L-Cysteine: A promising nutritional supplement for alleviating anxiety disorders.

Anxiety disorders are prevalent chronic psychological disease with complex pathogenic mechanisms. Current anxiolytics have limited efficacy and numerous side effects in many anxiety patients, highlighting the urgent need for new therapies. Recent research has been focusing on nutritional supplements, particularly amino acids, as potential therapies for anxiety disorders. Among these, L-Cysteine plays a crucial role in various biological processes. L-Cysteine exhibits antioxidant properties that can enhance the antioxidant functions of the central nervous system (CNS). Furthermore, metabolites of L-cysteine, such as glutathione and hydrogen sulfide have been shown to alleviate anxiety through distinct molecular mechanisms. Long-term administration of L-Cysteine has anxiolytic, antidepressant, and memory-improving effects. L-Cysteine depletion can lead to increased oxidative stress in the brain. This review delves into the potential mechanisms of L-Cysteine and its main products, glutathione (GSH) and hydrogen sulfide (H2S) in the management of anxiety and related diseases.

Therapeutic effects of S-allyl-L-cysteine in a mouse endometriosis model and its immunomodulatory effects via regulation of T cell subsets and cytokine expression.

BACKGROUND: Endometriosis is a female hormone-dependent gynecological disorder characterized by chronic inflammation. Therefore, the development of novel treatment strategies that can diminish the side effects of the long-term use of hormone-based drugs has been emphasized. S-Allyl-L-cysteine (SAC) is the major constituent of aged garlic extracts. Although the therapeutic effects resulting from the antioxidant properties of SAC have been extensively studied in inflammatory diseases, the therapeutic efficacy of SAC in endometriosis has not been described. In this study, we investigated the therapeutic potential of SAC for endometriosis using a mouse model. METHODS: An endometriosis mouse model was surgically induced, and oral treatment with 30 mg/kg SAC was administered daily for 28 days. The development of endometriotic lesions was assessed by histological analysis, and the expression profiles of adhesion-, apoptosis-, and inflammation-related genes were evaluated by PCR. Flow cytometric analysis of mouse spleen was conducted to assess changes in lymphocyte subpopulations. RESULTS: SAC treatment significantly inhibited endometriotic lesion growth. Transcriptional expression analysis revealed the antiadhesion and apoptosis-promoting effects of SAC. In particular, SAC showed an effective immune modulatory response by altering splenic CD4+ and CD8+ T cell subsets and inflammatory cytokine production in the spleen and endometriotic lesions. CONCLUSION: This study newly elucidates the inhibitory effects of SAC on the growth of endometriosis in a mouse model and describes its immunomodulatory effects.

Farm to Fork Stability of Phytochemicals and Micronutrients in Brassica oleracea and Allium Vegetables.

Brassica oleracea and Allium vegetables are known for their unique, family specific, water-soluble phytochemicals, glucosinolates, and S-alk(en)yl-l-cysteine sulfoxides, respectively. However, they are also important delivery systems of several other health-related compounds, such as carotenoids (lipid-soluble phytochemicals), vitamin C (water-soluble micronutrient), and vitamin K1 (lipid-soluble micronutrient). When all-year-round availability or transport over long distances is targeted for these often seasonal, locally grown vegetables, processing becomes indispensable. However, the vegetable processing chain, which consists of multiple steps (e.g., pretreatment, preservation, storage, preparation), can impact the nutritional quality of these vegetables corresponding to the nature of the health-related compounds and their susceptibility to (bio)chemical conversions. Since information about the impact of the vegetable processing chain is scattered per compound or processing step, this review targets an integration of the state of the art and discusses needs for future research. Starting with a discussion on substrate-enzyme location within the vegetable matrix, an overview is provided of the impact and potential of processing, encompassing a wide range of (nonenzymatic) conversions.

Anti-Inflammatory and Anti-Oxidant Properties of N-Acetylcysteine: A Fresh Perspective.

N-acetyl-L-cysteine (NAC) was initially introduced as a treatment for mucus reduction and widely used for chronic respiratory conditions associated with mucus overproduction. However, the mechanism of action for NAC extends beyond its mucolytic activity and is complex and multifaceted. Contrary to other mucoactive drugs, NAC has been found to exhibit antioxidant, anti-infective, and anti-inflammatory activity in pre-clinical and clinical reports. These properties have sparked interest in its potential for treating chronic lung diseases, including chronic obstructive pulmonary disease (COPD), bronchiectasis (BE), cystic fibrosis (CF), and idiopathic pulmonary fibrosis (IPF), which are associated with oxidative stress, increased levels of glutathione and inflammation. NAC's anti-inflammatory activity is noteworthy, and it is not solely secondary to its antioxidant capabilities. In ex vivo models of COPD exacerbation, the anti-inflammatory effects have been observed even at very low doses, especially with prolonged treatment. The mechanism involves the inhibition of the activation of NF-kB and neurokinin A production, resulting in a reduction in interleukin-6 production, a cytokine abundantly present in the sputum and breath condensate of patients with COPD and correlates with the number of exacerbations. The unique combination of mucolytic, antioxidant, anti-infective, and anti-inflammatory properties positions NAC as a safe, cost-effective, and efficacious therapy for a plethora of respiratory conditions.

S-Allyl-L-cysteine (SAC) inhibits copper-induced apoptosis and cuproptosis to alleviate cardiomyocyte injury.

Cardiomyocyte injury is closely related to various myocardial diseases, and S-Allyl-L-cysteine (SAC) has been found to have myocardial protective effects, but its mechanism is currently unclear. Meanwhile, copper also has various physiological functions, and this study found that copper inhibited cell viability in a concentration and time-dependent manner, and was associated with multiple modes of death. Elesclomol plus CuCl2 (ES + Cu) significantly inhibited cell viability, and this effect could only be blocked by copper chelator TTM, indicating that "ES + Cu" induced cuproptosis in cardiomyocytes. SAC reduced the inhibitory effects of high concentration copper and "ES + Cu" on cell viability in a concentration and time-dependent manner, indicating that SAC plays a cardioprotective role under stress. Further mechanism study showed that high concentration of copper significantly induced cardiomyocyte apoptosis and increased the levels of LDH, MDA and ROS, while SAC inhibited the apoptosis and injury of cardiomyocytes induced by copper. "ES + Cu" significantly increased intracellular copper levels and decreased the expression of FDX1, LIAS, Lip-DLST and Lip-DLAT; FDX1 siRNA did not affect the expression of LIAS, but further reduced the expression of Lip-DLST and Lip-DLAT; SAC did not affect the expression of these genes, but enhanced the effect of "ES + Cu" in down-regulating these gene expression and restored intracellular copper levels. In addition, "ES + Cu" reduced ATP production, weakened the activity of mitochondrial complex I and III, inhibited cell viability, and increased the contents of injury markers LDH, MDA, CK-MB and cTnI, while SAC significantly improved mitochondrial function injury and cardiomyocyte injury induced by "ES + Cu". Therefore, SAC can inhibit apoptosis and cuproptosis to play a cardioprotective role.

Bridging the Gap in Cancer Research: Sulfur Metabolism of Leukemic Cells with a Focus on L-Cysteine Metabolism and Hydrogen Sulfide-Producing Enzymes.

Leukemias are cancers of the blood-forming system, representing a significant challenge in medical science. The development of leukemia cells involves substantial disturbances within the cellular machinery, offering hope in the search for effective selective treatments that could improve the 5-year survival rate. Consequently, the pathophysiological processes within leukemia cells are the focus of critical research. Enzymes such as cystathionine beta-synthase and sulfurtransferases like thiosulfate sulfurtransferase, 3-mercaptopyruvate sulfurtransferase, and cystathionine gamma-lyase play a vital role in cellular sulfur metabolism. These enzymes are essential to maintaining cellular homeostasis, providing robust antioxidant defenses, and supporting cell division. Numerous studies have demonstrated that cancerous processes can alter the expression and activity of these enzymes, uncovering potential vulnerabilities or molecular targets for cancer therapy. Recent laboratory research has indicated that certain leukemia cell lines may exhibit significant changes in the expression patterns of these enzymes. Analysis of the scientific literature and online datasets has confirmed variations in sulfur enzyme function in specific leukemic cell lines compared to normal leukocytes. This comprehensive review collects and analyzes available information on sulfur enzymes in normal and leukemic cell lines, providing valuable insights and identifying new research pathways in this field.

The Impact of Vitamin D and L-Cysteine Co-Supplementation on Upregulating Glutathione and Vitamin D-Metabolizing Genes and in the Treatment of Circulating 25-Hydroxy Vitamin D Deficiency.

Vitamin D receptors are expressed in many organs and tissues, which suggests that vitamin D (VD) affects physiological functions beyond its role in maintaining bone health. Deficiency or inadequacy of 25(OH)VD is widespread globally. Population studies demonstrate that a positive association exists between a high incidence of VD deficiency and a high incidence of chronic diseases, including dementia, diabetes, and heart disease. However, many subjects have difficulty achieving the required circulating levels of 25(OH)VD even after high-dose VD supplementation, and randomized controlled clinical trials have reported limited therapeutic success post-VD supplementation. Thus, there is a discordance between the benefits of VD supplementation and the prevention of chronic diseases in those with VD deficiency. Why this dissociation exists is currently under debate and is of significant public interest. This review discusses the downregulation of VD-metabolizing genes needed to convert consumed VD into 25(OH)VD to enable its metabolic action exhibited by subjects with metabolic syndrome, obesity, and other chronic diseases. Research findings indicate a positive correlation between the levels of 25(OH)VD and glutathione (GSH) in both healthy and diabetic individuals. Cell culture and animal experiments reveal a novel mechanism through which the status of GSH can positively impact the expression of VD metabolism genes. This review highlights that for better success, VD deficiency needs to be corrected at multiple levels: (i) VD supplements and/or VD-rich foods need to be consumed to provide adequate VD, and (ii) the body needs to be able to upregulate VD-metabolizing genes to convert VD into 25(OH)VD and then to 1,25(OH)2VD to enhance its metabolic action. This review outlines the association between 25(OH)VD deficiency/inadequacy and decreased GSH levels, highlighting the positive impact of combined VD+LC supplementation on upregulating GSH, VD-metabolizing genes, and VDR. These effects have the potential to enhance 25(OH)VD levels and its therapeutic efficacy.

In-situ co-immobilization of lipase, lipoxygenase and L-cysteine within a metal-amino acid framework for conversion of soybean oil into higher-value products.

We propose a co-immobilized chemo-enzyme cascade system to mitigate random intermediate diffusion from the mixture of individual immobilized catalysts and achieve a one-pot reaction of multi-enzyme and reductant. Catalyzed by lipase and lipoxygenase, unsaturated lipid hydroperoxides (HPOs) were synthesized. 13(S)-hydroperoxy-9Z, 11E-octadecadienoic acid (13-HPODE), one compound of HPOs, was subsequently reduced to 13(S)-hydroxy-9Z, 11E-octadecadienoic acid (13-HODE) by cysteine. Upon the optimized conditions, 75.28 mg of 13-HPODE and 4.01 mg of 13-HODE were produced from per milliliter of oil. The co-immobilized catalysts exhibited improved yield compared to the mixture of individually immobilized catalysts. Moreover, it demonstrated satisfactory durability and recyclability, maintaining a relative HPOs yield of 78.5% after 5 cycles. This work has achieved the co-immobilization of lipase, lipoxygenase and the reductant cysteine for the first time, successfully applying it to the conversion of soybean oil into 13-HODE. It offers a technological platform for transforming various oils into high-value products.

Association of 1-bromopropane exposure with asthma prevalence: A Korean National Health and Nutritional Examination Survey (2020-2021)-based study1.

Exposure to 1-bromopropane (1-BP) is an emerging environmental and health concern due to its increasing environmental prevalence. Although the health effects of 1-BP exposure have been under-recognized, current evidence suggests the possibility of adverse pulmonary health effects due to 1-BP exposure. However, the association between 1-BP exposure and asthma prevalence remains unclear. Thus, we aimed to examine the association between 1-BP exposure and asthma prevalence in the general population. Using nationally representative data, we explored the potential impacts of indoor air quality (IAQ)-related behavioral factors on the level of 1-BP exposure. This study included 1,506 adults from the 2020-2021 Korea National Health and Nutrition Examination Survey. The prevalence of asthma was based on self-reported physician-diagnosed asthma. Urinary N-acetyl-S-(n-propyl)-L-cysteine (BPMA) levels were measured as a biomarker of 1-BP exposure, using high-performance liquid chromatography-mass spectrometry. Multiple logistic regression models were performed to investigate the associations between urinary BPMA metabolite and asthma prevalence after adjusting for potential confounders. Log-linear multiple regression models were used to examine the association between IAQ-related behavior and urinary BPMA concentration. Forty-seven individuals with asthma and 1,459 without asthma were included. Individuals in the highest quartile of urinary BPMA concentration had a 2.9 times higher risk of asthma than those in the lowest quartile (odds ratio [OR]: 2.85, 95% confidence interval [CI]: 1.02-7.98). The combination of natural and mechanical ventilation was associated with a reduced urinary BPMA concentration. Our findings suggest that 1-BP exposure is associated with the prevalence of asthma in adults and revealed higher urinary levels of BPMA in our study population compared to those in other countries. Given the emerging importance of IAQ, actively managing and modifying behavioral patterns to reduce 1-BP exposure in indoor environments could substantially attenuate the risk of asthma-related to 1-BP exposure.

S-(N,N-diethyldithiocarbamoyl)-N-acetyl-l-cysteine for the treatment of non-small cell lung cancer through regulating NF-κB signalling pathway without neurotoxicity.

The discovery of novel targeted agents for non-small cell lung cancer (NSCLC) remains an important research landscape due to the limited efficacy, side effects and drug resistance of current treatment options. Among many repurposed drugs, disulphiram (DSF) has shown the potential to target tumours. However, its unpleasant neurotoxicity greatly limits its use. A DSF derivative, S-(N,N-diethyldithiocarbamoyl)-N-acetyl-l-cysteine (DS-NAC), was synthesised against NSCLC. The therapeutic effects, mechanism and toxicities of DS-NAC were evaluated in A549 and H460 cells and the mouse model of in situ lung cancer. The in vitro results exhibited that DS-NAC had potent anti-proliferation, apoptotic, anti-metastasis and epithelial-mesenchymal transition (EMT) inhibition effects. In the orthotopic lung cancer mouse model, therapeutic effects of DS-NAC were better than those of DSF and were similar to docetaxel (DTX). Also, results from western blot and immunohistochemistry showed that DS-NAC in combination with copper exerted therapeutic effects via regulating NF-κB signalling pathway and ROS-related proteins such as HIF-1α, Nrf2 and PKC-δ rather than regulating ROS level directly. Moreover, the safety evaluation study showed that DS-NAC had low haematologic and hepatic toxicities in comparison with DTX as well as low neurological toxicity compared with DSF. DS-NAC could be a promising anti-lung cancer agent with a favourable safety profile.

The effect of L-cysteine on starch and protein degradation during barley germination.

OBJECTIVES: In order to investigate the impact of L-cysteine (L-Cys) on starch and protein degradation during barley germination. The amylase activities, degradation of macromolecules during germination were determined in this study. METHODS: Barley was germinated in petri dish for 0 to 5 days with different levels of L-Cys (0 mM, 2.5 mM, 5 mM, 10 mM). RESULTS: L-Cys addition increased the total limit dextrinase (LD) activities and decreased the LD inhibitor activities during whole germination stage. The activities of α-amylase, ß-amylase and free LD were increased with the addition of 2.5, 5 mM L-Cys at germination days 1 to 4. Due to higher amylase in malt with the addition of L-Cys, the non-fermentable sugars were reduced and the glucose, maltotriose were improved. Furthermore, the protein degradation analysis showed that low molecular weight protein increased and middle molecular weight protein decreased obviously in wort from the malt germinated with L-Cys, demonstrating that the L-Cys promote the protein degradation. Lastly, the filtration performance of malt with the addition of L-Cys during malting was better than the control. CONCLUSION: In conclusion, L-Cys can promote the degradation of storage material (starch, protein) during barley germination, leading to a better green malt quality.

Crystal to Hydrogel Transformation in S-Benzyl-L-Cysteine-Containing Cyclic Dipeptides - Nanostructure Elucidation and Applications.

Cyclic dipeptides (CDPs) are crucial building blocks for a range of functional nanomaterials due to their simple chemical structure and high molecular stability. In this investigation, we synthesized a set of S-benzyl-L-cysteine-based CDPs (designated as P1-P6) and thoroughly examined their self-assembly behavior in a methanol-water solvent to elucidate the relationship between their structure and gelation properties. The hydrophobicity of the amino acids within the CDPs was gradually increased. The present study employed a comprehensive array of analytical techniques, including NMR, FT-IR, AFM, thioflavin-T, congo-red CD, X-ray crystallography, and biophysical calculations like Hirshfield Surface analysis and DFT analysis. These methods revealed that in addition to hydrogen bonding, the hydrophobic nature of the amino acid side chain significantly influences the propensity of CDPs to form hydrogels. Each CDP yielded distinct nanofibrillar networks rich in ß-sheet structures, showcasing unique morphological features. Moreover, we explored the practical application of these CDP-based hydrogels in water purification by utilizing them to remove harmful organic dyes from contaminated water. This application underscores the potential of CDPs in addressing environmental challenges, offering a promising avenue for the future development of these materials in water treatment technologies.

Ultrasound-assisted synthesis of a Eu3+-functionalized ZnII coordination polymer as a fluorescent dual detection probe for highly sensitive recognition of HgII and L-Cys.

A new ZnII coordination polymer (CP) based on 2,3-pyrazine dicarboxylic acid (H2pzdc) and 4,4'-bipyridine (bpy) (ZCP) was synthesized using a facile slow evaporation method. Single-crystal X-ray diffraction revealed that ZCP is a two-dimensional porous CP, [Zn2(pzdc)2(bpy)(H2O)2]n, with van der Waals forces as the dominant interaction within its layers forming a 63 network. Employing energetic ultrasound irradiation, nanoscale ZCP (nZCP) was successfully synthesized and Eu3+ ions were incorporated within its host lattice (Eu@nZCP). The resulting platform exhibits superior fluorescence characteristics and demonstrates notable optical durability. Therefore, it was used as a dual detection fluorescent sensing platform for the detection of mercury and L-cysteine (L-Cys) in aqueous media through a turn-off/on strategy. In the turn-off process, the fluorescence emission of Eu@nZCP progressively quenches by the addition of HgII via a photo-induced electron transfer (PET) mechanism. The fluorescence of Eu@nZCP is quenched to establish a low fluorescence background through the incorporation of HgII. This devised turn-on fluorescent system is suitable for the recognition of L-Cys (based on the strong affinity of L-Cys to the HgII ion) through a quencher detachment mechanism. This method attained a relatively wide linear range, spanning from 0.001 to 25 µM, with the low detection limit of 5 nM for the sensing of HgII. Also, the corresponding limit of detection (LOD) for L-Cys is 8 nM in a relatively wide linear range, spanning from 0.001 to 40 µM.

Sensitive SERS assay for L-cysteine based on functionalized silver nanoparticles.

L-cysteine, an indispensable amino acid present in natural proteins, plays pivotal roles in various biological processes. Consequently, precise and selective monitoring of its concentrations is imperative. Herein, we propose a Surface-enhanced Raman Scattering (SERS) sensor for detecting L-cysteine based on the anti-aggregation of 4-mercaptobenzoic acid (4-MBA) and histidine (His) functionalized silver nanoparticles (Ag NPs). The presence of Hg2+ ions can induce the aggregation of Ag NPs@His@4-MBA due to the unique nanostructures of Ag NPs@His@4-MBA, resulting in a robust SERS intensity of 4-MBA. However, in the presence of L-cysteine, the stronger affinity between L-cysteine and Hg2+ reduces the concentration of free Hg2+, causing the dispersion of the aggregated functionalized Ag NPs and the reduction of the SERS signal intensity of 4-MBA. The developed SERS platform demonstrates excellent performance with a low detection limit of 5 nM (S/N = 3) and linear detection capabilities within the range of 0.01-100 µM for L-cysteine. Additionally, the method was successfully employed for the determination of L-cysteine in spiked serum samples, yielding recoveries ranging from 95.0 % to 108.1 % with relative standard deviations of less than 3.3 %. This study not only presents a novel approach for fabricating highly sensitive and specific SERS biosensors for biomolecule detection but also offers a significant strategy for the development and construction of SERS substrates using anti-aggregation design.

Amino acid transporters in neurological disorders and neuroprotective effects of cysteine derivatives.

For most diseases and disorders occurring in the brain, the full causes behind them are yet unknown, but many show signs of dysfunction of amino acid transporters or abnormalities in amino acid metabolism. The blood-brain barrier (BBB) plays a key role in supporting the function of the central nervous system (CNS). Because of its unique structure, the BBB can maintain the optimal environment for CNS by controlling the passage of hydrophilic molecules from blood to the brain. Nutrients, such as amino acids, can cross the BBB via specific transporters. Many amino acids are essential for CNS function, and dysfunction of these amino acid transporters can lead to abnormalities in amino acid levels. This has been linked to causes behind certain genetic brain diseases, such as schizophrenia, autism spectrum disorder, and Huntington's disease (HD). One example of crucial amino acids is L-Cys, the rate-limiting factor in the biosynthesis of an important antioxidant, glutathione (GSH). Deficiency of L-Cys and GSH has been linked to oxidative stress and has been shown as a plausible cause behind certain CNS diseases, like schizophrenia and HD. This review presents the current status of potential L-Cys therapies and gives future directions that can be taken to improve amino acid transportation related to distinct CNS diseases.

Impact of the Acetyl Group on Cysteine: A Study of N-Acetyl-Cysteine through Rotational Spectroscopy.

Herein, we report a spectroscopic study of N-acetyl-L-cysteine, an important antioxidant drug, using Fourier-transform microwave techniques and in isolated conditions. Two conformers are observed, where most stable structure adopts a cis disposition, and the second conformer has a lower abundance and adopts a trans disposition. The rotational constants and the barriers to methyl internal rotation are determined for each conformer, allowing a precise conformation identification. The results show that the cis form adopts an identical structure in the crystal, solution, and gas phases. Additionally, the structures are contrasted against those of cysteine.

Peroxymonosulfate activation by superparamagnetic mixed-valent Cu/N-(L-cysteine)-O-(carboxymethyl)chitosan/cobalt ferrate-rice hull hybrid nanocomposite for efficient degradation of naproxen: Synergetic adsorption-catalysis, kinetics, pathway, and relevant mechanism.

Naproxen (NPX) as an emerging anthropogenic contaminant was detected in many water sources, which can pose a serious threat to the environment and human health. Peroxymonosulfate (PMS) decomposed by Cu(I) has been considered an effective activation method to produce reactive species. However, this decontamination process is restricted by the slow transformation of Cu(II)/Cu(I) by PMS. Herein, new N-(L-cysteine/triazine)-O-(carboxymethyl)-chitosan/cobalt ferrate-rice hull hybrid biocomposite was constructed to anchor the mixed-valent Cu(I)-Cu (II) (CuI, II-CCCF) for removing pharmaceutical pollutants (i.e., naproxen, ciprofloxacin, tetracycline, levofloxacin, and paracetamol). The structural, morphological, and catalytic properties of the CuI,II-CCCF have been fully identified by a series of physicochemical characterizations. Results demonstrated that the multifunctional, hydrophilic character, and negative ζ-potential of the activator, accelerating the redox cycle of Cu(II)/Cu(I) with hydroxyl amine (HA). The negligible metal leaching, well-balanced thermodynamic-kinetic properties, and efficient adsorption-catalysis synergy are the main reasons for the significantly enhanced catalytic performance of CuI,II-CCCF in the removal of NPX (98.6 % at 7.0 min). The main active species in the catalytic degradation of NPX were identified (●OH > SO4●- > 1O2 > > O2●-) and consequently suggested a degradation path. It can be noted that these types of carbohydrate-based nanocomposite offer numerous advantages, encompassing simple preparation, excellent decontamination capabilities, and long-term stability.

Using L-cysteine to enhance calibration range and prevent a memory effect in mercury analysis of complex samples via ICP-OES.

BACKGROUND: Mercury (Hg) is a persistent pollutant occurring in the environment able to transition between different species. It can therefore be found in air, soil and water reservoirs becoming a present concern for the general population but also sensitive populations like pregnant women. Therefore, investigating organ-specific transfer mechanisms of Hg is mandatory for Hg toxicity testing. For this, an in vitro system using microporous inserts to monitor the transfer across an in vitro placental barrier has been used. However, due to the cytotoxicity of Hg only low concentrations (1.26 ×10-4 - 1.36 ×10-2 µg/µL Hg) can be applied, making Hg determination in cell culture medium using inductively coupled plasma-optical emission spectrometry challenging, especially when these trace amounts should be determined alongside other trace elements which are naturally occurring in cells and cell culture medium like the essential metals manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn). Additionally, Hg analysis on an ICP system holds also a number of challenges like a persistent memory effect and instability of Hg standard solutions. METHODS: The development of a rapid and sensitive ICP-OES method to determine Hg in different matrices like cell culture medium and cells has been performed on an Avio 220 Max ICP-OES (Perkin-Elmer) equipped with a cyclonic spray chamber and MicroMist® nebulizer. Cell lysates and cell culture medium were diluted in a mixture of 0.2 % L-cysteine, 2 % HNO3 and 0.1 % HCl and directly introduced into the ICP-OES system. Further method development included the suitability of the analysis of multiple elements like Mn, Fe, Cu, and Zn as well as the determination of the limit of detection and limit of quantification. RESULTS: The combination of 0.2 % L-cysteine, 2 % HNO3 and 0.1 % HCl is able to bind and stabilize Hg ions in standard solutions and in biological matrices over a wide dynamic concentration range (1 - 500 µg/L) also alongside other metals like Mn, Fe, Cu and Zn without losses of sensitivity. A short run time of 3 min enables high throughput analysis. Additionally, the high salt and carbon concentrations in the culture medium do not affect Hg sensitivity using the ICP-OES. CONCLUSION: This method is a useful tool for the quantification of Hg in a variety of complex matrices including cells and cell culture media (high salt and carbon-rich (∼1 % each)) with high sensitivity and minimal sample preparation allowing high throughput. Furthermore, not only Hg can be determined in biological matrices, but even multiple elemental analysis can be carried out to address the effect of Hg on other metals homeostasis.

Electrochemical and quantum chemical approaches to the study of dopamine sensing using bentonite and l-cysteine modified carbon paste electrode.

This work presents a significant investigation involving both electrochemical experiment and quantum chemical simulation approaches. The objective was to characterize the electrochemical detection of dopamine (DA). The detection was carried out using a modified carbon paste electrode (CPE) incorporating bentonite (Bent) and l-cysteine (CySH) (named as CySH/Bent/CPE). To understand and explain the oxidation mechanism of DA on the CySH/Bent modified electrode surface, the coupling of the two approaches were exploited. The CySH/Bent/CPE showed excellent electroactivity toward DA such as good sensibility, selectivity, stability, and regenerative ability. The developed sensor shows a dynamic linear range from 0.8 to 80 µM with a limit of detection and quantification of 0.5 µM and 1.5 µM, respectively. During the quantitative analysis of DA in presence of ascorbic acid (AA) and uric acid (UA) the electrochemical oxidation signals of AA, DA, and UA distinctly appear as three separate peaks. The potential differences between the peaks are 190 mv, 150 mv, and 340 mV for the AA-DA, DA-UA, and AA-UA oxidation pairs, respectively. These observations stem from square wave voltammetry (SWV) studies, along with the corresponding redox peak potential separations. The developed sensor is simple and accurate to monitor DA in human serum samples. On the other hand, CySH acts as an electrocatalyst on the CySH/Bent/CPE surface by increasing its active electron transfer sites, as suggested by the quantum chemical modeling with analytical results of Fukui. Furthermore, the voltammetric results obtained agree well with the theoretical calculations.

Exploring the molecular mechanisms of Lrp/AsnC-type transcription regulator DecR, an L-cysteine-responsive feast/famine regulatory protein.

The Lrp/AsnC family of transcriptional regulators is commonly found in prokaryotes and is associated with the regulation of amino acid metabolism. However, it remains unclear how the L-cysteine-responsive Lrp/AsnC family regulator perceives and responds to L-cysteine. Here, we try to elucidate the molecular mechanism of the L-cysteine-responsive transcriptional regulator. Through 5'RACE and EMSA, we discovered a 15 bp incompletely complementary pair palindromic sequence essential for DecR binding, which differed slightly from the binding sequence of other Lrp/AsnC transcription regulators. Using alanine scanning, we identified the L-cysteine binding site on DecR and found that different Lrp/AsnC regulators adjust their binding pocket's side-chain residues to accommodate their specific effector. MD simulations were then conducted to explore how ligand binding influences the allosteric behavior of the protein. PCA and in silico docking revealed that ligand binding induced perturbations in the linker region, triggering conformational alterations and leading to the relocalization of the DNA-binding domains, enabling the embedding of the DNA-binding region of DecR into the DNA molecule, thereby enhancing DNA-binding affinity. Our findings can broaden the understanding of the recognition and regulatory mechanisms of the Lrp/AsnC-type transcription factors, providing a theoretical basis for further investigating the molecular mechanisms of other transcription factors.