Synthesis and Insecticidal Evaluation of Chiral Neonicotinoids Analogs: The Laurel Wilt Case.

Xyleborus sp beetles are types of ambrosia beetles invasive to the United States and recently also to Mexico. The beetle can carry a fungus responsible for the Laurel Wilt, a vascular lethal disease that can host over 300 tree species, including redbay and avocado. This problem has a great economic and environmental impact. Indeed, synthetic chemists have recently attempted to develop new neonicotinoids. This is also due to severe drug resistance to "classic" insecticides. In this research, a series of neonicotinoids analogs were synthesized, characterized, and evaluated against Xyleborus sp. Most of the target compounds showed good to excellent insecticidal activity. Generally, the cyclic compounds also showed better activity in comparison with open-chain compounds. Compounds R-13, 23, S-29, and 43 showed a mortality percent of up to 73% after 12 h of exposure. These results highlight the enantioenriched compounds with absolute R configuration. The docking results correlated with experimental data which showed both cation-π interactions in relation to the aromatic ring and hydrogen bonds between the search cavity 3C79 and the novel molecules. The results suggest that these sorts of interactions are responsible for high insecticidal activity.

Design, synthesis, molecular docking and in vitro evaluation of benzothiazole derivatives as 11ß-hydroxysteroid dehydrogenase type 1 inhibitors.

11-Beta hydroxysteroid dehydrogenase type 1 (11ß-HSD1) regulates cortisol levels mainly in adipose, hepatic and brain tissues. There is a relationship between the high activity of this enzyme and the development of obesity and metabolic disorders. The inhibition of 11ß-HSD1 has been shown to attenuate the development of type 2 diabetes mellitus, insulin resistance, metabolic syndrome and other diseases mediated by excessive cortisol production. In this work, fifteen benzothiazole derivatives substituted with electron-withdrawing and electron-donating groups were designed to explore their affinity for 11ß-HSD1 using in silico methods. The results show that (E)-5-((benzo[d]thiazol-2-ylimino)(methylthio)methylamino)-2-hydroxybenzoic acid (C1) has good physicochemical properties and favorable interactions with 11ß-HSD1 through hydrogen bonding and hydrophobic interactions in the catalytic site formed by Y183, S170 and Y177. Furthermore, C1 was synthesized and evaluated in vitro and ex vivo using clobenzorex (CLX) as a reference drug in obese Zucker rats. The in vitro results showed that C1 was a better inhibitor of human 11ß-HSD1 than CLX. The ex vivo assay results demonstrated that C1 was capable of reducing 11ß-HSD1 overexpression in mesenteric adipose tissue. Therefore, C1 was able to decrease the activity and expression of 11ß-HSD1 better than CLX.

Antioxidant activity of curcuminoids.

An exploration of the antioxidant power of curcumin, demethoxycurcumin, and bisdemethoxycurcumin, three natural antioxidants found in Curcuma longa, is reported in this work. We exhaust all structural possibilities leading to intramolecular hydrogen bonding and evaluate 15 isomers in total. Calculations were carried out in the gas phase and in the presence of solvents (water, to mimic biological media, and ethanol, to reproduce experimental assays) following the hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms. CH3OH-O hydrogen bonds are directly related to the antioxidant power via both mechanisms. We provide evidence to explain the experimental observations and to understand the fundamental factors driving antioxidant activity from a molecular perspective. Noticeably, the solvent enhances the antioxidant power in every case. All structures considered here are predicted to have better antioxidant abilities than phenol, and come very close to or surpass vitamin E.

Structural basis of ConM binding with resveratrol, an anti-inflammatory and antioxidant polyphenol.

Resveratrol can also inhibit the activation of proinflammatory mediators and cytokines at the early gene expression stage. It is well known that lectins are sugar-binding proteins that act as both pro- and anti-inflammatory molecules. Thus, the objective of this work was to verify the binding of a polyphenol compound with a lectin of Canavalia maritima (ConM) based on their ability to inhibit pro-inflammatory processes. To accomplish this, ConM was purified and crystallized, and resveratrol was soaked at 5mM for 2h of incubation. The crystal belongs to the monoclinic space group C2, the final refinement resulted in an Rfactor of 16.0% and an Rfree of 25.5%. Resveratrol binds in the rigid ß-sheet through H-bonds and hydrophobic interaction with amino acids that compose the fifth and sixth ß-strands of the rigid ß-sheet of ConM. The ConM and resveratrol inhibited DPPH oxidation, showing synergic activity with the most effective ratio of 2:3 and carbohydrate binding site is not directly related to antioxidant activity. It is the interaction between ConM and resveratrol that indicates the synergism of these two molecules in acting as free radicals scavengers and in reducing the inflammatory process through the inhibition of many pro-inflammatory events.

Preventing the return of smallpox: molecular modeling studies on thymidylate kinase from Variola virus.

Smallpox was one of the most devastating diseases in the human history and still represents a serious menace today due to its potential use by bioterrorists. Considering this threat and the non-existence of effective chemotherapy, we propose the enzyme thymidylate kinase from Variola virus (VarTMPK) as a potential target to the drug design against smallpox. We first built a homology model for VarTMPK and performed molecular docking studies on it in order to investigate the interactions with inhibitors of Vaccinia virus TMPK (VacTMPK). Subsequently, molecular dynamics (MD) simulations of these compounds inside VarTMPK and human TMPK (HssTMPK) were carried out in order to select the most promising and selective compounds as leads for the design of potential VarTMPK inhibitors. Results of the docking and MD simulations corroborated to each other, suggesting selectivity towards VarTMPK and, also, a good correlation with the experimental data.

A comparative computational study of hydrogen and lithium-bonded complexes.

A computational study of hydrogen-bonded complexes of F(3)CH and C1H and of lithium-bonded complexes of F(3)CLi and CILi, with small molecules such as N(2) and H(2)O was undertaken at the MP2/6-311++G(d,p) level of theory. Bond extensions and redshifts were obtained for the Cl[Single Bond]H bond in the ClH complexes, while bond contractions and blueshifts were obtained for the C[Single Bond]H bond in the F(3)CH complexes. By contrast, bond extensions and blueshifts were obtained for all of the lithium-bonded species. These results were rationalized using a model derived from perturbation theory.

Understanding the HIV-1 protease nelfinavir resistance mutation D30N in subtypes B and C through molecular dynamics simulations.

A major concern in the antiretroviral (ARV) treatment of HIV infections with protease inhibitors (PI) is the emergence of resistance, which results from the selection of distinct mutations within the viral protease (PR) gene. Among patients who do not respond to treatment with the PI nelfinavir (NFV), the D30N mutation is often observed. However, several reports have shown that D30N emerges with different frequencies in distinct HIV-1 genetic forms or subtypes. In the present work, we analyzed the binding of NFV and the Gag substrate CA/p2 to PR from HIV-1 subtypes B and C through molecular dynamics (MD) simulations. The wild-type and drug-resistant D30N mutants were investigated in both subtypes. The compensatory mutations N83T and N88D, observed in vitro and in vivo when subtype C acquires D30N, were also studied. D30N appears to facilitate conformational changes in subtype B PR, but not in that from subtype C, and this could be associated with disestablishment of an alpha-helical region of the PR. Furthermore, the total contact areas of NFV or the CA/p2 substrate with the mutant PR correlated with changes in the resistance patterns and replicative capacity. Finally, we observed in our MD simulations that mutant PR proteins show different patterns for hydrophobic/van der Waals contact. These findings suggest that different molecular mechanisms contribute to resistance, and we propose that a single mutation has distinct impacts on different HIV-1 subtypes.

Merocyanine solvatochromic dyes in the study of synergistic effects in mixtures of chloroform with hydrogen-bond accepting solvents.

The molar transition energy (E(T)) polarity values for the solvatochromic probes 2,6-diphenyl-4-(2,4,6-triphenylpyridinium)phenolate (1), 4[(1-methyl-4-(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (2), and 4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (3) were collected in binary mixtures comprising chloroform and a hydrogen-bond accepting (HBA) solvent [dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetone or acetonitrile], aiming to investigate the ability of the chlorinated component to act as hydrogen-bond donating (HBD) solvent. Plots of E(T) as a function of X(2), the mole fraction of chloroform, were obtained and the data were analysed to investigate the preferential solvation (PS) of each probe in terms of both solute-solvent and solvent-solvent interactions. For dyes 1 and 2 a strong synergistic behavior was observed for all mixtures studied, indicating that the dyes are preferentially solvated by complexes formed through hydrogen bonding between chloroform and the HBA component in the mixtures. A study of 1 in deuterated chloroform with an HBA component (DMF and DMA) demonstrated that while almost no differences occur with the DMF mixtures, the presence of deuterated chloroform in its mixtures with DMA increases the synergistic effect, suggesting that it interacts more strongly with DMA, making its mixtures more polar. These data were successfully fitted to a model based on solvent-exchange equilibria. The features of the mixtures with dye 3 revealed a very different profile in comparison with the other two dyes, which suggests that in mixtures containing chloroform, the microenvironment of the dye seems to be important in determining the contribution of the structure resonances responsible for the stability of the dye.

A structure-activity study of antibacterial diterpenoids.

An analysis of the antibacterial activities of 15 terpenoids, eleven of which were previously described by us and four were extracted from the literature, suggested two structural requirements for activity of these and related compounds: a hydrophobic moiety,consisting of a substituted decalin skeleton, and a hydrophilic region possessing one hydrogen-bond-donor group. These structural requirements are responsible for an optimal insertion of these and related compounds into cell membranes, as suggested by the results of docking some of these compounds into a model phospholipid bilayer.

A micelle nucleation model for the interaction of dodecyl sulphate with Lys49-phospholipases A(2).

Bothropstoxin-I (BthTx-I) is a Lys49-PLA(2) from the venom of Bothrops jararacussu that lacks detectable catalytic activity, yet causes rapid Ca(2+)-independent membrane damage. With the aim of understanding the interaction between BthTx-I and amphiphilic molecules, we have studied the interaction of sodium dodecyl sulphate (SDS) with the protein. Circular dichroism and attenuated total reflection Fourier-transform infrared spectra of BthTx-I reveal changes in the alpha-helical organization of the protein at an SDS/BthTx-I molar ratio of 20-25. At SDS/BthTx-I ratios of 40-45 the alpha-helices return to a native-like conformation, although fluorescence emission anisotropy measurements of 2-amino-N-hexadecyl-benzamide (AHBA) demonstrate that the total SDS is below the critical micelle concentration when this transition occurs. These results may be interpreted as the result of SDS accumulation by the BthTx-I homodimer and the formation of a pre-micelle SDS/BthTx-I complex, which may subsequently be released from the protein surface as a free micelle. Similar changes in the alpha-helical organization of BthTx-I were observed in the presence of dipalmitoylphosphatidylcholine liposomes, suggesting that protein structure transitions coupled to organization changes of bound amphiphiles may play a role in the Ca(2+)-independent membrane damage by Lys49-PLA(2)s.

Study of the influence of ethanol on basic fibroblast growth factor structure.

The growth of cells is controlled by stimulatory or inhibitory factors. More than twenty different families of polypeptide growth factors have been structurally and functionally characterized. Basic fibroblast growth factor (bFGF) of the fibroblast growth factor family was characterized in 1974 as having proliferative activity for fibroblastic cells. The inhibitory effects of ethanol on cell proliferation result from interference with mitogenic growth factors (e.g., bFGF, EGF and PDGF). In order to better understand the mode of action of bFGF, particularly regarding the influence of ethanol on the biological activity of bFGF, three recombinant bFGF mutants were produced (M6B-bFGF, M1-bFGF and M1Q-bFGF). In the present study, wild bFGF and these mutants were examined by molecular dynamics simulations in systems consisting of a solute molecule in ethanol solution at 298 K and physiological pH over 4.0 ns. The hydrogen bonds, the root mean square deviations and specific radial distribution functions were employed to identify changes in the hydrogen bond structures, in the stability and in the approximation of groups in the different peptides to get some insight into the biological role of specific bFGF regions. The detailed description of the intramolecular hydrogen bonds, hydration, and intermolecular hydrogen bonds taking place in bFGF and its mutants in the presence of ethanol established that the residues belonging to the beta5 and beta9 strands, especially SER-73(beta5), TYR-112(beta9), THR-114(beta9), TYR-115(beta9), and SER-117(beta9), are the regions most affected by the presence of ethanol molecules in solution.

Study of the influence of ethanol on basic fibroblast growth factor structure

The growth of cells is controlled by stimulatory or inhibitory factors. More than twenty different families of polypeptide growth factors have been structurally and functionally characterized. Basic fibroblast growth factor (bFGF) of the fibroblast growth factor family was characterized in 1974 as having proliferative activity for fibroblastic cells. The inhibitory effects of ethanol on cell proliferation result from interference with mitogenic growth factors (e.g., bFGF, EGF and PDGF). In order to better understand the mode of action of bFGF, particularly regarding the influence of ethanol on the biological activity of bFGF, three recombinant bFGF mutants were produced (M6B-bFGF, M1-bFGF and M1Q-bFGF). In the present study, wild bFGF and these mutants were examined by molecular dynamics simulations in systems consisting of a solute molecule in ethanol solution at 298 K and physiological pH over 4.0 ns. The hydrogen bonds, the root mean square deviations and specific radial distribution functions were employed to identify changes in the hydrogen bond structures, in the stability and in the approximation of groups in the different peptides to get some insight into the biological role of specific bFGF regions. The detailed description of the intramolecular hydrogen bonds, hydration, and intermolecular hydrogen bonds taking place in bFGF and its mutants in the presence of ethanol established that the residues belonging to the beta5 and beta9 strands, especially SER-73(beta5), TYR-112(beta9), THR-114(beta9), TYR-115(beta9), and SER-117(beta9), are the regions most affected by the presence of ethanol molecules in solution.