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- 저자 : García-Hernández Edgar (검색결과 4 건)
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Understanding a Core Pilin of the Type IVa Pili of Acidithiobacillus thiooxidans, PilV
( Araceli Hernández-sánchez ),( Edgar D. Páez-pérez ),( Elvia Alfaro-saldaña ),( Vanesa Olivares-illana ),( J. Viridiana García-meza ) 한국미생물생명공학회 2024 Journal of microbiology and biotechnology Vol.34 No.3
Pilins are protein subunits of pili. The pilins of type IV pili (T4P) in pathogenic bacteria are well characterized, but anything is known about the T4P proteins in acidophilic chemolithoautotrophic microorganisms such as the genus Acidithiobacillus. The interest in T4P of A. thiooxidans is because of their possible role in cell recruitment and bacterial aggregation on the surface of minerals during biooxidation of sulfide minerals. In this study we present a successful ad hoc methodology for the heterologous expression and purification of extracellular proteins such as the minor pilin PilV of the T4P of A. thiooxidans, a pilin exposed to extreme conditions of acidity and high oxidation-reduction potentials, and that interact with metal sulfides in an environment rich in dissolved minerals. Once obtained, the model structure of A. thiooxidans PilV revealed the core basic architecture of T4P pilins. Because of the acidophilic condition, we carried out in silico characterization of the protonation status of acidic and basic residues of PilV in order to calculate the ionization state at specific pH values and evaluated their pH stability. Further biophysical characterization was done using UV-visible and fluorescence spectroscopy and the results showed that PilV remains soluble and stable even after exposure to significant changes of pH. PilV has a unique amino acid composition that exhibits acid stability, with significant biotechnology implications such as biooxidation of sulfide minerals. The biophysics profiles of PilV open new paradigms about resilient proteins and stimulate the study of other pilins from extremophiles.
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Rafael Eduardo Hernández-Guisao,Aranda-Barradas Juan Silvestre,Badillo-Corona Agustín,García-Peña Elvia Inés,Salgado-Manjarrez Edgar 한국생물공학회 2022 Biotechnology and Bioprocess Engineering Vol.27 No.5
Stoichiometric analysis is a crucial step in biochemical processes because it allows us to find the proportions in which the substrates and products react. A system of algebraic equation is obtained from an elemental balance of the participating substances and determined, overdetermined or underdetermined systems can result depending on the number of substances and elements. Underdetermined systems are the most common ones as there are, generally, more substances than elemental balances. However, such systems have been poorly studied and a straightforward way to establish the solution space has not yet been reported. In this work a novel approach for finding all the possible solutions to such underdetermined systems is reported for the first time. The solutions space is expressed as a set of vectors which are here referred as extreme stoichiometries. To illustrate the general applicability and some uses of the proposed approach, three different fermentation systems are analyzed: growth of Chlamydomonas reinhardtii, a mixed culture for hydrogen production, and the growth of Saccharomyces cerevisiae. It is shown how the full stoichiometric spaces can be calculated for heterotrophy, autotrophy, mixotrophy, growth of mixed cultures in mixed substrates and how the experimental results should be contained in such spaces, what permits a consistency analysis. With the proposed method, it is now possible to estimate the maximum yields for any given microbial growth reaction and to assess the congruence of experimental data, even when the system is underdetermined.
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Cauich-Cupul Javier I.,Herrera-Franco Pedro J.,García-Hernández Edgar,Moreno-Chulim Veronica,Valadez-González Alex 한국탄소학회 2019 Carbon Letters Vol.29 No.4
A two-level full factorial design 22 with three replications was employed to assess the effect of the incorporation of PSF into the epoxy matrix and the surface treatment of carbon fibers on the work of adhesion (WA) and the interfacial shear strength (IFSS) of carbon fiber–epoxy composites. The IFSS was determined using the microbond (or microdrop) micromechanical test, and the work of adhesion was estimated using two different procedures: (1) using the Owens and Wendt method, and (2) from the Dupre–Young expression using the contact angle θ of a cured epoxy resin on a single carbon fiber and the surface energy of the cured epoxy resin. It was found that the treatment of the carbon fiber with the silane-coupling agent appreciably increases its polar component because of the nitric acid oxidation and the chemisorption of the silane-coupling agent onto the carbon fiber surface. Also, the O=S=O group present in the polysulfone chain resin fairly increases the polar component of the epoxy–PSF blend. The results show that the wetting of the silane-treated carbon fiber by the thermoplastic-modified epoxy resin is better, thus increasing the fiber–matrix adhesion. It was also found that there is a similarity between the trends of both, the IFSS and the WA results. Also, from the ANOVA results it was also seen that both the incorporation of the PSF to the epoxy matrix and the surface treatment of the carbon fibers and their interaction were statistically significant to the IFSS and the WA.
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Javier I. Cauich‑Cupul,Pedro J. Herrera‑Franco,Edgar García‑Hernández,Veronica Moreno‑Chulim,Alex Valadez‑González 한국탄소학회 2019 Carbon Letters Vol.29 No.4
A two-level full factorial design 22 with three replications was employed to assess the effect of the incorporation of PSF into the epoxy matrix and the surface treatment of carbon fibers on the work of adhesion (WA) and the interfacial shear strength (IFSS) of carbon fiber–epoxy composites. The IFSS was determined using the microbond (or microdrop) micromechanical test, and the work of adhesion was estimated using two different procedures: (1) using the Owens and Wendt method, and (2) from the Dupre–Young expression using the contact angle θ of a cured epoxy resin on a single carbon fiber and the surface energy of the cured epoxy resin. It was found that the treatment of the carbon fiber with the silane-coupling agent appreciably increases its polar component because of the nitric acid oxidation and the chemisorption of the silane-coupling agent onto the carbon fiber surface. Also, the O=S=O group present in the polysulfone chain resin fairly increases the polar component of the epoxy–PSF blend. The results show that the wetting of the silane-treated carbon fiber by the thermoplastic-modified epoxy resin is better, thus increasing the fiber–matrix adhesion. It was also found that there is a similarity between the trends of both, the IFSS and the WA results. Also, from the ANOVA results it was also seen that both the incorporation of the PSF to the epoxy matrix and the surface treatment of the carbon fibers and their interaction were statistically significant to the IFSS and the WA.
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