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Green synthesis of nanoparticles through biogenic methods and plant secondary metabolites has gained significant importance due to their faster reduction rates, making them a more environmentally friendly and cost-effective alternative to traditional chemical and physical methods. This study presents a sustainable method for synthesizing fluorescent ZnS nanocrystals using Allium sativum extract. The synthesis utilizes sulfur-rich cysteine compounds and templating agents such as alkaloids and flavonoids of the Allium sativum extract. The resulting ZnS NPs were characterized using X-ray diffraction (XRD), UV–Vis spectroscopy, photoluminescence spectroscopy, while FE-SEM revealed an average particle size of 128nm and TEM showed particle size in the range of 42–78nm. The optical investigations reports showed that the biosynthesized ZnS NPs had an energy band gap of 4.9eV with absorption and excitation wavelengths of 214nm and 460nm, respectively. In vitro cytotoxicity assays showed significant anticancer activity against MCF-7 human breast cancer cells, with an IC50 value of 58.2$\mu$g/mL.

Penicillin resistance is a commonly present and controversial matter due to the misuse by people for various reasons. However, few studies have examined the bioactivity of 5- and 6- membered rings. In this study, we aimed to synthesize a new compound containing a 5-membered ring following a short and low-cost method and combined it with oxazepine ring via Schiff bases to produce a bicyclic molecule (Lactozepine). In vitro examinations were conducted to assess the bioactivity of the prepared compound, including anti-bacterial, anti-fungal and antioxidant activities, which showed a wide zone of inhibition of lactozepine against Streptococcus pneumoniae but no inhibition was shown against Klebsiella pneumoniae and Staphylococcus aureus except at a high concentration similar to the result of the anti-fungal assessment. Furthermore, lactozepine showed significant antioxidant activity against free radical formation. The molecular modeling and docking assessment showed the ability of lactozepine to bind to bacterial proteins and inhibit their growth with the lowest free energy for the greatest and strongest binding affinity with the PDB crystal structures 1VQQ, 2WAE, 1PYY and 1IYS ranging from −6.5 and −7.9 kcal/mol. Moreover, the molecular dynamics (MD) simulation showed that RMSF for the assessed protein’s amino acids remained consistent and tightly bound to lactozepine in the dynamic state. The novel compound lactozepine, with $\delta$-lactam rings attached to oxazepine showed bioactivity promising for in vivo studies in the future.

Cyclic voltammetry and spectroelectrochemistry studies are reported for the tetramethyl- tetrapyridinoporphyrazine complexes N,N′,N″,N‴-tetramethyltetra-2,3-pyridinoporphyrazine palladium(II) (1a), N,N′,N″,N‴-tetramethyltetra-3,4-pyridinoporphyrazine palladium(II) (1b), N,N′,N″,N‴-tetramethyltetra-2,3-pyridinoporphyrazine platinum(II) (2a) and N,N′,N″,N‴-tetramethyltetra-3,4-pyridinoporphyrazine platinum(II) (2b). Cyclic voltammetry on Pt disc electrodes showed two reductions. The first reduction was assigned to one-electron transfer to the ring with the formation of a monoanion species. All the tetramethyltetrapyridinoporphyrazine complexes are readily reduced to the monoanion species in the presence of histidine or cysteine. The rate constants for the interaction of complexes 1a, 1b, 2a and 2b with histidine and cysteine range from ~2 × 10⁻³ to 0.26 dm³mol⁻¹s⁻¹.

The interaction of histidine, cysteine, NO and nitrite with cobalt(II) N,N',N″,N‴-tetramethyltetra-3,4-tetrapyridinoporphyrazine ([Co^IItmtppa]⁴⁺) is reported. Metal-based autoreduction of [Co^IItmtppa]⁴⁺ occurs with the formation of the [Co^Itmtppa(-2)]³⁺ species in the presence of histidine and cysteine. Kinetic data for the auto reduction of [Co^IItmtppa]⁴⁺ in the presence of these amino acids gave the rate constants k_f = 2.1 × 10¹ and 2.8 dm³ mol^-1 s^-1, for cysteine and histidine, respectively. One molecule of NO or nitrite was found to coordinate to the [Co^IItmtppa]⁴⁺ species. The equilibrium and rate constants for the coordination of the nitric oxide were K = 2.3 × 10⁴dm³mol^-1 and k_f = 7.5 dm³mol^-1s^-1, respectively. The coordination of nitrite to [Co^IItmtppa]⁴⁺ occurred with an equilibrium constant of K = 2.0 × 10²dm³mol^-1 and a rate constant of k_f = 4.0 × 10^-3dm³mol^-1s^-1. There was no evidence for the coordination of two molecules of nitrite to the [Co^IItmtppa]⁴⁺ species.

In this paper, we study the electrical transport and Negative Differential Resistance (NDR) in a single molecular conductor consisting of a cysteine sandwiched between two Au(111) electrodes via the Density Functional Theory-based Nonequilibrium Green's Function (DFT-NEGF) method. We show that (surprisingly, despite their apparent simplicity, these Au/cysteine/Au nanowires are shown to be a convenient NDR device) the smallest two-terminal molecular wire can exhibit NDR behavior to date. Experiments with a conventional or novel self-assembled monolayer (SAM) are proposed to test these predictions.

The projected density of states (PDOSs) and transmission coefficients T(E) under various external voltage biases are analyzed, and it suggests that the variation of the coupling between the molecule and the electrodes with external bias leads to NDR.

Selective fluorescent and colorimetric sensing of cysteine in methanol-HEPES buffer (45 mM, pH $=$ 7.2, v/v $=$ 1/1) solution over various common amino acids and related thiol containing compounds has been achieved based on the cyclization reaction between the formyl group on 3-formylBODIPYs and cysteine/homocystein. Upon addition of cysteine/homocystein, 3-formylBODIPYs exhibited greatly enhanced fluorescence intensity as well as an abvious red-shift of the absorption peak (20–30 nm). The detection limits for cysteine were in the range of 1.18–2.73 $\times$10${}^{-6}$ M. The detection mechanism was studied by nuclear magnetic resonance and theoretical calculation.

The inverse protein folding problem is that of designing an amino acid sequence which has a prescribed native protein fold. This problem arises in drug design where a particular structure is necessary to ensure proper protein-protein interactions. The input to the inverse protein folding problem is a shape and the goal is to design a protein sequence with a unique native fold that closely approximates the input shape. Gupta et al.¹ introduced a design in the 2D HP model of Dill that can be used to approximate any given (2D) shape. They conjectured that the protein sequences of their design are stable but only proved the stability for an infinite class of very basic structures. The HP model divides amino acids to two groups: hydrophobic (H) and polar (P), and considers only hydrophobic interactions between neighboring H amino in the energy formula. Another significant force acting during the protein folding are sulfide (SS) bridges between two cysteine amino acids. In this paper, we will enrich the HP model by adding cysteines as the third group of amino acids. A cysteine monomer acts as an H amino acid, but in addition two neighboring cysteines can form a bridge to further reduce the energy of the fold. We call our model the HPC model. We consider a subclass of linear structures designed in Gupta et al.¹ which is rich enough to approximate (although more coarsely) any given structure. We refine the structures for the HPC model by setting approximately a half of H amino acids to cysteine ones. We conjecture that these structures are stable under the HPC model and prove it under an additional assumption that non-cysteine amino acids act as cysteine ones, i.e., they tend to form their own bridges to reduce the energy. In the proof we will make an efficient use of a computational tool 2DHPSolver which significantly speeds up the progress in the technical part of the proof. This is a preliminary work, and we believe that the same techniques can be used to prove this result without the artificial assumption about non-cysteine H monomers.

In this study, recombinantly produced human fetal hemoglobin (HbF) is used to examine the possibility of engineering redox active residues to explore oxidative reactivity in the Hb molecule. Cysteine residues at selected positions are removed or added to analyze functionality, oxidation rates, quantitative irreversible tri-oxidation and heme loss, between a wild-type and three different mutants. We conclude that adding a cysteine residue at a surfaced-exposed position on the α-chain gives a more oxidatively stable HbF, while removing a conserved cysteine in the γ-chain destabilizes the protein considerably.