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Recently, a large variety of engineered nanostructures possessing enzyme-like activities have been proposed, whose unique physical–chemical characteristics have enabled remarkable technological advances. In this review, we survey the recent advances in nanozymes for environmental applications. First, we give an updated overview of different types of nanomaterial-based artificial enzymes, including carbon, metal and metal oxide nanomaterials, metal–organic frameworks (MOFs) and hybrid nanostructures, and compare their properties (namely, the Michaelis–Menten constant (Km) and the maximal reaction velocity (Vmax)) with standard natural enzymes. Furthermore, the progress in nanozymes for detecting and removing various environmental contaminants (e.g., heavy metals, dyes, pesticides, and hormones) is also discussed. Then, we provide a comprehensive overview of the enlightening strategies employed (based on the modification of size, shape/morphology, surface coating, doping and use of hybrid structures, for instance) to modulate the properties of nanozymes in order to achieve the desired properties for environmental sensing and remediation. Finally, challenges and current opportunities are discussed to stimulate the interest of researchers in the development of novel multifunctional nanozymes for environmental applications.

In this paper, a new macroscopic traffic model is presented which characterizes driver response during transitions. The commonly employed Payne–Whitham (PW) model characterizes this response using a constant regardless of the reaction time and interaction and distance between vehicles. As a consequence, the resulting traffic behavior can be unrealistic. In this paper, a model is proposed which considers the reaction time, transition distance, and velocity profile based on the traffic density. This produces smooth changes in density and velocity during transitions compared to the PW model. Results are presented for a bottleneck along a circular road which show that the proposed model provides more realistic behavior than the PW model.

Enzyme activators lower Km (the Michaelis constant) and/or raise Vmax (the asymptotic reaction velocity at infinite substrate concentration); conversely, inhibitors raise Km and/or lower Vmax . But what if an effector moves both Km and Vmax in the same direction? Uncompetitive inhibitors, which decrease both Km and Vmax by the same factor, are the most common example of this. A less well-known example occurs often when crowding agents are added to the buffer in order to mimic the environment commonly encountered in vivo. Crowding agents tested on different enzymes have been shown to have every conceivable effect on Km or Vmax , causing them to rise, fall, or stay the same. In this article, a mathematical analysis is presented allowing biochemists to judge whether an effector that causes Km and Vmax to both move in the same direction serves as an inhibitor, an activator, or most surprising, as both. © 2019 International Union of Biochemistry and Molecular Biology, 47(4):446-449, 2019.

espanolEl objetivo principal de este trabajo es ensenar la aplicacion del metodo de minimos cuadrados disponible en el software Matlab( con sus comandos nlinfit y lsqcurvefit para determinar parametros cineticos, sus incertidumbres y las bandas asociadas a diferentes intervalos de confianza (95% y 99%). Para la ilustracion de la metodologia se emplearon datos cineticos de tres procesos avanzados de oxidacion, obtenidos experimentalmente, los cuales involucran: una unica ecuacion de velocidad de reaccion en terminos explicitos, una ecuacion de velocidad de reaccion en terminos implicitos y un sistema de ecuaciones de velocidad de reaccion en terminos implicitos. Para cada uno se obtuvo los ajustes respectivos con diferencias significativas entre los parametros y las desviaciones asociadas a los sistemas de pocos datos experimentales. En consecuencia, se ha demostrado que el tipo de modelo propuesto requiere de mas valores experimentales para un buen ajuste u otro modelo que cumpla con los criterios logicos y fenomenologicos esperados. EnglishThe main objective of this work is to teach the application of the least squares method available in the Matlab( software with its nlinfit and lsqcurvefit commands to determine kinetic parameters, their uncertainties and the bands associated with different confidence intervals (95% and 99%). To illustrate the methodology, kinetic experimental data obtained using three advanced oxidation processes, were fitted. Different approaches were used: a single equation of reaction velocity in explicit terms, an equation of reaction velocity in implicit terms and a system of reaction rate equations in implicit terms. For each one, the respective fittings were performed with significant differences between the parameters and the deviations associated with the systems with few experimental data. Consequently, it was shown that the type of proposed model required more experimental values ​​for a good fit or another model that meets the expected logical and phenomenological criteria.

We consider non-autonomous evolution inclusions and hemivariation inequalities with possibly non-monotone multidimensional “reaction-velocity” law. The dynamics of all weak solutions defined on the positive semi-axis of time is investigated. We prove the existence global attractor. New properties of complete trajectories are justified. The pointwise behavior of such problem solutions on attractor is described in the autonomous case.

The driving reaction was recognized and predicted was complicated. The driving reaction samples of various driving reactions were gained, by means of 3 settings of driving reactions including driving action of automobile in front, roadblocks cutting off in other lanes were planed and simulated in the real road environment. Experimental data of driving reactions including automobile velocity, reaction velocity, and reaction time were acquired by the driving action collecting system. Taking advantage of fuzzy aggregation analysis, the driving reaction samples were unified for the fuzzy cluster making (FCM) and probabilistic neural network (PNN). Under different groups of driving reaction data selected from driving reaction samples, the PNN driving reaction network was constructed and trained. The analytical results show that the hit rate is 95.3% when the training driving reaction sample number is 46. Meanwhile, the results show that the PNN and FCM are useful with sufficient driving reaction samples. The driving reaction PNN with FCM is a valid way for the driving reaction time forecast.

Modeling human behavior within mathematical models of infectious diseases is a key component to understand and control disease spread. We present a mathematical compartmental model of Susceptible–Infectious–Removed to compare the infected curves given by four different functional forms describing the transmission rate. These depend on the distance that individuals keep on average to others in their daily lives. We assume that this distance varies according to the balance between two opposite thrives: the self-protecting reaction of individuals upon the presence of disease to increase social distancing and their necessity to return to a culturally dependent natural social distance that occurs in the absence of disease. We present simulations to compare results for different society types on point prevalence, the peak size of a first epidemic outbreak and the time of occurrence of that peak, for four different transmission rate functional forms and parameters of interest related to distancing behavior, such as: the reaction velocity of a society to change social distance during an epidemic. We observe the vulnerability to disease spread of close contact societies, and also show that certain social distancing behavior may provoke a small peak of a first epidemic outbreak, but at the expense of it occurring early after the epidemic onset, observing differences in this regard between society types. We also discuss the appearance of temporal oscillations of the four different transmission rates, their differences, and how this oscillatory behavior is impacted through social distancing; breaking the unimodality of the actives-curve produced by the classical SIR-model.

As part of a study to investigate metal chelates as possible inhibitors of acetylcholinesterase, copper chelates of 1 ,3 diaminopropanol-2, 1,3 diaminopropane , and hydroxy-1-proline are examined. Since the chelate s olutions contain mixtures of species in equilibrium, it is necessary to calculate the concentrations of pertinent species under experimental conditions . Equations are derived which can be used to calculate the concentrations of individual species in an equilibrium mixture of ligand and copper under fixed conditions of concentration and pH with the aid of an IBM 1410 computer. Initial measurements of reaction velocity of enzyme-substrate breakdown to enzyme plus acid products, are made by observing the speed of pH drop with the aid of a Beckman Automatic Titrator. Selection of equilibrium pH values and ligand-metal ratios is dependent on the formation constants calculated for each system. Enzyme kinetic studies are used in an effort to determine the nature of the inhibition of acetylcholinesterase. It is found that (a) 1-1 ligand-copper chelate inhibit the acetylcholinesterase system, (b) free cupric ion may inhibit the enzyme system if concentrations greater than 1 x 10-6M are present in the equilibrium mixture, (c) coordination vacancies on the metal ion are necessary prerequisites for inhibition, (d) 1-1 ligandcopper chelates of 1,3 diaminopropanol inhibit the enzyme in an essentially "competitive" manner, (e) 1-1 ligand-copper chelates of 1 ,3 diaminopropane inhibit the enzyme in an essentially "noncompetitive" manner, (f) 1-1 ligand-copper chelates of hydroxy

In searching non-standard ways of conformational regulation, various Michaelis–Menten-like schemes attract relentless attention, resulting in sometimes too sophisticated considerations. With the example of monomeric enzymes possessing an only binding site, we define the minimal schemes capable of bearing peculiar regulatory properties like “cooperativity” or substrate inhibition. The simplest ways of calculating the enzymatic reaction velocity are exemplified, either in the ensemble or single-molecule case., У пошуках нестандартних шляхiв конформацiйної регуляцiї активно використовують рiзноманiтнi, iнодi переускладненi, версiї схеми Мiхаелiса–Ментен. На прикладi мономерних ензимiв з одним мiсцем зв’язування визначено мiнiмальнi схеми, що уможливлюють особливi регуляторнi властивостi типу “кооперативностi”, субстратного iнгiбування тощо. Проiлюстровано найпростiшi шляхи розрахунку швидкостi ензиматичної реакцiї в ансамблi або на рiвнi поодинокої молекули ензиму.

The upper bound of enzyme concentration for accurately estimating the parameters in Michaelis-Menten (MM) equation is not completely determined and still under discussion, even though many researchers have investigated the equation’s validity for a long time. In the paper, we broadly investigated the correlation between the system of ordinary differential equations for monosubstrate irreversible enzyme reaction (HMM-system) and its derivative MM equation focusing on the relationship between initial enzyme concentration [E]0 and Michaelis constant Km by numerical simulation. According to the results, the initial reaction velocity v0 is still a function of initial substrate concentration [S]0 at [E]0

The objective of this study was to examine the changes in reaction velocity and visual perception between genders participating in driving simulator training. Driving simulator training was performed on 46 adults (male: 20, female: 26) twice a week, 20 minutes per time, 8 times for a month. The results showed that after driving simulator training was significantly more effective for males than females (p

A new algorithm for computation of the initial velocity of enzyme reaction at the time zero is proposed. This algorithm makes it possible to reduce the systematic error of measurements to the minimum, to estimate the reaction velocity in test samples regardless of the enzyme activity levels, and to minimize the assay time. The study is illustrated by an example of salivary alpha-amylase and standard reagent kit. The algorithm should not be applied if conjugated enzyme systems are used because there is a long initial lag phase in the kinetic curve.

Purpose: This study was conducted to test the impact of The Dynamic Visual-Motor integration training has effect on the visual perception reaction velocity. Dynavision were used to measure data from the participating 24 students(K college). Method : The participants were the 24 students of `K` College in Busan in there twenties. They were divided into the The Dynamic Visual-Motor integration training group and the control group. To know if the Dynamic Visual-Motor integration training has effect on the visual perception reaction velocity, the Dynamic Visual-Motor integration training was implemented triweekly for 4 weeks. In Dynamic Visual-Motor integration training the ball should be grasped with one hand and threw by an arm. Only the balls threw beyond the objective point were counted. The visual perception reaction velocity and the number of response were measured before and after experiment by Dynavision. Result : Firstly, the visual perception reaction velocity was increased in Dynamic Visual-Motor integration training group compared with control group. Secondly, the number of response was also increased in Dynamic Visual-Motor integration training group compared with control group. Conclusion : As a result of The Dynamic Visual-Motor integration training has an effect on the visual perception reaction velocity and the number of response. The Dynamic Visual-Motor integration training seems to be effective for cerebral apoplexy patient who has visual perceptional disability or cerebral palsy child in training for visual perceptional development or daily living activities development. Study participated by more detailed and practical patients in hospital is needed.

The Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics are two popular mathematical formulations used in many land biogeochemical models to describe how microbes and plants would respond to changes in substrate abundance. However, the criteria of when to use either of the two are often ambiguous. Here I show that these two kinetics are special approximations to the equilibrium chemistry approximation (ECA) kinetics, which is the first-order approximation to the quadratic kinetics that solves the equation of an enzyme–substrate complex exactly for a single-enzyme and single-substrate biogeochemical reaction with the law of mass action and the assumption of a quasi-steady state for the enzyme–substrate complex and that the product genesis from enzyme–substrate complex is much slower than the equilibration between enzyme–substrate complexes, substrates, and enzymes. In particular, I show that the derivation of the Michaelis–Menten kinetics does not consider the mass balance constraint of the substrate, and the reverse Michaelis–Menten kinetics does not consider the mass balance constraint of the enzyme, whereas both of these constraints are taken into account in deriving the equilibrium chemistry approximation kinetics. By benchmarking against predictions from the quadratic kinetics for a wide range of substrate and enzyme concentrations, the Michaelis–Menten kinetics was found to persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln k2+ of the reaction velocity v with respect to the maximum product genesis rate k2+, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln k1+ of v with respect to the intrinsic substrate affinity k1+, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln [E]T of v with respect the total enzyme concentration [E]T, and persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln [S]T of v with respect to the total substrate concentration [S]T. Meanwhile, the reverse Michaelis–Menten kinetics persistently underpredicts ∂ ln v / ∂ ln k2+ and ∂ ln v / ∂ ln [E]T, and persistently overpredicts ∂ ln v / ∂ ln k1+ and ∂ ln v / ∂ ln [S]T. In contrast, the equilibrium chemistry approximation kinetics always gives consistent predictions of ∂ ln v / ∂ ln k2+, ∂ ln v / ∂ ln k1+, ∂ ln v / ∂ ln [E]T, and ∂ ln v / ∂ ln [S]T, indicating that ECA-based models will be more calibratable if the modeled processes do obey the law of mass action. Since the equilibrium chemistry approximation kinetics includes advantages from both the Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics and it is applicable for almost the whole range of substrate and enzyme abundances, land biogeochemical modelers therefore no longer need to choose when to use the Michaelis–Menten kinetics or the reverse Michaelis–Menten kinetics. I expect that removing this choice ambiguity will make it easier to formulate more robust and consistent land biogeochemical models.

The emergence of creatine as a potential cognitive enhancement supplement for humans prompted an investigation as to whether supplemental creatine could enhance spatial memory in young swine. We assessed memory performance and brain concentrations of creatine and its precursor guanidinoacetic acid (GAA) in 14-16-week-old male Yucatan miniature pigs supplemented for 2 weeks with either 200 mg/kg∙d creatine (+Cr; n = 7) or equimolar GAA (157 mg/kg∙d) (+GAA; n = 8) compared to controls (n = 14). Spatial memory tests had pigs explore distinct sets of objects for 5 min. Objects were spatially controlled, and we assessed exploration times of previously viewed objects relative to novel objects in familiar or novel locations. There was no effect of either supplementation on memory performance, but pigs successfully identified novel objects after 10 (p < 0.01) and 20 min (p < 0.01) retention intervals. Moreover, pigs recognized spatial transfers after 65 min (p < 0.05). Regression analyses identified associations between the ability to identify novel objects in memory tests and concentrations of creatine and GAA in cerebellum, and GAA in prefrontal cortex (p < 0.05). The concentration of creatine in brain regions was not influenced by creatine supplementation, but GAA supplementation increased GAA concentration in cerebellum (p < 0.05), and the prefrontal cortex of +GAA pigs had more creatine/g and less GAA/g compared to +Cr pigs (p < 0.05). Creatine kinase activity and maximal reaction velocity were also higher with GAA supplementation in prefrontal cortex (p < 0.05). In conclusion, there appears to be a relationship between memory performance and guanidino compounds in the cerebellum and prefrontal cortex, but the effects were unrelated to dietary supplementation. The cerebellum is identified as a target site for GAA accretion.

Phosphotransacetylase activity and the kinetic properties of the enzyme from intestinal sulfate-reducing bacteria Desulfovibrio piger and Desulfomicrobium sp. has never been well-characterized and has not been studied yet. In this paper, the specific activity of phosphotransacetylase and the kinetic properties of the enzyme in cell-free extracts of both D. piger Vib-7 and Desulfomicrobium sp. Rod-9 intestinal bacterial strains were presented at the first time. The microbiological, biochemical, biophysical and statistical methods in this work were used. The optimal temperature and pH for enzyme reaction was determined. Analysis of the kinetic properties of the studied enzyme was carried out. Initial (instantaneous) reaction velocity (V0), maximum amount of the product of reaction (Pmax), the reaction time (half saturation period, τ) and maximum velocity of the phosphotransacetylase reaction (Vmax) were defined. Michaelis constants (Km) of the enzyme reaction (3.36 ± 0.35 mM for D. piger Vib-7, 5.97 ± 0.62 mM for Desulfomicrobium sp. Rod-9) were calculated. The studies of the phosphotransacetylase in the process of dissimilatory sulfate reduction and kinetic properties of this enzyme in intestinal sulfate-reducing bacteria, their production of acetate in detail can be perspective for clarification of their etiological role in the development of the humans and animals bowel diseases. These studies might help in predicting the development of diseases of the gastrointestinal tract, by providing further details on the etiology of bowel diseases which are very important for the clinical diagnosis of these disease types.

β-Agarase produced by Paenibacillus sp. WL (agarase WL) was purified using a combination of ammonium sulfate precipitation, DEAE-ion exchange, and gel-filtration chromatography. The purity of the agarase was increased by 11.9× with a recovery of 5.1% and a specific activity of 4,670.1 U/mg of protein. The molecular mass of the purified agarase was approximately 30 kDa (SDS-PAGE). The agarase was stable at temperature below 50°C and the favorable agar-hydrolysis activity was at 40°C. The agarase was active in the range of pH 5.0 to 8.0, and the optimal agar-hydrolysis pH value was approximately 6.0. Metal ions normally found in seawater (Na+, K+, Ca2+, Mg2+, and Al3+) could activate agarase WL. The Michaelis-Menten constant Km and maximal reaction velocity Vmax of purified agarase WL were 3.22 mg/mL and 41.5 μg/mL·min, respectively. The agarase WL was highly agar specific.

An encapsulation material based on a pressure sensitive adhesive (PSA) with a high water barrier and a low corrosive properties is presented. The reproducible water vapor transmission rate is less than 5.0 g·m−2·day−1 under 40°C, 90% RH condition. A calcium reaction velocity and an electrochemical migration of a copper electrode were evaluated by direct encapsulation of the test devices. This PSA possesses excellent encapsulation and electric insulation properties. It is expected as one of the most prospective materials as the direct encapsulation adhesive for the flexible electronic device.

Rice husk ash (RHA) is the product of rice husk pyrolysis or combustion, which contains inherent ash in original rice husk and non-converted fixed carbon. Due to large amounts of inherent silicon dioxide in rice husk, the decarbonized residue of RHA has great value as industrial materials. One basic method to remove carbon from RHA is roasting. Because of low carbon content in RHA and low roasting reaction velocity, the roasting process takes a long time. In this case, fixed-bed roasting is suitable for removing carbon from RHA. In the present work, experimental study on RHA decarbonization is conducted based on a specially-designed multi-section fixed-bed roasting. The experimental results show that under the experimental conditions, the flame propagation spread of RHA in fixed beds is in the range 0.833 to 0.121mm/s. The results documented in this paper provide the basis for further developing large-scale engineering devices.

Catalytic reactions have been favored nowadays in terms of economical and environmental requirements. On this point, the term TON (TurnOver Number) has widely been utilized because of its facile availability. However, during the optimization of reaction conditions, it is not as useful as its fame, because it does not reflect whether the reaction in question is fast or slow. We propose the term HCC (Hourly Conversion per Catalyst) in order to make experimenters easier to assess the ultimate reaction condition with quantitative conversion.

For the characteristics of serious formation damage and insufficient injecting in injection wells in the water flooding development process in low permeability oilfield, it carries the analysis of reasons for forming low efficient injection wells and the development of acidizing disentanglement agent. Through core damage experiment of wellhead sewage in S oilfield, formation damage is mainly caused by excessive levels of suspended matters and the multiple of exceeding standards is 45.3. Based on the result of core damage experiment and actual oilfield production data, the variation of apparent injectivity index in low efficient injection wells is researched. The research result indicates that formation damage radius of pollution wells is about 20m in this oilfield. Based on formation damage condition of this oilfield, compound acid is developed, which has the properties of strong penetration, retarding reaction velocity and strong-chelating. Plug removal experiment indicates that the recovery rate of core permeability is about 100% using developed compound acid.

UDP-glucuronosyltransferase (UGT) 1A1-catalyzed glucuronidation is an important elimination pathway of flavonoids, and mutually inhibitory interactions may occur when two or more flavonoids are coadministered. Our recent research suggested that glucuronidation of flavonoids displayed distinct positional preferences, but whether this will lead to the mutually regioselective inhibition of UGT1A1-mediated glucuronidation of flavonoids is unknown. Therefore, we chose three monohydroxyflavone isomers, 3-hydroxyflavone (3HF), 7-hydroxyflavone (7HF), and 4'-hydroxyflavone (4'HF), and one trihydroxyflavone, 3,7,4'-trihydroxyflavone (3,7,4'THF), as the model compounds to characterize the possible mutually regioselective inhibition of glucuronidation using expressed human UGT1A1. Apparent kinetic parameters [e.g., reaction velocity (V), Michaelis-Menten constant (Km), maximum rate of metabolism (Vmax), concentration at which inhibitor achieves 50% inhibition (IC50), and the Lineweaver-Burk plots were used to evaluate the apparent kinetic mechanisms of inhibition of glucuronidation. The results showed that UGT1A1-mediated glucuronidation of three monohydroxyflavones (i.e., 3HF, 7HF, and 4'HF) and 3,7,4'THF was mutually inhibitory, and the mechanisms of inhibition appeared to be the mixed-typed inhibition. Specifically, the inhibitory effects displayed certain positional preference. Glucuronidation of 3HF was more easily inhibited by 3,7,4'THF than that of 7HF or 4'HF. Compared to 7-O-glucuronidation of 3,7,4'THF, 3-O-glucuronidation of 3,7,4'THF was more inhibited by 3HF and 4'HF, whereas glucuronidation at both 3-OH and 7-OH positions of 3,7,4'THF was more easily inhibited by 7HF than by 3HF and 4'HF. In conclusion, 3HF, 7HF, 4'HF, and 3,7,4'THF were both substrates and inhibitors of UGT1A1, and they exhibited mutually regioselective inhibition of UGT1A1-mediated glucuronidation via a mixed-type inhibitory mechanism.

Al/Ni multilayer bridge films, which were composed of alternate Al and Ni layers with bilayer thicknesses of 50, 100 and 200 nm, were prepared by RF magnetron sputtering. In each bilayer, the thickness ratio of Al to Ni was maintained at 3:2 to obtain an overall 1:1 atomic composition. The total thickness of Al/Ni multilayer films was 2 μm. XRD measurements show that the compound of AlNi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ni multilayer films with bilayer thicknesses of 50, 100 and 200 nm are 389.43, 396.69 and 409.92 J g−1, respectively. The temperatures of Al/Ni multilayer films were obviously higher than those of Al bridge film and Ni bridge film. Al/Ni multilayer films with modulation of 50 nm had the highest electrical explosion temperature of 7000 K. The exothermic reaction in Al/Ni multilayer films leads to a more intense electric explosion. Al/Ni multilayer bridge films with modulation period of 50 nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity.

The properties of cellulase that was attached to the surface of the chitosan carrier in aqueous-ionic liquid (IL; 1,3-dimeth-ylimidazolium dimethylphosphate) mixture were studied. The optimal temperature for immobilized cellulase in aqueous-IL mixed solutions was 60 °C. The immobilized cellulase acquired the highest relative activity at a ratio of 1:4 (IL to water, v/v), compared to activity levels of 79% and 7%, when the ratio of IL to water (v/v) was 0:1 and 1:0, respectively. At 80 °C, the immobilized cellulase in the aqueous-IL mixture conserved 46.3% activity after 120 Min. The immobilized cellulase can be effectively reused three times. After 4 weeks, the activity of immobilized cellulase maintained 83.5%. The Michaelis constant (Km ) and maximum reaction velocity (Vm ) values for the immobilized cellulase were 4.8 mg/L and 0.156 mg/(mL Min), respectively. To the best of our knowledge, this is the first report on the properties of chitosan-immobilized cellulase in aqueous-IL.