Search results for "OXIDASE"
showing 10 items of 927 documents
Tuning the life-time of supramolecular hydrogels using ROS-responsive telechelic peptide-polymer conjugates
2019
Abstract The synthesis of multi-stimuli responsive peptide-poly(ethylene glycol) ABA-type conjugates is reported. The β-sheet encoded intramolecular folding and intermolecular self-assembly into 1D nanorods is based on a phenylalanine(F)-methionine(M)-histidine(H) FMHMHF hexapeptide sequence, and the supramolecular nanorods are stabilised by a shielding corona of hydrophilic PEG polymers. Interstrand crosslinking leads to the formation of physical networks and hydrogels at physiological pH and at room temperature. The thioether functional groups integrate oxidation responsive properties in the supramolecular polymer assemblies. We show that the glucose fuelled and glucose oxidase catalysed …
Oxidative Copolymerisation ofpara-Functionalized Phenols Catalyzed by Horseradish peroxidase and Thermocrosslinking via Diels-Alder and (1+3) Cycload…
2001
The horseradish peroxidase- (HRP-) catalyzed polyrecombination of N-(4-hydroxyphenyl)-2-furamide (2) and 4-hydroxyphenylmaleimide (1) is described. The resulting copolymer was used to build crosslinked materials via Diels-Alder and cycloaddition reactions. We followed the enzymatic copolymerization process of an equimolar mixture of 1 and 2 using high pressure liquid chromatography (HPLC), size-exclusion chromatography (SEC) and by matrix assisted laser desorption/ionization-time of flight mass spectroscopy (MALDI-TOF MS) analysis and found that the polymerization of 2, which has a significant higher highest occupied molecular orbital (HOMO) energy, proceeds much faster. The HOMO energies o…
Enzymatically catalyzed synthesis of photocrosslinkable oligophenols
2000
The HRP-catalyzed oligomerization of cinnamoyl-hydroquinone-ester and cinnamoyl-4-hydroxyanilide led to the formation of soluble polyphenols. The oligomers were synthexized in water/1,4-dioxane and in water/acetone mixtures and characterized by NMR, FTIR and SEC. Upon UV treatment of the homogenoes films the polyphenols were crosslinked due to [2+2]-cycloadditions of the cinnamoyl functions.
Polarographic determination of tyrosinase activity in enzymatic reaction with tyrosine as a substrate
2003
A voltammetric investigation of tyrosinase activity is proposed as an alternative to the spectrophotometric method. Voltammetric approach provides low detection limit, high sensitivity and resistivity to the solution inhomogenity, as well as enables one to simultaneously monitor the dioxygen consumption in the reaction, which is an additional indicator of the tyrosinase enzymatic activity.
POLYPHENOL OXIDASE ACTIVITY FROM THREE SICILIAN ARTICHOKE (CYNARA CARDUNCULUS L. VAR. SCOLYMUS L. (FIORI)) CULTIVARS: STUDIES AND TECHNOLOGICAL APPLI…
2010
Several papers helped with the development of more methods to control browning, or study thermal polyphenol oxidase (PPO) inactivation, but did not provide any solutions to technological process problems and food process improvement. Artichokes [ Cynara cardunculus L. var. scolymus L. (Fiori)] are susceptible to browning; this alteration could affect and reduce the suitability for its use, fresh or processed. Within this study, the catecholase and cresolase activities of PPO from three different Sicilian artichokes cultivar were characterized with regard to substrate specificity and enzyme kinetics, optimum pH and temperature, temperature and pH stability, and inhibitor test; all of the res…
OXIDASES ACTIVITIES AND ANTIOXIDANT CAPACITY OF MINIMALLY PROCESSED BABY ROMAINE LETTUCE (Lactuca sativa L. CV. DUENDE) CULTIVATED UNDER DIFFERENT SA…
2007
[SPA] El pardeamiento enzimático es uno de los principales problemas implicados en el procesamiento mínimo y en la siguiente conservación de hortalizas de hoja, reduciendo la vida comercial del producto. Se han evaluado las variaciones de las dos principales oxidasas, polifenol oxidasa (PPO) y peroxidasa (POD), así como del contenido en fenoles, del color y de la capacidad antioxidante (metodo ORAC) durante 10 días de conservación a 4 °C de lechuga Baby Romaine (Lactuca sativa L. cv. Duende) mínimamente procesada, cultivada bajo 3 distintas condiciones de salinidad (2,8, 3,8, 4,8 dS/m), para determinar la condición más apta al siguiente procesamiento. Niveles crecientes de salinidad redujer…
Is the host or the parasite the most locally adapted in an amphipod–acanthocephalan relationship? A case study in a biological invasion context
2007
8 pages; International audience; Manipulative endoparasites with complex life cycles can alter their intermediate host immunity and behaviour in ways that increase survival probability within the host body cavity and enhance successful transmission to the definitive host. These parasitic manipulations are variable among and within parasite species and may result from co-evolutionary processes, in which the parasite is constrained for adaptation to the local intermediate host. Hence, arrival of a new host species in a local host population may promote local parasite maladaptation. This study tested the occurrence of local adaptation in two distantly located populations of the acanthocephalan…
Application of 3-Quinolinoyl Picket Porphyrins to the Electroreduction of Dioxygen to Water: Mimicking the Active Site of Cytochromec Oxidase
2001
International audience
Antitumor effects of dehydroxymethylepoxyquinomicin, a novel nuclear factor-kappaB inhibitor, in human liver cancer cells are mediated through a reac…
2009
Activation of the nuclear transcription factor-kappa B (NF-kappa B) has been implicated in liver tumorigenesis. We evaluated the effects of a novel NF-kappa B inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), in two human liver cancer cell lines HA22T/VGH and HuH-6. DHMEQ treatment dose dependently decreased the DNA-binding capacity of the NF-kappa B p65 subunit, inhibited cell growth and proliferation, and increased apoptosis as shown by caspase activation, release of cytochrome c, poly(ADP-ribose) polymerase cleavage, and down-regulation of survivin. DHMEQ also induced a dose-dependent activation of mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling, …
Parthenolide induces caspase-independent and AIF-mediated cell death in human osteosarcoma and melanoma cells
2013
The mechanism of the cytotoxic effect exerted by parthenolide on tumor cells is not clearly defined today. This article shows that parthenolide stimulates in human osteosarcoma MG63 and melanoma SK-MEL-28 cells a mechanism of cell death, which is not prevented by z-VAD-fmk and other caspase inhibitors. In particular treatment with parthenolide rapidly stimulated (1-2 h) reactive oxygen species (ROS) generation by inducing activation of extracellular signal-regulated kinase 1/2 (ERK 1/2) and NADPH oxidase. This event caused depletion of thiol groups and glutathione, NF-κB inhibition, c-Jun N-terminal kinase (JNK) activation, cell detachment from the matrix, and cellular shrinkage. The increa…