Examinando por Materia "FTIR"

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    Antimycotic activity of fengycin C biosurfactant and its interaction with phosphatidylcholine model membranes
    (ELSEVIER SCIENCE BV, 2017-08-01) González-Jaramillo LM; Aranda FJ; Teruel JA; Villegas-Escobar V; Ortiz A; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)
    Lipopeptide biosurfactants constitute one of the most promising groups of compounds for the treatment and prevention of fungal diseases in plants. Bacillus subtilis strain EA-CB0015 produces iturin A, fengycin C and surfactin and it has been proven useful for the treatment of black Sigatoka disease in banana plants, an important pathology caused by the fungus Mycosphaerella fijiensis (Morelet). We have found that B. subtilis EA-CB0015 cell free supernatants and purified fractions inhibit M. fijiensis cellular growth. The effect of the purified lipopeptides mentioned above on fungal growth has been also evaluated, observing that iturin A and fengycin C inhibit mycelial growth and ascospore germination, whereas surfactin is not effective. On the hypothesis that the antifungal action of the lipopeptides is associated to their incorporation into biological membranes, ultimately leading to membrane permeabilization, a detailed biophysical study on the interaction of a new isoform of fengycin C with model dipalmitoyphosphatidylcholine (DPPC) membranes has been carried out. Differential scanning calorimetry shows that fengycin C alters the thermotropic phase transitions of DPPC, and is laterally segregated in the fluid bilayer forming domains. Fluorescent probe polarization measurements show that fengycin C does not affect the hydrophobic interior of the membrane. This latter perturbation is concomitant with a strong dehydration of the polar region of DPPC, as shown by FTIR. Fengycin-rich domains, where the surrounding DPPC molecules are highly dehydrated, may well constitute sites of membrane permeabilization leading to a leaky target membrane. These results are a solid support to explain the membrane perturbing action of fengycin, which has been related to its antifungal activity. (C) 2017 Elsevier B.V. All rights reserved.
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    Evaluación de las propiedades térmicas, reológicas y mecánicas de mezclas entre HDPE virgen con HDPE reciclado
    (Universidad EAFIT, 2023) Gómez Sandoval, Juan Camilo; González Villa, Sandra Milena
    The rheological, thermal, morphological and mechanical properties of high-density polyethylene (HDPE) are studied in virgin/recycled mixtures from the implementation of a mechanical recycling process of plastic guides, used as coupling devices in used plaster molds. in the ceramic industry. Despite finding losses in its properties, the feasibility of mixing with virgin and recycled material is demonstrated, still being useful for multiple applications.