Role of Lipoamide Dehydrogenase and Metallothionein on 1-Methyl-4-phenyl-1,2,3,6- tetrahydropyridine-induced Neurotoxicity

In the present study, we investigated the effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on lipoamide dehydrogenase activity and metallothionein content. Lipoamide dehydrogenase is a flavoprotein enzyme, which reduces lipoamide and low molecular weight thiols. This enzyme has also been involved in the conversion of ubiquinone (coenzyme Q-10, oxidized form) to ubiquinol (reduced form). Lipoamide dehydrogenase activity was measured spectrophotometrically following its incubation with different doses of MPTP, MPP⁺, and divalent metals. MPTP at higher concentrations inhibited the lipoamide dehydrogenase activity, whereas it’s potent toxic metabolite 1-methyl-4-phenylpyridinium (MPP⁺) had a similar effect at lower concentration. Calcium and copper did not affect the enzyme activity at any of the doses tested, whereas, zinc dose dependently enhanced the lipoamide dehydrogenase activity. Additionally, levels of metallothionein in the mouse nigrostriatal system were measured by cadmium affinity method following administration of MPTP. Metallothionein content was significantly reduced in the substantia nigra (SN), and not in the nucleus caudatus putamen (NCP) following a single administration of MPTP (30 mg/kg, i.p.). Our results suggests that both lipoamide dehydrogenase activity and metallothionein levels may be critical for dopaminergic neuronal survival in Parkinson’s disease and provides further insights into the neurotoxic mechanisms involved in MPTP-induced neurotoxicity.     

Biocalorimetric studies of the metabolic activity of Pseudomonas aeruginosa aerobically grown in a glucose-limited complex growth medium

Biocalorimetric experiments were performed to investigate the aerobic growth of Pseudomonas aeruginosa, isolated from tannery saline wastewater. Growth factors (pH, Inoculum size, carbon source, temperature, aeration rate, and agitation rate) were optimized in shaker and calorimeter based on the growth of P. aeruginosa and heat generation rates. A limiting value of 0.2% glucose concentration was found to be optimum for the growth of P. aeruginosa in a complex growth medium, and the heat flux (q(r)) profiles resulting from the metabolic activity of P. aeruginosa further confirmed this observation. The bacterial growth profile was found to correlate well with the metabolic heat generated. Heat-yield values were calculated for both glucose consumption and the growth of P. aeruginosa from the calorimetric results. Metabolic shifts in substrate uptake from glucose to peptone present in growth medium was observed by the variations in heat-flux profile. The calorimetric data presented in this study should be useful in understanding the behavior of the isolated bacterial strain in degrading complex and mixed substrates commonly observed in tannery saline waste stream, and further to extend the results for scale-up studies.     

Optimization of biobleaching of paper pulp in an expanded bed bioreactor with immobilized alkali stable xylanase by using response surface methodology

Purified alkali stable xylanase from Aspergillus fischeri was immobilized on polystyrene beads using diazotization method. An expanded bed bioreactor was developed with these immobilized beads to biobleach the paper pulp in continuous mode. Response surface methodology was applied to optimize the biobleaching conditions. Temperature (degrees C), flow rate of pulp (ml/min) and concentration of the pulp (%) were selected as variables in this study. Optimal conditions for biobleaching process were reaction temperature 60 degrees C, flow rate of 2 ml/min and 5% (w/v) of pulp. The kappa number reduced from 66 in the unbleached pulp to 20 (reduction of 87%). This system proves to be a better option for the conventional chlorine based pulp bleaching.     

Interactions of anticancer drugs with usual and mismatch base pairs - density functional theory studies

The antitumor activity of a drug is associated with its molecular properties as well as its interactions with target molecules. The molecular structures of usual, mismatch base pairs and their drug (Hydroxyurea and 5-Fluorouracil) interacting complexes were studied using density functional theory methods. The two and three-body interaction energies have been used to analyze the influence of a drug on the stability of base pairs. The sharing of electron density between the interacting molecules is shown through electron density difference maps. The Atoms in Molecules theory and Natural Bond Orbital analysis have been performed to study the hydrogen bonds in the drug interacting complexes.     

Serine substitution for cysteine residues in levansucrase selectively abolishes levan forming activity

Levansucrase is responsible for levan formation during sucrose fermentation of Zymomonas mobilis, and this decreases the efficiency of ethanol production. As thiol modifying agents decrease levan formation, a role for cysteine residues in levansucrase activity has been examined using derivatives of Z. mobilis levansucrase that carry serine substitutions of cysteine at positions 121, 151 or 244. These substitutions abolished the levan forming activity of levansucrase whilst only halving its activity in sucrose hydrolysis. Thus, polymerase and hydrolase activities of Z. mobilis levansucrase are separate and have different requirements for the enzyme's cysteine residues.     

Evaluating peptide mass fingerprinting-based protein identification

Identification of proteins by mass spectrometry (MS) is an essential step in proteomic studies and is typically accomplished by either peptide mass fingerprinting (PMF) or amino acid sequencing of the peptide. Although sequence information from MS/MS analysis can be used to validate PMF-based protein identification, it may not be practical when analyzing a large number of proteins and when high- throughput MS/MS instrumentation is not readily available. At present, a vast majority of proteomic studies employ PMF. However, there are huge disparities in criteria used to identify proteins using PMF. Therefore, to reduce incorrect protein identification using PMF, and also to increase confidence in PMF-based protein identification without accompanying MS/MS analysis, definitive guiding principles are essential. To this end, we propose a value-based scoring system that provides guidance on evaluating when PMF-based protein identification can be deemed sufficient without accompanying amino acid sequence data from MS/MS analysis.     

Evaluating Peptide Mass Fingerprinting-based Protein Identification

Identification of proteins by mass spectrometry (MS) is an essential step in pro- teomic studies and is typically accomplished by either peptide mass fingerprinting (PMF) or amino acid sequencing of the peptide. Although sequence information from MS/MS analysis can be used to validate PMF-based protein identification, it may not be practical when analyzing a large number of proteins and when high- throughput MS/MS instrumentation is not readily available. At present, a vast majority of proteomic studies employ PMF. However, there are huge disparities in criteria used to identify proteins using PMF. Therefore, to reduce incorrect protein identification using PMF, and also to increase confidence in PMF-based protein identification without accompanying MS/MS analysis, definitive guiding principles are essential. To this end, we propose a value-based scoring system that provides guidance on evaluating when PMF-based protein identification can be deemed sufficient without accompanying amino acid sequence data from MS/MS analysis.     

Participation of endomembrane cation/H+ exchanger AtCHX20 in osmoregulation of guard cells

Guard cell movement is induced by environmental and hormonal signals that cause changes in turgor through changes in uptake or release of solutes and water. Several transporters mediating these fluxes at the plasma membrane have been characterized; however, less is known about transport at endomembranes. CHX20, a member of a poorly understood cation/H+ exchanger gene family in Arabidopsis (Arabidopsis thaliana), is preferentially and highly expressed in guard cells as shown by promoterbeta-glucuronidase activity and by whole-genome microarray. Interestingly, three independent homozygous mutants carrying T-DNA insertions in CHX20 showed 35% reduction in light-induced stomatal opening compared to wild-type plants. To test the biochemical function of CHX20, cDNA was expressed in a yeast (Saccharomyces cerevisiae) mutant that lacks Na+(K+)/H+ antiporters (Deltanhx1 Deltanha1 Deltakha1) and plasma membrane Na+ pumps (Deltaena1-4). Curiously, CHX20 did not enhance tolerance of mutants to moderate Na+ or high K+ stress. Instead, it restored growth of the mutant on medium with low K+ at slightly alkaline pH, but had no effect on growth at acidic pH. Green fluorescent protein-tagged CHX20 expressed in mesophyll protoplasts was localized mainly to membranes of the endosomal system. Furthermore, light-induced stomatal opening of the Arabidopsis mutants was insensitive to external pH and was impaired at high KCl. The results are consistent with the idea that, in exchanging K+ for H+, CHX20 maintains K+ homeostasis and influences pH under certain conditions. Together, these results provide genetic and biochemical evidence that one CHX protein plays a critical role in osmoregulation through K+ fluxes and possibly pH modulation of an active endomembrane system in guard cells.     

3D Hierarchical Core–Shell Nanostructured Arrays on Carbon Fibers as Catalysts for Direct Urea Fuel Cells

Bifunctional cobalt oxide (Co₃O₄) nanowire catalysts grown on carbon cloth (CC) fibers and their modification with nickel oxide (NiO) and manganese dioxide (MnO₂) to produce core–shell nanoarchitectures are explored as catalysts for urea oxidation reaction and oxygen reduction reaction in direct urea fuel cells (DUFC). Based on a systematic electrochemical characterization of the catalyst, the as‐developed core–shell nanoarchitectures are optimized toward DUFC performance. Under alkaline conditions with an anion exchange membrane, the DUFC with a cell configuration of Co₃O₄@NiO(1:2)/CC(a|c)Co₃O₄@MnO₂(1:2)/CC exhibits a maximum power density of 33.8 mW cm^?2 with excellent durability for 120 h without any performance loss. Furthermore, the DUFC exhibits a maximum power density of 23.2 mW cm^?2 with human urine as a fuel. These findings offer an approach to convert human waste into treasure.