Oxidation Of Cystine Research Articles

Selective Voltammetric Determination of Sulfur-Containing Amino Acids in Drugs and Vitamin Complexes on an Electrode Modified by a Ruthenium-Hexachloroplatinate Film

An inorganic film of ruthenium hexachloroplatinate (RuPtCl6) deposited on the surface of a glassy-carbon electrode exhibited catalytic activity for oxidation of S-containing amino acids. Catalytic electrochemical oxidation of cysteine, cystine, and methionine occurred at various potentials. The optimum conditions for producing a RuPtCl6 film that gave the greatest catalytic effect were found. A method for selective voltammetric determination of cysteine, methionine, and cystine at an RuPtCl6-film electrode was developed. The lower limit of quantitation of cysteine and cystine was 5 × 10–6 M; of methionine, 5 × 10–7 M. The proposed voltammetric method was used to determine cysteine, cystine, and methionine in drugs and vitamin complexes.

Селективное вольтамперометрическое определение серусодержащих аминокислот в лекарственных средствах и витаминных комплексах на электроде, модифицированном пленкой из гексахлороплатината рутения

Неорганическая пленка из гексахлороплатината рутения (III) (RuPtCl6), осажденная на поверхности электрода из стеклоуглерода, проявляет каталитическую активность при окислении серусодержащих аминокислот. Каталитическое электроокисление цистеина, цистина и метионина происходит при различных потенциалах. Выявлены оптимальные условия получения пленки RuPtCl6, при которых регистрируется наибольший каталитический эффект. Разработан способ селективного вольтамперометрического определения цистеина, метионина и цистина на электроде с пленкой RuPtCl6. Нижняя граница определяемых содержаний цистеина и цистина составляет 5 · 10–6 М, а метионина – 5 · 10–7 М. Предложенный способ вольтамперометрического определения использован для определения цистеина, цистина и метионина в лекарственных средствах и витаминных комплексах.

Developing a non-invasive tool to assess the impact of oxidation on the structural integrity of historic wool in Tudor tapestries

Near infrared spectroscopy (NIR) can be a useful diagnostic tool in the assessment of quality in textile, agricultural and various other industries. In cultural heritage applications, NIR as a non-invasive assessment tool is advantageous for understanding the composition or degradation of fragile historic objects that cannot be sampled. The direct interpretation of measured NIR spectra is complicated by overlapping bands produced from overtone and combination bands of chemical bonds. However, in combination with multivariate partial least squares (PLS) models and principal component analysis, the physicochemical properties of historic materials can potentially be identified by calibrating against a measured component. In this research, wool fibres from a sacrificial collection of historic tapestry fragments housed at Hampton Court Palace were analysed. The cystine oxidation products of historic wools which can be related to the embrittlement of fibres and ultimately fibre loss, were recorded using Fourier transform infrared (FTIR) spectroscopy. A PLS predictive model was then developed using previously measured NIR spectra for the same historic tapestry fragments to predict the ratios of the cystine oxidation species in historic wools measured in this research. The prediction of a validation set of historic tapestry fragments with known oxidation product ratios was found to be accurate to root mean squared errors of prediction (RMSEP) of 0.11 for cysteic acid/cystine dioxide, 0.03 for an oxidation ratio of cysteic acid/cystine monoxide and 0.06 for cystine dioxide/cystine monoxide. The model was applied successfully to an independent set of historic tapestry fragments with unknown oxidation ratios with an M-distance pass limit of 3. The models were also applied to NIR measurements of historic tapestries on open display with limited success. Alternative methods to investigate and account for errors in this research are proposed. The potential for NIR to be used by conservators as a non-invasive tool for the assessment of textiles, complementing current condition audit practices in use at heritage institutions is also discussed.

Feather degradation potential of Stenotrophomonas maltophilia KB13 and feather protein hydrolysate (FPH) mediated reduction of hexavalent chromium.

An efficient keratinolytic strain of Stenorophomonas maltophilia KB13 was isolated from feather disposal site of Bilaspur, Chhattisgarh, India. The strain could metabolize 10 g/l chicken feathers as sole source of carbon and nitrogen. Soluble protein, amino acid, and cysteine content were found to be maximum (690.6 ± 8.7, 688.9 ± 9.12 and 21 ± 0.36 µg/ml, respectively) at late logarithmic phase of growth. Protease and keratinase activity reached its maximum level (103.26 ± 7.09 and 178.5 ± 9.10 U/ml) at the 4th day of incubation. The feather protein hydrolysate (FPH) obtained after degradation of chicken feathers was utilized to reduce hexavalent chromium. About 78.4 ± 2.4 and 63.6 ± 2.2 % reduction of 50 and 100 mg/l Cr(VI), respectively, was observed after 60 min of incubation with FPH. Further, there was no effect of autoclaved FPH on Cr(VI) reduction indicating that any bacterial enzyme was not involved in reduction process. Cr(VI) reduction was significantly inhibited by 10 mm Hg2+ ions indicating the role of sulfur-containing amino acids in reduction process. FTIR analysis confirmed that chromium reduction occurred due to oxidation of amino acids cysteine and cystine. This study shows that FPH arising after feather degradation can be employed as a potential candidate for the reduction of hexavalant chromium.

Effect of photodamage on the outermost cuticle layer of human hair

The surface of the hair is the region most exposed to solar radiation and to the environment in general. Many of the well-known damaging effects of sun exposure on hair must start or even be restricted to the most external cuticle layers. As such, this work investigates morphological, ultrastructural and chemical changes in the outermost cuticle layer of dark brown hair, using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The results showed that after 230h of irradiation with a mercury lamp, small bumps with globular shape (heights lying in the 1–5nm range) appeared on the cuticle surface and their size increased with increasing irradiation times. In addition, the enlargement of pre-existing holes was also observed (holes increase around 350% in depth) and the height of the steps formed between the edges of two cuticle scales increased around 65%, as a result of 500h of irradiation. The damages in hair strands were accurately identified by analyzing exactly the same surface region before and after irradiation by AFM images. Finally, the results were discussed in terms of the chemical differences between the non-irradiated and the irradiated hair, for instance, the increased level of cystine oxidation as a consequence of photodegradation.

Degradation of the ethyl glucuronide content in hair by hydrogen peroxide and a non-destructive assay for oxidative hair treatment using infra-red spectroscopy

The assessment of quantification results of the alcohol abuse marker ethyl glucuronide (EtG) in hair in comparison to the cut-off values for the drinking behavior may be complicated by cosmetic hair bleaching. Thus, the impact of increasing exposure to hydrogen peroxide on the EtG content of hair was investigated. Simultaneously, the change of absorbance in the range of 1000–1100cm−1 indicative for the oxidation of cystine was investigated non-destructively by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) using pulverized portions of the respective hair samples. Hair samples treated with hydrogen peroxide consistently displayed a significantly increased absorbance at 1040cm−1 associated with the formation of cysteic acid. The EtG content decreased significantly if the hair was treated with alkaline hydrogen peroxide as during cosmetic bleaching. It could be shown that ATR-FTIR is capable of detecting an exposure to hydrogen peroxide when still no brightening was visible and already before the EtG content deteriorated significantly. Thus, hair samples suspected of having been exposed to oxidative treatment may be checked non-destructively by a readily available technique. This assay is also possible retrospectively after EtG extraction and using archived samples.

동충하초 추출물에 의한 모발의 화학적·물리적 개선효과

Cordyceps militaris (CM) occurring from a fruiting body by a host insect is a kind of mushroom, which is composed of animal host and plant fruit body. CM contains large amounts of useful ingredients including polysaccharides, vitamins, amino acids, minerals, etc. The essential amino acids from CM including cystine, lysine, and methionine can be expected to improve damaged hair treatment as effective ingredients. In this study, the improvement effect of the CM extracts on chemical and physical properties for damaged-hair treatment was investigated. The cysteic acid and cystine monooxide produced by oxidation of cystine were analyzed their chemical structure by FT-IR spectroscopy. It was confirmed that the vibration absorption peak (<TEX>$1,041cm^{-1}$</TEX>) of cysteic acid was reduced and increased sulfur content considerably which means meaningful improvement effect on damaged-hair treatment. Apparently, the cuticle morphology of the damaged-hair was improved significantly by treatment with CM extracts. Especially, confocal laser scanning microscope images of the damaged-hair treated with the extract showed highly increased fluorescence intensity which means promising effect in hair treatment. The tensile strength of the damaged hair treated also increased by 168% compared with the damaged hair.

Electrocatalytic oxidation and flow-injection determination of sulfur amino acids on a glassy carbon electrode modified by a nickel(II) polytetrasulfophthalocyanine film

The electrochemical oxidation of sulfur amino acids, i.e., cysteine, cystine, and methionine, is studied on a glassy carbon electrode modified by a film of nickel(II) polytetrasulfophthalocyanine (poly-NiTsPc). Poly-NiTsPc demonstrates a selective mediator activity in the oxidation of sulfur amino acids, depending on the pH of solution. The proper conditions for fabricating a polymer film on the surface of glassy carbon are found and the conditions of registering the maximal electrocatalytic effect on the modified electrode are determined. A procedure is proposed for the voltammetric determination and amperometric detection of cysteine, cystine, and methionine on an electrode coated by a poly-NiTsPc film under the conditions of flow-injection analysis (FIA). The linear relation of the electrocatalytic response of a composite electrode to amino acid concentration is observed to the level n × 10−6 M in the static mode and n × 10−9 M under FIA conditions.

Analytical Studies on the oxidation of cysteine, cystine and Methionine with V(v) reagent

A simple, quick and convenient method has been developed for the micro estimation of S- containing amino acids. The sample 1-5 mg is allowed to react with 2 ml of 0.3N ammonium metavanadate (v) reagent and 10 ml of 10N H2SO4 was added, before the reaction helps in detecting the end point. The unconsumed reagent can be accurately titrate with 0.025 N ferrous ammonium sulphate solution using N-phenyl anthranilic acid as indicator. Standard deviation as well as coefficient of variation was calculated for reproducible and accurate result. The accuracy of the method in within + 1%

Sulfur containing amino acids – challenge of accurate quantification

For the first time, quantitative analysis of the proteinogenic sulfur containing amino acids methionine and cysteine was performed by LC-ICP-MS. A dedicated sample preparation procedure was implemented consisting of two steps, i.e. (1) protection of the redox sensitive amino acids by controlled oxidation of methionine, cystine and cysteine to methionine sulfone and cysteic acid, respectively, and (2) subsequent protein hydrolysis. Anion exchange chromatography enabled the separation of all relevant sulfur species within 10 min. Sulfur was detected on m/z32S16O using O2 as the reaction gas. Absolute limits of detection in the pmol range were achieved for methionine sulfone and cysteic acid. The method offered the possibility of protein quantification. Absolute amounts of 2 μg of hydrolyzed protein (on column) were investigated by LC-ICP-MS. Both oxidized forms of amino acids showed excellent recoveries from lysozyme and myoglobin standards, enabling accurate quantification. A repeatability of <10% (n = 6 independently prepared samples) was found without the application of isotope dilution strategies. The limits of detection of <1 μM protein were comparable to the limits of detection achieved by spectroscopy based protein quantification assays. Moreover, the validity of the approach was shown by implementing HPLC in combination with fluorescence detection as a reference method for the quantification of proteinogenic amino acids in yeast. Both methods were in good agreement and met the theoretical value in a yeast reference material certified for the methionine content.

Electrochemical behavior and voltammetric determination of cysteine and cystine at carbon-paste electrodes modified with metal phthalocyanines

The electrochemical behavior of cysteine and cystine on carbon-paste electrodes modified with Fe(II), Co(II), Ni(II), and Cu(II) phthalocyanines is studied. Metal phthalocyanines exhibit catalytic activity in the electrooxidation of cysteine and cystine and in the reduction of cystine. The best catalyst is the cobalt complex. In the electrooxidation of cysteine, the catalysts are electrogenerated complex species of Co(II)Pc or Co(III)Pc+, and in the oxidation of cystine, oxidized or reduced forms of the coordinated ligand. Various versions of the determination of cysteine and cystine by the electrocatalytic reactions on the modified electrodes are proposed.

Kinetic and mechanistic study of oxidation of cystine by hexacyanoferrate(III) ions catalyzed by IrIII in aqueous alkaline medium

Kinetic and mechanistic study of oxidation of cystine by hexacyanoferrate(III) ions catalyzed by IrIII in aqueous alkaline medium

Boron doped diamond and glassy carbon electrodes comparative study of the oxidation behaviour of cysteine and methionine

The electrochemical oxidation behaviour at boron doped diamond and glassy carbon electrodes of the sulphur-containing amino acids cysteine and methionine, using cyclic and differential pulse voltammetry over a wide pH range, was compared. The oxidation reactions of these amino acids are irreversible, diffusion-controlled pH dependent processes, and occur in a complex cascade mechanism. The amino acid cysteine undergoes similar three consecutive oxidation reactions at both electrodes. The first step involves the oxidation of the sulfhydryl group with radical formation, that undergoes nucleophilic attack by water to give an intermediate species that is oxidized in the second step to cysteic acid. The oxidation of the sulfhydryl group leads to a disulfide bridge between two similar cysteine moieties forming cysteine. The subsequent oxidation of cystine occurs at a higher potential, due to the strong disulfide bridge covalent bond. The electro-oxidation of methionine at a glassy carbon electrode occurs in two steps, corresponding to the formation of sulfoxide and sulfone, involving the adsorption and protonation/deprotonation of the thiol group, followed by electrochemical oxidation. Methionine undergoes a one-step oxidation reaction at boron doped diamond electrodes due to the negligible adsorption, and the oxidation also leads to the formation of methionine sulfone.

Structural, functional and chemical changes in Pseudozyma antarctica lipase B on exposure to hydrogen peroxide

The effect on primary, secondary, tertiary and quaternary structure of Pseudozyma (formerly Candida) antarctica lipase B (PalB) on exposure to hydrogen peroxide was investigated using nano-electrospray ionization-mass spectrometry (nano-ESI-MS), liquid chromatography tandem mass spectrometry (LC/MS/MS), circular dichroism (CD), and dynamic light scattering (DLS). Treatment with hydrogen peroxide generated heavier protein variants, with a mass gain that increased with increasing incubation time. Furthermore, elevated concentration of H 2O 2 was shown to result in partial fragmentation of the protein. Proteolytic digestion of the enzyme gave primary sequence coverage of more than 90%, revealing oxidation of methionine, tryptophan and cystine residues. The active site histidine was not observed in oxidized form in any of the experiments. However, oxidation of cystine to cysteic acid indicated disruption of disulphide bridges, and CD evaluations confirmed that severe changes to the secondary structure towards random coil had occurred. The structural changes could be an effect of the observed amino acid side chain oxidations, and was correlated with deactivation of the lipase. From DLS experiments, it was seen that the lipase exposed to both high temperature and H 2O 2 formed large and intermediate sized aggregates, not observed for the heat-treated enzyme. The findings reported here could lay the basis for developing enzyme variants with higher oxidative stability.

Electrocatalytic oxidation of some amino acids on a cobalt hydroxide nanoparticles modified glassy carbon electrode

In this study we investigated the electrocatalytic oxidation of cysteine, cystine, N-acetyl cysteine, and methionine on cobalt hydroxide nanoparticles modified glassy carbon electrode in alkaline solution. Different electrochemical techniques such as cyclic voltammetry, chronoamperometry and steady-state polarization were used to track the oxidation process and its kinetics. From voltammetric studies we concluded that in the presence of amino acids the anodic peak current of Co(IV) species increased, followed by a decrease in the corresponding cathodic current peak. This indicates that amino acids were oxidized on the redox mediator which was immobilized on the electrode surface via an electrocatalytic mechanism. Using Laviron’s equation, the values of α s and k s for the immobilized redox species were determined as α s , a = 0.63, α s,c = 0.38 and k s = 0.28 s −1, respectively. The catalytic rate constants, the electron transfer coefficients and the diffusion coefficients involved in the electrocatalytic oxidation of amino acids were determined.

Direct Electrocatalytic Oxidation of Cysteine and Cystine Based on Nafion/Lead Oxide‐Manganese Oxide Combined Catalyst

AbstractThis article reports direct electrocatalytic oxidation of cysteine (CySH) and cystine (CyS‐SCy) at an inexpensive Nafion/lead oxide‐manganese oxide combined catalyst in physiological pH. The synthesized lead oxide‐manganese oxide material is simply mixed with Nafion in the form of cast solution and modified on a disposable screen‐printed carbon electrode (designated as SPE/Nf‐PMO) for biosensing application. Electrochemical study with a standard redox couple of quinone/hydroquinone demonstrates an enhanced current response at the combined catalyst compared to its individual component. Surface characterization further provides information regarding the structural morphology of the catalyst to its catalytic performance. Direct electrocatalytic oxidation signals are observed at +0.75 and +1.20 V vs. Ag/AgCl for cysteine and cystine, respectively, at the SPE/Nf‐PMO. To extend the applicability, we further apply the proposed system for the detection of cysteine and cystine by flow injection analysis (FIA). Under optimized conditions, the detection limit (S/N=3) is 0.43 μM and 0.33 μM for cysteine and cystine, respectively.

Kinetics of oxidation of L-cystine by pyridinium bromochromate

The kinetics of oxidation of cystine by pyridinium bromochromate (PBC) was studied spectrophotometrically under pseudo-first order conditions in perchloric acid medium at 370 nm. It was found that the reaction is first order in [PBC], fractional order in [cystine] and the reaction rate is increased with [H + ] showing an order of more than unity. Product analysis confirmed cysteic acid as the final product of oxidation.

Reactive Sulfur Species: Kinetics and Mechanism of the Oxidation of Cystine by Hypochlorous Acid to Give N,N‘-Dichlorocystine

Cystine and HOCl (a neutrophil-derived oxidant) react to form an intermediate that has a half-life of ca. 5 min at pH 7.5. The intermediate subsequently decomposes to eventually yield a mixture of cystine, higher oxides of Cys, and other uncharacterized species. Spectral titrations, transitory (1)H NMR and UV-vis spectra, and the reaction properties of the intermediate are consistent with a formulation of N,N'-dichlorocystine {NDC = [-SCH(2)CH(NHCl)(CO(2)H)](2)}. The reaction of equimolar amounts of HOCl with cystine at pH 11.3 does not yield N-chlorocystine [NCC = (-O2C)(H3N+)CHCH(2)SSCH(2)CH(NHCl)(CO(2)H)] but rather a 1:1 mixture of NDC and cystine. This result could be explained by two mechanisms: rapid disproportionation of NCC to produce NDC and cystine or a faster reaction of the second equivalent of HOCl with NCC than the first equivalent of HOCl reacts with cystine. The latter mechanism is favored because of our observation by NMR spectroscopy that NDC decomposes via a species that we have assigned as NCC. Thus, disproportionation of NCC is apparently a relatively slow process. The rates of reaction of cystine(0) = [-SCH(2)CH(NH(3)(+))(CO(2)(-))](2) degrees , cystine(1-) = [((-)O(2)C)(H(2)N)CHCH(2)SSCH(2)CH(NH(3)(+))(CO(2)(-))](-), and cystine(2-) = [-SCH(2)CH(NH2)(CO2)(-))]2(2-) have been investigated, and it is clear that cystine(0) is unreactive, whereas cystine(2-) is about four times more reactive than cystine(1-). Accordingly, the following mechanism is proposed (constants for 5 degrees C): HOCl = H+ + OCl-, pK1 = 7.47; cystine(0) = cystine(1-) + H+, pK2 = 8.15; cystine(1-) = cystine(2-) + H+, pK3 = 9.00; cystine(1-) + HOCl --> NCC(1-) + H2O, k4 = 4.3(2) x 10(6) M(-1) s(-1); cystine(2-) + HOCl --> NCC(2)(-) + H2O, k5 = 1.6(2) x 10(7) M(-1) s(-1); NCC(1-) --> NCC(2-) + H+, k6 = fast; NCC(2-) + HOCl --> NDC(2-) + H2O, k7 = fast. At physiologic pH, the k4 pathway dominates. The generation of long-lived chloramine derivatives of cystine may have physiological consequences, since such compounds are known to react with nucleophiles via mechanisms that are also characteristic of HOCl, electrophilic transfer C+.

Dyeing of wool with antibiotics to develop novel infection resistance materials for extracorporeal end use

AbstractTwo antibiotics, doxycycline (Doxy) and ciprofloxacin (Cipro), were applied under a variety of conditions to wool and to hydrolyzed wool at 40°C. Nylon was used as a synthetic control. Sorption of Doxy was much higher in wool than in nylon, whereas sorption of Cipro was similar in both fibers. FTIR spectroscopy confirmed that a drastic increase in sorption of antibiotics by hydrolyzed wool was attributed to an increase in polar functional groups by peptide scission and in oxidized sulfur groups by cystine oxidation. Both sorption and zone of inhibition (ZOI) values were improved by hydrolysis of wool. Wool hydrolyzed for 20 or 40 min at 40°C and dyed with Doxy at 45°C for 3.5 h maintained around 30 mm of ZOI after 24 h of challenge by a simulated flow of blood. Wool hydrolyzed for 60 min at 40°C and dyed with Cipro at 45°C for 3.5 h also maintained its antibiotic activity for an extended time. For the most part, ZOI values for nylon dyed by both antibiotics were zero within 24 h. This technique produced infection‐resistant biomaterials of potential use in extra‐corporeal biomedical and biological applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3343–3354, 2004

Electrocatalytic Oxidation of Cysteine and Cystine at a Carbon-Paste Electrode Modified with Ruthenium(IV) Oxide

The electrocatalytic activity of ruthenium(IV) oxide incorporated into a carbon-paste electrode was studied in the oxidation of cysteine and cystine. The oxidation potentials of the amino acids decreased and the current peaks of their oxidation increased at a modified electrode as compared to an unmodified one. Procedures for the voltammetric determination of cysteine and cystine with the use of electrodes chemically modified with ruthenium(IV) oxide were proposed.