Cysteine Derivatives Research Articles

Poly(S-ethylsulfonyl-l-homocysteine): An α-Helical Polypeptide for Chemoselective Disulfide Formation

Homocysteine and cysteine are the only natural occurring amino acids that are capable of disulfide bond formations in peptides and proteins. The chemoselective formation of asymmetric disulfide bonds, however, is chemically challenging and requires an activating group combining stability against hard nucleophiles, e.g., amines, with reactivity toward thiols and soft nucleophiles. In light of these considerations, we introduced the S-alkylsulfonyl cysteines in our previous work. Here, we present the synthesis and ring-opening polymerization of S-ethylsulfonyl-l-homocysteine N-carboxyanhydrides. We demonstrate that the polymerization leads to narrowly distributed polypeptides (Đ = 1.1–1.3) with no detectable side reactions in a chain length regime from 11 to 165. In contrast to the already reported cysteine derivatives, poly(S-ethylsulfonyl-l-homocysteine)s do not form β-sheets, which reduce solubility and limit the degree of polymerization of poly(S-ethylsulfonyl-l-cysteine)s to 50. Instead, these polymers...

Anti-inflammatory action of cysteine derivative S-1-propenylcysteine by inducing MyD88 degradation

The degradation of target proteins by small molecules utilizing the cellular proteolytic system is featured as a treatment strategy of several diseases. We found that S-1-propenylcysteine (S1PC) among several cysteine derivatives in aged garlic extract inhibited TLR-mediated IL-6 production by inducing the degradation of adaptor protein MyD88. We showed that S1PC directly denatured MyD88 and induced the formation of protein aggregates. Consequently, MyD88 was degraded by aggresome-autophagy pathway. On the other hand, S-allylcysteine, a structural analog of S1PC, failed to induce the degradation of MyD88 because of its inability to denature MyD88 although it also activated autophagy. Our findings suggest that S1PC induces MyD88 degradation through the denaturation of MyD88 and the activation of autophagy. Thus, S1PC may serve as the base to develop a therapeutic means for immune diseases associated with aberrant TLR signaling pathways.

Speciation of reactive sulfur species and their reactions with alkylating agents: do we have any clue about what is present inside the cell?

Buffered aqueous solutions of inorganic, organic, cysteine, GSH and GAPDH polysulfide species were used. Additional experiments in human plasma and serum revealed that monobromobimane can extract sulfide from the endogenous sulfur pool by shifting speciation equilibria, suggesting caution should be exercised when interpreting experimental results using this tool. In the majority of cases, the speciation of alkylated polysulfide/thiol derivatives depended on the experimental conditions. Alkylation perturbed sulfur speciation in both a concentration- and time-dependent manner and strong alkylating agents cleaved polysulfur chains. Moreover, the labelling of sulfenic acids with dimedone also affected cysteine speciation, suggesting that part of the endogenous pool of products previously believed to represent sulfenic acid species may represent polysulfides. We highlight methodological caveats potentially arising from these pitfalls and conclude that current derivatization strategies often fail to adequately capture physiological speciation of sulfur species. This article is part of a themed section on Chemical Biology of Reactive Sulfur Species. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.4/issuetoc.

Preparation and Physicochemical Properties of a Cysteine Derivative‐Loaded Deformable Liposomes in Hydrogel for Enhancing Whitening Effects

Whitening materials cannot easily cross the skin barrier (stratum corneum) to reach melanocytes in the basal layer for inhibiting melanin production. This study aims to construct a novel deformable liposome using polyglyceryl‐3‐methylglucose distearate as an edge activator and a hydrogel containing hyaluronic acid (HA) and hydroxyethyl cellulose (HEC), as well as to investigate the synergistic effect of this system on the delivery of a cysteine derivative, methyl‐2‐acetylamino‐3‐(4‐hydroxyl‐3,5‐dimethoxybenzoylthio)propanoate (MP) as a whitening agent. The optimized deformable liposome (DL2) contains 10% edge activator and has a particle size of 78.2 ± 2.7 nm, a zeta potential of −29.9 ± 1.8 mV, a polydispersity index of 0.248, and an entrapment efficiency of 90.7 ± 1.7%. MP‐loaded DL2 has higher stability and deformability than DL2 without MP, as well as exerting a higher whitening effect than that observe with MP alone. In addition, MP‐loaded DL2 is incorporated into a hydrogel in a dual drug‐delivery system and the stability after hydrogel incorporation is evaluated. In Franz cells, the MP‐loaded deformable liposome‐hydrogel complex shows the highest skin permeation and penetration of MP.Practical Applications: In general, it is very difficult for whitening agents to penetrate a skin layer for reducing skin pigmentation. It is important to transfer whitening agents to the basal layer without causing physical damage to the skin. Deformable liposomes containing 10% polyglyceryl‐3‐methylglucose distearate in a hydrogel complex maximize the skin permeation of a cysteine derivative as a whitening agent. This finding indicates that the deformable liposome‐hydrogel complex is a potential delivery system for treatment of skin hyperpigmentation.The penetration mechanism of drugs in the skin by deformable liposome‐hydrogel complexes is as follows: Hydrogel hydrates stratum corneum to secure the route of drugs or nanocarrier permeation. polyglyceryl‐3‐methylglucose distearate as an edge activator enhances the fluidity of the stratum corneum lipid layer and the deformability of liposome. The edge activator‐based deformable liposomes pass through the stratum corneum stably.

Molecular diversity and function of jasmintides from Jasminum sambac

BackgroundJasmintides jS1 and jS2 from Jasminum sambac were previously identified as a novel family of cysteine-rich peptides (CRPs) with an unusual disulfide connectivity. However, very little else is known about jasmintides, particularly their molecular diversity and functions. Here, we report the discovery and characterization of a novel suite of jasmintides from J. sambac using transcriptomic, peptidomic, structural and functional tools.ResultsTranscriptomic analysis of leaves, flowers and roots revealed 14 unique jasmintide precursors, all of which possess a three-domain architecture comprising a signal peptide, a pro-domain and a mature jasmintide domain. Peptidomic analysis, using fractionated mixtures of jasmintides and chemical derivatization of cysteine to pseudolysine, trypsin digestion and MS/MS sequencing, revealed an additional 86 jasmintides, some of which were post-translationally modified. NMR analysis showed that jasmintide jS3 has three anti-parallel β-strands with a three-disulfide connectivity of CysI−CysV, CysII−CysIV and CysIII−CysVI, which is similar to jasmintide jS1. Jasmintide jS3 was able to withstand thermal, acidic and enzymatic degradation and, importantly, exhibited antifeedant activity against mealworm Tenebrio molitor.ConclusionTogether, this study expands the existing library of jasmintides and furthers our understanding of the molecular diversity and cystine framework of CRPs as scaffolds and tools for engineering peptides targeting pests.

Radiolabeling and Preclinical Evaluation of a New S-Alkylated Cysteine Derivative Conjugated to C-Substituted Macrocycle for Positron Emission Tomography.

A new S-alkylated cysteine-derivatized tumor targeting agent, 2,2′-(12-(2-((2-acetamido-2-carboxyethyl)thio)acetamido)-11,13-dioxo-1,4,7,10-tetraazacyclotridecane-4,7-diyl)diacetic acid was developed for positron emission tomography (PET) imaging. N-Acetyl cysteine (NAC) was conjugated to ATRIDAT as a specific targeting agent toward L-type and ASC amino acid transporter systems in the oncogenic cells. NAC was attached via S-alkylation to prevent its incorporation at undesired recognition sites affecting the signal-to-noise ratio. NAC-ATRIDAT was subjected to gallium-68 complexation with >75% radiolabeling yield. The radiocomplex was purified through the tc18 cartridge to obtain 99.89% radiochemical yield. IC-50 of the NAC-ATRIDAT conjugate was 0.8 mM in A549 cells as evaluated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazonium bromide assay. Binding affinity experiments on A549 cells showed noteworthy binding with KD in the nanomolar range. A time course study showed a Km value of 0.19 μM and Vmax value of 0.49 pmol/μg protein/min showing reasonable tumor kinetics. Efflux studies showed that the synthesized radioligand is transported majorly by LAT followed by the ASC system. Clearance was found to be renal with 7.67 ± 1.48% ID/g uptake at 30 min which substantially declined to 0.52 ± 0.% ID/g at 4 h. A significant uptake of 10.06 ± 1.056% ID/g was observed at the tumor site in mice at 1 h. μPET images revealed a high contrast with a tumor-to-kidney ratio of 4.8 and a tumor-to-liver ratio of 35.85 at 1 h after injection. These preclinical in vitro and in vivo evaluation supports its potential on the way of becoming a successful 68Ga-radiolabeled amino acid-based PET imaging agent.

Perylene diimide cysteine derivatives self-assembled onto (111) gold surface: Evidence of ordered aggregation

Perylene diimide derivatives containing pendant cysteine residues are subjected to a strong self-assembly onto [1 1 1] Au films due to the presence of thiol functionality. The preparation of two different Au surfaces easies the understanding of both surface packing and morphology of the aggregated ordered films, by means of the combination of X-ray photoelectron spectroscopy, atomic force microscopy, and grazing incident wide X-ray scattering - synchrotron radiation - techniques. A proper correlation of the resulting data, together with conformational calculations - using a detailed molecular modelling - allow supplying a coherent scenario.In particular, isolated ordered pillars upstanding to the substrate plane are detected on native gold surface, while a π-stacked aggregation “unregistered” normally to the film plane is observed when perylene derivatives are grafted onto thermally annealed gold surface.Such a surface organization is expected to be favourable to the charge mobility, therefore its use in organic field effect transistor is envisioned.

Impact Of Biological Liquid Composition On The Effectiveness Of Cold Atmospheric Pressure Plasmas

Cold atmospheric pressure plasma treatment shows promising results for the use in cancer therapy for in vitro and in vivo experiments. Even a selective effect on cancer cells is possible, but the underlying mechanisms need to be determined [1]. As plasmas are gaseous systems, important parts of the interaction between plasma and biological systems are mediated and modulated, by the liquid surrounding the treated cell or tissue. Small reactive oxygen or nitrogen species (RONS) serve as signaling molecules to modulate physiological processes within cells, for example via thiol-switches of cysteine residues within proteins [2]. These modifications lead to an altered enzymatic activity, or changes in protein expression levels as part of various redox signaling pathways. Many cancer cell types have a changed redox metabolism, offering the possibility to selectively target these cells with reactive molecules. It is hypothesized, that short-lived species generated by plasma may transfer their chemical energy to organic compounds within the biological liquids and such derivatives have a prolonged activity towards the cell. To challenge this hypothesis, we used cysteine as a model substance because of its important role in protein function. Its thiol group is able to undergo various covalent modifications and the molecule was successfully used to determine the chemical footprint of different plasma sources. Depending on plasma treatment parameters, the formation of various, potentially bioactive cysteine derivatives is possible [3]. Among them are disulfide-S-oxides, which can modify redox sensitive proteins [4]. Using various argon plasma jets with oxygen and nitrogen admixtures (kINPen MED, kINPen09, neoplas/neoplas tools) we treated cysteine in physiological buffer and applied the resulting product mix in various in vitro cell models. The effect on human keratinocytes, especially on their short and long term proliferative and migratory capability, the interleukin secretion, and the intracellular oxidative potential, was explored. To minimize the impact of plasma generated long lived ROS, catalase and a rest time between treatment and cell challenge was employed. In contrast to the hypothesis, no major impact on the tested cell functions was observed. Yet, interleukin secretion and intracellular ROS levels showed changes and will be discussed.

Potential impact of natural organic ligands on the colloidal stability of silver nanoparticles

Interaction of natural organic matter (NOM) with engineered nanoparticles (NPs) determine NP fate, transport, and environmental persistence. However, the effect of NOM chemical composition, structure, and concentration on aggregation kinetics and dissolution behavior of silver nanoparticles (AgNPs) are still poorly understood because of heterogeneity and variability in NOM and AgNP properties. Here, aggregation behavior of citrate-coated silver nanoparticles (cit-AgNPs with a z-average diameter of 18nm) was investigated in the presence of l-cysteine (l-cys) and N-acetyl l-cysteine (NAL-cys) using UV–vis spectroscopy. We also investigated the effect of Suwannee River fulvic acid (SRFA) and a NOM isolated from the Yukon River (YRNOM) on the stability of cit-AgNPs. The dissolution of cit-AgNPs decreased with increased L-cys and NAL-cys concentration from 0 to 10μM. The critical coagulation concentration (CCC) of cit-AgNPs decreased in the presence of l-cys and increased in the presence of NAL-cys. Similarly, l-cys destabilizes cit-AgNPs in the presence of SRFA. The differences in the stability of cit-AgNPs in the presence of l-cys and NAL-cys can be attributed to the differences in the functional groups in these two cysteine molecules. l-cys has both negatively charged carboxylic group and a positively charged amine group, resulting in bridging between different particles. NAL-cys is a derivative of cysteine wherein an acetyl group is attached to the nitrogen atom thus shielding the positive charge on the amine group and therefore eliminating the bridging interaction mechanism. SRFA and YRNOM enhanced the stability of cit-AgNPs and increased the CCC value to higher counter ion concentrations. The concentration of SRFA (1–5mgL−1) did not affect the CCC, whereas the increased concentration of YRNOM increased the CCC of cit-AgNPs to high Na+ concentrations likely due to increased sorption of higher molecular weight compounds on the surface of cit-AgNPs. The outcome of this study suggests the importance of understanding the molecular properties of NOM (e.g. functional groups and molecular weight) in determining cit-AgNP environmental behaviors.

Synthesis of Thelepamide via Catalyst-Controlled 1,4-Addition of Cysteine Derivatives and Structure Revision of Thelepamide.

The first enantioselective total synthesis and structural reassignment of (-)-thelepamide, a cytotoxic tetraketide-amino acid from the marine worm Thelepus crispus, is reported. A convergent approach provides access to all thelepamide diastereomers in six steps from four simple building blocks. Key features of the synthesis include the application of Melchiorre's organocatalytic thia-Michael reaction and a sonication-assisted assembly of an unprecedented N,O-acetal-hemiacetal moiety. The corrected structure was confirmed by NMR-DFT analysis.

Reactive Cysteine Persulphides: Occurrence, Biosynthesis, Antioxidant Activity, Methodologies, and Bacterial Persulphide Signalling.

Cysteine hydropersulphide (CysSSH) is a cysteine derivative having one additional sulphur atom bound to a cysteinyl thiol group. Recent advances in the development of analytical methods for detection and quantification of persulphides and polysulphides have revealed the biological presence, in both prokaryotes and eukaryotes, of hydropersulphides in diverse forms such as CysSSH, homocysteine hydropersulphide, glutathione hydropersulphide, bacillithiol hydropersulphide, coenzyme A hydropersulphide, and protein hydropersulphides. Owing to the chemical reactivity of the persulphide moiety, biological systems utilize persulphides as important intermediates in the synthesis of various sulphur-containing biomolecules. Accumulating evidence has revealed another important feature of persulphides: their potent reducing activity, which implies that they are implicated in the regulation of redox signalling and antioxidant functions. In this chapter, we discuss the biological occurrence and possible biosynthetic mechanisms of CysSSH and related persulphides, and we include descriptions of recent advances in the analytical methods that have been used to detect and quantitate persulphide species. We also discuss the antioxidant activity of persulphide species that contributes to protecting cells from reactive oxygen species-associated damage, and we examine the signalling roles of CysSSH in bacteria.

Asymmetric Synthesis of β-Lactams by Intramolecular Conjugate Addition of Serine and Cysteine Derivatives via Memory of Chirality

Asymmetric Synthesis of β-Lactams by Intramolecular Conjugate Addition of Serine and Cysteine Derivatives via Memory of Chirality

Influence of long-term per oral taurine treatment on activity of liver enzymes in mature rats

Taurine is sulfur-containing derivative of methionin and cysteine that plays a key role in glucose and lipid metabolism. Taurine regulates antioxidant defense system, membrane potential of mitochondria, and glycolysis. Thus, it might have a serious impact on cell metabolism in mammals. The aim of this work was to study the influence of long-term per oral taurine treatment (5, 10 and 20 mg/kg) on the antioxidant defense system, cholesterol content, activity of transaminases and lactate dehydrogenase in rat liver. To achieve that goal, mature Wistar rats (weight 140–160 g, age – 4 months) were divided in four groups – control, rats which once a day during 28 days were injected drinking water in esophagus, and three experimental groups, that were injected taurine solution in concentrations: І – 5 mg/kg, ІІ – 10 mg/kg and ІІІ – 20 mg/kg of body mass. After 28 days, rats were decapitated under light chloroform narcosis and liver mass was determined. In liver, content of cholesterol, TBA-active products and activity of antioxidant defense enzymes, transaminases, and lactate dehydrogenase were measured. Our results show that after a long-term per oral taurine treatment liver mass decreased by 27.5 % comparing to control group. Lactate dehydrogenase activity increased two times, while the activity of alanine aminotranferase and aspartate aminotransferase in mitochondrial fraction increased by 40–90 % in liver of animals of all experimental groups. Total activity of these enzymes in rat liver increased by 20–37 % in all experimental groups. Cholesterol content increased dy 32.4 % in rats of experimental group II. This may indicate intensification of liver metabolism. The content of TBA-active products in submitochondrial and mitochondrial fractions increased more than two times in rats of experimental groups II and III. The activity of superoxide dismutase in the submitochondrial fraction increased by 49.8 and 36.5 % in liver of that rats. The activation of superoxi­de dismutase and a rise in content of TBA-active products may suggest a rise of free oxygen radicals production and inability of antioxidant defense system. These results may indicate a negative influence of taurine in doses higher than 5 mg/kg, since the balance between antioxidant protection and lipid peroxidation processes was violated.

Disulphide bond exchange inhibited by air - kinetic and thermodynamic products in a library of macrocyclic cysteine derivatives.

In this paper we present the synthesis and reactivity of dithiols comprising of two cysteine moieties attached to a dipicolinic acid core. Oxidation of these thiols provides oligomeric macrocycles. Monomers with 13-membered rings are kinetic products which are, however, strained and readily transform into higher oligomers under basic conditions or elevated temperature via a disulphide exchange reaction. Dimers, which are the most stable thermodynamic products, equilibrate only under inert conditions with thiolate as a catalyst. Under aerobic conditions, the thiols are oxidised before the equilibrium is reached.

Mechanism of N-to-S acyl transfer of N-(2-hydroxybenzyl) cysteine derivatives and origin of phenol acceleration effect

N-(2-Hydroxybenzyl)cysteine derivatives were recently disclosed to be efficient crypto-thioesters for native chemical ligation (NCL). To elucidate the mechanism of the relevant N-to-S acyl transfer process as well as the origin of the acceleration effect of the phenol substitutes, a density functional theory (DFT) study was performed. It was found that the N-to-S acyl transfer of N-(2-hydroxybenzyl)cysteine derivatives involve four major steps: concerted nucleophilic addition of thiolate/proton transfer, inversion of an amine moiety, water-assisted proton transfer and CN bond cleavage. The phenol substitutes promote the nucleophilic addition of thiolate by protonating the carbonyl oxygen atom synergistically and the proton transfer from hydroxyl to amide nitrogen atom is the rate-determining step of the N-to-S acyl transfer. By contrast, changing the phenolic hydroxyl to methoxyl was found to significantly slow down the nucleophilic addition of thiolate and thus hinders the N-to-S acyl transfer overall. These computational results are consistent with the observation of previously reported control experiments, by which our proposed mechanism is further validated.

A zinc Schiff base complex inhibits cancer progression both in vivo and in vitro by inducing apoptosis

Cancer chemotherapy suffers from selectivity and undesired toxicity of the drugs. Since zinc is a biocompatible tracer element and cysteine derivatives are used in cancer chemoprevention, we intend to develop a complex of zinc and cysteine-derivatives as potent, non-toxic anticancer agents. Herein, we synthesized and characterized cysteine based ligand, 2-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-3-mercapto-propionic acid and its Zn-complex, which are found to be non-toxic towards normal human PBMC. Data also revealed that only Zn-complex exhibited remarkable apoptosis in drug-sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 cancer cells as assessed by MTT, Cell cycle and AnnexinV binding assay. Moreover, Zn-complex altered ROS and GSH level of the respective cell lines. Finally, treatment of Zn-complex in Swiss albino mice did not show any systemic toxicity in preliminary trials in normal mice and remarkably increased the life-span of EAC bearing mice. In conclusion, the synthesized Zn-complex may be developed for efficacious, multidrug resistance reversal, non-toxic chemotherapeutic agents in future.

Norbornene probes for the study of cysteine oxidation

Cysteine residues on proteins can react with cellular oxidants such as hydrogen peroxide. While this process is important for scavenging excess reactive oxygen species, the products of this oxidation may also mediate cell signalling. To understand the role of cysteine oxidation in biology, selective probes are required to detect and quantify its occurrence. Cysteine oxidation products such as sulfenic acids are sometimes unstable and therefore short-lived. If such cysteine derivatives are to be analysed, rapid reaction with the probe is required. Here we introduce norbornene derivatives as probes for cysteine oxidation, and demonstrate their ability to trap sulfenic acids. The synthesis of norbornene derivatives containing alkyne or biotin affinity tags are also reported to facilitate the use of these probes in chemical biology and proteomics.

CdSe Quantum Dots Functionalized with Chiral, Thiol-Free Carboxylic Acids: Unraveling Structural Requirements for Ligand-Induced Chirality.

Functionalization of colloidal quantum dots (QDs) with chiral cysteine derivatives by phase-transfer ligand exchange proved to be a simple yet powerful method for the synthesis of chiral, optically active QDs regardless of their size and chemical composition. Here, we present induction of chirality in CdSe by thiol-free chiral carboxylic acid capping ligands (l- and d-malic and tartaric acids). Our circular dichroism (CD) and infrared experimental data showed how the presence of a chiral carboxylic acid capping ligand on the surface of CdSe QDs was necessary but not sufficient for the induction of optical activity in QDs. A chiral bis-carboxylic acid capping ligand needed to have three oxygen-donor groups during the phase-transfer ligand exchange to successfully induce chirality in CdSe. Intrinsic chirality of CdSe nanocrystals was not observed as evidenced by transmission electron microscopy and reverse phase-transfer ligand exchange with achiral 1-dodecanethiol. Density functional theory geometry optimizations and CD spectra simulations suggest an explanation for these observations. The tridentate binding via three oxygen-donor groups had an energetic preference for one of the two possible binding orientations on the QD (111) surface, leading to the CD signal. By contrast, bidentate binding was nearly equienergetic, leading to cancellation of approximately oppositely signed corresponding CD signals. The resulting induced CD of CdSe functionalized with chiral carboxylic acid capping ligands was the result of hybridization of the (achiral) QD and (chiral) ligand electronic states controlled by the ligand's absolute configuration and the ligand's geometrical arrangement on the QD surface.

Visible‐Light‐Mediated Selective Arylation of Cysteine in Batch and Flow

AbstractA mild visible‐light‐mediated strategy for cysteine arylation is presented. The method relies on the use of eosin Y as a metal‐free photocatalyst and aryldiazonium salts as arylating agents. The reaction can be significantly accelerated in a microflow reactor, whilst allowing the in situ formation of the required diazonium salts. The batch and flow protocol described herein can be applied to obtain a broad series of arylated cysteine derivatives and arylated cysteine‐containing dipeptides. Moreover, the method was applied to the chemoselective arylation of a model peptide in biocompatible reaction conditions (room temperature, phosphate‐buffered saline (PBS) buffer) within a short reaction time.

Visible-Light-Mediated Selective Arylation of Cysteine in Batch and Flow.

A mild visible‐light‐mediated strategy for cysteine arylation is presented. The method relies on the use of eosin Y as a metal‐free photocatalyst and aryldiazonium salts as arylating agents. The reaction can be significantly accelerated in a microflow reactor, whilst allowing the in situ formation of the required diazonium salts. The batch and flow protocol described herein can be applied to obtain a broad series of arylated cysteine derivatives and arylated cysteine‐containing dipeptides. Moreover, the method was applied to the chemoselective arylation of a model peptide in biocompatible reaction conditions (room temperature, phosphate‐buffered saline (PBS) buffer) within a short reaction time.