nitrophenols and metaperiodate

Aqueous solutions of p-nitrophenol (PNP) were treated with UV-activated potassium periodate (UV/KPI) in an efficient photo-reactor. Either periodate or UV alone had little effect; however, their combination led to a significant degradation and mineralization. The response surface methodology was employed for design of experiments and optimization. The optimum conditions for treatment of 30 mg/L of the substrate were determined as [KPI] = 386.3 mg/L, pH = 6.2 and T = 34.6°C, under which 79.5% degradation was achieved after 60 min. Use of 25 and 40 kHz ultrasound waves caused the degradation to enhance to 88.3% and 92.3%, respectively. The intermediates were identified by gas chromatography-mass spectroscopy analysis, leading to propose the reaction pathway. The presence of water conventional bicarbonate, chloride, sulfate and nitrate anions caused unfavorable effects in efficiency. Meanwhile, the kinetic study showed that PNP degradation follows a pseudo-first-order reaction and the activation energy was determined. The irradiation energy consumption required for one order of magnitude degradation was estimated as 11.18 kWh/m

Topics: Nitrophenols; Oxidation-Reduction; Periodic Acid; Solutions; Ultraviolet Rays; Water Pollutants, Chemical; Water Purification

Two yeast strains, Saccharomyces cerevisiae CBS 7764 and Debaryomyces hansenii Hfl CBS 8339, with a high capacity to colonize fish intestine were used in this study. The ability to adhere to crude mucus obtained from fish intestine was demonstrated for both strains. Scatchard analysis of the binding indicated a positive cooperativity for D. hansenii Hfl and absence of cooperativity for S. cerevisiae CBS 7764. In neither of the strains was adhesion extensively affected by reducing the hydrophobic interaction with p-nitrophenol, or by enhancing the hydrophobic interaction with ammonium sulfate. The adhesion was heat sensitive but resistant to trypsin treatment. We conclude that adhesion is mediated partly by specific mechanisms and partly by cell surface hydrophobicity.

Topics: Ammonium Sulfate; Animals; Candida; Cell Adhesion; Intestinal Mucosa; Nitrophenols; Oncorhynchus mykiss; Periodic Acid; Saccharomyces cerevisiae; Sodium Chloride; Species Specificity

1. The reaction of alpha-chymotrypsin with sodium periodate at pH5.0 has been investigated. The enzyme consumes 2 moles of periodate/mole, and there is a concomitant fall in enzymic activity (with respect to l-tyrosine ethyl ester) to 55% of that of the native enzyme. After 3hr. no further change is observed in periodate uptake or in catalytic activity. 2. The oxidized enzyme is a homogeneous preparation of partially active chymotrypsin. 3. In the oxidized enzyme, one of the two methionine residues in the molecule has been converted into its sulphoxide. It is this reaction only that is responsible for the loss of activity. 4. The rate constants for the enzyme-catalysed acylation and deacylation reactions are unaltered by oxidation of the enzyme, both for a non-specific substrate (p-nitrophenyl acetate), and for three specific substrates: N-acetyl-l-tryptophan ethyl ester, N-acetyl-l-tryptophanamide and N-acetyl-l-valine ethyl ester. 5. The K(m) values for the aromatic substrates with the oxidized enzyme are twice those with the native enzyme. No change in Michaelis constant is seen for the non-aromatic substrate N-acetyl-l-valine ethyl ester. 6. The evidence points to the oxidized methionine residue in the modified enzyme being situated in the locus of the active site at which aromatic (or bulky) side chains of the substrates are bound.

Topics: Acylation; Amides; Amino Acids; Biochemical Phenomena; Biochemistry; Catalysis; Chymotrypsin; Imidazoles; Kinetics; Methionine; Nitrophenols; Periodic Acid; Research; Spectrophotometry; Tryptophan; Tyrosine; Ultracentrifugation; Valine