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Highlights: [•] Three heteroarylacrylonitriles-derived fluorescent probes were synthesized. [•] Three heteroarylacrylonitriles-derived fluorescent probes were assessed as Michael acceptors toward cysteine. [•] New compounds for cysteine detection are reported. [•] New probes for cysteine detection localize preferentially at the cytoplasm and endosomes of living cells. [ABSTRACT FROM AUTHOR]

Abstract: 1,3-Dipolar cycloaddition of nitrile imines with α,β-unsaturated five- and six-membered lactones, thiolactones and lactams gave ring-fused pyrazoles. Regioisomeric mixtures have been obtained with the 5-substituted pyrazole as the major cycloadduct. Only with the five-membered lactone the major product was the 4-acyl derivative. Computational studies, the use of the topological analysis of the Fukui functions and the potential energy surfaces (PES) theory allowed a theoretical description of the local reactivity in agreement with the observed high regiochemistry and with the role of the heteroatom adjacent to the carbonyl group. [Copyright &y& Elsevier]

This study delves into the potential of MB 36 clusters (where M = Fe, Co, Ni) supported on graphene as effective single-atom catalysts (SACs). Our research is methodically segmented into several stages, each designed to validate the feasibility of the proposed material. We begin by investigating the potential energy surface of MB 36 clusters. Our findings reveal a preference for metallic atoms to position themselves above the central hexagonal vacancy of the B 36 cluster. This factor significantly contributes to the stabilization of the resultant MB 36 system. Subsequently, we employ ab-initio molecular dynamic simulations to affirm the stability of the graphene-supported MB 36 clusters. In the final stage, we evaluate the system's catalytic capability for the oxygen reduction reaction (ORR) by calculating the dissociation energy of O 2 and OOH post their adsorption on the M atom of the graphene-supported MB 36 cluster. These simulations suggest that FeB 36 could maintain stability at room temperature, exhibiting activation energies for O 2 and OOH dissociation lower than those previously reported on Fe/N/C-type SACs, approaching those found on the Pt(111) surface, the most efficient ORR electrocatalyst. This computational study suggests that graphene-supported FeB 36 clusters could emerge as a promising candidate for SACs. [Display omitted] [ABSTRACT FROM AUTHOR]

The antioxidant activity of nine lichen substances, including methylatrarate (1), methyl haematommate (2), lobaric acid (3), fumarprotocetraric acid (4), sphaerophorin (5), subsphaeric acid (6), diffractaic acid (7), barbatolic acid (8) and salazinic acid (9) has been determined through cyclic voltammetry. The compounds 1–4 presented slopes close to the Nernst constant of 0.059 V, indicating a 2H+/2e− relation between protons and electrons, as long as the compounds 5, 6, 7, 8, and 9 present slopes between 0.037 V and 0.032 V, indicating a 1H+/2e− relation between protons and electrons. These results show a high free radical scavenging activity by means of the release of H+, suggesting an important antioxidant capacity of these molecules. Theoretical calculations of hydrogen bond dissociation enthalpies (BDE), proton affinities (PA), and Proton Transfer (PT) mechanisms, at M06-2x/6-311+G(d,p) level complement the experimental results. Computations support that the best antioxidant activity is obtained for the molecules (3, 4, 5, 6, 7 and 8), that have a carboxylic acid group close to a phenolic hydroxyl group, through hydrogen atomic transfer (HAT) and sequential proton loss electron transfer (SPLET) mechanisms. Additional computations were performed for modelling binding affinity of the lichen substances with CYPs enzymes, mainly CYP1A2, CYP51, and CYP2C9*2 isoforms, showing strong affinity for all the compounds described in this study. • Lichenic substances show enzyme inhibition and antioxidant activity. • Methylatrarate and Methylhaeatommate show antioxidant effect by interaction with CYPs enzymes. • SPLET mechanism could be the most appropriate for study the antioxidant activity. • The electrochemistry measurements provide interesting results with antioxidant activity. [ABSTRACT FROM AUTHOR]

The purpose of this study is to show that H 2 is easily dissociated on lithium edge decorated carbon systems to form strong C–H and Li–H bonds. This mechanism has not been considered in previous studies where these kinds of systems have been proposed as good candidates to serve as hydrogen storage materials. The reactivity of molecular hydrogen (H 2 ) on three representative lithium edge-decorated carbon systems (on the clusters C 5 Li 7 + (1) and C 6 Li 6 (2), and on lithium edge-decorated zig-zag graphene nanoribbon (GNR-Li) (3)) have been studied using ab initio calculations based on the density functional theory with dispersion-corrected van der Waals exchange correlation functional. Our calculations show, on the one hand, that heterolytic hydrogen dissociation can precede with relatively low reaction barriers (0.60, 0.45 and 0.56 eV for systems 1, 2 and 3, respectively) along the minimum energy path and, on the other hand, that chemisorption energies are highly stabilizing (in the range of 1.15–1.54 eV). It is important to note that the highest activation barrier is found for the unique system, characterized as global minimum, on its corresponding potential energy surface (PES), which is system 1. These findings suggest that reversibility of the hydrogen absorption/desorption reactions, required in promising hydrogen storage materials, does not apply in these systems. [ABSTRACT FROM AUTHOR]

We established that the transformation from Si 5 2− to Al 5 H 5 2− could be possible by the successive isoelectronic substitution of silicon atoms by Al H units. The potential energy surfaces for the series Si 5− n (AlH) n 2− ( n = 0–5) systems were explored in detail, and the global minima maintained the same overall deltahedral structure as the one of the Si 5 2− cluster. The conservation of the overall structure upon isoelectronic substitution was proven to happen due to the preservation of the chemical bonding pattern. Theoretical VDEs were calculated for the series LiSi 5− n (AlH) n − ( n = 1–4) systems to facilitate their experimental detection. [ABSTRACT FROM AUTHOR]

Abstract: The potential energy surfaces of the Si4Li n (n =1–7) systems have been explored in detail and the global minimum structures were identified. The stability and growth patterns of the title clusters is rationalized in terms of the phenomenological shell model in which the tetrahedral Si4Li4 cluster is a closed shell (20 valence electron) highly stable cluster. Given that the structures reported herein are global minima on their corresponding potential energy surfaces, we propose them as good candidates for experimental detection. [Copyright &y& Elsevier]

Cocoa beans contain antioxidant molecules with the potential to inhibit type 2 coronavirus (SARS-CoV-2), which causes a severe acute respiratory syndrome (COVID-19). In particular, protease. Therefore, using in silico tests, 30 molecules obtained from cocoa were evaluated. Using molecular docking and quantum mechanics calculations, the chemical properties and binding efficiency of each ligand was evaluated, which allowed the selection of 5 compounds of this series. The ability of amentoflavone, isorhoifolin, nicotiflorin, naringin and rutin to bind to the main viral protease was studied by means of free energy calculations and structural analysis performed from molecular dynamics simulations of the enzyme/inhibitor complex. Isorhoifolin and rutin stand out, presenting a more negative binding ΔG than the reference inhibitor N-[(5-methylisoxazol-3-yl)carbonyl]alanyl- l -valyl-N~1~-((1R,2Z)−4-(benzyloxy)−4-oxo-1-{[(3R)−2-oxopyrrolidin-3-yl]methyl}but-2-enyl)- L -leucinamide (N3). These results are consistent with high affinities of these molecules for the major SARS-CoV-2. The results presented in this paper are a solid starting point for future in vitro and in vivo experiments aiming to validate these molecules and /or test similar substances as inhibitors of SARS-CoV-2 protease. [ABSTRACT FROM AUTHOR]