Browsing by Author "Fuentes, Juan A."

Now showing 1 - 11 of 11
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    New Cationic fac-[Re(CO)3(deeb)B2]+ Complex, Where B2 Is a Benzimidazole Derivative, as a Potential New Luminescent Dye for Proteins Separated by SDS-PAGE
    (2021) Carreno, Alexander; Gacitua, Manuel; Solis-Cespedes, Eduardo; Paez-Hernandez, Dayan; Swords, Wesley B.; Meyer, Gerald J.; Preite, Marcelo D.; Chavez, Ivonne; Vega, Andres; Fuentes, Juan A.
    Sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) can be used to separate proteins based mainly on their size such as in denaturing gels. Different staining methods have been reported to observe proteins in the gel matrix, where the most used dyes are generally anionic. Anionic dyes allow for interactions with protonated amino acids, retaining the dye in the proteins. Fluorescent staining is an alternative technique considered to be sensitive, safe, and versatile. Some anionic complexes based on d(6) transition metals have been used for this purpose, where cationic dyes have been less explored in this context. In this work, we synthesized and characterized a new monocationic rhenium complex fac-[Re(CO)(3)(deeb)B2](+) (where deeb is 4,4 '-bis(ethoxycarbonyl)-2,2 '-bpy and B2 is 2,4-di-tert-butyl-6-(3H-imidazo[4,5-c]pyridine-2-yl)phenol). We carried out a structural characterization of this complex by MS+, FTIR, H-1 NMR, D2O exchange, and HHCOSY. Moreover, we carried out UV-Vis, luminescence, and cyclic voltammetry experiments to understand the effect of ligands on the complex's electronic structure. We also performed relativistic theoretical calculations using the B3LYP/TZ2P level of theory and R-TDDFT within a dielectric continuum model (COSMO) to better understand electronic transitions and optical properties. We finally assessed the potential of fac-[Re(CO)(3)(deeb)B2](+) (as well as the precursor fac-Re(CO)(3)(deeb)Br and the free ligand B2) to stain proteins separated by SDS-PAGE. We found that only fac-[Re(CO)(3)(deeb)B2](+) proved viable to be directly used as a luminescent dye for proteins, presumably due to its interaction with negatively charged residues in proteins and by weak interactions provided by B2. In addition, fac-[Re(CO)(3)(deeb)B2](+) seems to interact preferentially with proteins and not with the gel matrix despite the presence of sodium dodecyl sulfate (SDS). In future applications, these alternative cationic complexes might be used alone or in combination with more traditional anionic compounds to generate counterion dye stains to improve the process.
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    New Properties of a Bioinspired Pyridine Benzimidazole Compound as a Novel Differential Staining Agent for Endoplasmic Reticulum and Golgi Apparatus in Fluorescence Live Cell Imaging
    (2018) Llancalahuen, Felipe M.; Fuentes, Juan A.; Carreño, Alexander; Zúñiga, César; Páez-Hernández, Dayán; Gacitúa Santelices, Manuel Alejandro; Polanco, Rubén; Preite, Marcelo Daniel; Arratia-Perez, Ramiro; Otero, Carolina
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    Physicochemical and Theoretical Characterization of a New Small Non-Metal Schiff Base with a Differential Antimicrobial Effect against Gram-Positive Bacteria
    (2022) Gacitua, Manuel; Carreno, Alexander; Morales-Guevara, Rosaly; Paez-Hernandez, Dayan; Martinez-Araya, Jorge I.; Araya, Eyleen; Preite, Marcelo; Otero, Carolina; Rivera-Zaldivar, Maria Macarena; Silva, Andres; Fuentes, Juan A.
    Searching for adequate and effective compounds displaying antimicrobial activities, especially against Gram-positive bacteria, is an important research area due to the high hospitalization and mortality rates of these bacterial infections in both the human and veterinary fields. In this work, we explored (E)-4-amino-3-((3,5-di-tert-butyl-2-hydroxybenzylidene)amino) benzoic acid (SB-1, harboring an intramolecular hydrogen bond) and (E)-2-((4-nitrobenzilidene)amino)aniline (SB-2), two Schiff bases derivatives. Results demonstrated that SB-1 showed an antibacterial activity determined by the minimal inhibitory concentration (MIC) against Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus (Gram-positive bacteria involved in human and animal diseases such as skin infections, pneumonia, diarrheal syndrome, and urinary tract infections, among others), which was similar to that shown by the classical antibiotic chloramphenicol. By contrast, this compound showed no effect against Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, and Salmonella enterica). Furthermore, we provide a comprehensive physicochemical and theoretical characterization of SB-1 (as well as several analyses for SB-2), including elemental analysis, ESMS, H-1 and C-13 NMR (assigned by 1D and 2D techniques), DEPT, UV-Vis, FTIR, and cyclic voltammetry. We also performed a computational study through the DFT theory level, including geometry optimization, TD-DFT, NBO, and global and local reactivity analyses.
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    Spectral, theoretical characterization and antifungal properties of two phenol derivative Schiff bases with an intramolecular hydrogen bond
    (2015) Carreño, Alexander; Gacitúa Santelices, Manuel Alejandro; Páez Hernández, Dayan; Polanco, Rubén; Preite, Marcelo Daniel; Fuentes, Juan A.; Mora, Guido C.; Chávez Madariaga, Ivonne; Arratia Pérez, Ramiro
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    Synthesis, Physicochemical Characterization, and Antimicrobial Evaluation of Halogen-Substituted Non-Metal Pyridine Schiff Bases
    (2024) Carreno, Alexander; Morales-Guevara, Rosaly; Cepeda-Plaza, Marjorie; Paez-Hernandez, Dayan; Preite, Marcelo; Polanco, Ruben; Barrera, Boris; Fuentes, Ignacio; Marchant, Pedro; Fuentes, Juan A.
    Four synthetic Schiff bases (PSB1 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4,6-dibromophenol], PSB2 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4,6-diiodophenol], PSB3 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4-iodophenol], and PSB4 [(E)-2-(((4-aminopyridin-3-yl)imino)methyl)-4-chloro-6-iodophenol]) were fully characterized. These compounds exhibit an intramolecular hydrogen bond between the hydroxyl group of the phenolic ring and the nitrogen of the azomethine group, contributing to their stability. Their antimicrobial activity was evaluated against various Gram-negative and Gram-positive bacteria, and it was found that the synthetic pyridine Schiff bases, as well as their precursors, showed no discernible antimicrobial effect on Gram-negative bacteria, including Salmonella Typhi (and mutant derivatives), Salmonella Typhimurium, Escherichia coli, and Morganella morganii. In contrast, a more pronounced biocidal effect against Gram-positive bacteria was found, including Bacillus subtilis, Streptococcus agalactiae, Streptococcus pyogenes, Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus haemolyticus. Among the tested compounds, PSB1 and PSB2 were identified as the most effective against Gram-positive bacteria, with PSB2 showing the most potent biocidal effects. Although the presence of reactive oxygen species (ROS) was noted after treatment with PSB2, the primary mode of action for PSB2 does not appear to involve ROS generation. This conclusion is supported by the observation that antioxidant treatment with vitamin C only partially mitigated bacterial inhibition, indicating an alternative biocidal mechanism.
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    The Salmonella Typhi hlyE gene plays a role in invasion of cultured epithelial cells and its functional transfer to S. Typhimurium promotes deep organ infection in mice
    (2008) Fuentes, Juan A.; Villagra, Nicolas; Castillo-Ruiz, Mario; Mora, Guido C.
    Comparison of genome sequences of Salmonella enterica serovars Typhi and Typhimurium reveals that S. Typhi has a small 2.3 kb genomic island missing in S. Typhimurium, designated Salmonella pathogenicity island 18 (SPI-18), which includes two potential genes. One of these, hlyE, encodes a hemolysin related to the Escherichia coli K12 HlyE hemolysin. PCR assays show that SPI-18 is present in S. Typhi and in many other, but not all, serovars of S. enterica subsp. enterica belonging to the SARB collection. HlyE activity cannot be detected in S. Typhi by means of standard plate assays. Nevertheless, we were able to reveal this activity upon lysis of bacterial cells with phages, in the presence of ampicillin, and in a ompA genetic background, conditions that compromise the integrity of the bacterial envelope. Almost all serovars of the SARB collection shown to cause systemic infections in humans have SPI-18 and hlyE and express an active hemolysin revealed upon bacterial envelope destabilization. S. Typhi hlyE mutants are impaired in invasion of human epithelial cells in vitro, and its heterologous expression in S. Typhimurium improves the colonization of deep organs in mice, demonstrating that the HlyE hemolysin is a new virulence determinant. (C) 2008 Published by Elsevier Masson SAS.
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    The carbon source influences the efflux pump-mediated antimicrobial resistance in clinically important Gram-negative bacteria
    (OXFORD UNIV PRESS, 2012) Villagra, Nicolas A.; Fuentes, Juan A.; Jofre, Matias R.; Hidalgo, Alejandro A.; Garcia, Patricia; Mora, Guido C.
    Multidrug efflux pumps are proteins known to play an important role in resistance in bacteria. These proteins are located in the inner membrane (IM), together with many other proteins, including inducible permeases that participate in the uptake of non-phosphotransferase system (PTS) carbohydrates (i.e. carbohydrates uptaken by mechanisms other than the PTS). However, lipid bilayer space in the IM is limited. Therefore, we examined whether the overexpression of unrelated IM proteins is able to interfere with the efflux-mediated resistance mechanism, consequently increasing the susceptibility towards different antimicrobial compounds.
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    The cotranscribed Salmonella enterica sv. Typhi tsx and impX genes encode opposing nucleoside-specific import and export proteins
    (2006) Bucarey, Sergio A.; Villagra, Nicolas A.; Fuentes, Juan A.; Mora, Guido C.
    The Salmonella, enterica tsx gene encodes a nucleoside-specific outer membrane channel. The Tsx porin is essential for the prototrophic growth of S. enterica sv. Typhi in the absence of nucleosides. RT-PCR analysis shows that the tsx gene is cotranscribed with an open reading frame unique to S. enterica, impX (STY0450), which encodes an inner membrane protein 108 amino acids in length, which is predicted to have only two transmembrane a-helices. Fusions of the lacZgene to both tsx and impX reveal that the transcription of both genes is induced in the presence of adenosine. A null mutation in the S. Typhi impX gene suppresses the induced auxotrophy for adenosine or thymidine resulting from a tsx mutation and confers sensitivity to high concentrations of adenosine or thymidine. The ImpX protein, when tagged with a 3xFLAG epitope, is functional and associates with the inner membrane; impX mutants are defective in the export of H-3-radiolabeled thymidine. Taken together, these and other results suggest that the S. Typhi Tsx porin and ImpX inner membrane protein facilitate competing mechanisms of thymidine influx and efflux, respectively, to maintain the steady state levels of internal nucleoside pools.
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    Theoretical and experimental characterization of a novel pyridine benzimidazole : suitability for fluorescence staining in cells and antimicrobial properties
    (2016) Carreño, Alexander; Gacitúa Santelices, Manuel Alejandro; Fuentes, Juan A.; Páez Hernández, Dayán; Araneda, Carmen; Chávez Madariaga, Ivonne; Soto Arriaza, Marco; Manríquez M., Juan Manuel; Polanco, Rubén; Mora, Guido C.; Otero, Carolina; Swordsk, Wesley B.; Arratia Pérez, Ramiro
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    Two New Fluorinated Phenol Derivatives Pyridine Schiff Bases: Synthesis, Spectral, Theoretical Characterization, Inclusion in Epichlorohydrin-β-Cyclodextrin Polymer, and Antifungal Effect
    (2018) Carreño, Alexander; Rodríguez, Leonardo; Páez Hernández, Dayán; Martin-Trasanco, Rudy; Zúñiga, César; Oyarzún, Diego P.; Gacitúa Santelices, Manuel Alejandro; Schott Verdugo, Eduardo Enrique; Arratia Pérez, Ramiro; Fuentes, Juan A.
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    Xylose Improves Antibiotic Activity of Chloramphenicol and Tetracycline against K. Pneumoniae and A. Baumannii in a Murine Model of Skin Infection
    (2018) Hidalgo, Alejandro A.; Arias, Angel J.; Fuentes, Juan A.; García Cañete, Patricia; Mora, Guido C.; Villagra, Nicolas A.