Modulation of the enzymatic activity of papain by interdomain residues remote from the active site

The two main catalytic residues Cys25 and Hisl59 of the monomericcysteine protease papain are located on different walls of acleft formed by two domains. This topology suggests a possiblerelationship between relative domain organization and catalyticmechanism. The effect on enzymatic parameters of structuralmodifications at various locations of the twodomain interfaceof papain was examined by individual or double replacementsby Ala of pairs of interacting residues. Most modificationshad no effect on enzyme activity. However, the enzyme's substrateturnover (k_cat) decreased following simultaneous alterationof the two most conserved residues, forming an apolar contactlocated 15 Å away from the active site. The pH activityprofile of the double mutant was unchanged, indicating a conservedionization state of the active site thiolate-imidazolium ionpair. This state is strongly dependent on the distance separatingthe two residues, thus suggesting that the active site geometryhas not been significantly altered. Efficient enzymatic activityin papain requires more than a correct active site geometryand is influenced by domain packing properties in a region remotefrom the active site.     

Believing what you feel: Using proprioceptive feedback to reduce unilateral neglect.

Unilateral spatial neglect declines when participants reach to grip the center of long metal rods compared with when they point to the perceived center, suggesting that visuomotor control systems are less affected by neglect than other representational systems (I. H. Robertson, D. Nico, & B. Hood, 1995). In this study, 16 participants with unilateral left neglect actually picked up rods, and we predicted short-term improvements in neglect because of induced conflict between a phenomenally symmetrical visual world on the one hand and a proprioceptively conveyed rightward-biased world on the other. With participants serving as their own controls, significant short-term improvements in neglect were found on 2 out of 4 neglect tasks after participants experienced proprioceptive feedback discrepant from the judgments they made on the basis of visual information alone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potential Mechanisms Linking Atherosclerosis and Increased Cardiovascular Risk in COPD: Focus On Sirtuins

The development of atherosclerosis is a multi-step process, at least in part controlled by the vascular endothelium function. Observations in humans and experimental models of atherosclerosis have identified monocyte recruitment as an early event in atherogenesis. Chronic inflammation is associated with ageing and its related diseases (e.g., atherosclerosis and chronic obstructive pulmonary disease). Recently it has been discovered that Sirtuins (NAD⁺-dependent deacetylases) represent a pivotal regulator of longevity and health. They appear to have a prominent role in vascular biology and regulate aspects of age-dependent atherosclerosis. Many studies demonstrate that SIRT1 exhibits anti-inflammatory properties in vitro (e.g., fatty acid-induced inflammation), in vivo (e.g., atherosclerosis, sustainment of normal immune function in knock-out mice) and in clinical studies (e.g., patients with chronic obstructive pulmonary disease). Because of a significant reduction of SIRT1 in rodent lungs exposed to cigarette smoke and in lungs of patients with chronic obstructive pulmonary disease (COPD), activation of SIRT1 may be a potential target for chronic obstructive pulmonary disease therapy. We review the inflammatory mechanisms involved in COPD-CVD coexistence and the potential role of SIRT1 in the regulation of these systems.     

Pressure-induced pH changes in aqueous solutions - On-line measurement and semi-empirical modelling approach

The main aim of this work is to investigate the effect of CO₂ and N₂O under pressure in aqueous solution - both on-line and in real-time. In particular, the paper presents the kinetics of pH behaviour of either slightly buffered minimal medium (MM) or non-buffered solution (Ringer solution) during high-pressure treatment at 5, 30 and 60 bar at 25 °C.An innovative spectrophotometric approach has been developed: an optical fiber conducted the inlet signal of a light source into the high-pressure reactor, while another fiber conducted the outlet signal to a spectrometer, thus, obtaining measurements on-line and real-time.CO₂ treatment resulted in a pH decrease down to 3.0 in Ringer solution with the equilibrium being reached after 800 s, while the slightly buffered MM allows only for a decrease down to 4.5 with equilibrium being reached after slightly more than 40 s at 60 bar.N₂O treatment, as expected, did not lead to any acidification of the treated medium at any conditions tested.Furthermore, a mathematical model describing both the solubilization kinetics of CO₂ and in aqueous solution and the decrease of extracellular pH has been implemented. This model may easily be applied to different reactor configurations. The theoretical results and the goodness of the fit has been verified using the experimental results showing a good accuracy of the complex phenomena with a simplification that is of vital relevance for technical processes.     

New processes in the environmental chemistry of nitrite. 2. The role of hydrogen peroxide

The oxidation of nitrite and nitrous acid to *NO2 upon irradiation of dissolved Fe(III), ferric (hydr)oxides, and nitrate has previously been shown to enhance phenol nitration. This allowed the proposal of a new role for nitrite and nitrous acid in natural waters and atmospheric aerosols. This paper deals with the interaction between hydrogen peroxide, a key environmental factor in atmospheric oxidative chemistry, and nitrite/nitrous acid. The reaction between nitrous acid and hydrogen peroxide yields peroxynitrous acid, a powerful nitrating agent and an important intermediate in atmospheric chemistry. The kinetics of this reaction is compatible with a rate-determining step involving either H3O2+ and HNO2 or H2O2 and protonated nitrous acid. In the former case the rate constant between the two species would be 179.6 +/- 1.4 M(-1) s(-1), in the latter case it would be as high as (1.68 +/- 0.01) x 10(10) M(-1) s(-1) (diffusion-controlled reaction). Due to the more reasonable value of the rate constant, the reaction between H3O2+ and HNO2 seems more likely. In the presence of HNO2 + H2O2 the nitration of phenol is strongly enhanced when compared with HNO2 alone. The nitration rate of phenol in the presence of peroxynitrous acid decreases as pH increases, thus HOONO is a potential source of atmospheric nitroaromatic compounds in acidic water droplets. The mixture Fe(II) + H2O2 (Fenton reagent) can oxidize nitrite and nitrous acid to nitrogen dioxide, which results in phenol nitration. The nitration in the presence of Fe(II) + H2O2 + NO2-/HNO2 occurs more rapidly than the one with H2O2 + NO2-/HNO2 at pH 5, where little HNO2 is available to directly react with hydrogen peroxide. Both systems, however, are more effective than NO2-/HNO2 alone in producing nitrophenols from phenol. Another process leading to the oxidation of nitrite to nitrogen dioxide is the photo-Fenton one. It can be relevant at pH > or = 6, as nitrite does not react with H2O2 at room temperature. Under such conditions the source of Fe(II) is the photolysis of ferric (hydr)oxides (heterogeneous photo-Fenton reaction). In the presence of nitrite this reaction induces very effective nitrophenol formation from phenol.     

2-Phenyloxazole-4-carboxamide as a Scaffold for Selective Inhibition of Human Monoamine Oxidase B

A series of 2-phenyloxazoles bearing an amide group at position 4 were designed and synthesized for evaluation as potential inhibitors of human recombinant monoamine oxidases (hrMAOs). Results of kinetics experiments demonstrated that all compounds behave as competitive MAO inhibitors, with good selectivity toward the MAO-B isoform. The most potent and selective derivatives are characterized by inhibition constant (K_i) values in the sub-micromolar range and a good selectivity index (K_{i MAO-A}/K_{i MAO-B}>50). Some derivatives were also found to be able to inhibit MAO activity in nerve growth factor (NGF)-differentiated PC12 cells, taken as a model of neuronal cells. In particular, 2-(2-hydroxyphenyl)-N-phenyloxazole-4-carboxamide (compound 4 a ) may be a promising new scaffold, exerting the highest selectivity and inhibitory effect toward MAOs in NGF-differentiated PC12 cell lysates, without compromising cell viability. Molecular docking analysis allowed a rationalization of the experimentally observed binding affinity and selectivity.     

Global asymptotic stabilization of the attitude and the angular rates of an underactuated non-symmetric rigid body

The paper deals with the global stabilization of both the attitude and the angular velocities of an underactuated rigid body. First a stability theorem is proven for a class of systems; subsequently, the equations describing the physics of the rigid body are presented, showing that the rigid body belongs to the considered class of systems, and a sufficient condition for the application of the theorem to the stability of the rigid body equilibrium is pointed out. Finally, some simulation results are reported showing the effectiveness of the proposed methodology.     

Laccase Mediator Cocktail System as a Sustainable Skin Whitening Agent for Deep Eumelanin Decolorization

The overproduction of eumelanin leads to a panel of unaesthetic hyper-pigmented skin diseases, including melasma and age spots. The treatment of these diseases often requires the use of tyrosinase inhibitors, which act as skin whitening agents by inhibiting the synthesis of eumelanin, with harmful side effects. We report here that laccase from Trametes versicolor in association with a cocktail of natural phenol redox mediators efficiently degraded eumelanin from Sepia officinalis, offering an alternative procedure to traditional whitening agents. Redox mediators showed a synergistic effect with respect to their single-mediator counterpart, highlighting the beneficial role of the cocktail system. The pro-oxidant DHICA sub-units of eumelanin were degraded better than the DHI counterpart, as monitored by the formation of pyrrole-2,3,5-tricarboxylic acid (PTCA) and pyrrole-2,3-dicarboxylic acid (PDCA) degradation products. The most effective laccase-mediated cocktail system was successively applied in a two-component prototype of a topical whitening cream, showing high degradative efficacy against eumelanin.