (and, therefore, of the sequestration) of any Ln 3+ cations in the presence of GSH in different conditions of T and I, like those featuring many natural waters and biological fluids.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

et al. 2014

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“…Presaturated nitrogen gas was bubbled through the solutions in order to remove dissolved oxygen and carbon dioxide. The procedure adopted for the potentiometric measurements is reported elsewhere (Cigala et al 2012 ). Solubility measurements were performed for Leu and Phe as described in previous works (Bretti et al 2012 ).…”

Section: Methodsmentioning

confidence: 99%

Modeling solubility and acid–base properties of some amino acids in aqueous NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures

et al. 2016

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New potentiometric experiments have been performed in NaCl and in (CH3)4NCl media, to determine the protonation constants, the protonation enthalpy changes and the solubility of six natural α-amino acids, namely Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Serine (Ser) and Phenylalanine (Phe). The aim of the work is the rationalization of the protonation thermodynamics (log , solubility and ) in NaCl, determining recommended, tentative or provisional values in selected experimental conditions and to report, for the first time, data in a weak interacting medium, as (CH3)4NCl. Literature data analysis was performed selecting the most reliable values, analyzed together with new data here reported. Significant trends and similarities were observed in the behavior of the six amino acids, and in some cases it was possible to determine common parameters for the ionic strength and temperature dependence. In general, the first protonation step, relative to the amino group, is significantly exothermic (average value is = −44.5 ± 0.4 kJ mol−1 at infinite dilution and T = 298.15 K), and the second, relative to the carboxylate group, is fairly close to zero ( = −2.5 ± 1.6, same conditions). In both cases, the main contribution to the proton binding reaction is mainly entropic in nature. For phenylalanine and leucine, solubility measurements at different concentrations of supporting electrolyte allowed to determine total and specific solubility values, then used to obtain the Setschenow and the activity coefficients of all the species involved in the protonation equilibria. The values of the first protonation constant in (CH3)4NCl are lower than the corresponding values in NaCl, due to the weak interaction between the deprotonated amino group and (CH3)4N+. In this light, differences between the protonation functions in NaCl and (CH3)4NCl were used for the quantification of the stability of the weak [(CH3)4N+–L−] complexes that resulted log K = −0.38 ± 0.07 as an average value for the six amino acids.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-2568-8) contains supplementary material, which is available to authorized users.

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“…The apparatus used in the potentiometric measurements has been widely described elsewhere (Cigala et al, 2010(Cigala et al, , 2012. The titrand solution consisted of different amounts of monosodium phosphate [1-20 mmol L À1 ], a suitable amount of HNO 3 [1-20 mmol L À1 ], and NaNO 3 to obtain the pre-established pH and ionic strength values (0.15 6 I/mol L À1 6 1.0).…”

Section: Apparatus and Procedures For Potentiometric Measurementsmentioning

confidence: 99%

The inorganic speciation of tin(II) in aqueous solution

Cigala

Crea

Stefano

et al. 2012

Geochimica et Cosmochimica Acta

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Modeling the acid–base properties of glutathione in different ionic media, with particular reference to natural waters and biological fluids

Cited by 41 publications

References 53 publications

Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

Modeling solubility and acid–base properties of some amino acids in aqueous NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures

The inorganic speciation of tin(II) in aqueous solution

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