Cysteine Derivatives Research Articles

Memory of Chirality in the Electrochemical Oxidation of Thiazolidine-4-carboxylic Acid Derivatives

Memory of chirality in the electrochemical oxidation of thiazolidine-4-carboxylic acid derivatives was observed. The relatively larger size of sulphur atom than the oxygen atom for oxazolidine-4-carboxylic acid derivative may slightly improved the enantioselectivities of the oxidized products. The bulkier penicillamine derivative 1c furnished 2c with much better enantioselectivity (91% ee) than that of the cysteine derivative 2b (85% ee). The presence of two extra dimethyl groups, for the penicillamine derivative improved the enantioselectivities of the thiazolidine derivatives from 85% ee to 91 % ee.

Preparation of Arylmercapturic Acids by S‐Arylation of N,N′‐Diacetylcystine

AbstractA simple convenient method has been developed for the preparation of N‐acetyl‐S‐arylcysteines based on the Chan–Lam–Evans arylation of N,N′‐diacetylcystine dimethyl ester with arylboronic acids and used to synthesize a series of arylmercapturic acids. Unlike copper‐mediated N‐arylation, the S‐arylation of neither cysteine nor cystine derivatives proceeded satisfactorily in the presence of air.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Wavelength-Selective Photoactivatable Protecting Groups for Thiols

We developed and characterized efficient, remarkably water-soluble photolabile protecting groups for thiols based on 2-nitrobenzyl and (coumarin-4-yl)methyl chromophores, among them two new ones. The protecting groups allow, due to their different absorption maxima, wavelength-selective photocleavage of binary mixtures of cysteine derivatives protected at the thiol function with various photolabile protecting groups by irradiation with light. The concept was also functional with the two different S-protected cysteine residues in derivatives of the model peptide resact. Selective photolysis could be achieved for the peptides Ac(0)-Cys(1)(BCMACMOC),Cys(8)(7,8BCMCMOC)-resact and Ac(0)-Cys(1)(C4MNB),Cys(8)(BCMACMOC)-resact by irradiation with light of > or = 402 nm or > or = 436 nm wavelength, respectively, followed by irradiation at lambda > or = 325 nm.

Thiol‐Ene Radical Addition of L‐Cysteine Derivatives to Low Molecular Weight Polybutadiene

AbstractThe functionalisation of a low molecular weight, liquid 1,2‐polybutadiene (PBL) was performed by the addition of either N‐acetyl‐L‐cysteine or its methyl ester through the thiol‐ene radical reaction. The functionalisation runs were carried out in 1,4‐dioxane solution and in the presence of a free radical initiator (2,2′‐azobisisobutyrronitrile, AIBN). The initial feed ratio polymer/cysteine derivative/initiator was varied, in order to highlight the occurrence of side reactions and to understand their possible influence on the process. The 1H NMR determination of the functionalisation degree brought out high addition degrees of thiols, regardless of the initial thiol/double bonds ratio. This caused a drastic change in the macroscopic properties of the PBL with improved solubility in hydrophilic solvents (for instance in alkaline aqueous solutions) and impressive increase of the glass transition temperature. The propagation of chiral properties from the functionalising agents to the modified polymers was evaluated by polarimetry and circular dichroism in solution.magnified image

Safener responsiveness and multiple herbicide resistance in the weed black‐grass (Alopecurus myosuroides)

Safeners enhance the selectivity of graminicidal herbicides such as fenoxaprop ethyl in cereals, by increasing their rates of detoxification in the crop. While studying the selectivity of fenoxaprop ethyl in wheat, we determined that the safeners mefenpyr diethyl and fenchlorazole ethyl also enhanced herbicide tolerance in the competing weed black-grass (Alopecurus myosuroides). Fenoxaprop ethyl was detoxified by conjugation with glutathione in both wheat and black-grass, with the resulting metabolites processed to the respective cysteine derivatives, which were then N-glycosylated. In black-grass, these detoxification pathways were only slightly enhanced by safeners, suggesting that metabolism alone was unlikely to account for increased herbicide tolerance. Instead, it was determined that safening was associated with an accumulation of glutathione and hydroxymethylglutathione and enzymes with antioxidant functions including phi and lambda glutathione transferases, active as glutathione peroxidases and thiol transferases respectively. These safener-induced changes closely mirrored those determined in two independent black-grass populations that had acquired multiple herbicide resistance (MHR) in the field. In addition to enhanced glutathione metabolism, both safener treatment and MHR resulted in elevated levels of flavonoids in the foliage of black-grass plants, notably flavone-C-glycosides and anthocyanins. Our results demonstrate that safening in a grass weed is associated with an inducible activation in antioxidant and secondary metabolism which mirrors the biochemical phenotype exhibited in plants that are resistant to multiple classes of herbicides.

Enhanced Electron Transfer Dissociation through Fixed Charge Derivatization of Cysteines

Electron transfer dissociation (ETD) has proven to be a promising new ion activation method for proteomics applications due to its ability to generate c- and z-type fragment ions in comparison to the y- and b-type ions produced upon the more conventional collisional activation of peptides. However, low precursor charge states hinder the success of electron-based activation methods due to competition from nondissociative charge reduction and incomplete sequence coverage. In the present report, the reduction and alkylation of disulfide bonds prior to ETD analysis is evaluated by comparison of three derivatization reagents: iodoacetamide (IAM), N,N-dimethyl-2-chloro-ethylamine (DML), and (3-acrylamidopropyl)-trimethyl ammonium chloride (APTA). While both the DML and APTA modifications lead to an increase in the charge states of peptides, the APTA-peptides provided the most significant improvement in percent fragmentation and sequence coverage for all peptides upon ETD, including formation of diagnostic ions that allow characterization of both the C- and N-termini. In addition, the formation of product ions in multiple charge states upon ETD is minimized for the APTA-modified peptides.

Radiographic repair in three Japanese patients with rheumatoid arthritis treated with bucillamine

Bucillamine (Bc) is a cysteine derivative with two SH groups, and a homolog of D-penicillamine, a disease-modifying antirheumatic drug (DMARD) widely used in Japan. However, it remains unclear whether Bc repairs bone erosion in patients with RA. Here, we treated three RA patients with Bc who subsequently showed radiographic repair of erosions and cysts.

Chromatographic methods for determination of S-substituted cysteine derivatives—A comparative study

A novel HPLC method for determination of a wide variety of S-substituted cysteine derivatives in Allium species has been developed and validated. This method allows simultaneous separation and quantification of S-alk(en)ylcysteine S-oxides, γ-glutamyl- S-alk(en)ylcysteines and γ-glutamyl- S-alk(en)ylcysteine S-oxides in a single run. The procedure is based on extraction of these amino acids and dipeptides by methanol, their derivatization by dansyl chloride and subsequent separation by reversed phase HPLC. The main advantages of the new method are simplicity, excellent stability of derivatives, high sensitivity, specificity and the ability to simultaneously analyze the whole range of S-substituted cysteine derivatives. This method was critically compared with other chromatographic procedures used for quantification of S-substituted cysteine derivatives, namely with two other HPLC methods (derivatization by o-phthaldialdehyde/ tert-butylthiol and fluorenylmethyl chloroformate), and with determination by gas chromatography or capillary electrophoresis. Major advantages and drawbacks of these analytical procedures are discussed. Employing these various chromatographic methods, the content and relative proportions of individual S-substituted cysteine derivatives were determined in four most frequently consumed alliaceous vegetables (garlic, onion, shallot, and leek).

N-Acetyl cysteine (NAC) inhibits proliferation, collagen gene transcription, and redox stress in rat palatal mucosal cells

Objectives Control of hyperplastic and invasively growing gingival tissue is crucial for maintaining normal oral function and for successful bone regenerative therapy. We tested the hypothesis that materials containing N-acetyl cysteine (NAC), an antioxidant cysteine derivative, can control proliferation and function of oral mucosal cells. Methods Oral mucosal cells derived from the rat palatal tissue were cultured with or without NAC at different concentrations (2.5–10.0 mM). To simulate inflammatory conditions, cultures were treated with hydrogen peroxide. NAC was also applied via collagen materials in membrane and sponge forms to explore the clinical applicability. The redox balance inside the cells was evaluated by measuring the concentration of intracellular glutathione (GSH). Results Adding NAC into cultures of oral mucosal cells reduced their proliferation, transcriptional expression, and collagen production in an NAC-concentration-dependent manner without cytotoxic effects. Furthermore, NAC substantially reduced the hydrogen peroxide-induced elevation of cellular proliferation and collagen production. The controlling effects of NAC were also demonstrated in cells cultured on NAC-containing collagen materials and were associated with an increase in intracellular glutathione (GSH) reserves and a decrease in the oxidized form of glutathione (GSSG). Significance These results indicate that NAC may abrogate inflammation- or oxidative-stress-induced hyperfunction of oral mucosal cells and that it can be delivered effectively via biodegradable materials. This study provides a basis to explore NAC-containing biomaterials that are functionalized to control oral soft tissue growth and function without cytotoxicity.

Cysteine and Selenocysteine Deprotection Chemistry in Peptide Synthesis

One of the most challenging areas in the field of peptide science is the chemistry of cysteine and the need for multiple protecting groups that can be removed orthogonally to facilitate regioselective disulfide bond formation. This article reviews the methods and reagents used to remove the various protecting groups of cysteine derivatives with subsequent disulfide bond formation used in peptide synthesis. Also reviewed is the related amino acid selenocysteine, which requires benzyl-type protecting groups during synthesis. As these benzyl groups are difficult to remove using older methods, we highlight the use of electrophilic, aromatic disulfides for the removal of selenocysteine (and cysteine) protecting groups with concomitant disulfide and diselenide bond formation. Keywords: Cysteine, selenocysteine, protecting groups, deprotection, peptides

In Situ Analysis of Protein S-Glutathionylation in Lung Tissue Using Glutaredoxin-1-Catalyzed Cysteine Derivatization

Protein S-glutathionylation (PSSG) is a posttranslational modification that involves the conjugation of the small antioxidant molecule glutathione to cysteine residues and is emerging as a critical mechanism of redox-based signaling. PSSG levels increase under conditions of oxidative stress and are controlled by glutaredoxins (Grx) that, under physiological conditions, preferentially deglutathionylate cysteines and restore sulfhydryls. Both the occurrence and distribution of PSSG in tissues is unknown because of the labile nature of this oxidative event and the lack of specific reagents. The goal of this study was to establish and validate a protocol that enables detection of PSSG in situ, using the property of Grx to deglutathionylate cysteines. Using Grx1-catalyzed cysteine derivatization, we evaluated PSSG content in mice subjected to various models of lung injury and fibrosis. In control mice, PSSG was detectable primarily in the airway epithelium and alveolar macrophages. Exposure of mice to NO(2) resulted in enhanced PSSG levels in parenchymal regions, while exposure to O(2) resulted in minor detectable changes. Finally, bleomycin exposure resulted in marked increases in PSSG reactivity both in the bronchial epithelium as well as in parenchymal regions. Taken together, these findings demonstrate that Grx1-based cysteine derivatization is a powerful technique to specifically detect patterns of PSSG expression in lungs, and will enable investigations into regional changes in PSSG content in a variety of diseases.

Properties of Arsenite Efflux Permeases (Acr3) from Alkaliphilus metalliredigens and Corynebacterium glutamicum

Members of the Acr3 family of arsenite permeases confer resistance to trivalent arsenic by extrusion from cells, with members in every phylogenetic domain. In this study bacterial Acr3 homologues from Alkaliphilus metalliredigens and Corynebacterium glutamicum were cloned and expressed in Escherichia coli. Modification of a single cysteine residue that is conserved in all analyzed Acr3 homologues resulted in loss of transport activity, indicating that it plays a role in Acr3 function. The results of treatment with thiol reagents suggested that the conserved cysteine is located in a hydrophobic region of the permease. A scanning cysteine accessibility method was used to show that Acr3 has 10 transmembrane segments, and the conserved cysteine would be predicted to be in the fourth transmembrane segment.

Chemodynamics underlying N-acetyl cysteine-mediated bone cement monomer detoxification

Methyl methacrylate (MMA)-based bone cement monomer is cytotoxic. N-Acetyl cysteine (NAC), a cysteine derivative, may alleviate this toxicity by inactivating the monomer components with its sulfhydryl moiety. This study examined the chemical interaction dynamics between bone cement monomer and NAC resulting in detoxification of the monomer. A monomer/NAC mixture was prepared by mixing and incubating a commercially available MMA-based bone cement monomer with NAC for various time periods of 1 min, 1 h, 6 h and 24 h. Rat bone marrow-derived osteoblastic cells were cultured with either the monomer/NAC mixture or the monomer alone. Only 17% of the cells were viable 24 h after seeding in the culture containing the monomer alone. The proliferation rate and alkaline phosphatase activity of the cells were substantially reduced under this condition. In contrast, when cultured with the monomer/NAC mixture, the viability and function of the cells were improved with increasing time of monomer/NAC incubation. For instance, the monomer/NAC mixture that was pre-reacted for 1 min increased cell viability from 17% to 55%. The monomer/NAC mixture that was pre-reacted for 24 h nearly completely restored cell viability, proliferation and ALP activity to the level of an untreated control culture. The DPPH radical-scavenging capacity of monomer/NAC mixture decreased with an increase in their reaction time, indicating time-dependent depletion of the NAC anti-oxidant moiety. Within the limit of this experimental condition, these data demonstrate the immediate initiation and rapid completion of bone cement monomer/NAC interaction, resulting in abrogation of the monomer’s cytotoxicity.

Activation and inhibition of soluble guanylyl cyclase by S-nitrosocysteine: Involvement of amino acid transport system L

In this study the mechanism by which S-nitrosocysteine (CysNO) activates soluble guanylyl cyclase (sGC) has been investigated. CysNO is the S-nitrosated derivative of the amino acid cysteine and has previously been shown to be transported into various cell types by amino acid transport system L. Here we show, using both neuroblastoma and pulmonary artery smooth muscle cells, that CysNO stimulates cGMP formation at low concentrations, but this effect is lost at higher concentrations. Stimulation of cGMP accumulation occurs only after its transport into the cell and subsequent flavoprotein reductase-mediated metabolism to form nitric oxide (NO). Consequently, CysNO can be regarded as a cell-targeted NO-releasing agent. However, CysNO also functions as an NO-independent thiol-modifying agent and can compromise cellular antioxidant defenses in a concentration-dependent manner. The observed biphasic nature of CysNO-dependent cGMP accumulation seems to be due to these two competing mechanisms. At higher concentrations, CysNO probably inactivates guanylyl cyclase through modification of an essential thiol group on the enzyme, either directly or as a result of a more generalized oxidative stress. We show here that higher concentrations of CysNO can increase cellular S-nitrosothiol content to nonphysiological levels, deplete cellular glutathione, and inhibit cGMP formation in parallel. Although the inhibition of sGC by S-nitrosation has been suggested as a mechanism of nitrovasodilator tolerance, in the case of CysNO, it seems to be more a reflection of a generalized oxidative stress placed upon the cell by the nonphysiological levels of intracellular S-nitrosothiol generated upon CysNO exposure.

Inhibitory Effects of Cysteine and Cysteine Derivatives on Germination of Sporangiospores and Hyphal Growth of Different Zygomycetes

The in vitro antifungal activity of cysteine (D- and L-cysteine) and its four derivatives (L-cysteine-methyl-ester, N-acetyl-cysteine, N-isobutyryl-D-cysteine, and N-isobutyryl-L-cysteine) were investigated on 20 fungal isolates representing 16 genera (Absidia, Actinomucor, Backusella, Gilbertella, Micromucor, Mortierella, Mucor, Mycotypha, Phycomyces, Rhizomucor, Rhizopus, Saksenaea, Syncephalastrum, Thamnostylum, Umbellopsis, and Zygorynchus). The inhibitory potential of different concentrations of these compounds, ranging from 0.625 to 10 mM, were investigated on the germination of sporangiospores as well as on hyphal extension, using broth microdilution method and agar plate test. Treatment with cysteine and its derivatives resulted in a strong inhibition in most studied strains. At 10 mM of compounds, complete blockage of growth was observed for some isolates. Sensitive species exhibited severe changes in colony morphology in the presence of 10 mM L-cysteine, N-acetyl-cysteine, and N-isobutyryl-L-cysteine. Microscopic observations revealed that 10 mM N-acetyl-cysteine induced dramatic modifications in the structural organization of the hyphae. Results suggest that cysteine and its derivatives have a therapeutic potential against fungal infections caused by Zygomycetes species.

Enrichment of the amino acid L-isovaline by aqueous alteration on CI and CM meteorite parent bodies.

The distribution and enantiomeric composition of the 5-carbon (C(5)) amino acids found in CI-, CM-, and CR-type carbonaceous meteorites were investigated by using liquid chromatography fluorescence detection/TOF-MS coupled with o-phthaldialdehyde/N-acetyl-L-cysteine derivatization. A large L-enantiomeric excess (ee) of the alpha-methyl amino acid isovaline was found in the CM meteorite Murchison (L(ee) = 18.5 +/- 2.6%) and the CI meteorite Orgueil (L(ee) = 15.2 +/- 4.0%). The measured value for Murchison is the largest enantiomeric excess in any meteorite reported to date, and the Orgueil measurement of an isovaline excess has not been reported previously for this or any CI meteorite. The L-isovaline enrichments in these two carbonaceous meteorites cannot be the result of interference from other C(5) amino acid isomers present in the samples, analytical biases, or terrestrial amino acid contamination. We observed no L-isovaline enrichment for the most primitive unaltered Antarctic CR meteorites EET 92042 and QUE 99177. These results are inconsistent with UV circularly polarized light as the primary mechanism for L-isovaline enrichment and indicate that amplification of a small initial isovaline asymmetry in Murchison and Orgueil occurred during an extended aqueous alteration phase on the meteorite parent bodies. The large asymmetry in isovaline and other alpha-dialkyl amino acids found in altered CI and CM meteorites suggests that amino acids delivered by asteroids, comets, and their fragments would have biased the Earth's prebiotic organic inventory with left-handed molecules before the origin of life.

Synthesis and Application of a N-1′ Fluorescent Biotinyl Derivative Inducing the Specific Carboxy-Terminal Dual Labeling of a Novel RhoB-Selective scFv

The fluorescent site-specific labeling of protein would provide a new, easy-to-use alternative to biochemical and immunochemical methods. We used an intein-mediated strategy for covalent labeling of the carboxy-terminal amino acid of a RhoB-selective scFv previously isolated from a phage display library (a human synthetic V(H) + V(L) scFv phage library). The scFv fused to the Mxe intein was produced in E. coli and purified and was then labeled with a newly synthesized fluorescent biotinyl cysteine derivative capable of inducing scFv-Mxe intein splicing. In this study, we investigated the splicing and labeling properties of various amino acids in the hinge domain between scFv and Mxe under thiol activation. In this dual labeling system, the fluorescein is used for antibody detection and biotin is used for purification, resulting in a high specific activity for fluorescence. We then checked that the purified biotinylated fluorescent scFv retained its selectivity for RhoB without modification of its affinity.

Structure-Function Relationship of the Chloroplastic Glutaredoxin S12 with an Atypical WCSYS Active Site

Glutaredoxins (Grxs) are efficient catalysts for the reduction of mixed disulfides in glutathionylated proteins, using glutathione or thioredoxin reductases for their regeneration. Using GFP fusion, we have shown that poplar GrxS12, which possesses a monothiol (28)WCSYS(32) active site, is localized in chloroplasts. In the presence of reduced glutathione, the recombinant protein is able to reduce in vitro substrates, such as hydroxyethyldisulfide and dehydroascorbate, and to regenerate the glutathionylated glyceraldehyde-3-phosphate dehydrogenase. Although the protein possesses two conserved cysteines, it is functioning through a monothiol mechanism, the conserved C terminus cysteine (Cys(87)) being dispensable, since the C87S variant is fully active in all activity assays. Biochemical and crystallographic studies revealed that Cys(87) exhibits a certain reactivity, since its pK(a) is around 5.6. Coupled with thiol titration, fluorescence, and mass spectrometry analyses, the resolution of poplar GrxS12 x-ray crystal structure shows that the only oxidation state is a glutathionylated derivative of the active site cysteine (Cys(29)) and that the enzyme does not form inter- or intramolecular disulfides. Contrary to some plant Grxs, GrxS12 does not incorporate an iron-sulfur cluster in its wild-type form, but when the active site is mutated into YCSYS, it binds a [2Fe-2S] cluster, indicating that the single Trp residue prevents this incorporation.

Radiolabeling of monoclonal anti-CD105 with 177Lu for potential use in radioimmunotherapy

In this study, we carried out a radioimmunoconjugation using 177Lu with anti-CD105 (endoglin) monoclonal antibody for an angiogenesis targeting. CD105 has been shown to be a more useful marker to identify proliferating endothelium involved in tumor angiogenesis than panendothelial markers. We optimized the labeling of the anti-CD105 monoclonal antibody with 177Lu by using cysteine derivative isothiocyanatobenzyl-DTPA (DTPA-NCS) as BFCA. Under the optimal conditions, labeling yield was greater than 99%. Immunoactivity of the radioimmunoconjugate was investigated using combinations of radioanalytical and bioanalytical techniques (ITLC-SG, Cyclone phosphorimager, SDS-PAGE and ELISA). For the biological evaluations we carried out a cell binding assay and a biodistribution study using mice bearing Calu6 lung cancer cell xenografts. The tumor-to-blood ratio was 11.16:1 24 h post-injection. In conclusion, the anti-CD105 monoclonal antibody for an angiogenesis targeting was effectively radioconjugated with 177Lu. And the biodistribution study showed a high specificity for accumulating in tumor tissues. This radioimmunoconjugate is applicable to detect angiogenesis sites in various diseases and to treat tumors.

Lipeo-sCT: A novel reversible lipidized salmon calcitonin derivative, its biophysical properties and hypocalcemic activity

We have previously described the design and synthesis of Mal-sCT and compared its biological activity with its reversible counterpart, REAL-sCT. Mal-sCT was salmon calcitonin (sCT) conjugated with two molecules of an ɛ-maleimido lysine derivative of palmitic acid via non-reversible thioether bonds at its cysteine residues while REAL-sCT was sCT conjugated with two molecules of a cysteine derivative of palmitic acid via reducible disulfide bonds at its cysteine residues. Neither compounds when dissolved in water could reproducibly improved the oral deliverability of sCT. The purpose of this study was to characterize and evaluate Lipeo-sCT, a novel sCT analog conjugated via reducible disulfide bonds with two amphiphilic groups consisting of a hydrophobic hexadecyl moiety attached via an ether bond to a hydrophilic triethylene glycol moiety. Lipeo-sCT was successfully synthesized by a 4-step reaction, purified and identified by ESI–MS. Analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM) suggested it had a propensity to form aggregates in water, although the aggregation behavior was controllable by modulating solvent polarity. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay indicated a lack of cytotoxicity against the Caco-2 cells at up to 100 μM. Compared with sCT, Lipeo-sCT lowered plasma calcium to comparable levels when injected subcutaneously at 0.15 mg/kg into female Wistar rats, but the hypocalcemic activity of Lipeo-sCT was prolonged by at least 6 more hours. This was attributable to a continual regeneration of sCT from Lipeo-sCT. sCT was detectable in plasma 8 h following subcutaneous injection of Lipeo-sCT (1.90 mg/kg), while Lipeo-sCT was not observed in plasma at all time points. By comparison, sCT was detectable in plasma for less than 2.5 h following subcutaneous injection at an equivalent dose (1.50 mg/kg). Data from this study complement those of previous studies, and add to the body of knowledge correlating the in vivo activity of lipidized peptides to their physical properties.