Tyrosinase is a bifunctional enzyme mediating the o-hydroxylation and two-electron oxidation of monophenols to o-quinones. The monophenolase activity of tyrosinase is much desired for the industrial synthesis of catechols. However, the generally low ratio of monophenolase/diphenolase activity of tyrosinase limited its utilization in the industry. In this study, a novel tyrosinase from Armillaria ostoyae strain C18/9 (AoTyr) was characterized, and the results showed that the enzyme has an optimal temperature of 25°C and an optimal pH of 6. The enzyme has comparable monophenolase and diphenolase activities and exhibits substrate inhibition in both of the activities. In silico analysis and mutagenesis experiments showed that residues 262 and 266 play important roles in modulating the substrate inhibition and enzymatic activities of AoTyr, and the replacement of D262 with asparagine significantly increased the monophenolase/diphenolase catalytic efficiencies (kcat/Km ratios) (1.63-fold) of the enzyme. The results from this study indicated that this novel tyrosinase could be a potential candidate for the industrial biosynthesis of catechols. IMPORTANCE Tyrosinase is able to oxidize various phenolic compounds, and its ability to convert monophenols into diphenols has caught great attention in the research field and industrial applications. However, the utilization of tyrosinase for the industrial synthesis of catechols has been limited due to the fact that the monophenolase activity of most of the known tyrosinases is much lower than the diphenolase activity. In the present study, a novel tyrosinase with comparable monophenolase and diphenolase activities was characterized. The enzyme exhibits substrate inhibition in both monophenolase and diphenolase activities. In silico analysis followed by mutagenesis experiments confirmed the important roles of residues 262 and 266 in the substrate inhibition and activity modulation of the enzyme, and the D262N variant showed an enhanced monophenolase/diphenolase catalytic efficiency ratio compared to the wild-type enzyme.
Armillaria/enzymology , Fungal Proteins , Monophenol Monooxygenase , Amino Acid Sequence , Catalysis , Cloning, Molecular , Computer Simulation , Detergents/chemistry , Enzyme Inhibitors/chemistry , Escherichia coli/genetics , Fungal Proteins/antagonists & inhibitors , Fungal Proteins/chemistry , Fungal Proteins/genetics , Hydrogen-Ion Concentration , Metals/chemistry , Monophenol Monooxygenase/antagonists & inhibitors , Monophenol Monooxygenase/chemistry , Monophenol Monooxygenase/genetics , Oxidoreductases/chemistry , Solvents/chemistry , Substrate Specificity , Temperature
Studies on interactions between oppositely charged polysaccharides have gathered great interest. We proposed that the association between oppositely charged polymers could be regulated via hydration. A comparison study was carried out by using quaternary chitosan with different counterions(Cl-, Ac-, OH-) and sodium alginate. The results showed that the association between quaternary chitosan with less hydrated counter anion Cl- and sodium alginate was weaker than that between quaternary chitosan with more hydrated counter anion Ac- and sodium alginate. There was a pH transition point of thermal change of association between oppositely charged polymers, as the solution's pH had more effect on the hydration of polymers than counter ions. Further studies showed that a fraction of Cl- was still attracted by polycation in the complex and competed with the interaction of polyanion after complexation. The competitive combination was critical for the property (such as self healing behavior) of the carbohydrate polymer complex.
Relative orientation estimation between the hand and its fingers is important in many applications, such as virtual reality (VR), augmented reality (AR) and rehabilitation. It is still quite a big challenge to do the estimation by only exploiting inertial measurement units (IMUs) because of the integration drift that occurs in most approaches. When the hand is functionally used, there are many instances in which hand and finger tips move together, experiencing almost the same angular velocities, and in some of these cases, almost the same accelerations are measured in different 3D coordinate systems. Therefore, we hypothesize that relative orientations between the hand and the finger tips can be adequately estimated using 3D IMUs during such designated events (DEs) and in between these events. We fused this extra information from the DEs and IMU data with an extended Kalman filter (EKF). Our results show that errors in relative orientation can be smaller than five degrees if DEs are constantly present and the linear and angular movements of the whole hand are adequately rich. When the DEs are partially available in a functional water-drinking task, the orientation error is smaller than 10 degrees.
Algorithms , Fingers , Hand , Movement , Acceleration , Biomechanical Phenomena , Humans
Alginate is a family of industrially important linear polymers consisting of ß-D-mannuronic acid (M) and its C-5 epimer α-L-guluronic acid (G). The function of alginate is closely related to the ratio of M/G. Mannuronan C-5 epimerase, which converts M to G, is a key enzyme involved in the biosynthesis of alginate. A new mannuronan C-5 epimerase isolated from Pseudomonas mendocina. sp. DICP-70 named PmC5A was characterized in this study. From the 1H NMR analysis of the products, we have found that PmC5A possesses alginate lyase function in addition to mannuronan C-5-epimerase. The optimal pH and temperature of lyase and epimerase were found to be 8.0, 9.0 and 40 °C, 30 °C, respectively. PmC5A also shows lyase activity toward PolyMG and G-blocks.
Bacterial Proteins/chemistry , Carbohydrate Epimerases/chemistry , Polysaccharide-Lyases/chemistry , Pseudomonas mendocina/enzymology , Alginates/chemistry , Alginates/metabolism , Nuclear Magnetic Resonance, Biomolecular
This study presents a quick, simple and accurate method to calculate the degree of polymerization (DP) of alginate oligosaccharides (AOS) and low molecular weight alginates from the concentration of reducing sugar determined by 3,5-dinitrosalicylic acid (DNS) assay. 1H NMR spectroscopy, mass spectroscopy (MS) and certified standards were used to verify the accuracy of this method, and the results showed DP calculated from DNS assay agreed with the actual DP. This method has great potential to simplify the process of measuring DP of alginate in lab and thus could be incorporated into various researches on alginates in the future. Moreover, similar method could be applied when studying the DP of other oligosaccharides.
Alginates/chemistry , Oligosaccharides/chemistry , Polymerization , Molecular Weight
We generalize the concept of Fraunhofer diffraction to partially coherent electromagnetic beams and show how the state of polarization is affected by a circular aperture. It is illustrated that the far-zone properties of a random beam can be tuned by varying the aperture radius. We find that even an incident beam that is completely unpolarized can sometimes produce a field that is highly polarized.
We study the field that is produced by a paraxial refractive axicon lens. The results from geometrical optics, scalar wave optics, and electromagnetic diffraction theory are compared. In particular, the axial intensity, the on-axis effective wavelength, the transverse intensity, and the far-zone field are examined. A rigorous electromagnetic diffraction analysis shows that the state of polarization of the incident beam strongly affects the transverse intensity distribution, but not the intensity distribution in the far zone.
Magnetic detection techniques have been widely used in many fields, such as virtual reality, surgical robotics systems, and so on. A large number of methods have been developed to obtain the position of a ferromagnetic target. However, the angular rotation of the target relative to the sensor is rarely studied. In this paper, a new method for localization of moving object to determine both the position and rotation angle with three magnetic sensors is proposed. Trajectory localization estimation of three magnetic sensors, which are collinear and noncollinear, were obtained by the simulations, and experimental results demonstrated that the position and rotation angle of ferromagnetic target having roll, pitch or yaw in its movement could be calculated accurately and effectively with three noncollinear vector sensors.
Magnetic detection technology has wide applications in the fields of geological exploration, biomedical treatment, wreck removal and localization of unexploded ordinance. A large number of methods have been developed to locate targets with static magnetic fields, however, the relation between the problem of localization of moving objectives with alternating magnetic fields and the localization with a static magnetic field is rarely studied. A novel method of target localization based on coherent demodulation was proposed in this paper. The problem of localization of moving objects with an alternating magnetic field was transformed into the localization with a static magnetic field. The Levenberg-Marquardt (L-M) algorithm was applied to calculate the position of the target with magnetic field data measured by a single three-component magnetic sensor. Theoretical simulation and experimental results demonstrate the effectiveness of the proposed method.
[equation: see text] An efficient one-pot route to unsymmetrical diorganyl selenides has been developed by ruthenium(III) chloride catalyzed reactions of dibenzyl or diphenyl diselenides with alkyl halides in the presence of zinc. Organic iodides, bromides, and activated chlorides underwent the reactions efficiently. Unreactive organic chlorides also underwent the same type of selenation with sodium bromide as the additive.
