Search

Carbendazim (MBC) is a fungicide widely used in agriculture which allows the high productivity of several cultures, a necessary condition considering the growing of the world population. Moreover, MBC has environmental impact mainly on the soil and water sources, and consequently, on animal and human lives. However, even though the toxicity of fungicides is well established, their action mechanism in cell membranes are not completely understood. Herein, we investigate the interaction of different polar headgroups: dimethyldioctadecylammonium bromide (DODAB), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG); and different chain unsaturation degrees DPPC, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with MBC. Lipid monolayers at the air/water interface were applied as mimetic systems of cell membranes to investigate the interaction with MBC dissolved in the ultrapure water subphase. It was found that the interaction is driven preferably by electrostatic forces of the headgroups, with higher affinity for DODAB (cationic), intermediate for DPPC (zwitterionic), and absent for DPPG (anionic), considering the monolayer in the condensed phase. DODAB-MBC electrostatic interaction was consistent with FTIR (cast films). We also investigated giant unilamellar vesicles (GUVs) of zwitterionic lipids (DPPC, POPC, and DOPC) with distinct chain unsaturations in the presence of MBC by confocal microscopy and molecular dynamic (MD) simulations. The results indicate that, unlike the chain unsaturation, the polar headgroups play key role on the lipid-MBC interaction.

Made available in DSpace on 2022-04-28T19:40:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Dengue fever is a widespread infectious disease caused by Dengue viruses and responsible for millions of cases per year. One of the key steps during the infection is the fusion between the cell membrane and the lipidic bilayer of the virus, done by the glycoprotein envelope. At the tip of the envelope there is a fusion peptide widely conserved among the four known virus serotypes. Here dengue fusion peptides were studied in buffer solution and interacting with model membranes using fluorescence techniques. Peptides have the tryptophan residue exposed to aqueous environment when in buffer, while is exposed to a hydrophobic environment when interacting with negatively charged vesicles, as shown by the blue shift of fluorescence emission and increase in the lifetime decay. Fluorescence anisotropy results confirm that the residue is in a more restrictive environment when interacting with vesicles. Finally, fluorescence correlation spectroscopy results support the importance of electrostatic interaction, showing that dengue peptide promotes a significant increase in diameter of negatively charged vesicles, compared to the absence of effect in the size of neutral vesicles. Faculty of Philosophy,Sciences and Letters of Ribeiraõ Preto University of Saõ Paulo Universidade Federal Do Tocantins, Araguaína Campus Institute of Chemistry Saõ Paulo State University School of Technology and Applied Sciences Saõ Paulo State University

Since the first report of a new pneumonia disease in December 2019 (Wuhan, China) up to now WHO reported more than 50 million confirmed cases and more than one million losses, globally. The causative agent of COVID-19 (SARS-CoV-2) has spread worldwide resulting in a pandemic of unprecedented magnitude. To date, no clinically safe drug or vaccine is available and the development of molecules to combat SARS-CoV-2 infections is imminent. A well-known strategy to identify molecules with inhibitory potential against SARS-CoV-2 proteins is the repurposing of clinically developed drugs, e.g., anti-parasitic drugs. The results described in this study demonstrate the inhibitory potential of quinacrine and suramin against SARS-CoV-2 main protease (3CLpro). Quinacrine and suramin molecules present a competitive and non-competitive mode of inhibition, respectively, with IC50 and KD values in low μM range. Using docking and molecular dynamics simulations we identified a possible binding mode and the amino acids involved in these interactions. Our results suggested that suramin in combination with quinacrine showed promising synergistic efficacy to inhibit SARS-CoV-2 3CLpro. The identification of effective, synergistic drug combinations could lead to the design of better treatments for the COVID-19 disease. Drug repositioning offers hope to the SARS-CoV-2 control.

Phospholipase-B-like (SVPLB-like) enzymes are present in relatively small amounts in a number of venoms, however, their biological function and mechanisms of action are un-clear. A three-dimensional model of the SVPLB-like enzyme from Crotalus adamanteus was generated by homology modeling based on the crystal structures of bovine Ntn-hydrolyases and the modeled protein possesses conserved domains characteristic of Ntn-hydrolases. Molecular dynamics simulations indicate that activation by autocatalytic cleavage results in the removal of 25 amino acids which increases accessibility to the active site. SVPLB-like enzymes possess a highly reactive cysteine and are hence amidases that to belong to the N-terminal nucleophile (Ntn) hydrolase family. The Ntn-hydrolases (N-terminal nucleophile) form a superfamily of diverse enzymes that are activated autocatalytically; wherein the N-terminal catalytic nucleophile is implicated in the cleavage of the amide bond.

Herein we reported the synthesis of 20 novel fluorescent 5-carbonylated 2-arylindolizines derivatives through the reaction between organolithium intermediates with different electrophiles. To investigate the effects of the substituents on the wavelengths of electronic absorption spectra, fluorescence emission, quantum yield and Stokes shift, the photophysical properties of these molecules were evaluated. Maximum absorbance peaks were observed around 256–460 nm and maximum fluorescence emission around 485–548 nm. The fluorescence decay curves showed one or two decay times depending on the substituents with emission lifetime around 4–11 ns in methanol and 5–12 ns in DMSO. Quantum yield values ranged from 0.04 to 0.39 and Stokes shifts varied among 3.6–25 × 103cm−1. DFT calculations were also performed.

Made available in DSpace on 2019-10-06T16:29:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-04-23 Vitamin B12 acts as a cofactor for various metabolic reactions important in living organisms. The Vitamin B12 biosynthesis is restricted to prokaryotes, which means, all eukaryotic organisms must acquire this molecule through diet. This study presents the investigation of Vitamin B12 metabolism and the characterization of precorrin-4 C(11)-methyltransferase (CobM), an enzyme involved in the biosynthesis of Vitamin B12 in Corynebacterium pseudotuberculosis. The analysis of the C. pseudotuberculosis genome identified two Vitamin B12-dependent pathways, which can be strongly affected by a disrupted vitamin metabolism. Molecular dynamics, circular dichroism, and NMR-STD experiments identified regions in CobM that undergo conformational changes after s-adenosyl-L-methionine binding to promote the interaction of precorrin-4, a Vitamin B12 precursor. The binding of s-adenosyl-L-methionine was examined along with the competitive binding of adenine, dATP, and suramin. Based on fluorescence spectroscopy experiments the dissociation constant for the four ligands and the target protein could be determined; SAM (1.4 ± 0.7 µM), adenine (17.8 ± 1.5 µM), dATP (15.8 ± 2.0 µM), and Suramin (6.3 ± 1.1 µM). The results provide rich information for future investigations of potential drug targets within the C. pseudotuberculosis's Vitamin B12 metabolism and related pathways to reduce the pathogen's virulence in its hosts. Multiuser Center for Biomolecular Innovation Departament of Physics Instituto de Biociências Letras e Ciências Exatas (Ibilce) Universidade Estadual Paulista (UNESP), São Jose do Rio Preto-SP Institute of Physics Federal University of Mato Grosso do Sul Multiuser Center for Biomolecular Innovation Departament of Physics Instituto de Biociências Letras e Ciências Exatas (Ibilce) Universidade Estadual Paulista (UNESP), São Jose do Rio Preto-SP

Made available in DSpace on 2019-10-06T16:09:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Currently no effective treatment is available to combat infections caused by Corynebacterium pseudotuberculosis in livestock. Survival of this Gram-positive bacterium in rapidly-growing pathogens in hostile environments is strongly dependent on the existence of a robust DNA repair system to prevent DNA mutations and contribute to bacterial colonization and virulence. The adenine/guanine-specific DNA glycosylase (MutY) is evolutionarily conserved and has been well characterized due to its central role in the prevention of mutagenesis and DNA repair. The aim of this study was the characterization of the target protein interaction with free adenine, suramin, and heparin, as well as the binding competition characterization between the molecules. The dissociation constant for free adenine interaction with Corynebacterium pseudotuberculosis MutY (Cp-MutY) was determined, 86 ± 2.5 μM. NMR competition experiments demonstrated, that the polyanions heparin and suramin compete with adenine for the protein active site. The determined dissociation constant for the heparin/Cp-MutY interaction was 5.9 ± 1.0 μM and for suramin was 16 ± 1.5 μM. Docking of both polyanions with Cp-MutY revealed a possible mode of interaction and indicates that these molecules can interfere with the protein interaction with damaged DNA or prevent the binding of the adenine base in the enzyme active site. Multiuser Center for Biomolecular Innovation Department of Physics Instituto de Biociências Letras e Ciências Exatas (Ibilce) Universidade Estadual Paulista (UNESP) Departamento de Física e Biofísica Instituto de Biociências Universidade Estadual Paulista Júlio de Mesquita Filho -UNESP Laboratory of Molecular Biology Universidade Federal de São João Del-Rei (CCO), Av. Sebastião Gonçalves Coelho, 400 Laboratório de Genética Celular e Molecular Instituto de Ciências Biológicas Universidade Federal de Minas Gerais, Av, Antônio Carlos, 6627 - Pampulha, CP 486, CEP 31 Multiuser Center for Biomolecular Innovation Department of Physics Instituto de Biociências Letras e Ciências Exatas (Ibilce) Universidade Estadual Paulista (UNESP) Departamento de Física e Biofísica Instituto de Biociências Universidade Estadual Paulista Júlio de Mesquita Filho -UNESP FAPESP: 2009/53989-4 FAPESP: 2015/13765-0 FAPESP: 2015/18868-2 FAPESP: 2016/08104-8 FAPESP: 2016/12904-0 CNPq: 307338/2014-2 CNPq: 401270/2014-9 CNPq: 435913/2016-6

Vitamin B

TD-DFT and a combination of polarized continuum model (PCM) and microhydration methods helped to simulate the optical electronic absorption spectrum of ortho-aminobenzoic acid (o-Abz). The microhydration method involved the use of different numbers, from 1 to 5, of first solvation layer water molecules. We examined how implicit and explicit water affected the energies of the HOMO-LUMO transition in the o-Abz/water systems. Adding until five water molecules, the theoretical spectrum becomes closer to the experimental data. Microhydration combined with the PCM method leads to agreement between the theoretical result for five water molecules and the experimentally measured absorption bands.

Made available in DSpace on 2018-12-11T17:20:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul In pathogens, the thioredoxin system forms part of the defense against oxidative stress and ensures the formation of the proper disulfide bonds to ensure protein function. In Corynebacterium pseudotuberculosis, the role and mechanism of TrxA1 has not been elucidated, but, the significant homology among different Trxs and the conservation of the residues that form their active sites underline the importance of the Trx systems. Proteins involved in redox metabolism and low molecular weight thiols, which might interact with them, become attractive targets to modulate the activity of pathogens. The activity of the protein was investigated using a turbidimetric assay system. The influence of different pH and low molecular weight thiols were tested. Additionally, this assay was used to investigate the inhibitory potential of ligands from different molecular families, such as, polyanions (suramin and heparin) and flavonoids (hesperetin and hesperidin). All four compounds showed inhibition of the protein activity by approximately 80%. The interactions between these compounds and Cp-TrxA1 were investigated using CD spectroscopy, NMR, molecular docking and dynamics. Our results demonstrate that suramin and hesperetin can serve as lead molecules for the development of specific inhibitors for the C. pseudotuberculosis TrxA1. Multiuser Center for Biomolecular Innovation Department of Physics Instituto de Biociências Letras e Ciências Exatas (Ibilce) Universidade Estadual Paulista (UNESP) Institute of Physics Federal University of Mato Grosso do Sul Chemical Biology Laboratory Organic Chemistry Department Institute of Chemistry University of Campinas (UNICAMP) Multiuser Center for Biomolecular Innovation Department of Physics Instituto de Biociências Letras e Ciências Exatas (Ibilce) Universidade Estadual Paulista (UNESP) CNPq: 150444/2017-6 FAPESP: 2009/53989-4 FAPESP: 2015/13765-0 FAPESP: 2015/18868-2 FAPESP: 2016/08104-8 FAPESP: 2016/12904-0 Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul: 23/200.307/2014 CNPq: 307338/2014-2 CNPq: 401270/2014-9 CNPq: 435913/2016-6

Green propolis, a mixture of beeswax and resinous compounds processed by Apis mellifera, displays several pharmacological properties. Artepillin C, the major compound in green propolis, consists of two prenylated groups bound to a phenyl group. Several studies have focused on the therapeutic effects of Artepillin C, but there is no evidence that it interacts with amphiphilic aggregates to mimic cell membranes. We have experimentally and computationally examined the interaction between Artepillin C and model membranes composed of dimyristoylphosphatidylcholine (DMPC) because phosphatidylcholine (PC) is one of the most abundant phospholipids in eukaryotic cell membranes. PC is located in both outer and inner leaflets and has been used as a simplified membrane model and a non-specific target to study the action of amphiphilic molecules with therapeutic effects. Experimental results indicated that Artepillin C adsorbed onto the DMPC monolayers. Its presence in the lipid suspension pointed to an increased tendency toward unilamellar vesicles and to decreased bilayer thickness. Artepillin C caused point defects in the lipid structure, which eliminated the ripple phase and the pre-transition in thermotropic chain melting. According to molecular dynamics (MD) simulations, (1) Artepillin C aggregated in the aqueous phase before it entered the bilayer; (2) Artepillin C was oriented along the direction normal to the surface; (3) the negatively charged group on Artepillin C was accommodated in the polar region of the membrane; and (4) thinner regions emerged around the Artepillin C molecules. These results help an understanding of the molecular mechanisms underlying the biological action of propolis.