Effect of Environmental Factors of Mannanase on Konjac Glucomannan Molecular Dimension

2011 ◽  
Vol 689 ◽  
pp. 308-314
Author(s):  
Xiao Yan Long ◽  
Xue Gang Luo ◽  
Ju Bai ◽  
Jia Feng Zhu
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Reaction Time ◽  
Environmental Factors ◽  
Weight Distribution ◽  
Degradation Process ◽  
Konjac Glucomannan ◽  
Molecular Dimension ◽  
Degradation Reaction ◽  
Theoretical Foundations

The environmental factors of mannanase konjac glucomannan (KGM) have been investigated in aqueous solution. Molecular weight (Mw) and molecular weight distribution (WMD) of the degraded KGM were measured by GPC. During the degradation process, the molecular weight of the enzymatic products decreases with reaction time, degradation reaction combining two reactions processed with different orders, while WMD broadens at first and then becomes narrow. The reduction of molecular dimension of KGM was lowered with temperature increase, but WMD increases. WMD was reduced with concentration of enzyme increase, but the reduction of molecular dimension of KGM was insignificant in the range of 2.0~6.5 u.mL-1of mannanase concentration. The results show that molecular dimension of KGM could be controlled by soft changes of reaction environment, dimension of KGM molecule could be decreased more than 100 times so as to obtain oligosaccharides, which offers the reference to reliable theoretical foundations and practical ground in exploiting KGM potential function and activity.

Laboratory Simulation Study of Photo-Degradation Process of Fenvalerate in Aqueous Solution

2013 ◽  
Vol 312 ◽  
pp. 886-892
Author(s):  
Yan Ru Liang ◽  
Yu Yun Wen ◽  
Xiao Yan Hong ◽  
Zhen Bin Gong ◽  
Wen Quan Li
Keyword(s):  
Aqueous Solution ◽  
Reaction Rate ◽  
Organic Molecules ◽  
Spectral Characteristics ◽  
Degradation Process ◽  
Laboratory Simulation ◽  
Fluorescent Substance ◽  
Photo Degradation ◽  
Small Organic Molecules ◽  
Degradation Reaction

A laboratory-made the efficient photochemical degradation experimental device, combined with high performance liquid chromatography-tandem diode array detector device (DAD), fluorescence detector (FLD), mass spectrometer detector (MS), research fenvalerate its photo degradation. The structure of the spectral characteristics is the product, photo degradation reaction kinetics of degradation products, suggesting fenvalerate light chemical degradation process in an aqueous solution. The spectral characteristics of fenvalerate under ultraviolet light can be degraded into smaller organic molecules; maternal and main product have strong UV - visible absorption, fenvalerate are weakly fluorescent substance in the aqueous solution. The major products are strong fluorescent substance. Almost no effect The photo degradation kinetic data show fenvalerate photo degradation in an aqueous solution to approximate a reaction of the reaction; pesticide initial concentration, the pH value of the aqueous solution of pesticides photo degradation reaction rate; To accelerate the increase of salinity, light intensity fenvalerate in aqueous photo degradation reaction rate; significant influence of small organic molecules, with the type of small organic molecules.

Substrate-Dependent Features of Polyethylene Oxide (Peo) Adsorption from Aqueous Solution: Competitive Adsorption Versus Surface Relaxations

1994 ◽  
Vol 366 ◽  
Author(s):  
M. M. Santore ◽  
V. A. Rebar
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Polyethylene Oxide ◽  
Weight Distribution ◽  
Adsorption Process ◽  
Polymer Concentration ◽  
Hydroxyethyl Cellulose ◽  
Total Internal Reflectance ◽  
The Impact

ABSTRACTThis work employed total internal reflectance fluorescence (TIRF) to examine the adsorption kinetics of polyethylene oxide (PEO) on silica from aqueous solution in controlled shearing flow. Studies with PEO, fluorescently labeled such that TIRF tracked the chain number on the surface, exhibited an overshoot in the early stages of adsorption. This overshoot was not seen with other polymers such as polyvinyl alcohol, and hydroxyethyl cellulose, possibly because these other polymers were labeled such that TIRF measured the interfacial mass. Indeed, reflectometry studies of PEO adsorption, sensitive to interfacial mass, showed no overshoot. This suggests that the overshoot results from the selectivity of the surface for high molecular weight populations within a polydisperse sample. Initially short chains adsorb because they diffuse to the surface quickly. At longer times, higher molecular weight chains reach the surface and replace the short chains. This evolution occurs as the mass coverage increases (according to reflectivity) but the number of adsorbed chains, and hence the TIRF signal decrease at long times. A study of the impact of the molecular weight distribution confirmed this hypothesis.Several complications to the molecular weight selectivity hypothesis, however, arose: First, the same PEO samples which overshot during adsorption on silica showed no overshoot on a polystyrene substrate. This suggested that the ability to overshoot was governed by the substratesegment interactions, even though the molecular weight distribution within the sample determined the overshoot shape. Further, the effect of transport conditions (wall shear rate, bulk polymer concentration) were not completely consistent with the molecular weight competition hypothesis, which was based on surface-solution equilibrium, taking into account transport-limited rates of adsorption. Finally certain runs, where the adsorption process was interrupted by solvent flow and later allowed to proceed, never reached the full coverage seen for uninterrupted runs. Hence, the surface coverage and possibly the chain configurations can depend on the history of the adsorption process, a feature which points to surface relaxations and non-equilibrium structures.

Photo-Degradation of Cypermethrin in Aqueous Solution Studied by HPLC-DAD

2013 ◽  
Vol 634-638 ◽  
pp. 1044-1048
Author(s):  
Yan Ru Liang ◽  
Zhen Bin Gong ◽  
Wen Quan Li
Keyword(s):  
Aqueous Solution ◽  
High Performance ◽  
Degradation Products ◽  
Degradation Process ◽  
Mass Spectrometric ◽  
Photochemical Degradation ◽  
Pseudo First Order Reaction ◽  
Photo Degradation ◽  
Mass Spectrometric Detector ◽  
Degradation Reaction

The photo-degradation process of cypermethrin in aqueous solution was studied using the laboratory-built photochemical degradation device and commercial high performance liquid chromatography (HPLC) with ultraviolet-visible absorbance detector and mass spectrometric detector. Spectrometric characteristics of cypermethrin and its main degradation products suggest that cypermethrin could be photo-degradated and converted into smaller molecular under ultraviolet irradiation. The photo-degradation reaction of cypermethrin in aqueous solution is approximately pseudo-first-order reaction. Light strength, pH and salinity have significant effects on the photo-degradaiton reaction of cypermethrin. Mass spectrometric results show that cypermethrin pesticide can be degraded into new and easily photochemical degrading products through the removal of chlorine.

Reactions of silanes with bis(cyclopentadienyl)dialkylzirconium complexes

1991 ◽  
Vol 69 (2) ◽  
pp. 264-276 ◽  
Author(s):  
Ying Mu ◽  
Clare Aitken ◽  
Bruno Cote ◽  
John F. Harrod ◽  
Edmond Samuel
Keyword(s):  
Molecular Weight ◽  
Reaction Time ◽  
Nmr Spectroscopy ◽  
Key Words ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Active Catalyst ◽  
Systematic Comparison ◽  
H Nmr ◽  
Cyclic Polymer

A systematic comparison between the dimethylzirconocene (DMZ) and dimethyltitanocene (DMT) catalyzed dehydrocoupling of organosilanes is reported. The polymerization rates of primary silanes are about ten times faster for DMZ than for DMT, but the characteristics of the polymers produced are essentially identical. Variations of molecular weight and molecular weight distribution with varying monomer and reaction time, and the relative amounts of linear and cyclic polymer are also essentially the same for the two catalysts.Oligomerizations of phenylmethylsilane, diphenylsilane, and 1,2-diphenyldisilane are described. The compound Cp2Zr(SiPhMeH)(μ-H)2(SiPhMe2)ZrCp2 (1b) is isolated from the reaction of phenylmethylsilane with DMZ and its structure confirmed by crystallography and 1H-NMR spectroscopy. The compound Cp2Zr(Me)(μ-H)2(SiPh2H)ZrCp2 (1d) is isolated from the reaction of diphenylsilane with DMZ and its structure assigned by NMR spectroscopy. A number of other hydride bridged species are observed by 1H-NMR in the reactions of DMZ with phenylmethyl-, diphenyl-, and n-butylmethylsilanes and their structures are tentatively assigned. The implications of these observations on the mechanism of transformation of DMZ into active catalyst and our current views of the polymerisation mechanism are also discussed. Key words: silanes, dehydrocoupling, titanocene, zirconocene, polysilanes.

Sodium Citrate Kolbe Electrolysis Polymerization in Aqueous Solution with Controlled Molecular Weight Distribution

2020 ◽  
Vol 221 (13) ◽  
pp. 2000092
Author(s):  
Ting‐Ran Liu ◽  
Zhi‐Yang Hu ◽  
Jian‐Qiu Chen ◽  
Yu‐Zeng Zhao ◽  
Hong‐Hua Ge
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Sodium Citrate ◽  
Kolbe Electrolysis

Studies on the Molecular Chain Conformation and Morphology of Konjac Glucomannan in Aqueous Solution

2010 ◽  
Vol 658 ◽  
pp. 388-391
Author(s):  
Xiao Yan Long ◽  
Xue Gang Luo ◽  
Ju Bai ◽  
Jia Feng Zhu
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Electron Microscope ◽  
Laser Light ◽  
Konjac Glucomannan ◽  
Chain Conformation ◽  
Molecular Chain ◽  
Atomic Force ◽  
Transmission Electron ◽  
Refractive Index Detector

The molecular chain conformation of konjac glucomannan (KGM) was studied by multi-angle laser light scatter (MALLS) and differential refractive index detector (RI) with GPC. The absolute Molecular weight (MW), toot-mean-square ratio of gyration (<S2>1/2), second viral coefficient and molecular weight distribution (MWD) were 5.38×105g•mol-1, 201.9 nm, 1.18×10-2 mol mL g-2 and 1.07, respectively by MALLS when KGM concentration was 1 mg mL-1. RI with GPC was used to determine MW and MWD of five different concentration of KGM aqueous solution. MW varied from 7.46×105 to 6.34×105 g•mol-1 when KGM concentration ranged from 0.05 to1.00 mg mL-1, but MWD was all about 1.06. Mark-Houwink equation was established as η=5.19×10-3 MW 0.92. The morphology of konjac glucomannan was observed by atomic force microscope (AFM), transmission electron microscope (TEM) and scanning electron microscope (SEM). The image showed that KGM in aqueous solution was displayed with reticulation. The results obtained show that KGM in aqueous solution is displayed with reticulation; molecular chain is rigid; molecular scale increases with decreasing KGM concentration in aqueous solution.

Application of the Monte Carlo simulation method to the Investigation of the effect of chain-length-dependent bimolecular termination on ATRP

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohammad Najafi ◽  
Vahid Haddadi-Asl ◽  
Mehdi Salami-Kalajahi ◽  
Hossein Roughani Mamaghani
Keyword(s):  
Molecular Weight ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Reaction Time ◽  
Chain Length ◽  
Molecular Weight Distribution ◽  
Rate Constant ◽  
Weight Distribution ◽  
Polymer Chains ◽  
Termination Rate

AbstractAn optimized and high-performance Monte Carlo simulation is developed to take thorough account of the influence of chain-length-dependent termination rate constant on polymer microstructure in ATRP. According to the simulation results, bimolecular termination rate constant sharply drops throughout the polymerization when chain length dependency is applied to the program. The dependence of on reaction time, as a common feature of ATRP, is almost linear. Moreover, the polymerization proceeds to higher conversion when the chain-length-dependent termination rate constant is applied to the simulation model. In addition, the plot of against reaction time is completely linear; also, the initiator is entirely decomposed at the early stages of the polymerization as the plot of CIagainst time shows. The concentration of the catalyst in lower oxidation state decreases first and then plateaus at higher conversion. Furthermore, the amount of Mtn Y/L used in the polymerization is lower when the chain-length-dependent termination rate constant is employed in the simulation. Finally, the peak of molecular weight distribution of polymer chains shifts toward higher molecular weight during the reaction. Besides, the molecular weight distribution broadens at higher conversion. However, the molecular weight distribution of polymer chains produced under conditions of applying chain-lengthdependent termination rate constant is narrower.

Extraction and Partial Purification of Protease from Bilimbi (Averrhoa bilimbi L.)

2013 ◽  
Vol 10 (2) ◽  
pp. 29
Author(s):  
Normah Ismail ◽  
Nur' Ain Mohamad Kharoe
Keyword(s):  
Molecular Weight ◽  
Protein Content ◽  
Ammonium Sulfate ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Protease Activity ◽  
Protein Concentration ◽  
Temperature Stability ◽  
Partial Purification ◽  
Ammonium Sulfate Precipitation

Unripe and ripe bilimbi (Averrhoa bilimbi L.) were ground and the extracted juices were partially purified by ammonium sulfate precipitation at the concentrations of 40 and 60% (w/v). The collected proteases were analysed for pH, temperature stability, storage stability, molecular weight distribution, protein concentration and protein content. Protein content of bilimbi fruit was 0.89 g. Protease activity of both the unripe and ripe fruit were optimum at pH 4 and 40°C when the juice were purified at 40 and 60% ammonium sulfate precipitation. A decreased in protease activity was observed during the seven days of storage at 4°C. Molecular weight distribution indicated that the proteases protein bands fall between IO to 220 kDa. Protein bands were observed at 25, 50 and 160 kDa in both the unripe and ripe bilimbi proteases purified with 40% ammonium sulfate, however, the bands were more intense in those from unripe bilimbi. No protein bands were seen in proteases purified with 60% ammonium sulfate. Protein concentration was higher for proteases extracted with 40% ammonium sulfate at both ripening stages. Thus, purification using 40% ammonium sulfate precipitation could be a successful method to partially purify proteases from bilimbi especially from the unripe stage. 

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