Quantitation of trace polyfunctional thiols in wine by liquid chromatography quadrupole Orbitrap high-resolution mass spectrometry in parallel reaction monitoring.

Polyfunctional thiols are key contributors to wine aroma due to their extremely low odor thresholds, and their quantitative analysis remains challenging as a result of their ultratrace concentrations and high reactivity. This work presents the first method based on ultra-high-performance liquid chromatography (UHPLC) coupled to quadrupole Orbitrap high-resolution mass spectrometry (HRMS) in parallel reaction monitoring (PRM) mode for quantifying thiols at nanograms per liter (ng/L) levels in wine. Thiols in wine were derivatized using 4,4'-dithiodipyridine and isolated by liquid-liquid extraction. This protocol allowed rapid sample preparation with minimum labor input and low consumable expenses. Instrumental analysis was conducted using UHPLC-quadrupole Orbitrap HRMS in PRM mode. Twenty thiol analytes, including literature-known, recently identified, and novel thiols were selected and validated by the optimized method in three wine matrices. The overall analytical performances demonstrated by this method were equivalent, and in most cases, greater than many previously developed GC-MS or LC-MS methods. The validated method was applied to analyze a selection of wines in which 12 thiols were quantified.

Glutathione-Conjugated Fluorometric Ratiometric NIR-Silicon Nanoparticles and Its Applications for In Vitro and In Vivo Imaging.

Glutathione (GSH), a tripeptide molecule, is the most abundant nonprotein biothiol in living cells, playing a crucial role in preventing oxidative damage to cellular components and maintaining intracellular redox homeostasis. As a thiol molecule, GSH contains a sulfhydryl (-SH) group that is vital for the body's response to reactive oxygen species (ROS). To confirm whether GSH can be used as a bioindicator or in the early diagnosis of cancers at the cellular level, it is essential to achieve highly selective detection and conjugation of GSH to silicon nanoparticles (SiNPs) under pathological conditions. We are herein excited to report a type of fluorescent ratiometric near-infrared silicon nanoparticle (NIR-SiNP) probe, that is, glutathione peptide conjugated (NIR-SiNPs-GSH), which simultaneously possess small pore sizes at an average of 6.7 nm, an emission of 670 nm, a bioimaging functionality of living cancer cells and animals, and favorable biocompatibility. Taking advantage of these virtues, we further manifest that such resulting NIR-SiNPs, NIR-SiNPs-GSH bioprobes are marvelously worthy for immunofluorescence imaging of cancer cells and living mice. Furthermore, it was shown that DAPI and probes could selectively stain malignant tumor cell nuclei, indicating the possibility for bioimaging and identification of cancer cells and animals. In summary, the suggested NIR-SiNPs-GSH probe has the potential to be a very effective chemical tool for early tumor detection in the future.

Dynamic thiol/disulfide homeostasis and myeloperoxidase levels in Gilbert's syndrome with mild hyperbilirubinemia.

Aim: This study aimed to compare dynamic thiol/disulfide homeostasis and myeloperoxidase (MPO) levels in patients with Gilbert's syndrome (GS) and healthy controls. Background: Thiol/disulfide homeostasis and MPO levels are both associated with increased progression of atherosclerosis. Methods: The study included a total of 130 voluntary participants comprising 65 patients with GS and 65 healthy controls. These patients were selected randomly and dynamic thiol/disulfide homeostasis, MPO, complete blood count results, and biochemistry and lipid parameters were evaluated. Patients with known chronic diseases, medication usage, and acute infections were excluded from the study. Serum total thiol and native thiol levels were measured using the fully automated colorimetric method, while serum MPO levels were measured using the sandwich ELISA method. Results: We found that patients with GS had significantly higher total thiol (352.3±38.6 vs. 317.9±47.9, p<0.001) and native thiol (386.6±42.6 vs. 348.0±51.1, p<0.001) and significantly lower disulfide (15.7±4.0 vs. 17.3±4.0, p=0.022) and MPO (130.7 vs. 166.3, p=0.006). In patients with bilirubin of <1 mg/dL, total thiol and native thiol levels were lower and disulfide, disulfide/native thiol (DNT) and disulfide/total thiol (DTT) ratios, and MPO levels were higher. Patients with bilirubin of <1 mg/dL also had higher total cholesterol. Conclusion: In these patients with GS, the thiol/disulfide balance shifted towards thiols and proinflammatory MPO levels were lower. When bilirubin was <1 mg/dL, disulfide, DNT and DTT ratios, and MPO were higher. Bilirubin levels affected all parameters of thiol/disulfide homeostasis and MPO levels independently of other risk factors. In light of our results, we suggest that mild hyperbilirubinemia in cases of GS has an anti-inflammatory and antioxidant effect and may be protective against atherosclerosis.

Intermolecular sulfenoamination of alkenes with free-thiols and NIS to access ß-succinimide sulfides.

A convenient and practical multicomponent strategy for the sulfenoamination of alkenes was realized, which using free-thiols as the sulfur-reagent, NIS both as radical initiator and an N-nucleophile. This protocol excellent in terms of transition-metal-free, good functional group tolerance, easily available substrates and facile scale-up. And provided a direct- and general way to synthesize various ß-succinimide sulfides with high regioselectivity.

Precursors consumption preferences and thiol release capacity of the wine yeasts Saccharomyces cerevisiae, Torulaspora delbrueckii, and Lachancea thermotolerans.

The aromatic profile of wine determines its overall final quality, and among the volatile molecules that define it, varietal thiols are responsible for shaping the distinctive character of certain wine varieties. In grape must, these thiols are conjugated to amino acids or small peptides in a non-volatile form. During wine fermentation, yeasts play a principal role in expressing these aromatic compounds as they internalise and cleavage these precursors, releasing the corresponding free and aroma-impacting fraction. Here, we investigate the impact of three wine yeasts (Saccharomyces cerevisiae, Torulaspora delbrueckii and Lachancea thermotolerans) on thiol releasing in synthetic grape must fermentations supplemented with different cysteinylated (Cys-4MSP and Cys-3SH) and glutathionylated (GSH-4MSP and GSH-3SH) precursors. We demonstrate higher consumption levels of cysteinylated precursors, and consequently, higher amounts of thiols are released from them compared to glutathionylated ones. We also report a significant impact of yeast inoculated on the final thiols released. Meanwhile T. delkbrueckii exhibits a great 3SHA releasing capacity, L. thermotolerans stands out because of its high 3SH release. We also highlight the synergic effect of the co-inoculation strategy, especially relevant in the case of S. cerevisiae and L. thermotolerans mixed fermentation, that has an outstanding release of 4MSP thiol. Although our results stem from a specific experimental approach that differs from real winemaking situations, these findings reveal the potential of unravelling the specific role of different yeast species, thiol precursors and their interaction, to improve wine production processes in the context of wine aroma enhancement.

Facile synthesis of ß-trifluoromethyl thioethers via DBN-catalyzed hydrothiolation of a-trifluoromethyl styrenes with thiols.

A very simple and atom-economical method for the synthesis of vicinal trifluoromethyl thioethers via DBN-catalyzed hydrothiolation of α-trifluoromethyl styrenes with thiols was reported. The reaction proceeded smoothly under mild reaction conditions and provided the ß-CF3-thioethers in moderate to good yields in an anti-Markovnikov manner.

(E)-2-Benzylidenecyclanones: Part XIX. Reaction of (E)-2-(4'-X-Benzylidene)-1-tetralones with Cellular Thiols: Comparison of Thiol Reactivities of Open-Chain Chalcones and Their Six- and Seven-Membered Cyclic Analogs.

Non-enzyme-catalyzed thiol addition onto the α,ß-unsaturated carbonyl system is associated with several biological effects. Kinetics and diastereoselectivity of non-enzyme catalyzed nucleophilic addition of reduced glutathione (GSH) and N-acetylcysteine (NAC) to the six-membered cyclic chalcone analogs 2a and 2b were investigated at different pH values (pH 3.2, 7.4 and 8.0). The selected compounds displayed in vitro cancer cell cytotoxicity (IC50) of different orders of magnitude. The chalcones intrinsically reacted with both thiols under all incubation conditions. The initial rates and compositions of the final mixtures depended both on the substitution and the pH. The stereochemical outcome of the reactions was evaluated using high-pressure liquid chromatography with UV detection (HPLC-UV). The structures of the formed thiol-conjugates and the retro-Michael products (Z)-2a and (Z)-2b were confirmed by high-pressure liquid chromatography-mass spectrometry (HPLC-MS). Frontier molecular orbitals and the Fukui function calculations were carried out to investigate their effects on the six-membered cyclic analogs. Data were compared with those obtained with the open-chain (1) and the seven-membered (3) analogs. The observed reactivities do not directly relate to the difference in in vitro cancer cell cytotoxicity of the compounds.

MarR family proteins sense sulfane sulfur in bacteria.

Members of the multiple antibiotic resistance regulator (MarR) protein family are ubiquitous in bacteria and play critical roles in regulating cellular metabolism and antibiotic resistance. MarR family proteins function as repressors, and their interactions with modulators induce the expression of controlled genes. The previously characterized modulators are insufficient to explain the activities of certain MarR family proteins. However, recently, several MarR family proteins have been reported to sense sulfane sulfur, including zero-valent sulfur, persulfide (R-SSH), and polysulfide (R-SnH, n ≥ 2). Sulfane sulfur is a common cellular component in bacteria whose levels vary during bacterial growth. The changing levels of sulfane sulfur affect the expression of many MarR-controlled genes. Sulfane sulfur reacts with the cysteine thiols of MarR family proteins, causing the formation of protein thiol persulfide, disulfide bonds, and other modifications. Several MarR family proteins that respond to reactive oxygen species (ROS) also sense sulfane sulfur, as both sulfane sulfur and ROS induce the formation of disulfide bonds. This review focused on MarR family proteins that sense sulfane sulfur. However, the sensing mechanisms reviewed here may also apply to other proteins that detect sulfane sulfur, which is emerging as a modulator of gene regulation.

Role of antioxidants in modulating anti-tumor T cell immune resposne.

It has been well established that in addition to oxygen's vital in cellular respiration, a disruption of oxygen balance can lead to increased stress and oxidative injury. Similarly, reduced oxygen during tumor proliferation and invasion generates a hypoxic tumor microenvironment, resulting in dysfunction of immune cells and providing a conducive milieu for tumors to adapt and grow. Strategies to improve the persistence tumor reactive T cells in the highly oxidative tumor environment are being pursued for enhancing immunotherapy outcomes. To this end, we have focused on various strategies that can help increase or maintain the antioxidant capacity of T cells, thus reducing their susceptibility to oxidative stress/damage. Herein we lay out an overview on the role of oxygen in T cell signaling and how pathways regulating oxidative stress or antioxidant signaling can be targeted to enhance immunotherapeutic approaches for cancer treatment.

Thia- and Seleno-Michael Reactions for the Synthesis of Carbonic Anhydrases Inhibitors.

Novel chalcogen-containing amides and esters bearing the benzenesulfonamide moiety have been synthesised upon nucleophilic conjugate addition of thiols and selenols to suitable electron-deficient alkenes. The activity of the synthesised compounds as Carbonic Anhydrases inhibitors has been investigated in vitro and the inhibition mechanism has been elucidated by X-rays studies.

Competitive Binding Kinetics of Methylmercury-Cysteine with Dissolved Organic Matter: Critical Impacts of Thiols on Adsorption and Uptake of Methylmercury by Algae.

Complexes with low-molecular-weight thiols are crucial species of methylmercury (MeHg) excreted by anaerobic Hg-methylating microbes, notably, MeHg-cysteine (MeHg-Cys). As MeHg-Cys diffuses into surface water, it would undergo a ligand exchange process with dissolved organic matter (DOM) under nonsulfidic conditions, inevitably altering MeHg speciation and bioavailability to phytoplankton. In this study, we investigated the competitive binding kinetics between MeHg-Cys and Suwannee River natural organic matter, and their influence on the adsorption and uptake of MeHg by the cyanobacterium, Synechocystis sp. PCC6803. Liquid chromatography-inductively coupled plasma mass spectrometry was employed to monitor the kinetics processes involving competition of DOM with Cys for MeHg binding, which revealed that competitive binding kinetics were dictated by the abundance of thiol moieties in DOM. Thiol concentrations of 0.97 and 49.34 µmol of thiol (g C)-1 resulted in competitive binding rate constant (k values) of 0.30 and 3.47 h-1, respectively. Furthermore, the time-dependent competitive binding of DOM toward MeHg-Cys significantly inhibited MeHg adsorption and uptake by cyanobacteria, an effect that was amplified by an increased thiol abundance in DOM. These findings offer valuable insights into the kinetic characteristics of MeHg's fate and transport, as well as their impact on bioconcentration in aquatic organisms within natural aquatic ecosystems.

Thiols-rich peptide from water buffalo horn keratin alleviates oxidative stress and inflammation through co-regulating Nrf2/Hmox-1 and NF-κB signaling pathway.

Water buffalo horn (WBH), a traditional Chinese medicine, is known for its antipyretic, anti-inflammatory and antioxidant properties. This study aims to investigate the therapeutic potential of WBH keratin (WBHK) and its derived thiol-rich peptide fractions (SHPF) for oxidative stress and inflammation. WBHK and SHPF were prepared and tested using various models including LPS-induced fever in rabbits, H2O2-induced oxidative damage in bEnd.3 cells, TNF-α-induced inflammation in bEnd.3 cells and LPS-induced inflammation in RAW 264.7 cells. Expression of key markers, such as Nrf2, Hmox-1 and NF-κB, were analyzed using qRT-PCR, ELISA and Western blotting. Label-free quantitative proteomic analysis was used to identify key differential proteins associated with the efficacy of SHPF. Our results demonstrated that treatment with WBHK significantly reduced body temperature after 0.5 h of administration in the fever rabbit model. SHPF could alleviate cellular inflammatory injury and oxidative damage by activating the key transcription factor Nrf2 and increasing the expression level of Hmox-1. SHPF could inhibit the NF-κB pathway by reducing IκB phosphorylation. It was also found that SHPF could reduce pro-inflammatory cytokine (IL-6, COX-2 and PGE2) and inhibit the expression of VCAM-1, ICAM-1, IL-6 and MCP-1. Proteomics analysis showed that SHPF could inhibit HMGB1 expression and release. The results indicated that SHPF could significantly reduce inflammation and oxidative stress by regulating the Nrf2/Hmox-1 and NF-κB pathways. These findings suggest the potential therapeutic applications of WBH components in the treatment of oxidative stress and inflammation-related diseases.

Synthesis and Photovoltaic Performance of ß-Amino-Substituted Porphyrin Derivatives.

New ß-amino-substituted porphyrin derivatives bearing carboxy groups were synthesized and their performance as sensitizers in dye-sensitized solar cells (DSSC) was evaluated. The new compounds were obtained in good yields (63-74%) through nucleophilic aromatic substitution reactions with 3-sulfanyl- and 4-sulfanylbenzoic acids. Although the electrochemical studies indicated suitable HOMO and LUMO energy levels for use in DSSC, the devices fabricated with these compounds revealed a low power conversion efficiency (PCE) that is primarily due to the low open-circuit voltage (Voc) and short-circuit current density (Jsc) values.

Protein vicinal thiols as intrinsic probes of brain redox states in health, aging, and ischemia.

The nature of brain redox metabolism in health, aging, and disease remains to be fully established. Reversible oxidations, to disulfide bonds, of closely spaced (vicinal) protein thiols underlie the catalytic maintenance of redox homeostasis by redoxin enzymes, including thioredoxin peroxidases (peroxiredoxins), and have been implicated in redox buffering and regulation. We propose that non-peroxidase proteins containing vicinal thiols that are responsive to physiological redox perturbations may serve as intrinsic probes of brain redox metabolism. Using redox phenylarsine oxide (PAO)-affinity chromatography, we report that PAO-binding vicinal thiols on creatine kinase B and alpha-enolase from healthy rat brains were preferentially oxidized compared to other selected proteins, including neuron-specific (gamma) enolase, under conditions designed to trap in vivo protein thiol redox states. Moreover, measures of the extents of oxidations of vicinal thiols on total protein, and on creatine kinase B and alpha-enolase, showed that vicinal thiol-linked redox states were stable over the lifespan of rats and revealed a transient reductive shift in these redox couples following decapitation-induced global ischemia. Finally, formation of disulfide-linked complexes between peroxiredoxin-2 and brain proteins was demonstrated on redox blots, supporting a link between protein vicinal thiol redox states and the peroxidase activities of peroxiredoxins. The implications of these findings with respect to underappreciated aspects of brain redox metabolism in health, aging, and ischemia are discussed.

Photosynthetic variation and detoxification strategies based on cadmium uptake, non-protein thiols, and secondary metabolites in Miscanthus sacchariflorus under cadmium exposure.

Miscanthus sacchariflorus is previously demonstrated to be a potential candidate for remediation of cadmium (Cd) pollution. To explore its resistance strategy to Cd, a hydroponic experiment was conducted to determine the variations of photosynthetic activity in leaves and physiological response in roots of this plant. Results showed that the root of M. sacchariflorus was the primary location for Cd accumulation. The bioconcentration factor in the roots and rhizomes was >1, and the translocation factor from underground to aboveground was <1. Throughout the experimental period, treatment with 0.06 mM Cd2+ did not significantly alter the contents of chlorophyll a, chlorophyll b, or carotenoid. By contrast, treatment with 0.15 and 0.30 mM Cd2+ decreased the contents of chlorophyll a, chlorophyll b, and carotenoid; caused the deformation of the chlorophyll fluorescence transient curve; reduced the photochemical efficiency of photosystem II; and increased the contents of non-protein thiols, total flavone, and total phenol. These results indicate that M. sacchariflorus has good adaptability to 0.06 mM Cd2+. Moreover, the accumulation of the non-protein thiols, total flavone, and total phenol in roots may promote the chelation of Cd2+, thus alleviating Cd toxicity. This study provides theoretical support for using M. sacchariflorus to remediate Cd-polluted wetlands.

Multimodal Acridine Photocatalysis Enables Direct Access to Thiols from Carboxylic Acids and Elemental Sulfur.

Development of photocatalytic systems that facilitate mechanistically divergent steps in complex catalytic manifolds by distinct activation modes can enable previously inaccessible synthetic transformations. However, multimodal photocatalytic systems remain understudied, impeding their implementation in catalytic methodology. We report herein a photocatalytic access to thiols that directly merges the structural diversity of carboxylic acids with the ready availability of elemental sulfur without substrate preactivation. The photocatalytic transformation provides a direct radical-mediated segue to one of the most biologically important and synthetically versatile organosulfur functionalities, whose synthetic accessibility remains largely dominated by two-electron-mediated processes based on toxic and uneconomical reagents and precursors. The two-phase radical process is facilitated by a multimodal catalytic reactivity of acridine photocatalysis that enables both the singlet excited state PCET-mediated decarboxylative carbon-sulfur bond formation and the previously unknown radical reductive disulfur bond cleavage by a photoinduced HAT process in the silane-triplet acridine system. The study points to a significant potential of multimodal photocatalytic systems in providing unexplored directions to previously inaccessible transformations.

Design, Synthesis and Catalytic Activity of Protein Containing Thiotyrosine as an Active Site Residue.

Native chemical ligation is a key reaction in the toolbox of chemical methods for the synthesis of native and modified proteins. The catalysis of ligation is commonly performed by using small aryl-thiol molecules added at high concentrations. In this work, we incorporated thiotyrosine, a non-canonical amino acid containing an aryl-thiol moiety, into a designed cyclic protein « sans queue ni tête ¼. Importantly, the protein environment reduced the pKa of the thiol group to 5.8-5.9, which is significantly lower than the previously reported value for thiotyrosine in a short peptide (pKa 6.4). Furthermore, we demonstrated the catalytic activity of this protein both as hydrolase and in native chemical ligation of peptides. These results will be useful for the development of efficient protein catalysts (enzymes) for protein synthesis and modification.

Products of Selenite/Thiols Interaction Have Reducing Properties, Cleave Plasmid DNA and Decrease Rat Blood Pressure and Tension of Rat Mesenteric Artery.

Selenium compounds exert their antioxidant activity mostly when the selenium atom is incorporated into selenoproteins. In our work, we tested the possibility that selenite itself interacts with thiols to form active species that have reducing properties. Therefore, we studied the reduction of 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazol-1-yloxy-3-oxide radical (•cPTIO), damage of plasmid DNA (pDNA), modulation of rat hemodynamic parameters and tension of isolated arteries induced by products of interaction of selenite with thiols. We found that the products of selenite interaction with thiols had significant reducing properties that could be attributed mainly to the selenide and that selenite had catalytic properties in the access of thiols. The potency of thiols to reduce •cPTIO in the interaction with selenite was cysteine > homocysteine > glutathione reduced > N-acetylcysteine. Thiol/selenite products cleaved pDNA, with superoxide dismutase enhancing these effects suggesting a positive involvement of superoxide anion in the process. The observed •cPTIO reduction and pDNA cleavage were significantly lower when selenomethionine was used instead of selenite. The products of glutathione/selenite interaction affected several hemodynamic parameters including rat blood pressure decrease. Notably, the products relaxed isolated mesenteric artery, which may explain the observed decrease in rat blood pressure. In conclusion, we found that the thiol/selenite interaction products exhibited significant reducing properties which can be used in further studies of the treatment of pathological conditions caused by oxidative stress. The results of decreased rat blood pressure and the tension of mesenteric artery may be perspective in studies focused on cardiovascular disease and their prevention.

[High performance liquid chromatography combined with the 2,2'-dithiodipyridine derivatization reaction for determination of different types of free thiols in human serum and analysis of their relationship with coronary heart disease].

Oxidative stress, which is characterized by an imbalance between antioxidants and free radicals, plays a pivotal role in the pathogenesis of coronary heart disease, a common and serious cardiovascular condition, and contributes significantly to its development and progression. Serum free thiols are crucial components of the body's antioxidant defense system. The accurate determination of serum free thiol levels provides a reference basis for understanding the body's status and monitoring the risk factors associated with the occurrence and progression of coronary heart disease. In this study, a high performance liquid chromatographic (HPLC) method based on the derivatization reaction of 2,2'-dithiodipyridine was developed to simultaneously obtain the concentrations of total free thiols (Total-SH), low-molecular-mass free thiols (LMM-SH), and protein-free thiols (P-SH) in human serum. An Agilent Eclipse XDB-C18 column (150 mm×4.6 mm, 5 µm) was used for the analysis, and gradient elution was performed at a flow rate of 1 mL/min. A 0.1% formic acid aqueous solution was used as mobile phase A, and a 0.1% formic acid acetonitrile solution was used as mobile phase B. The gradient elution program was as follows: 0-0.1 min, 12%B-30%B; 0.1-2 min, 30%B; 2-2.1 min, 30%B-100%B; 2.1-6 min, 100%B; 6-6.1 min, 100%B-12%B; 6.1-7 min, 12%B. Well-separated peaks appeared after a run time of 5 min. The peak of 2-thiopyridone represented the Total-SH content of the samples, and the peak of the pyridyldithio derivative represented the LMM-SH content. The difference between these two peaks indicated the P-SH content. The derivatization reaction conditions were optimized, and the method was validated. The method demonstrated good linearity, with a correlation coefficient ≥0.9994, over the concentration range of 31.25-1000 µmol/L. The limits of detection for Total-SH and LMM-SH were 2.61 and 0.50 µmol/L, and the limits of quantification for Total-SH and LMM-SH were 8.71 and 1.67 µmol/L, respectively. The recoveries of Total-SH and LMM-SH were in the range of 91.1%-106.0%. The intra- and inter-day precisions ranged from 0.4% to 9.1%. The developed method was used to analyze serum samples from 714 volunteers. The Total-SH concentrations ranged from 376.60 to 781.12 µmol/L, with an average concentration of 555.62 µmol/L. The LMM-SH concentrations varied from 36.37 to 231.65 µmol/L,with an average of 82.34 µmol/L. The P-SH concentrations ranged from 288.36 to 687.74 µmol/L, with an average of 473.27 µmol/L. Spearman's correlation test showed that serum thiol levels were correlated with the severity of coronary artery disease and common clinical biochemical indicators. The proposed study provides a simple and reliable HPLC method for detecting serum free thiols and exploring their relationship with coronary heart disease, offering a new reference for the study of markers related to the risk of coronary heart disease.

Formation of Supplementary Metal-Binding Centers in Proteins under Stress Conditions.

In many proteins, supplementary metal-binding centers appear under stress conditions. They are known as aberrant or atypical sites. Physico-chemical properties of proteins are significantly changed after such metal binding, and very stable protein aggregates are formed, in which metals act as "cross-linking" agents. Supplementary metal-binding centers in proteins often arise as a result of posttranslational modifications caused by reactive oxygen and nitrogen species and reactive carbonyl compounds. New chemical groups formed as a result of these modifications can act as ligands for binding metal ions. Special attention is paid to the role of cysteine SH-groups in the formation of supplementary metal-binding centers, since these groups are the main target for the action of reactive species. Supplementary metal binding centers may also appear due to unmasking of amino acid residues when protein conformation changing. Appearance of such centers is usually considered as a pathological process. Such unilateral approach does not allow to obtain an integral view of the phenomenon, ignoring cases when formation of metal complexes with altered proteins is a way to adjust protein properties, activity, and stability under the changed redox conditions. The role of metals in protein aggregation is being studied actively, since it leads to formation of non-membranous organelles, liquid condensates, and solid conglomerates. Some proteins found in such aggregates are typical for various diseases, such as Alzheimer's and Huntington's diseases, amyotrophic lateral sclerosis, and some types of cancer.