Combination Of L-cysteine Research Articles

Theoretical and experimental studies on the electrodeposited nanocrystalline Ag coatings from a novel Ag2O-based non-cyanide electrolyte

Functional silver coatings have been widely applied in fields of electrochemical energy conversion systems, electronics industry and antibacterial materials, and exploiting new non-cyanide silver electroplating bath system is of great significance for promoting the application. In this work, a new type of cyanide-free electrodeposited silver (Ag) system was developed with Ag2O as the main salt, 5,5-dimethyl hydantoin (DMH) as the silver ion complexing agent and potassium carbonate as the conductive salt. Comprehensive quantum chemical calculations demonstrate that the new silver-based system has the solvation structure of [Ag(C5H7N2O2)2]−(5N(2)-Ag). To further, roles of additives combination (L-cysteine and 2,2-bipyridine) and their fundamental mechanism on the silver electrodeposition process was further investigated by electrochemical tests and theoretical calculations. First-Principles calculation and simulation of molecular dynamics reveal that this additive couple have coordination interactions with Ag+, while strong adsorption on the Ag (111) surface. SEM and XRD analyses showed that the combination of L-cysteine and 2,2-bipyridine achieved an ideal silver coating with good morphology and a low grain size of 22.1 nm, verifying the great potential of the novel system to prepare high-quality silver coatings.

Application of different redox mediators induced bio-promoters to accelerate the recovery of denitrification and denitrifying functional microorganisms inhibited by transient Cr(VI) shock

The transient hexavalent chromium (Cr(VI)) shock may directly inhibit the denitrification process of municipal wastewater treatment plants (WWTPs), which is difficult to recover in a short time. This study developed four nontoxic bio-promoters (combination of L-cysteine, flavin adenine dinucleotide (FAD), biotin, cytokinin and different redox mediators) to quickly restore the denitrification performance after high-loading Cr(VI) suppressing. After feeding with 100 mg/L of Cr(VI) for 42 cycles (T, 4 h), the removal efficiency of nitrate was reduced by 85.00%, and nitrite was accumulated simultaneously. The denitrification performance was recovered quickly with the addition of bio-promoters, introducing redox mediators showed noticeable superiority on the bio-inhibition release. Compared with sodium humate and riboflavin, the AQDS induced bio-promoter achieved the best nitrate removal recovery performance within only 28 T, and the recovery rate was 2.16 times faster than the natural recovery. Microbial analysis showed that Cr(VI) specially inhibited napA-type denitrifiers, and the OTU numbers sharply dropped by 48.74%. Redox mediators induced bio-promoters could effectively recover the abundance of napA-type and nirS-type denitrifying microorganisms, which was consistent with the change of nitrate removal efficiency. This study offers a cost-effective approach to deal with Cr(VI) shock problem, which may promote the development of bio-promoters for WWTPs.

Rapid recovery of inhibited denitrification with cascade Cr(VI) exposure by bio-accelerant: Characterization of chromium distributions, EPS compositions and denitrifying communities

Hexavalent chromium (Cr(VI)) may inhibit denitrification in biological wastewater treatment systems, and the inhibited denitrification process is difficult to recover in a short time. This study explored Cr(VI) cascade impact (20–125 mg L−1) on denitrification and developed one nontoxic biological accelerant (combination of L-cysteine, flavin adenine dinucleotide, biotin and cytokinin) for denitrification recovery. The results showed that NO3−-N removal efficiency decreased from 75.7% to 21.5% when Cr(VI) concentration increased from 80 to 125 mg L−1. Addition of accelerant could effectively promote the removal of NO3--N, and observably reduce the recovery time (42 T) compared with natural recovery (63 T). Furthermore, the main site of Cr(VI) reduction and Cr(III) immobilization was located in the intercellular compartment of the biofilm. Microbes produced more tightly bound extracellular polymeric substances (TB-EPS) to protect them from toxicity under the low Cr(VI) concentrations, while low EPS was secreted when Cr(VI) concentration was higher than 60 mg L−1. Compared to natural recovery system, bio-accelerant addition was beneficial to the recovery of denitrifiers activities, especially for the bacteria containing nirS gene. The results facilitated an understanding of Cr(VI) impact on denitrification, and the proposed bio-accelerant can be potentially applied to heavy metal shock-loading emergency situations.

Synthesis of Antibiotic Penicillin-G Enzymatically by Penicillium chrysogenum

Penicillin-G antibiotic was used as the basic ingredient of making antibiotic type β-lactam such as tetracycline, amoxicillin, ampicillin and other antibiotics. Penicillin-G was splited into 6-amino penicillanic acid as the source of β-lactam. The biosynthetic pathway for the formation of penicillin-G in Penicillium chrysogenum cell through the formation of intermediates was carried out in the form of amino acids such as α-aminoadipate, L-cysteine, L-valine which are formed from glucose (food ingredients).The formation of 6-amino penicillanic acid is an amino acid combination of L-cysteine and L-valine, a step part of the formation of antibiotic penicillin-G in P. chrysogenum cells, thus, it is obvious that there are enzymes involved in its formation. The objective of this study was to examine the use of enzymes present in P. chrysogenum cells to produce penicillin-G and 6-amino penicillanic acid using the intermediate compounds α-aminoadipate, L-cysteine, L-valine and phenylacetic acid assisted by NAFA® coenzymes in P. chrysogenum cells which is more permeable. The research method started from producing biomass of P. chrysogenum cells that demonstrated penicillin-producing antibiotic capability, as the source of the enzyme, followed by addition of permeability treatment of P. chrysogenum cell membrane to get immobile of enzyme by its own cell therefore it can be used more than once. After that the enzyme activity was proven by adding α-aminoadipate, L-cysteine, L-valine, phenylacetic acid and NAFA® coenzyme for the formation of penicillin-G, whereas the addition of L-cystein, L-valine and NAFA® coenzyme were aimed to form 6-amino penicillanic acid. The results showed that P. chrysogenum is able to produce antibiotics with stationary early phase on day 6. The best increased permeability of P. chrysogenum cell membranes was obtained using a 1:4 of toluene:ethanol ratio mixture with the highest antibiotic concentration (130.06 mg/L) after testing for the enzymatic formation of antibacterial penicillin-G.

Evaluation of AA5052 alloy anode in alkaline electrolyte with organic rare-earth complex additives for aluminium-air batteries

Behaviours of the AA5052 aluminium alloy anode of the alkaline aluminium-air battery are studied by the hydrogen evolution test, the electrochemical measurements and the surface analysis method. The combination of amino-acid and rare earth as electrolyte additives effectively retards the self-corrosion of AA5052 aluminium alloy in 4 M NaOH solution. It shows that the combination of l-cysteine and cerium nitrate has a synergistic effect owing to the formation of a complex film on AA5052 alloy surface. The organic rare-earth complex can decrease the anodic polarisation, suppress the hydrogen evolution and increase the anodic utilization rate.

An electrogenerated chemiluminescence sensor based on gold nanoparticles@C60 hybrid for the determination of phenolic compounds

This paper described a novel strategy for the construction of an electrogenerated chemiluminescence (ECL) sensor based on gold nanoparticles@C60 (AuNPs@C60) hybrid for detecting phenolic compounds. First, C60 was functionalized with l-cysteine. Subsequently, with C60 as the core, gold nanoparticles (AuNPs) are synthesized and grown through an in situ reduction method in the presence of ascorbic acid (AA). The resulted flowerlike AuNPs@C60 nanoparticles were modified onto the glassy carbon electrode to achieve the sensor (AuNPs@C60/GCE). Here, l-cysteine not only can improve the biocompatibility and hydrophilicity of C60 but also can enhance the electrogenerated chemiluminescence (ECL) of peroxydisulfate system. Furthermore, both AuNPs and C60 are also beneficial to the ECL of the peroxydisulfate system. Due to the combination of l-cysteine, AuNPs and C60, the proposed ECL sensor exhibited an excellent analytical performance. Under an optimum condition, the ECL intensity increased linearly with phenolic compounds. The linear ranges of 6.2×10−8–1.2×10−4M, 5.0×10−8–1.1×10−4M and 5.0×10−8–1.1×10−4M were obtained for catechol (CC), hydroquinone (HQ) and p-cresol (PC), respectively, and the detection limits were 2.1×10−8M, 1.5×10−8M and 1.7×10−8M, respectively. The AuNPs@C60 hybrid might hold a new opportunity to develop an ECL sensor.

The combined effect of metformin and l-cysteine on inflammation, oxidative stress and insulin resistance in streptozotocin-induced type 2 diabetes in rats

Increasing evidence has established causative links between obesity, chronic inflammation and insulin resistance; the core pathophysiological feature in type 2 diabetes mellitus. This study was designed to examine whether the combination of l-cysteine and metformin would provide additional benefits in reducing oxidative stress, inflammation and insulin resistance in streptozotocin-induced type 2 diabetes in rats. Male Wistar rats were fed a high-fat diet (HFD) for 8 weeks to induce insulin resistance after which they were rendered diabetic with low-dose streptozotocin. Diabetic rats were treated with metformin (300mg/kg/day), l-cysteine (300mg/kg/day) and their combination along with HFD for another 2 weeks. Control rats were fed normal rat chow throughout the experiment. At the end of treatment, fasting blood glucose, fasting serum insulin, homeostasis model assessment-insulin resistance index (HOMA-IR) and serum free fatty acids (FFAs) were measured. Serum levels of the inflammatory markers; monocyte chemoattractant protein-1 (MCP-1), C-reactive protein (CRP) and nitrite/nitrate were also determined. The liver was isolated and used for determination of malondialdehyde (MDA), reduced glutathione (GSH), caspase-3 and cytochrome c levels. The hypoglycemic effect of the combination therapy exceeded that of metformin and l-cysteine monotherapies with more improvement in insulin resistance. All treated groups exhibited significant reductions in serum FFAs, oxidative stress and inflammatory parameters, caspase-3 and cytochrome c levels compared to untreated diabetic rats with the highest improvement observed in the combination group. In conclusion, the present results clearly suggest that l-cysteine can be strongly considered as an adjunct to metformin in management of type 2 diabetes.

English

  Transformation efficiency enhancement in maize Agrobacterium-mediated transformation was tested using four different basal media, five levels of N6 salts, two antioxidants and copper sulfate. In the absence of the antioxidants L-cysteine and dithiothreitol (DTT), the frequencies of transient GUS expression was higher using Linsmaier and Skoog (LS) and Murashige and Skoog (MS) media as an alternative to Chu (N6) and Ducan (D). N6 basal medium exhibited better performance in the presence of antioxidants than MS, LS and D basal media. Five different levels of N6 medium salts (10, 30, 50, 70 and 100%) were tested, and the highest transformation efficiency was 15.9% under a 50% salt concentration, followed by 6.4% transformation efficiency with 70 and 3.2% under 100% salt conditions. More than 95% of infected immature embryos exhibited GUS staining under 10 and 30% salt concentrations, however none of the embryos developed into embryogenic callus, indicating that low salt levels favored T-DNA delivery, but not stable transformation. Additions of DTT or L-cysteine, or a combination of L-cysteine and DTT, showed a significant improvement in the frequency of transient GUS expression, however increases were not observed with independent CuSO4treatments. Polymerase chain reaction (PCR) and Southern-blot analysis confirmed T-DNA integration into the maize genome.   Key words: Maize (Zea mays L.), Agrobacterium tumefaciens, transformation.

Chemosorption of radiometals of interest to nuclear medicine by synthetic melanins

Melanins are high-molecular-weight pigments that are ubiquitous in nature and can also be synthesized in the laboratory from a variety of precursors. Melanins possess numerous interesting physicochemical characteristics, including electromagnetic radiation absorption properties and ability to chelate metals. We have recently reported that melanin has remarkable ionizing-radiation-shielding properties, possibly because it can interact with photons via Compton scattering. We hypothesized that, if administered internally, melanin could play a beneficial role by scavenging various radionuclides, in addition to radiation shielding. Three melanins were synthesized from dopamine, 3,4-dihydroxyphenylalanine (l-Dopa) and a combination of l-cysteine and l-Dopa. For control, synthetic melanin made from tyrosine polymerization (Sigma) was used. Melanins were characterized by elemental analysis. The chemosorption of 111In, 225Ac and 213Bi by melanins was studied at 37 degrees C for up to 48 h. The C-to-N molar ratios for dopamine, l-Dopa and tyrosine melanins were very close at 7.92, 8.39 and 8.48, respectively, while in mixed l-cysteine/l-Dopa melanin, that ratio was much lower at 3.63. This mixed melanin also contained 22.33% sulfur, thus confirming incorporation of S-containing motifs into its structure. Dopamine, l-Dopa and tyrosine melanins were very similar in their abilities to decrease the activity of 111In, 225Ac and 213Bi and their radioactive daughters in supernatants by >10-fold in comparison with the starting levels, while mixed l-cysteine/l-Dopa melanin was able to chemosorb only 111In. We have demonstrated that synthetic melanins made of diverse precursors can chemosorb 111In, 213Bi and 225Ac, with dopamine, l-Dopa and tyrosine melanins being the most efficient towards all three of these radionuclides. Such properties of synthetic melanins can contribute to the development of the novel melanin-based radioprotective materials.

Effect of l-cysteine, kojic acid and 4-hexylresorcinol combination on inhibition of enzymatic browning in Amasya apple juice

In this study, the effect of different anti-browning agents on the enzymatic browning in the cloudy apple juice from Amasya cultivar was compared by considering colour changes. For this purpose, l-cysteine, kojic acid and 4-hexylresorcinol were used at different concentrations in the apple juice (0–4 mM). They were found as effective inhibitors. The combination of l-cysteine, kojic acid and 4-hexylresorcinol was also studied for the control of enzymatic browning. The results showed that 89.2% inhibition was obtained at the end of 24 h storage period with the combination of 3.96 mM l-cysteine, 2.78 mM kojic acid and 2.34 mM 4-hexylresorcinol in the cloudy apple juice. l-Cysteine was found to be the most significant anti-browning agent. The interaction of kojic acid and 4-hexylresorcinol was found to have a positive effect on the inhibition of enzymatic browning.

Chemically defined media for growing anaerobic bacteria of the genus Veillonella.

A chemically defined medium for Veillonella parvula and V. alcalescens is described. Some nutritional aspects of the two strains used were examined: the optimum concentration of reducing agents, the requirements for amino acids, diamines, vitamins and other growth factors, and the conditions needed for well balanced nutrition. No specific requirements for single amino acids were observed. A combination of L-cysteine, DL-aspartic acid, L-glutamic acid, L-serine and L-tyrosine, promoted growth. In V. alcalescens, serine could substitute both arginine and tryptophan (or histidine). No growth was obtained with ammonium salts as the sole N source. Decarboxylation of L-ornithine, L-lysine and L-arginine was not demonstrated in the Veillonella parvula strain, which required putrescine or cadaverine for growth. Spermine, spermidine, L-lysine, L-ornithine and L-arginine, could not substitute putrescine in Veillonella parvula. Veillonella alcalescens, which does not require putrescine in the medium, was able to decarboxylate L-ornithine while forming putrescine.

Protection against acetaldehyde toxicity in the rat by L-cysteine, thiamin and L-2-methylthiazolidine-4-carboxylic acid.

Acetaldehyde is 10–30 times more toxic than ethanol and has been implicated in alcoholic cardiomyopathy. Its oral LD50 and LD90 Litchfield-Wilcoxon values were found to be 15.0 (14.4–15.6) mM/kg and 18.0 (15.5–20.5) mM/kg, respectively. Protection against acetaldehyde lethality was obtained by oral intubation of test compounds 30–45 minutes prior to oral intubation of 18 mM/kg of acetaldehyde. At 2.0 mM/kg, survival after 24–72 hours withl-cysteine free base(FB)was80%;withl-2-methylthiazolidine-4-carboxylic acid (l-MTCA), 75%; with thiamin·HCl, 90%; and only 10% with saline control. At 0.3 mM/kg, thiamin·HCl gave virtually no protection (13% survival). The combination ofl-cysteine FB plus thiamin·HCl, each at 2.0 mM/kg, gave 100% survival. The oral LD50 dose (Litchfield-Wilcoxon) in mM/kg forl-cysteine FB was 15.6(14.8–16.4); forl-MTCA, 17.9 (17.0–18.8), and for thiamin·HCl, 11.0 (10.4–11.6). The ratio of toxic dose-protective dose of the first two compounds warrants further study of them in combination with thiamin as possible protective agents against the chronic toxicity of acetaldehyde associated with heavy ethanol intake and heavy smoking.