Determination of configurational isomers in cyclic polysulfides by Raman spectroscopy

Krafft, Christoph; Pigorsch, Enrico; Weber, Berthold; Ott, Frank; Brennecke, Stefan; Krammer, Gerhard; Salzer, Reiner

doi:10.1016/j.vibspec.2006.06.009

Cited by 8 publications

(8 citation statements)

References 6 publications

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“…In addition, the appearance of a band at 482 cm −1 could be due to the formation of polysulfides (S-S-S). [32] The formation of disulfide and polysulfides might lead to the release of the chelated Zn(II) ions, analogously to that observed for rabbit Zn-MT and Zn/Cd-MT undergone to oxidative stress. [33,34] Because Cd(II) is known to be bound more tightly than Zn(II) [35] and, therefore, might have come off more difficultly during stress conditions, this could explain the lesser formation of disulfides in our Cdcontaining MT, in agreement with no founding of free cadmium from rabbit Zn/CdMT under oxidative stress conditions.…”

Section: Sulfur-containing Residuesmentioning

confidence: 66%

Structural modifications in metal complexes of a plant metallothionein caused by reductive radical stress: a Raman study

Torreggiani¹,

Doménech

Tinti

2009

J Raman Spectroscopy

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The effect of radical stress in the biological environment is a very active field of research connecting various disciplines of life science. Thus, a comprehensive vision of all possible reactive species is necessary for contributing to the solution of puzzling questions on free radicals. In this contest, damages to Zn(II) and Cd(II) complexes of a plant metallothionein (Quercus suber -QsMT), because of reductive radical stress, were investigated by Raman spectroscopy. QsMT is a low-molecular-weight cysteine-rich protein obtained by in vivo synthesis to have a physiologically representative model. Gamma-irradiation was used to simulate the endogenous formation of reductive species. By changing the appropriate conditions of irradiation, a selection of the reacting radical species (hydrogen atom and hydrated electron) was carried out. Specific damages occur at sensitive amino acid sites, selectively, rather than indiscriminately. In particular, Cys resulted to be among the most sensitive residues toward radical attack, suggesting that the thiolate clusters of both metal and QsMTs act as efficient interceptors of reducing species. Under reductive stress, Zn-QsMT undergoes a significant thiolate group oxidation and the participation of ligands other than the cysteine-derived thiolate bonds (i.e. His) in zinc coordination becomes necessary for the protein stabilization. Regarding Met residues, they resulted to be more sensitive to the reductive radical attack when the protein binds Cd(II) ions, indicating that the protein structure can play a significant role in blocking the ready access of free radicals to the sulfur-containing residues, so strongly affecting the radiosensitivity of the protein. In conclusion, the results obtained from γ -irradiation experiments indicate that reductive stress causes changes in the primary QsMT structure and in the secondary and tertiary structures, and the radical-induced effects are dependent on the metal bound.

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Section: Sulfur-containing Residuesmentioning

confidence: 66%

Structural modifications in metal complexes of a plant metallothionein caused by reductive radical stress: a Raman study

Torreggiani¹,

Doménech

Tinti

2009

J Raman Spectroscopy

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“…Therefore, vibrational spectroscopy is frequently used to study the conformations of disulfides in solution. While dialkyl disulfides are basically investigated as model structures [11,12], the sensitive characterization of macromolecular protein chains, where disulfide linkages stabilize the tertiary structure, is also possible in vitro and in vivo [13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Conformations and vibrational properties of disulfide bridges: Potential energy distribution in the model system diethyl disulfide

2009

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“…For Zn-QsMT, a significant increase in intensity of the band at about 520 cm À1 due to the S À S stretching mode of disulfide bridges was observed, as well as the appearance of a band at about 480 cm À1 that could be due to the formation of polysulfides (S n ). [45] These spectral modifications are in accordance with oxidation of the protein upon irradiation, which can be a consequence of partial deconstruction of the Cys-Zn clusters. Similar behaviour has been observed for rabbit Zn-MT and Zn/Cd-MT undergoing oxidative stress.…”

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confidence: 68%

Zinc and Cadmium Complexes of a Plant Metallothionein under Radical Stress: Desulfurisation Reactions Associated with the Formation of trans‐Lipids in Model Membranes

Torreggiani

Doménech

Orihuela

et al. 2009

Chemistry A European J

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Metallothioneins (MTs) are sulfur-rich proteins capable of binding metal ions to give metal clusters. The metal-MT aggregates used in this work were Zn- and Cd-QsMT, where QsMT is an MT from the plant Quercus suber. Reactions of reductive reactive species (H(*) atoms and e(aq)(-)), produced by gamma irradiation of water, with Zn- and Cd-QsMT were carried out in both aqueous solutions and vesicle suspensions, and were characterized by different approaches. By using a biomimetic model based on unsaturated lipid vesicle suspensions, the occurrence of tandem protein/lipid damage was shown. The reactions of reductive reactive species with methionine residues and/or sulfur-containing ligands afford diffusible sulfur-centred radicals, which migrate from the aqueous phase to the lipid bilayer and transform the cis double bond of the oleate moiety into the trans isomer. Tailored experiments allowed the reaction mechanism to be elucidated in some detail. The formation of sulfur-centred radicals is accompanied by the modification of the metal-QsMT complexes, which were monitored by various spectroscopic and spectrometric techniques (Raman, CD, and ESI-MS). Attack of the H(*) atom and e(aq)(-) on the metal-QsMT aggregates can induce significant structural changes such as partial deconstruction and/or rearrangement of the metal clusters and breaking of the protein backbone. Substantial differences were observed in the behaviour of the Zn- and Cd-QsMT aggregates towards the reactive species, depending on the different folding of the polypeptide in these two cases.

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Determination of configurational isomers in cyclic polysulfides by Raman spectroscopy

Cited by 8 publications

References 6 publications

Structural modifications in metal complexes of a plant metallothionein caused by reductive radical stress: a Raman study

Structural modifications in metal complexes of a plant metallothionein caused by reductive radical stress: a Raman study

Conformations and vibrational properties of disulfide bridges: Potential energy distribution in the model system diethyl disulfide

Zinc and Cadmium Complexes of a Plant Metallothionein under Radical Stress: Desulfurisation Reactions Associated with the Formation of trans‐Lipids in Model Membranes

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