Browsing by Author "Briones, Ximena"
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Item Adsorption of As (V) by poly (N-octyl-4-vinylpyridinium) bromide: Determination of As (V) by direct measurement of fluorescence on the solid phase(Elsevier, 2016) Gonzalez, Javier; Toral, Maria; Leiva, Angel; Yazdani, Mehrdad; Rios, Hernan; Briones, Ximena; Urzua, MarcelaAdsorption of As (V) by poly (N-octyl-4-vinylpyridinium) bromide (P4VPyC8), used as solid phase, was studied. Determination of As (V) was carried out by direct measurement of the fluorescence intensity on the solid phase. Adsorption variables were optimized for obtaining optimum values of pH and agitation time, where pH 9.0 and 60 min were established as optimum values. The adsorption of arsenic (V) was characterized by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. It was found that the fluorescence of the solid phase increases as the concentration of arsenic increases. Linearity was observed in the concentration range 6.80 to 90.0 μg L− 1. The detection limit for determination of As (V) by this method was 2.24 μg L− 1 and the relative standard deviation (RSD) was 1.72%. The amount of retained As (V) was 0.154 mg/g of solid phase. The determination of As (V) in a sample of tap water by this method was well compared with the value reported by an external certified laboratory. Therefore, the method of analysis proposed here could be used as a screening methodology for monitoring the fulfillment of the norm for arsenic concentration in tap water.Item Surfaces based on amino acid functionalized polyelectrolyte films towards active surfaces for enzyme immobilization(2019) Briones, Ximena; Villalobos, Valeria; Queneau, Yves; Silva Danna, Caroline; Muñoz, Rodrigo; Ríos, Hernán E.; Pavez, Jorge; Páez, Maritza; Cabrera, Ricardo; Tamayo, Laura; Urzúa, Marcela D.Surface based on polyelectrolytes functionalized with amino acids onto amino-terminated solid surfaces of silicon wafers was prepared, with the purpose of evaluate the chemical functionality of the polyelectrolyte films in adsorption and catalytic activity of an enzyme. In this work, the adsorption of the enzyme glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides (LmG6PD) was studied as model. The polyelectrolytes were obtained from poly (maleic anhydride-alt-vinylpyrrolidone) [poly(MA-alt-VP)] and functionalized with amino acids of different hydropathy index: glutamine (Gln), tyrosine (Tyr) and methionine (Met). The polyelectrolytes were adsorbed onto the amino-terminated silicon wafer at pH 3.5 and 4.5 and at low and high ionic strength. At low ionic strength and pH 3.5, the largest quantity of adsorbed polyelectrolyte was on the films containing glutamine moiety as the most hydrophilic amino acid in the side chain of polymer chain (5.88 mg/m2), whereas at high ionic strength and pH 4.5, the lowest quantity was in films containing tyrosine moiety in the side chain (1.88 mg/m2). The films were characterized by ellipsometry, contact angle measurements and atomic force microscopy (AFM). The polyelectrolyte films showed a moderate degree of hydrophobicity, the methionine derivative being the most hydrophobic film. With the aim of evaluate the effect of the amino acid moieties on the ability of the surface to adsorb enzymes, we study the activity of the enzyme on these surfaces. We observed that the polarity of the side chain of the amino acid in the polyelectrolyte affected the quantity of LmG6PD adsorbed, as well as its specific activity, showing that films prepared from poly(MA-alt-VP) functionalized with Met provide the best enzymatic performance. The results obtained demonstrated that the surfaces prepared from polyelectrolytes functionalized with amino acids could be an attractive and simple platform for the immobilization of enzymes, which could be of interest for biocatalysis applications