Use Of L-cysteine Research Articles

Heterogeneous nucleation on defects in MoS2 nanostructures as a proxy for assessing active sites for hydrogen production

In the present work, we applied heterogeneous nucleation of gold nanoparticles to assess the density of defects on MoS2 nanostructures presenting different morphologies and surface areas. The use of L-cysteine resulted in the formation of flower-shaped MoS2 nanostructures with a diameter of about 300 nm and petals measuring around 30 nm. In contrast, when 3-mercaptopropionic acid was employed, it led to the formation of large agglomerates, here referred to as nanoclouds, with a diameter of approximately 500 nm. The nucleation of gold nanoparticles on defect sites of MoS2 suggested that MoS2 obtained from 3-mercaptopropionic acid has a higher content of active sites for hydrogen production compared to MoS2 obtained from L-cysteine.

PRODUCTOS ALTERNATIVOS EN LA DESINFESTACIÓN IN VITRO EN EXPLANTES DE PORTAINJERTO DUKE-7 E IDENTIFICACIÓN DE MICROORGANISMOS ENDÓFITOS

<p><strong>Background. </strong>The vegetative material for <em>in vitro</em> establishment of avocado explants is from the field, for this reason, the proportion of contamination, oxidation and mortality of explants is elevated, therefore we are looking for alternatives to decreased. <strong>Objective. </strong>To evaluate concentrations of alternative products for disinfestation in avocado explants cv Duke 7, and decrease oxidation with the addition of L-cysteine in the <em>in vitro</em> establishment. <strong>Methodology. </strong>The products used were: peroxyacetic acid (AP), chlorine dioxide (DC), and quaternary ammonium salts (ACS), in three concentrations. 54 explants were used in each treatment, and placed in culture medium for establishment, evaluating contamination (%) and oxidation (%). Two weeks later, 50% of viable explants from each treatment were immersed in L-cysteine (100 mgL<sup>-1</sup>) and placed in a culture medium for multiplication, the rest was placed a in multiplication medium containing L-cysteine; only oxidation was evaluated (%). Contaminated explants were isolated, identified, and characterized fungi and bacteria. <strong>Results. </strong>The best results of the disinfestation were with ACS with 3.7% contamination, without oxidation. Regarding the use of L-cysteine (100 mgL<sup>-1</sup>), the lowest percentage of oxidation (47%) was obtained when immersed in a cysteine solution. Three genera of fungi were identified: <em>Aspergillus</em> (3), <em>Penicillium</em> (1) and <em>Cladosporium</em> (1), and <em>Agrobacterium</em> as a bacterium. <strong>Implications. </strong>With the proposed methodology, we can continue with the following stages of <em>in vitro</em> culture, to establish methodologies for budding, growth, and rooting of avocado clonal rootstocks. <strong>Conclusions</strong>. The use of ACS and cysteine in solution reduces both contamination and oxidation of explants, but it is necessary to modify concentrations and exposure times in the disinfestation protocol, in addition to identifying even the genus the microorganisms found.</p>

Case–control study related to the use of L-cysteine in the differential diagnosis of oral halitosis

Oral halitosis is characterized by a foul, unpleasant breath that emanates from the oral cavity due to local or systemic conditions. Approximately 90% of offensive odors are caused by volatile sulfur compounds (VSCs). L-cysteine, used as a test solution to control bad breath, induces the formation of VSCs and serves as a preliminary rinse. The study aim was to investigate the effectiveness of L-cysteine solution in differentiating the origin of oral halitosis using a gas chromatography apparatus. Methods: In total, 37 patients with an average age of 49.56 years were evaluated and divided into two groups: halimetry before the use of L-cysteine (n = 37) and halimetry after the use of L-cysteine (n = 37). Patients over 18 years of age, without severe systemic health impairment or infectious/contagious diseases, and who did not use medicines that influenced their breath were included. Halimetry was performed using the OralCroma™ device. In the halimetry before the use of L-cysteine group, 5.40%, 5.40%, and 64.86% of the patients had high levels of sulfide, methyl mercaptan, and dimethyl sulfide, respectively. After the use of L-cysteine, 48.64%, 8.10%, and 37.84% of the patients had high levels of sulfide, methyl mercaptan, and dimethyl sulfide. In this study, L-cysteine proved to be important for the assessment of oral halitosis and effective in differentiating the origin of oral halitosis; therefore, this compound could be used for the differential diagnosis of oral halitosis origin using the OralChroma™ device.

L-cysteine modified silver nanoparticles for selective and sensitive colorimetric detection of vitamin B1 in food and water samples

The use of L-cysteine modified silver nanoparticles (Cys-capped AgNPs) as a colorimetric probe for determination of vitamin B1 (thiamine) is described in the present work. This method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) band of Cys-capped AgNPs in the region of 200–800 nm. The color of Cys-capped AgNPs was changed from yellow to colorless by the addition of vitamin B1. The mechanism for detection of vitamin B1 is based on the electrostatic interaction between positively charged vitamin B1, which causes the red shift of LSPR band from 390 nm to 580 nm. The interaction between Cys-capped AgNPs and vitamin B1 was theoretically explored by density function theory (DFT) using LANL2DZ basis sets with help of Gaussian 09 (C.01) program. The morphology, size distribution and optical properties of Cys-capped AgNPs were characterized by transmission electron microscope (TEM), UV-Visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) techniques. The method is linear in the range of 25–500 μg mL−1 with correlation coefficient (R2) 0.992 and limit of detection of 7.0 μg mL−1. The advantages of using Cys-capped AgNPs as a chemical sensor in colorimetry assay are being simple, low cost and selective for detection of vitamin B1 from food (peas, grapes and tomato) and environmental (river, sewage and pond) water samples.

Effect of Cysteine on Methylglyoxal-Induced Renal Damage in Mesangial Cells.

Methylglyoxal (MGO), a highly reactive dicarbonyl compound, is a key precursor of the formation of advanced glycation end products (AGEs). MGO and MGO-AGEs were reportedly increased in patients with diabetic dysfunction, including diabetic nephropathy. The activation of glyoxalase-I (GLO-I) increases MGO and MGO-AGE detoxification. MGO-mediated glucotoxicity can also be ameliorated by MGO scavengers such as N-acetylcysteine (NAC), aminoguanidine (AG), and metformin. In this study, we noted that l-cysteine demonstrated protective effects against MGO-induced glucotoxicity in renal mesangial cells. l-cysteine prevented MGO-induced apoptosis and necrosis, together with a reduction of reactive oxygen species (ROS) production in MES13 cells. Interestingly, l-cysteine significantly reduced MGO-AGE formation and also acted as an MGO-AGE crosslink breaker. Furthermore, l-cysteine treatment accelerated MGO catabolism to D-lactate via the upregulation of GLO-I. The reduction of AGE formation and induction of AGE breakdown, following l-cysteine treatment, further supports the potential use of l-cysteine as an alternative for the therapeutic control of MGO-induced renal complications in diabetes, especially against diabetic nephropathy.

Synthesis of TiNi by a green method

A green method for the synthesis of titanium–nickel (TiNi) using Penicillium sp. fungus as a bioreactor and its comparison with the titanium–nickel synthesis produced by l-cysteine as a reducing agent are reported. In this work, the authors show that Penicillium sp. in contact with titanium (Ti) and nickel (Ni) salt solutions produces a nanocomposite material: titanium–nickel/titanium dioxide (TiO2). The experimental procedure was carried out at room temperature. The concentrations of the solutions used for both metal ions were 2·54 × 10−4 M. The analysis by ultraviolet–visible showed the characteristic bandgap absorption for titanium dioxide at 250 nm, and the X-ray powder diffraction analysis showed the phase reflections of titanium–nickel alloy and titanium dioxide. In order to propose a route for the biosynthesis using the fungus, titanium–nickel was synthesised using l-cysteine as a reducing agent at 25°C. Analysis by field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy shows agglomerates of nanosized particles corresponding to nickel and titanium metals. The use of l-cysteine and heat treatment at 250°C after the contact between l-cysteine and the ion salts in aqueous solution allow the easy synthesis of titanium–nickel. These processes represent new routes for the synthesis of titanium–nickel alloy under a non-exhaustive reaction.

Suppression of methionine-induced colon injury of young rats by cysteine and N-acetyl-l-cysteine

Changes in the methionine metabolism can cause a state called hyperhomocysteinemia, inducing oxidative stress in the gut. The production of free radicals is important in the colon damage caused by methionine. This study aimed at evaluating the effect of the use of L-cysteine and N-acetyl-L-cysteine on the colon morphometry of young rats treated with methionine. A total number of 32 male rats were distributed in a randomized experimental design in 4 groups: control group treated with saline; methionine group; cysteine+methionine group, and N-acetyl-L-cysteine+methionine group. After 21days of treatment, rats were sacrificed and the colon samples were taken for histological and biochemical analysis. Methionine load increased depth of crypts, the lamina muscularis mucosae thickness, the mucosal height, and the number of cells in lamina propria (p<0.01). Combination of methionine with L-cysteine (C group) and with N-acetyl-L-cysteine (N group) reversed methionine effects. Methionine treatment increased the GPx activity and MDA concentration, while L-cysteine and N-acetyl-L-cysteine increased the catalase activity compared to methionine group. It was concluded that the use of L-cysteine and N-acetyl-L-cysteine was beneficial to decrease intestinal mucosal height and oxidative damage when methionine was used in combination with them.

Aqueous-Medium Selective Modification of Cysteine and Related Thiols with Tricyclic Oxygen-Heterocycles

The utility of tricyclic oxygen-heterocycles as a reagent for the thiol-selective modification toward bioconjugation was demonstrated by the use of l-cysteine, homocysteine, captopril, and glutathione as a nucleophile having a thiol group. These trapping reactions proceeded under the mild and aqueous reaction conditions.

Sensitive fluorescence immunoassay of alpha-fetoprotein through copper ions modulated growth of quantum dots in-situ

A novel fluorescence immunoassay has been developed for alpha-fetoprotein (AFP) detection based on copper ions (Cu2+) regulated formation of quantum dots in situ. In place of traditionally used fluorophore or enzyme for signal amplification, CuO nanoparticles (NPs) were used as signal amplifier to enhance the detection sensitivity. In the presence of AFP, CuO NPs-labeled antibody can be specifically captured through the sandwich-type immunoreaction. By the use of l-cysteine (Cys) as stabilizer, aqueous fluorescent CdS quantum dots (QDs) can be formed by a facile synthesis method. After acid dissolution, numerous Cu2+ ions were released from the CuO NPs, which can act as catalyst to catalyze the oxidization of Cys and thus greatly reduce the amount of CdS QDs formed. The fluorescence intensity showed a good linear relationship with the AFP concentration in the range from 1 to 80ng/mL, as low as 0.45ng/mL AFP can be detected. The high throughput, disposability, sensitivity and accuracy of the proposed fluorescence immunoassay showed good applicability in clinical diagnosis.

L-Cysteine metabolism and its nutritional implications.

L-Cysteine is a nutritionally semiessential amino acid and is present mainly in the form of L-cystine in the extracellular space. With the help of a transport system, extracellular L-cystine crosses the plasma membrane and is reduced to L-cysteine within cells by thioredoxin and reduced glutathione (GSH). Intracellular L-cysteine plays an important role in cellular homeostasis as a precursor for protein synthesis, and for production of GSH, hydrogen sulfide (H(2)S), and taurine. L-Cysteine-dependent synthesis of GSH has been investigated in many pathological conditions, while the pathway for L-cysteine metabolism to form H(2)S has received little attention with regard to prevention and treatment of disease in humans. The main objective of this review is to highlight the metabolic pathways of L-cysteine catabolism to GSH, H(2)S, and taurine, with special emphasis on therapeutic and nutritional use of L-cysteine to improve the health and well-being of animals and humans.

Ergothioneine protects Streptomyces coelicolor A3(2) from oxidative stresses

Thiol compounds with low-molecular weight, such as glutathione, mycothiol (MSH), bacillithiol, and ergothioneine (ERG), are known to protect microorganisms from oxidative stresses. Mycobacteria and actinobacteria utilize both MSH and ERG. The biological functions of MSH in mycobacteria have been extensively studied by genetic and biochemical studies, which have suggested it has critical roles for detoxification in cells. In contrast, the biological functions of ERG remain ambiguous because its biosynthetic genes were only recently identified in Mycobacterium avium. In this study, we constructed mutants of Streptomyces coelicolor A3(2), in which either the MSH or ERG biosynthetic gene was disrupted, and examined their phenotypes. A mshC (SCO1663)-disruptant completely lost MSH productivity. In contrast, a disruptant of the egtA gene (SCO0910) encoding γ-glutamyl-cysteine synthetase unexpectedly retained reduced productivity of ERG, probably because of the use of l-cysteine instead of γ-glutamyl-cysteine. Both disruptants showed delayed growth at the late logarithmic phase and were more susceptible to hydrogen peroxide and cumene hydroperoxide than the parental strain. Interestingly, the ERG-disruptant, which still kept reduced ERG productivity, was more susceptible. Furthermore, the ERG-disruptant accumulated 5-fold more MSH than the parental strain. In contrast, the amount of ERG was almost the same between the MSH-disruptant and the parental strain. Taken together, our results suggest that ERG is more important than MSH in S.coelicolor A3(2).

Evaluation of L-Cysteine as Anti-Browning Agent in Fresh-Cut Lettuce Processing

Fresh-cut iceberg lettuce was treated with two different concentrations of L-cysteine, in order to select the proper treatment able to improve the storage in air. L-cysteine at 0.1% was selected because it significantly slowed down browning, respiration activity and soluble o-quinones formation and preserved the antioxidant activity. Thus, a second experiment in which this concentration was applied to fresh-cut lettuce processing was carried out. The effectiveness of the treatment with L-cysteine was confirmed and enhanced by the storage in modified atmosphere, increasing the shelf life of 40% respect to control samples. Sensory analysis confirmed the effectiveness of the treatment, showing that fresh-cut lettuce dipped with L-cysteine obtained better scores for appearance, texture, and absence of browning and of unpleasant odor than control. Finally, treatment with L-cysteine resulted with a suitable anti-browning agent, which could be used in fresh-cut lettuce processing. Practical Applications Browning of fresh-cut iceberg lettuce represents one of the major causes of quality loss, which limits its shelf life. This research provides scientific evidence of the use of L-cysteine, as anti-browning agent, in alternative to washing with only hypochlorite in fresh-cut lettuce processing. This treatment could be easily implemented in fresh-cut lettuce processing, as it does not require additional facilities or investment; moreover, it gives advantages to processors and consumers in terms of shelf-life extension and in the improvement of fresh-cut lettuce sensory and quality traits.

Kinetic Studies of Polyphenol Oxidase from White Yam (Dioscorea rotundata Poir) Tuber

Enzymatic browning is engendered by conversion of monophenols (cresolase activity) and ortho-diphenols (catecholase activity) to reactive ortho-quinones in the presence of molecular oxygen by polyphenol oxidases (PPOs). The present study ascertained the inhibition kinetics of PPO extracted from Dioscorea rotundata tuber in the presence of non-toxic sulfhydryl amino acid (L-cysteine) and appraised other connecting kinetic and thermodynamic properties of D. rotundata PPO (DR-PPO). DR-PPO was extracted and purified by (NH4)2SO4 precipitation, ultrafiltration and dialysis. Thermodynamic parameters and DR-PPO activity were measured by standard methods. Kinetic analyses showed that 4.0 mM L-cysteine displayed non-competitive inhibition prototype with DR-PPO experimental substrate. The affinity of L-cysteine for DR-PPO inhibitor binding site was ≈ 25 folds greater than that of catechol for the enzyme active site. Arrhenius plot gave an approximate first-order reaction with activation energy (Ea)=60.07 kJ mole-1. DR-PPO activity upon incubation at T=50°C for 5 min resulted to 28.11 ± 0.05% decay in relative enzyme activity. Likewise, within experimental pH values (pH 7.5-10.5 units), decay in relative DR-PPO activity ranged between 19.39 ± 0.01% - 65.11 ± 0.05%. Furthermore, pH/DR-PPO activity profile displayed three peak values, which suggests the presence of DR-PPO isoforms. The present study propose the use of L-cysteine as an alternative inhibitor for DR-PPO activity alongside with thermal inactivation (T>70°C for 15 min) and pH adjustment (pH<7.5 units for 15 min) to alleviative and serve as control measures against enzymatic browning reactions in D. rotundata tuber.

Scientific Opinion on the safety and efficacy of L‐cysteine hydrochloride monohydrate as a flavouring additive for pets

L-Cysteine is a non-essential amino acid produced by hydrolysis of natural keratin (typically from duck feathers). In the absence of information on bacterial fermentation, the FEEDAP Panel cannot conclude on this way of manufacturing. The addition of L-cysteine to the food of cats and dogs is safe if the balance between cysteine and methionine in the complete diet is maintained. Owing to the unknown total content of free L-cysteine in the final diet, it cannot be assessed whether or not the addition of L-cysteine as a feed flavouring would disrupt this balance. In the absence of data, the FEEDAP Panel considers it prudent to assume that exposure of the skin, eyes and mucous membranes poses a risk to users. As L-cysteine is intended for use in pets, assessment of the safety for the environment is not needed. It is not clear if the use of L-cysteine, applied as described by the applicant, is the same as that for human food and, therefore, efficacy cannot be assumed and has not been demonstrated. The FEEDAP Panel made a recommendation regarding the specification of the additive.

Biomolecule-assisted synthesis of nickel sulfides/reduced graphene oxide nanocomposites as electrode materials for supercapacitors

The present communication demonstrates the first environmentally friendly hydrothermal synthesis of nickel sulfide nanospheres/reduced graphene oxide (nickel sulfides/rGO) nanocomposites with the use of l-cysteine as a reducing agent, sulfur donor, and linker. The nanosphere consists of ultrafine particles leading to textural pores. The resulting nickel sulfides/rGO nanocomposites were further used as an electrode material for supercapacitors and found to exhibit very high specific capacitances of 1169Fg−1 and 761Fg−1 at current rates of 5Ag−1 and 50Ag−1, respectively, with good cycling stability.

Biomolecule-Assisted, Environmentally Friendly, One-Pot Synthesis of CuS/Reduced Graphene Oxide Nanocomposites with Enhanced Photocatalytic Performance

In this work, we develop a novel environmentally friendly strategy toward one-pot synthesis of CuS nanoparticle-decorated reduced graphene oxide (CuS/rGO) nanocomposites with the use of L-cysteine, an amino acid, as a reducing agent, sulfur donor, and linker to anchor CuS nanoparticles onto the surface of rGO sheets. Upon visible light illumination (λ > 400 nm), the CuS/rGO nanocomposites show pronounced enhanced photocurrent response and improved photocatalytic activity in the degradation of methylene blue (MB) compared to pure CuS. This could be attributed to the efficient charge transport of rGO sheets and hence reduced recombination rate of excited carriers.

Reparative histogenesis of skin: Reaction on the application of l-cysteine of argentum nitrate gel

The effect of L-cysteine of argentum nitrate gel on the wound process of experimental animals is investigated. The results show that the nanogel, being bacteriostatic, accelerates the course of inflammation phase resulting in fast cleansing of the wound surface and stimulation of the granulation tissue formation. The main cell elements of this tissue—fibroplasts are characterized by the state of functional excitation. The time of wound healing with the use of L-cysteine of argentum nitrate gel was reduced by three days, and the index of wound repair acceleration was about 20%.

Mercury Extraction from Contaminated Soils by l-Cysteine: Species Dependency and Transformation Processes

A new approach in soil remediation washing techniques is the use of l-cysteine based on the formation of organic complexes. In this study, the applicability of l-cysteine for the mobilisation of different mercury species from contaminated soils was evaluated. Soils were treated with l-cysteine solutions with S–Hg molar ratios of 1, 2, 10, 20, 100 and 200. In 24 h batch experiments, leachates with water could mobilise 1% of Hg. The addition of l-cysteine led to an increase of Hg mobilisation of 42% for soils with inorganically bound Hg. In column experiments, the maximum Hg removal rate was 75%. For soils with organically bound Hg or HgS, only 1–5% of Hg was mobilised. Thus, the extraction of Hg from soils with l-cysteine is highly dependent on the Hg-binding form. Hg speciation analyses of leachates indicate that Hg–l-cysteine complexes are labile complexes which can be easily transformed. Soil samples speciation analysis revealed that reduction to elemental mercury takes place at low S–Hg ratios (1 to 10), assumingly by microbial activity. At higher S–Hg ratios of 10 and 100, precipitation of stable Hg–S complexes could be observed. These species transformation processes are limitations for considering l-cysteine leaching as a remediation strategy.

Use of l-cysteine for minimization of inorganic Hg loss during thermal neutron irradiation

Thermal neutron irradiation experiments performed with cellulose-based l-cysteine-treated and untreated Hg standards showed Hg losses of 59–81% for untreated standards but only about a 0.2% loss for treated standards. These results and others for multielement standards showed that Hg loss is highly dependent on total mass and placement of materials in the irradiation vessel and that distribution of volatilized Hg was fairly uniform throughout the sample-containing region of the vessel. Polyethylene trapped volatile Hg much more efficiently than cellulose and a multielement standard containing inorganic Se selectively trapped Hg lost from a co-irradiated multielement standard containing Hg.

Shelf-life of minimally processed lettuce and cabbage treated with gaseous chlorine dioxide and cysteine

Gaseous ClO 2 was evaluated for effectiveness in prolonging the shelf-life of minimally processed (MP) lettuce and MP cabbage, previously immersed in a cysteine solution in order to inhibit browning occurring during ClO 2 treatment. Each vegetable was shredded, washed, and separated in two portions, one to be treated with ClO 2 gas and the other to remain untreated as reference sample. The batch to be treated with ClO 2 gas was immersed for 1 min in a 0.5% solution of HCl · l-cysteine monohydrate. Then both batches were spun dried. MP vegetables were decontaminated in a cabinet at 90–91% relative humidity and 22–25 °C up to 10 min, including 30 s of ClO 2 injection into the cabinet. The ClO 2 concentration rose to 1.74 mg/L (MP lettuce) and 1.29 mg/L (MP cabbage). Then samples were stored under modified atmosphere at 7 °C for shelf-life studies. Changes in O 2 and CO 2 headspace concentrations, microbiological quality (aerobic plate count (APC), psychrotrophs, lactic acid bacteria, and yeasts), sensory quality, and pH were followed during storage. The respiration rate of the minimally processed vegetables was significantly increased by the ClO 2 gas treatment only in the case of MP cabbage ( P < 0.05). The gas treatment reduced initially APC and psychrotroph count of MP lettuce and APC, psychrotroph counts, yeast counts and pH of MP cabbage ( P < 0.05). ClO 2 treatment did not cause initially any significant ( P < 0.05) sensorial alteration, except for a weak off-odour in MP lettuce. Interestingly, no browning was observed after treating, which can be accounted to the use of l-cysteine. Although an initial microbiological reduction was observed due to ClO 2 gas treatment, APC and psychrotroph counts reached in the samples treated with ClO 2 higher levels than in those non-treated with ClO 2 before the third day of the shelf-life study. Untreated and treated samples of MP lettuce were sensorial unacceptable due to bad overall visual quality after 4 days, while treated and untreated MP cabbage remained sensorial acceptable during the 9 days of the study. l-cysteine reduced ( P < 0.05) the decontamination efficacy of ClO 2 when applied to MP cabbage but not in the case of MP lettuce. Gaseous ClO 2 failed to prolong the shelf-life of MP lettuce and MP cabbage, the reason for the enhanced growth of microorganisms in decontaminated samples should be investigated. Nonetheless, our results prove that it is possible to inhibit browning caused by ClO 2.