Enzymatic reaction of ethanol and oleic acid by lipase and lignin peroxidase in rhamnolipid(RL) reversed micelles

An environment friendly bio-surfactant of rhamnolipid(RL) was used as a solvent. The enzymatic reaction of oleic acid catalyzed by lipase and lignin peroxidase(lip) was evaluated. The optimum conditions of enzymatic reaction catalyzed by lipase(lip) were water to amphiphile molar ratio of 30(20), RL of 60(60) critical micelle concentration(CMC), pH of 7.0(3.0) and temperature of 40(30) °C, respectively. The change of enzyme conformation indicates that, for catalytic of lipase, water content is the most important factor of the enzymatic reaction of oleic acid, and p H for lip. With individual optimum conditions, the enzymatic efficiency of oleic acid catalyzed by lipase is higher than that by lip. In the presence of ethanol, the enzymatic reaction of oleic acid catalyzed by lipase suits Ping-Pong Bi-Bi mechanism. As an alternative to chemical reversed micelles, the RL reversed micelles are promising methods to enzymatic reaction of oleic acid.

Enzymatic Determination of Glucose by Optical-Fiber Sensor Sequential Injection Renewable Surface Spectrophotometry

On the basis of oxidative decoloration of bromopyrogallol red （BPR） with H2O2, catalyzed by horseradish peroxidase（ HRP）, and the sequential injection renewable surface technique（ SI-RST）, a highly sensitive optical-fiber sensor spectrophotometric method for the enzymatic determination of hydrogen peroxide was proposed. By coupling with a glucose oxidase（GOD）-catalyzed reaction, the method was used to determine glucose in human serum. The considerations in system and flow cell design, and factors that influence the determination performance are discussed. With 100μL of sample loaded and 0. 6 mg of bead trapped, the linear response range from 5.0 × 10^-8 to 5.2 × 10^-6 mol/L BPR with a detection limit（3σ） of 2. 5 ×10 ^-8 mol/L BPR, and a precision of 1.1% RSD（ n = 11 ） and a throughput of a 80 samples per hour can be achieved. Under the conditions of a 8. 7 × 10^ -6 mol/L BPR substrate, 0. 04 unit/mL HRP, 600 s reaction time and a reaction temperature of 37℃, the linear response range for H2O2 was from 5.0 × 10^-8 to 7.0 × 10^-6 mol/L with a detection limit（3σ） of 1.0 × 10^-8 mol/L and a precision of 3.7% RSD （ n = 11 ）. The linear response range by coupling with a GOD-catalyzed reaction was from 1.0 × 10^-7 to 1.0 × 10^-5 mol/L. The method was directly applied to determine glucose in human serum. Glucose contents obtained by the proposed procedure were compared with those obtained by using the phenol-4-AAP method, the error was found to be less than 3%.

STUDIES OF THE REACTION BETWEEN LACCASE AND p-PHENYLENEDIAMIME BY MICROCALORIMETRY

The molar reation enthalpy,the Michaelis constant and the observed rate constant of the reaction between the Rhus vernicifera laccase and p-phenylenediamine have been determined at 298. 15 K by LKB-2107 microcalorimetry system in 0.1 mol/L phosphate salt buffer (pH7. 4) to be △rHm=-136.36±0. 36kJ/mol, Km= 5. 58×10-3 mol/L and k1 =8. 63×10-3s-1, respectively. The catalyst activity of laccase withp-phenylenediamine as substrate has been determined to be EA=0. 045 IU in the experimental condition.The observed activation energy of non-enzymic step of the reaction, the Gibbs binding energy of the combination process of laccase and substrate have been also calculated. The physical significance of the determined parameters were discussed for different step of the reaction.

Mathematical Study of A Memory Induced Biochemical System

In this work, to study the effect of memory on a bi-substrate enzyme kinetic reaction, we have introduced an approach to fractionalize the system, considering it as a threecompartmental model. Solutions of the fractionalized system are compared with the corresponding integer-order model. The equilibrium points of the fractionalized system are derived analytically. Their stability properties are discussed from numerical aspect. We determine the changes of the substances due to the changes of "memory effect". The effect is discussed critically from the perspective of product formation. We have also analyzed the memory induced system with a control measure in view of optimizing the product. Our numerical result reveals that the solutions of the fractionalized system, when it is free from memory, are in good agreement with the integer-order system.It is noticed that the effect of memory influences the reaction in the forward direction and assists in yielding the product more quickly. However, an extensive use of memory makes the system slower, but introduction of a control input makes the reaction faster. It is possible to overcome the slowness of the reaction due to the undue effect of memory by appropriate use of a control measure.

Time-Fractal in Living Objects

Homeostasis creates self-organized synchrony of the body’s reactions, and despite the energetically open system with intensive external and internal interactions, it is robustly stable. Importantly the self-organized system has scaling behaviors in its allometry, internal structures, and dynamic processes. The system works stochastically. Deterministic reductionism has validity only by the great average of the probabilistic processes. The system’s dynamics have a characteristic distribution of signals, which may be characterized by their frequency distribution, creating a particular “noise” 1/f of the power density. The stochastic processes produce resonances pumped by various noise spectra. The chemical processes are mostly driven by enzymatic processes, which also have noise-dependent resonant optimizing. The resonance frequencies are as many as many enzymatic reactions exist in the target.

Catalytic reaction mechanism of L-lactate dehydrogenase: an ab initio study

Studies on the catalytic reaction mechanism of L-lactate dehydrogenase have been carried out by using quantum chemical ab initio calculation at HF/6-31G* level. It is found that the interconversion reaction of pyruvate to L-lactate is dominated by the hydride ion Hr transfer, and the transfers of the hydride ionH r and protonH r are a quasi-coupled process, in which the energy barrier of the transition state is about 168.37 kJ/mol. It is shown that the reactant complex is 87.61 kJ/mol lower, in energy, than the product complex. The most striking features in our calculated results are that pyridine ring of the model cofactor is a quasi-boat-like configuration in the transited state, which differs from a planar conformation in some previous semiempirical quantum chemical studies. On the other hand, the similarity in the structure and charge between theH r transfer process and the hydrogen bonding with lower barrier indicates that the Hr transfer process occurs by means of an unusual manner. In addition, in the transition state the electrostatic interaction between the substrate and the active site of LDH is quite strong and the polarization of the carbonyl in the substrate is gradually enhanced accompanying the formation of the transition state. These calculated results are well in accord with the previous experimental studies, and indicate that the charge on the hydride ion Hr is only +0.13e in the transition state, which is in agreement with the reported semiempirical quantum chemical calculations.

Precursor-involved and Conversion Rate-controlled Self-assembly of a ＇Super Gelator＇ in Thixotropic Hydrogels for Drug Delivery

Enzymatic hydrogelation is a totally different process to the heating-cooling gelation process, in which the pre- cursors of the gelators can be involved during the formation of self-assembled structures. Using thixotropic hy- drogels formed by a super gelator as our studied system, we demonstrated that the enzyme concentration/conversion rate of enzymatic reaction had a strong influence on the morphology of resulting self-assembled nanostructures and the property of resulting hydrogels. The principle demonstrated in this study not only helps to understand and elucidate the phenomenon of self-assembly triggered by enzymes in biological systems, but also offers a unique methodology to control the morphology of self-assembled structures for specific applications such as controlled drug re- lease.

Self-assembled Nanosheets of Perylene Monoamide Derivative as Sensitive Fluorescent Biosensor for Exonuclease Ⅲ Activity

Enzymes containing 3′→5′exonuclease activities play an important role in various key cellular and physiological processes.The development of fluorescence biosensor is an efficient method to detecting enzyme activity.Herein,a fluorescence resonance energy transfer(FRET)“on”and“off”strategy for detecting exonuclease III(Exo III)activity has been developed.We report here that the double-stranded DNA(dsDNA)enables to bind tightly to self-assembled nanosheets of cationic perylene monoimide derivative(PMI-O7)through electrostatic interaction,and the 6-carboxyfluorescein(FAM)-modified dsDNA could be efficiently quenched via FRET between FAM and PMI-O7.Upon the addition of Exo III,the dsDNA will be digested and the FAM fluorophore will be released,resulting in the fluorescence recovery of FAM.This method provides a simple and sensitive biosensor platform with a low detection limit of 0.077 U/mL for Exo III.Importantly,this method exhibits similar and calibration curves for the detection of Exo III in both buffer and fetal bovine serum samples,indicating that this platform has potential to detect Exo III activity in complex samples.