L-cysteine Amino Acids Research Articles

Dual nitrogen-sulfur-doping induce microwave absorption and EMI shielding in nanocomposites based on graphene

Graphene-oxide (GO) is one of the most commonly used carbon nanomaterials in advanced applications such as microwave absorption and EMI shielding, due to various advantages such as ease of synthesis and exfoliation, effective doping capability, and superior composite compatibility. In this study, we used the modified Hummer’s method to synthesize GO by exfoliating graphite powder, and a simple hydrothermal approach was employed for elemental doping and GO reduction. As nitrogen–sulfur (N, S) dual-doping precursors, thiourea and l-cysteine amino acids were utilized. The structural features and microporous network structure of GO aerogel foams were investigated. The microwave absorption capabilities of polyethersulfone-based nanocomposite films incorporating the as-produced nitrogen–sulfur enrich reduced GO (NS-rGO) are also explored. According to the physicochemical characterization, the existence of remarkable structural defects with a porous three-dimensional (3D) network was discovered due to heteroatom insertion and hydrothermal doping. Additionally, the dual-doped sample exhibited high Nitrogen and sulfur content of 8.93% and 13.19%, respectively. While NS-rGO possesses a higher conductivity of 174.7[Formula: see text][Formula: see text]S compared to 12.65[Formula: see text][Formula: see text]S for GO. The nanocomposites filled with NS-rGO foams demonstrated a high shielding efficiency (SE) of 45[Formula: see text]dB in the X-band with a filler loading of 0.5[Formula: see text]wt.%. This high SE arises from dopant heteroatoms and the heterogeneous interface, which induce interface polarization, thereby increasing microwave absorption and dielectric constant. It also results from multi-level reflections caused by the 3D porous structures. These findings offer valuable insights into the functionalization of carbon nanostructures and the development of 3D networks in GO-based functional materials, providing further guidance for engineering high-performance electromagnetic interference shielding materials.

Blue-light-driven photoactivity of L-cysteine-modified graphene quantum dots and their antibacterial effects

The widespread abuse of traditional antibiotics has led to a global rise in antibiotic-resistant bacteria, which give in return unprecedented health risks. Therefore, there is a large and urgent need for the development of new, smart antibacterial agents able to efficiently kill or inhibit bacterial growth. In this study, we investigated the antibacterial activity of S, N-doped Graphene Quantum Dots (GQDs) as a light-triggered antibacterial agent. Gamma irradiation was employed as a tool to achieve one-step modification of GQDs in the presence of L-cysteine amino acid as a source of heteroatoms. X-ray Photoelectron Spectroscopy (XPS), nuclear magnetic resonance (NMR), and zeta potential measurements provided the necessary data to clarify the structure of modified dots and verify the introduction of both S- and N-atoms in GQDs structure, but also severe changes in the aromatic, sp2 domains. Namely, γ-irradiation caused a bonding of S atoms in 1.14 at.% mainly as thiol groups, and N in 1.81 at.% as amino groups, but sp2 contribution in GQD structure was lowered from 63.00 to 4.86 at.%, as measured in dots irradiated at a dose of 200 kGy. Fluorescence quenching measurements showed that L-cysteine-modified dots are able to bind to human serum albumin. The antibacterial activity of GQDs combined with 1 and 6 h of blue light (470 nm) irradiation was tested against 8 bacterial strains. GQD-cys-25 sample provided the best results, with minimum inhibitory concentration (MIC) as low as 125 μg/mL against S. aureus, E. faecalis, and E. coli after only 1 h of blue light exposure.

The performance of heteroatom-doped carbon nanotubes synthesized via a hydrothermal method on the oxygen reduction reaction and specific capacitance

Due to the increasing demand for electrochemical energy storage, various novel electrode and catalysis materials for supercapacitors and rechargeable batteries have developed over the last decade. The structure and characteristics of these catalyst materials have a major effect on the device's performance. In order to lower the costs associated with electrochemical systems, electrochemical systems, metal-free catalysis materials can be employed. In this study, metal-free catalysts composed of nitrogen (N) and sulfur (S) dual-doped multi-walled carbon nanotubes were synthesized using a straightforward and cost-effective single-step hydrothermal method. Carbon nanotubes served as the carbon source, while l-cysteine amino acid and thiourea acted as doping elements. As a result of the physicochemical characterization, many defects and a porous structure were noted, along with the successful insertion of nitrogen and sulfur into the carbon nanotube was confirmed. According to the cyclic voltammetry tests for the dual-doped samples in alkaline conditions, the D-CNT2 catalyst exhibited onset potentials of -0.30 V higher than the -0.37 V observed for the D-CNT3 catalyst. This indicates enhanced oxygen–reduction reaction due to the synergistic effects of the heteroatoms in the structure and the presence of chemically active sites. Moreover, the outstanding specific capacitance of the D-CNT2 catalyst (214.12 F g-1 at scanning rates of 1 mV s-1) reflects the effective porosity of the proposed catalyst. These findings highlight the potential of N/S dual–doped carbon nanotubes for electrocatalytic applications, contributing to efficient energy conversion.

Biologically Derived Metal–Cysteine Coordination Complexes Crosslink Carboxylated Nitrile Rubber and Enable Room Temperature Self-Healing, Stretchability, and Recyclability

In this study, we investigated a network of carboxylated nitrile rubber crosslinked by biologically derived coordination complexes that possesses good room temperature self-healing properties in addition to high tensile strength, stretchability, and recyclability. First, we showed the synthesis and analysis of coordination complexes composed of two metal salts (nickel nitrate and zinc nitrate), whose corresponding thiol and amino groups engage with the l-cysteine amino acid to produce the complex. Infrared spectrum, X-ray pattern, mass spectroscopy, energy-dispersive X-ray analyses (EDX), and morphology (SEM and TEM) analysis have all been used to characterize the metal–cysteine complexes. These Ni–cysteine and Zn–cysteine complexes have an apparent behavior after addition to XNBR rubber, as observed by several investigations (including swelling experiment, rubber process analysis, universal testing machine (UTM) analysis, and morphological analysis). Therefore, compared to the Ni-cysteine- and pristine cysteine-cured XNBR compounds, the Zn–cysteine complex-cured XNBR compound showed extreme stretchability, recyclability, and strong tensile strength of 3.8 ± 0.2 MPa. It also had a remarkable healing performance of 89.5%. This concept is strongly approved by the increased physico-mechanical properties of XNBR rubber and the recyclability with self-healing capability.

Prussian blue nanoparticles anchored on activated 3D printed sensor for the detection of L-cysteine

The use of 3D printing technology has enabled the development of low-cost and versatile electrochemical sensors. Commercial conductive filaments have been widely used due to their easiness of acquisition ready for application, and the possibility of surface modification. Generally, these filaments are composed of polymers and conductive material. However, it can present different compositions according to the manufacturing, which includes other additives and impurities. Iron has been reported as one of these impurities in conductive filaments based on polylactic acid and graphene. In this case, we have explored the presence of iron species for the electrochemical synthesis of stable nanoparticles of Prussian blue on 3D printed graphene electrodes. Prussian blue was used for the catalyst and electro-oxidation of L-cysteine amino acid, which is a biomarker related to several health problems and neurodegenerative diseases, such as Alzheimer's and Parkinson's. An arrangement of all 3D printed electrodes was used and presented comparable results to a conventional electrodes array. Also, the proposed sensors have shown good sensitivity, selectivity in presence of other amino acids, repeatability, and intra-day reproducibility for L-cysteine detection, compared to other 3D printed sensors obtained at different ages. The detection of L-cysteine was performed in spiked human blood serum samples, demonstrating no significant matrix interference.

Activated carbon materials with a rich surface chemistry prepared from L-cysteine amino acid

A series of activated carbon materials have been successfully prepared from a non-essential amino acid, such as L-cysteine. The synthesized carbons combine a widely developed porous structure (BET surface area up to 1000 m2/g) and a rich surface chemistry (mainly oxygen, nitrogen and sulphur functionalities). These surface functional groups are relatively stable even after a high temperature thermal treatment (O>N∼S). Experimental results show that these samples with a rich surface chemistry exhibit a significant improvement in their hydrophilic character. Although the role of the surface functional groups is less pronounced for the adsorption of non-polar molecules such as CO2, CH4 and C2H4, their adsorption at atmospheric pressure is to some extend conditioned by the characteristics of the adsorbent-adsorbate interactions. The synthesized carbons exhibit an excellent adsorption performance for CO2 (up to 3 mmol/g at 0 °C). Furthermore, samples with a low activation degree exhibit molecular sieving properties with very promising CO2/CH4 (up to 4.5) and C2H4/CH4 (up to 6) selectivity ratios. These results anticipate that non-essential amino acids are a versatile platform to obtain carbon materials combining a tailored porous structure and rich multifunctional surface chemistry and with potential application for gas adsorption/separation processes.

PH-Responsive Vesicle Formation by PEGylated Cholesterol Derivatives: Physicochemical Characterization, Stability, Encapsulation, and Release Study.

PEGylated vesicles are known to serve as blood-persistent drug-delivery systems (DDSs) with potential applications in intravenous drug administration. pH-responsive PEGylated vesicles are also among the most promising stimuli-responsive carriers for drug delivery and controlled release for cancer chemotherapy. Herein, we report design and synthesis of two novel pH-responsive amphiphiles by coupling a cholesterol (Chol) and poly(ethylene glycol) chain with l-cysteine amino acid through hydrolysable linkages. The objective of this work is to physicochemically characterize the nanoaggregates of the amphiphiles under different experimental conditions. We have demonstrated spontaneous vesicle formation by the amphiphiles in water using various spectroscopic, calorimetric, and microscopic techniques. The size of vesicles was observed to increase on reduction of solution pH and increase in amphiphile concentration. The vesicles were found to be sufficiently stable under physiological conditions and were shown to be able to encapsulate not only hydrophilic dyes in their aqueous core but also hydrophobic guest molecules in the bilayer membrane constituted by the Chol units. These nanosized vesicles exhibit pH-triggered release of encapsulated dye molecules in acidic pH. Thus, these spontaneously formed stable vesicles might hold potential as biocompatible DDSs in cancer chemotherapy.

Bioevaluation of 99mTc(I) carbonyl-radiolabeled amino acid coated magnetic nanoparticles in vivo

In this paper, amino acid coated and radiolabeled magnetic nanoparticles (MNPs) were prepared as a potential diagnostic agent. Magnetic nanoparticles were synthesized and functionalized by l-alanine and l-cysteine amino acids in one step. Besides surface functionalization, amino acid coating also provided favourable particle size. Structural characterization was performed by scanning electron microscopy. We obtained 30–38 nm and 22–30 nm diameter ranges with spherical shape for l-alanine and l-cysteine coated nanoparticles, separately. Then l-alanine and l-cysteine coated MNPs were radiolabeled with 99mTc(I)-tricarbonyl core (99mTc(CO)3-Alanine-MNP, 99mTc(CO)3-Cysteine-MNP) with a labeling yield of 63 ± 3% and 74 ± 2%. Pure radiolabeled magnetic particles were obtained by washing them with saline solution, and the radiochemical purity of 99mTc(CO)3-Alanine-MNP and 99mTc(CO)3-Cysteine-MNP were found as 94.3 ± 0.47% and 97.6 ± 1.06% in each of the final solution, respectively. In addition, both radiolabeled nanoparticles were stabile up to 4 h at 37 °C temperature in vitro conditions.After radiolabeling with 99m-Technetium tricarbonyl core, biological behaviour of nanoparticles was evaluated for each in vivo on male Wistar Albino rats.

Effects of optical and dielectric properties of l-cysteine doped tris thiourea zinc sulphate single crystals

The nonlinear optical single crystals of pure and l-cysteine amino acid doped Tris Thiourea Zinc Sulphate (TTZS) was synthesized and successfully grown by slow solvent evaporation technique. The present crystal was characterized by various analytical techniques. The lattice parameter values, cell volume and structure of the present crystal were identified by single crystal X-ray diffraction technique. The optical transparency and lower cut-off wavelength has been observed by UV–Vis spectrometer and further optical parameters were calculated. The FTIR analysis reveals the presence of functional groups and the kinds of vibrations. The NLO characteristics and laser damage threshold can be determined using Nd: YAG laser. The NLO efficiency and laser induced damage value of the L-cysteine doped tris thiourea zinc sulphate single crystal was found to be greater than pure TTZS crystal. In PL spectrum, sharp and narrow peaks are identified it denoted that the material having multi emission and it is suitable for applications in the light emitting diodes. The energy corresponding to the particular wavelength is also calculated. Growth nature of the title crystal was observed by etching analysis. The strength of the pure and doped crystals was determined using Vicker’s micro hardness test.

Enhancing photovoltaic performance of PbS/rGO nanocomposites: The role of buffer layer of ZnS/rGO nanocomposites

In the present study, we attempt to report an improvement in the photovoltaic performance of PbS/graphene nanocomposites, which were employed as the photovoltaic materials, using the layers of ZnS nanoparticles (NPs) and ZnS/graphene nanocomposites as n-type buffer layers. Graphene oxide (GO) sheets were used as graphene source and the ZnS/GO and PbS/GO nanocomposites were synthesized by a simple and cost-effective co-precipitation method using l-cysteine amino acid and Dodecylbenzenesulfonic acid (DBSA) as the surfactants, respectively. Characterization results such as X-ray diffractometer (XRD) patterns and X-ray photoelectron spectroscopy (XPS) results indicated that, the GO sheets were changed into reduced graphene oxide (rGO) during synthesis process. The photovoltaic measurements indicated that rGO in ZnS/rGO buffer layer had a more significant role in enhancing the photovoltaic performance of the photovoltaic device compared to ZnS (NPs) buffer layer. Moreover, these measurements demonstrated that the ZnS/rGO caused an increase in the short-circuit current (JSC) of the photovoltaic device, which led to improving the photovoltaic performance of the device.

Photovoltaic and UV detector applications of ZnS/rGO nanocomposites synthesized by a green method

The effect of graphene concentration on the photovoltaic and UV detector applications of ZnS/graphene nanocomposites was investigated. The nanocomposites were synthesized by a green, cost-effective, and simple co-precipitation method with different graphene concentrations (5, 10, and 15wt%) using L-cysteine amino acid as a surfactant and graphene oxide (GO) powder as a graphene source. Transmission electron microscopy (TEM) images showed that the ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in ZnS diameter size. The results of X-ray diffraction (XRD) patterns, Raman, and Fourier transform infrared (FTIR) spectroscopy indicated that the GO sheets were changed into reduced graphene oxide (rGO) during synthesis process. Therefore, L-cysteine amino acid played its role as a reducing agent to reduce the GO. Photovoltaic measurements showed that the graphene caused to increase the efficiency of solar-cell application of ZnS/rGO nanocomposites. In addition, our observation showed that the nanocomposites were suitable as ultraviolet (UV) detectors and graphene concentration increased the responsibility of the detectors.

Electric-field-driven alignment of chiral conductive polymer thin films.

We investigated the effect of an electric field on the alignment and structural properties of thin films of a chiral polybithiophene-based conductive polymer, functionalized with a protected l-cysteine amino acid. Thin films were obtained by exploiting both drop-casting and spin-coating procedures. The electric properties, the polarized Raman spectrum, the UV-vis spectrum, and the CD spectra were measured as a function of the electric field intensity applied during film formation. It was found that beyond the enhancement of the conductivity observed when the electric field aligns the polymer, the electric field significantly affects the chiral properties and the effect depends on the method of deposition.

Growth and spectroscopy studies of ADP single crystals with l-glutamine and l-cysteine amino acids

Ammonium dihydrogen orthophosphate (ADP) crystals were grown with l-glutamine C5H10N2O3 (gln) and l-cysteine C3H7NO2S (cys) amino acids, with polar side-chains, as additives at 4% molar concentrations. X-ray diffractograms, vibrational FT-IR, and Raman and NMR MAS of 31P, 1H and of pure and treated compounds were recorded at room temperature and interpreted. A lift of degeneracies of the ν4 asymmetric bending modes of both PO4 and NH4 tetrahedron species, as well as a shift of the wavenumbers of some of their internal modes was observed. At the same time, some characteristic vibrational modes of the organic molecules appeared. However, NMR results show a little shift of the resonance of the phosphorus and hydrogen nucleus, associated with some shoulders for this latter. The presence of the organic molecules was also revealed by 13C MAS NMR. These observations indicate that the host-additives interactions were achieved.

Comparative Study of Plasmonic Properties of Cysteine-Functionalized Gold and Silver Nanoparticle Aggregates

The absorptance spectra of gold and silver nanoparticle (NP) aqueous dispersions were measured by UV–visible spectroscopy and computed numerically by finite element method. Both NPs were functionalized by l-cysteine amino acid (Cys) in order to develop aggregate-based localized surface plasmon resonance biosensors. Absorptance spectra measured at an analogous pH value of ∼4.9 were compared, where Au-Cys conjugates have moderately split spectra with two commensurate maxima, while Ag-Cys conjugates exhibit the most pronounced secondary peak according to the highest degree of aggregation. The purpose of our theoretical study was to determine the simplest linear chain-like and wavy aggregate geometries, which result in maxima matching the measured peaks. The aggregates were characterized by N number and d diameter of NPs, g gap between the NPs, and t thickness of the l-cysteine covering. By tuning the angle of incidence and E-field oscillation direction in p-polarized light with respect to the aggregates, the contribution of longitudinal and transversal modes was varied. The comparison of measurements and computations revealed that spectra measured on bioconjugate dispersions include effects of numerous aggregates with various geometries, illuminated from different directions and are influenced by inter-aggregate coupling. Inspecting the normalized E-field distribution surrounding the aggregates, it was shown that fundamentally different multipolar modes can be identified at primary and secondary absorptance maxima, due to coupled plasmonic resonances on NPs.

Self-assembled monolayers of l-cysteine on palladium electrodes

l-cysteine modification of palladium (Pd) electrodes have been characterized using various electrochemical and surface analytical techniques such as cyclic voltammetry (CV), reductive/oxidative desorption, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and specular reflectance Fourier transform infrared (FT-IR) spectroscopy. The electron transfer reaction of l-cysteine modified Pd electrode was probed by employing Fe ( CN ) 6 3 - / 4 - redox couple using cyclic voltammetry and electrochemical impedance. The CVs results revealed a quasi-reversible voltammograms for the Pd modified electrode, demonstrating that the electron transfer is not blocked due to surface modification. EIS results for the Pd modified electrode showed a decrease in the resistance in comparison with the bare Pd electrode. The surface coverage was 6.4 ± 0.4 × 10 −10 mol/cm 2. The XPS survey study for the l-cysteine modified Pd electrode exhibited the presence of sulfur on the surface. High energy resolution XPS and FT-IR indicated that the l-cysteine molecules are sulfur bonded to the Pd surface. These results suggest the modification of palladium surface by the l-cysteine amino acids.

CoS spheres for high-rate electrochemical capacitive energy storage application

Sphere-like CoS nanostructures are synthesized in water/ethylene glycol mixed solvents by simple hydrothermal technique using l-cysteine amino acid as a source of sulfur. The results obtained by BET and BJH methods reveal that the CoS has mesoporous bimodal pore distribution in the range of 2–23 nm with a dominant peak around 12.4 nm and a small peak at 2.4 nm. The electrochemical experiments demonstrate that CoS has a high-rate capability for capacitor applications. The reduction of the specific capacitance is very marginal by about 13% of the available capacitance of 363 F g −1 when the scan rate is increased by 10 times. Even at very high frequency of 10 Hz, it retains the specific capacitance value of 150 F g −1, which confirms its higher power capability. Furthermore, during the cycling process, the Coulombic efficiency is better than 90% demonstrating excellent reversibility of CoS electrode.

Monolayers of Cyclopeptides: A New Concept for Molecular Recognition and Enantiomeric Discrimination

The suitability of the combinatorial chemistry approach for the design of a broad spectrum of new molecular-recognition compounds is demonstrated. A model system consisting of a monolayer of two synthetic cyclohexapeptides–one of which is illustrated in the Figure–containing three L-cysteine amino acids is reported to be able to distinguish more than 20 amino acids.

Chromatographic quantitation of the hydrophobicity of ionic compounds by the use of micellar mobile phases

Many biologically active compounds of interest in structure–activity relationships are ionic at physiological pH. However, ionic organic compounds are only weakly or not retained in conventional RPLC which impedes the chromatographic estimation of their hydrophobicity and the development of quantitative retention–activity relationship studies. The use of micellar mobile phases allows the retention of ionic compounds. Hydrophobic and electrostatic forces govern the retention of ionic compounds in micellar liquid chromatography. In this paper three different retention models log k–log P for ionic compounds are tested ( P=partition coefficient). The retention model (log k= a log P+ b α+ c) which includes the hydrophobicity and the molar total charge of compound at a given pH value has proven to be valid for all types of compounds tested, catecholamines, local anesthetics, diuretics and o-phthalaldehyde–N-acetyl- l-cysteine amino acid derivatives.