173 publications from this institution
Understanding towards chain-breaking antioxidants as potent inhibitors of lipid peroxyl radicals, high-throughput efforts have been investigated for antioxidant behaviour of 6-bromo-3,3-dimethyl-8 hexadecyltelluro [1,3]dioxepino[5,6-c]pyridin-9-ol and 2-methyl-2,3-dihydrobenzo[b]selenophene-5-ol in the two phase (chlorobenzene/water) lipid peroxidation model system at various pH 1-7 and mild co-antioxidants such as (glutathione, dithiothreitol, ascorbic acid, sodium ascorbate, and potassium hexacyanoferrate(II) trihydrate, sodium metasulfite, and tris(2-carboxyethyl)phosphine hydrochloride). The key chain-breaking mechanism profile was attributed towards the first oxygen transfer atom from the lipid peroxyl radical to the Se/Te atoms and then hydrogen atom transfer from the nearby phenolic group by the alkoxyl radical due to the weak O-H bond dissociation energy in the solvent cage. Finally, the regeneration could take place by the presence of aqueous soluble co-antioxidants that increased the inhibition time of antioxidants more efficiently than α-tocopherol. Tellurium analouge at pH 2-5 in presence of N -acetylcysteine offered better protection for chain-breaking capacity than the selenium analouge. In the presence of aqueous soluble N -acetylcysteine at pH 1-7, both antioxidants in the present study behaved very good inhibitors of lipid peroxyl radicals.
This review intends to provide an overview of bacterial degradation of nitrophenols (NPs) and their derivatives. The main scientific focus is on biochemical and genetic characterization of bacterial degradation of NPs. Other aspects such as bioremediation and chemotaxis correlated with biodegradation of NPs are also discussed. This review will increase our current understanding of bacterial degradation of NPs and their derivatives.
In an effort to improve the chain-breaking capacity of the natural antioxidants, an octyltelluro group was introduced next to the phenolic moiety in β- and δ-tocopherol. The new vitamin E analogues quenched peroxyl radicals more efficiently than α-tocopherol and were readily regenerable by aqueous N-acetylcysteine in a simple membrane model composed of a stirring chlorobenzene/water two-phase system. The novel tocopherol analogues could also mimic the action of the glutathione peroxidase enzymes.
Singlet Fission (SF) into two triplets offers exciting avenues for high-efficiency photovoltaics and optically initializable qubits. While the chemical space of SF chromophores is ever-expanding, the mechanistic details of electronic-nuclear motions that dictate the photophysics are unclear. Rigid SF dimers with well-defined orientations are necessary to decipher such details. Here, using polarization-controlled white-light two-dimensional and pump-probe spectroscopies, we investigate a new class of contorted naphthalenediimide dimers, recently reported to have a favorable intramolecular SF (iSF) pathway. 2D cross-peaks directly identify the two Davydov components of the dimer along with strongly wavelength-dependent TT1 formation kinetics depending on which Davydov component is excited, implicating a coherently coupled intermediate that mediates iSF. Enhanced quantum beats in the TT1 photoproduct suggest that inter-chromophore twisting and ruffling motions drive the ~200 fs evolution towards an excimer-like intermediate and its subsequent ~2 ps relaxation to the TT1 photoproduct. Polarization anisotropy directly tracks electronic motion during these steps and reveals surprisingly minimal electronic reorientation with significant singlet-triplet mixing throughout the nuclear evolution away from the Franck-Condon geometry towards relaxed TT1. The observations of coherent excimer-like intermediate and significant singlet-triplet mixing throughout the iSF process need to be carefully accounted for in the synthetic design and electronic structure models for iSF dimers aiming for long-lived high-spin correlated triplets.
Vitamin B6 is involved in a variety of enzymatic transformations. Some recent findings also indicate an antioxidant role of the vitamin in biological systems. We set out to turn pyridoxine (1a) into a catalytic chain-breaking and hydroperoxide-decomposing antioxidant by replacing the 2-methyl substituent with an alkyltelluro group. Target molecules 12 and derivatives 14, 17, 18, and 20 thereof were accessed by subjecting suitably substituted 2-halopyridin-3-ols to aromatic substitution using sodium alkanetellurolates as nucleophiles and then LAH-reduction of ester groups. The novel pyridoxine compounds were found to inhibit azo-initiated peroxidation of linoleic acid an order of magnitude more efficiently than α-tocopherol in a water/chlorobenzene two-phase system containing N-acetylcysteine as a reducing agent in the aqueous phase. The most lipid-soluble pyridoxine derivative 20c was regenerable and could inhibit peroxidation for substantially longer time (>410 min) than α-tocopherol (87 min). The chalcogen-containing pyridoxines could also mimic the action of the glutathione peroxidase enzymes. Thus, compound 20a catalyzed reduction of hydrogen peroxide three times more efficiently than Ebselen in the presence of glutathione as a stoichiometric reducing agent.
An inflammatory reaction occurs following biomaterial implantation in the body, which produce toxic byproducts such as reactive oxygen species (ROS). Although ROS is required to clear the wound, excessive ROS can damage the tissue around the implant site, eventually leading to implant failure. One approach to control the inflammatory response is to incorporate an antioxidant into the biomaterial in order to scavenge ROS produced by activated phagocytes. In the present study, an organoselenium antioxidative compound was incorporated into a brushite cement, with the goal of scavenging ROS generated from activated primary human mononuclear leukocytes (MNCs), in vitro. The effect of the antioxidant on the physical properties of brushite cement, and its release from the cement were investigated via compressive strength, setting time, phase composition, and UV spectroscopy analysis. The physical properties of brushite remained unchanged following incorporation of the antioxidant. The antioxidant was slowly released from the cement, following a non-Fickian transport mechanism, with approximately 60% of the loaded antioxidant released over five days. The released antioxidant was then tested for its ability to scavenge ROS released by MNCs using the luminol amplified chemiluminescence assay. The results show that antioxidative released at both early stages (24h) and late stages (120h) retained its scavenging capacity and effectively reduced ROS production. These results indicate that brushite cements loaded with organoselenium compounds can modulate ROS production after implantation and potentially modulate the inflammatory response to improve device integration.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Background Dysphagia is frequently encountered by the otolaryngologist and due to its diverse aetiologies often poses a diagnostic challenge. Of particular importance in diagnosis is to distinguish between oropharyngeal and oesophageal dysphagia. This article aims to provide a systematic, concise and evidence‐based method of managing the patient with dysphagia. Method This review was based on a literature search last undertaken on 15 January 2013. The MEDLINE , EMBASE and Cochrane databases were searched using the subject heading dysphagia in combination with classification, diagnosis, investigations, management, treatment and surgery. Results were limited to English language articles including case series, clinical trials, randomised controlled trials, meta‐analyses, systematic reviews and review articles. Relevant references from selected articles were also reviewed. Results The majority of published literature for dysphagia is of level II / III evidence, with 16 relevant randomised controlled trials identified. The clinical history is of paramount importance in delineating the cause of dysphagia. There is no significant difference regarding the diagnostic efficacy of fibreoptic endoscopic evaluation of swallowing compared to videofluoroscopy, and where indicated and practicable, these investigations complement each other. In general, structural causes of dysphagia are managed surgically, whereas swallowing therapy is efficacious in managing dysphagia due to neuromyogenic disorders. Conclusions A structured history of dysphagia and its associated symptoms, flexible laryngoscopy and endoscopic assessment of swallowing where relevant in addition to targeted investigations should lead to the correct diagnosis and appropriate management.
Arachidonic acid metabolites, prostaglandins and leukotrienes are detected in clinical cases of herniated nucleus pulposus. However, little is known about
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