Radiometric determination of stability constants of mercury species complexes with L-cysteine

Starý, J.; Kratzer, K.

doi:10.1007/bf02164804

Cited by 23 publications

(17 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(Table 2) our determined constants are significantly lower than in these previous studies. 9,13,15,[17][18][19] Our experimental approach, based on a direct quantification of specific Hg were determined with comparably large number of data points covering extensive ranges in pH and ionic strength (Figure 1 and 2). The constants of Hg(SR)2 complexes were established with diverse types of LMM thiol containing multitude different functional groups ( Figure S1).…”

Section: Calculation Of Pka Values For Lmm Thiolsmentioning

confidence: 99%

“…16 A similar magnitude of the stability constant for Hg II -LMM thiol complexes has been reported using a methodology in which the thermodynamics of the Hg II speciation are shifted towards a separable, identifiable, and measurable Hg II complex with the addition of a competing ligand such as iodide (I -) or bromide (Br -) ions or the lipophilic thiol dithizone. 9,[17][18][19] Even with this progress in methodological development it remains a challenge to determine the exceptionally high stability constant for Hg II -LMM thiol complexes, as exemplified by log β2 constants reported for the Hg(Cys)2 complex in recent literature, ranging between 38.2 9 and 43.5. 18 Thus, there is still a substantial uncertainty remaining before a consensus on Hg II -LMM thiols stability constants can be reached.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory

et al. 2017

View full text Add to dashboard Cite

Environmental contextThe chemical speciation of mercury (Hg) largely controls its biogeochemical cycling and exposure to biota. Here, we investigate the thermodynamic stabilities of complexes formed between inorganic divalent Hg (HgII) and 15 biogeochemically relevant low-molecular-mass (LMM) thiol ligands. This information is critical for accurate modelling of the chemical speciation of HgII and to clarify the role of HgII–LMM thiol complexes in the cycling of Hg in the environment. AbstractInorganic divalent mercury (HgII) has a very high affinity for reduced sulfur functional groups. Reports from laboratory experiments suggest that HgII complexes with specific low-molecular-mass (LMM) thiol (RSH) ligands control rates of HgII transformation reactions. Because of methodological limitations for precise determination of the highly stable HgII complexes with LMM thiol ligands, constants reported in the literature remain inconsistent. This uncertainty impedes accurate modelling of the chemical speciation of HgII and the possibility to elucidate the role of HgII complexes with LMM thiols for Hg transformation reactions. Here, we report values of thermodynamic stability constants for 15 monodentate, two-coordinated HgII complexes, Hg(SR)2, formed with biogeochemically relevant LMM thiol ligands. The constants were determined by a two-step ligand-exchange procedure where the specific Hg(SR)2 complexes were quantified by liquid chromatography–inductively coupled plasma mass spectrometry. Thermodynamic stability constants (log β2) determined for the Hg(SR)2 complexes ranged from 34.6, N-cysteinylglycine, to 42.1, 3-mercaptopropionic acid, for the general reaction Hg2++2RS– ⇌ Hg(SR)2. Density functional theory (DFT) calculations showed that electron-donating carboxyl and carbonyl groups have a stabilising effect on the HgII–LMM thiol complexes, whereas electron-withdrawing protonated primary amino groups have a destabilising effect. Experimental results and DFT calculations demonstrated that the presence of such functional groups in the vicinity of the RSH group caused significant differences in the stability of Hg(SR)2 complexes. These differences are expected to be important for the chemical speciation of HgII and its transformation reactions in environments where a multitude of LMM thiol compounds are present.

show abstract

Section: Calculation Of Pka Values For Lmm Thiolsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory

et al. 2017

View full text Add to dashboard Cite

show abstract

“…are low molecular weight (LMW) organic ligands with high affinities for Hg(II), 39,40 occurring in nanomolar to submicromolar concentrations in the environment. 41,42 However, the main reason for choosing cysteine and EDTA as model organic ligands was their wide application in experimental studies and their difference in Hg(II) complexation.…”

Section: Materials and Reagentsmentioning

confidence: 99%

Kinetics of Hg(II) Exchange between Organic Ligands, Goethite, and Natural Organic Matter Studied with an Enriched Stable Isotope Approach

Jiskra

Saile

Wiederhold

et al. 2014

Environ. Sci. Technol.

View full text Add to dashboard Cite

The mobility and bioavailability of toxic Hg(II) in the environment strongly depends on its interactions with natural organic matter (NOM) and mineral surfaces. Using an enriched stable isotope approach, we investigated the exchange of Hg(II) between dissolved species (inorganically complexed or cysteine-, EDTA-, or NOM-bound) and solid-bound Hg(II) (carboxyl-/thiol-resin or goethite) over 30 days under constant conditions (pH, Hg and ligand concentrations). The Hg(II)-exchange was initially fast, followed by a slower phase, and depended on the properties of the dissolved ligands and sorbents. The results were described by a kinetic model allowing the simultaneous determination of adsorption and desorption rate coefficients. The time scales required to reach equilibrium with the carboxyl-resin varied greatly from 1.2 days for Hg(OH)2 to 16 days for Hg(II)-cysteine complexes and approximately 250 days for EDTA-bound Hg(II). Other experiments could not be described by an equilibrium model, suggesting that a significant fraction of total-bound Hg was present in a non-exchangeable form (thiol-resin and NOM: 53-58%; goethite: 22-29%). Based on the slow and incomplete exchange of Hg(II) described in this study, we suggest that kinetic effects must be considered to a greater extent in the assessment of the fate of Hg in the environment and the design of experimental studies, for example, for stability constant determination or metal isotope fractionation during sorption.

show abstract

“…Moreover, a decrease of the rate of PET The lower inhibitory effect of organomercury compounds on PET compared with HgCl 2 can be probably caused by the fact that the chemical affinity of organomercury for ligands, including amino acid residues in peptides, is similar to that of Hg 2+ but the stability constants of methylmercury complexes with these ligands are consistently lower than those of the corresponding Hg 2+ complexes [42]. This was confirmed by Stary and Kratzer [43] who found that mercury forms thiolate complexes exhibiting extraordinarily high formation constants. Whereas for HgCys 2 complexes this value was reported to be about 10 42 , similar formation constants for methylmercury and phenylmercury achieve only 10 15 and 10 16 , respectively.…”

Section: Discussionmentioning

confidence: 68%

Action of Some Organomercury Compounds on Photosynthesis in Spinach Chloroplasts

Šeršeň¹,

Kráľová²

2013

Ecological Chemistry and Engineering S

View full text Add to dashboard Cite

Abstract:The effects of five organomercury compounds (methylmercuric chloride, phenylmercuric acetate, phenylmercuric borate, phenylmercuric citrate and diphenylmercury) on photosynthetic electron transport (PET) in spinach chloroplasts were investigated. The IC50 values of organomercury compounds related to PET inhibition in spinach chloroplasts varied in the range from 468 µmol dm -3 to 942 µmol dm -3 and were approximately by one order higher than the corresponding value determined for HgCl2 applied also in DMSO solution (IC50 = 58 µmol dm ). Due to extremely low aqueous solubility of diphenylmercury, the corresponding IC50 value could not be determined. Using EPR spectroscopy as probable sites of action of organomercury compounds in photosynthetic apparatus ferredoxin on the acceptor side of PS 1 and the quinone electron acceptors QA or QB on the reducing side of PS 2 were suggested.

show abstract

Radiometric determination of stability constants of mercury species complexes with L-cysteine

Cited by 23 publications

References 5 publications

Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory

Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory

Kinetics of Hg(II) Exchange between Organic Ligands, Goethite, and Natural Organic Matter Studied with an Enriched Stable Isotope Approach

Action of Some Organomercury Compounds on Photosynthesis in Spinach Chloroplasts

Contact Info

Product

Resources

About