scholarly journals Laccase-Based CLEAs: Chitosan as a Novel Cross-Linking Agent

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Alexandre Arsenault ◽  
Hubert Cabana ◽  
J. Peter Jones
Keyword(s):  
Thermal Degradation ◽  
Specific Activity ◽  
Low Ph ◽  
Cross Linking ◽  
Carbodiimide Hydrochloride ◽  
Formation Conditions ◽  
The Cross ◽  
The Stability ◽  
First Time ◽  
Thermal Stability Of

Laccase from Coriolopsis Polyzona was insolubilized as cross-linked enzyme aggregates (CLEAs) for the first time with chitosan as the cross-linking agent. Concentrations between 0.01 and 1.867 g/L of chitosan were used and between 0.05 and 600 mM of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. The laccase was precipitated using ammonium sulphate and cross-linked simultaneously. Specific activity and thermal stability of these biocatalysts were measured. Activities of up to 737 U/g were obtained when 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) was used as a substrate. Moreover, the stability of these biocatalysts was improved with regards to thermal degradation compared to free laccase when exposed to denaturing conditions of high temperature and low pH. The CLEAs stability against chemical denaturants was also tested but no significant improvement was detected. The total amount of ABTS to be oxidized during thermal degradation by CLEAs and free laccase was calculated and the insolubilized enzymes were reported to oxidize more substrate than free laccase. The formation conditions were analyzed by response surface methodology in order to determine an optimal environment for the production of efficient laccase-based CLEAs using chitosan as the cross-linking agent. After 24 hours of formation at pH 3 and at 4°C without agitation, the CLEAs exhibit the best specific activity.

scholarly journals The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2623
Author(s):  
Monika Wójcik-Bania ◽  
Jakub Matusik
Keyword(s):  
Total Pore Volume ◽  
Cross Linking ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Cross ◽  
Chain Lengths ◽  
First Time ◽  
Substituent Influence ◽  
Benzyl Substituent

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

Some properties of 2-5A binding/nucleolytic activities in gel filtered rabbit reticulocyte lysates

1985 ◽  
Vol 5 (12) ◽  
pp. 1041-1051 ◽  
Author(s):  
Joseph M. Wu ◽  
Stanley J. Wertheimer ◽  
Behruz Eslami ◽  
Joanne C. Figuereido ◽  
Biswendu B. Goswami
Keyword(s):  
Binding Activity ◽  
Time Dependent ◽  
Cross Linking ◽  
Elution Profile ◽  
Viral Mrna ◽  
Reticulocyte Lysates ◽  
Atp Analogs ◽  
The Cross ◽  
The Stability

Rabbit reticulocyte lysates, gel filtered on Sephadex G-25 with or without ATP (or its analogs), were preincubated at 37°C and their subsequent binding to p3A4,3′-[32P]pCp was studied. Lysates filtered without ATP or in the presence of 0.1 mM 8-bromo-ATP, 1,N6-etheno-ATP, or ITP showed a time-dependent decrease in binding activity. This decrease was completely prevented when lysates were filtered with 0.1 mM ATP, 2′-deoxy-ATP, β-γ-methylene-ATP, or ATP-γ-S. The stability of binding provided by ATP or 2′-deoxy-ATP analogs corresponds to a more active 2–5A dependent endonucleolytic (RNAase L) activity based on studies using [3H] viral mRNA. Chromatography on heparin-agarose showed that ATP-supplemented gel-filtered reticulocyte lysates had a different p3A4,3′-[32P]pCp binding activity elution-profile than lysates gel-filtered in the absence of ATP. Covalent cross-linking of periodate-oxidized p3A4,3′-[32P]pC to gelfiltered lysates, preincubated at 0°C or 37°C for 30 min, showed the following results: (1) all lysates gave a major cross-linking of the radioactive ligand to an 80 000 dalton polypeptide, regardless of the temperature of preincubation, (2) Iysates gel-filtered without ATP, with 0.1 mM ITP, or β-γ-methylene-ATP, showed a significant reduction in the cross-linking of the 80 000 dalton protein, after preincubation at 37°C for 30 min. This decrease was accompanied by an increase in the labeling of two smaller polypeptides.

Preparation of Stable Hydrophilic Polyethyleneimine Cross-Linked Graphene Oxide/Titanium Dioxide Membranes for Dye Separation

NANO ◽  
2021 ◽  
pp. 2150008
Author(s):  
Hongwei Liu ◽  
Jinhua Liu ◽  
Jun Li ◽  
Zhanchao Liu ◽  
Weifu Wu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Titanium Dioxide ◽  
Graphene Oxide ◽  
Water Flux ◽  
Cross Linking ◽  
Sunset Yellow ◽  
Water Contact ◽  
Static Water ◽  
The Cross ◽  
The Stability

An excellent novel laminar and hierarchical polyethyleneimine cross-linked graphene oxide/titanium dioxide (GO–TiO2–PEI) membrane was successfully prepared by vacuum filtration technology using polyethyleneimine (PEI) as the cross-linking agent and a GO–TiO2 nanocomposite as the substrate. The resultant membrane (GO–TiO2–PEI) displayed a favorable antifouling performance with bovine serum albumin (BSA) and showed good hydrophilicity and wettability, with a static water contact angle of 13.2∘. The stability of the GO–TiO2–PEI membrane in aqueous solution obviously improved with the cross-linking of PEI compared with that of the GO and GO–TiO2 membranes. The GO–TiO2–PEI membrane also exhibited a satisfactory water flux of 48.6[Formula: see text]L m[Formula: see text] h[Formula: see text] bar[Formula: see text]. The GO–TiO2–PEI membrane exhibited a good performance for effectively separating different dyes including methylene blue (MB), rhodamine B (RB), methyl orange (MO), sunset yellow (SY), new coccine (NC) and amaranth. All the above results suggested that the GO–TiO2–PEI membrane could be used as an excellent stable hydrophilic membrane for efficiently separating dyes from aqueous solution.

Characterization of Thermal Reversible Cross-Linking Agents for Flexible Poly(vinyl chloride)

2014 ◽  
Vol 900 ◽  
pp. 3-6 ◽  
Author(s):  
Jing Wang ◽  
Wei Fang ◽  
Yuan Yuan ◽  
Xiao Ming Liu
Keyword(s):  
Thermal Stability ◽  
Vinyl Chloride ◽  
Congo Red ◽  
Cross Linking ◽  
Gel Content ◽  
Ethyl Mercaptan ◽  
Poly Vinyl Chloride ◽  
The Cross ◽  
Thermal Stability Of

In order to improve thermal stability of Poly (Vinyl Chloride), a kind of thermal reversible cross-linking agents, the end cyclopentadienyl ethanethiol salts, sodium cyclopentadienyl ethyl mercaptan (CPD-C2H4SNa) was synthesized in this paper. The DSC results proved that the prepared CPD-C2H4SNa has obvious thermal reversible characteristics and the thermal reversible temperature was at 177 °C. The effects of cross-linking agent amount, cross-linking reactive time and temperature on flexible PVC compounds were evaluated through gel content testing. It was showed that the cross-linking agent with 3 Phr is optimum for PVC compounds. Moreover, both the cross-linking reactive time and temperature has effects on gel content of PVC compounds. The gel content of CPD-C2H4SNa cross-linked PVC compounds reaches maximum at 76% for 20 min at 160 °C.The static thermal stability of flexible PVC was measured according to congo red method. The results showed that the thermal stability of PVC compounds was enhanced with increasing cross-linking agent amount.

scholarly journals Stability of the Cross Linking Component of the Biosensor Receptor Layer after Addition of Gold Nanoparticles

2021 ◽  
Vol 25 (1) ◽  
pp. 49-52
Author(s):  
Aleksandra Kłos-Witkowska ◽  
Vasyl Martsenyuk
Keyword(s):  
Gold Nanoparticles ◽  
Conformational Changes ◽  
Cross Linking ◽  
Relative Percentage ◽  
Pure Protein ◽  
The Cross ◽  
The Stability ◽  
Changes Over Time ◽  
Over Time ◽  
Receptor Layer

In this study, the stability of the receptor layer component of a biosensor after addition of gold nanoparticles was investigated. Accelerated conformational changes under the influence of Au were demonstrated. The relative percentage changes over time between the pure protein and the Au doped protein were calculated. It was shown that these changes are greater with time and exceed 20 % in the last days of the experiment.

A Hydroxyapatite-Collagen Composite Useful to Make Bioresorbable Scaffolds for Bone Reconstruction

2010 ◽  
Vol 76 ◽  
pp. 133-138 ◽  
Author(s):  
Giulio D. Guerra ◽  
Caterina Cristallini ◽  
Elisabetta Rosellini ◽  
Niccoletta Barbani
Keyword(s):  
Weight Ratio ◽  
Average Diameter ◽  
Cross Linking ◽  
Bone Reconstruction ◽  
Scanning Calorimetry ◽  
Bioresorbable Scaffolds ◽  
Micro Particles ◽  
Ft Ir ◽  
The Cross ◽  
The Stability

Composites between hydroxyapatite (HA) and collagen (Col) may be used to make bioresorbable scaffolds for bone reconstruction. A suspension of micro-particles (average diameter ≅ 30 µm) of HA annealed at 1100°C in Col solution (80:20 HA to Col weight ratio) was manufactured in films by casting, and then some films were cross-linked by glutaraldehyde vapours. Cross-linked sponges were obtained by treating the suspension with transglutaminase, and by lyophilizing the so obtained gel. Characterization by scanning electron microscopy, water sorption test, Col release in water, thermogravimetric analysis and differential scanning calorimetry shows that the cross-linking enhances the stability of the composite. Conversely, neither the interactions between HA and Col, detected by spotlight FT-IR, nor the degradation by collagenase, which is a requirement for the bioresorbibility, are affected by the cross-linking.

scholarly journals Enhancing the stability of organolead halide perovskite films through polymer encapsulation

RSC Advances ◽  
2017 ◽  
Vol 7 (52) ◽  
pp. 32942-32951 ◽  
Author(s):  
Barry McKenna ◽  
Joel R. Troughton ◽  
Trystan M. Watson ◽  
Rachel C. Evans
Keyword(s):  
Thermal Stability ◽  
Thermal Degradation ◽  
Early Onset ◽  
Epifluorescence Microscopy ◽  
Polymer Encapsulation ◽  
Halide Perovskite ◽  
The Stability ◽  
Organolead Halide ◽  
Thermal Stability Of ◽  
Insight Into

The ability of different polymer encapsulants to enhance the thermal stability of organolead halide perovskite films has been investigated. Epifluorescence microscopy provides crucial insight into early onset thermal degradation.

Elasticity of networks with permanent and thermoreversible cross-links

2009 ◽  
Vol 1234 ◽  
Author(s):  
Jack F. Douglas
Keyword(s):  
Elastic Properties ◽  
Cross Linking ◽  
Simplified Models ◽  
Flexible Chain ◽  
Fiber Networks ◽  
Cross Links ◽  
The Cross ◽  
The Stability

AbstractSimplified models of flexible chain and stiff fiber networks are introduced to address how the network elasticity becomes modified when the cross-linking is thermoreversible in nature and changes in the stability of the network with deformation. These idealized models apparently able to capture many aspects of the elastic properties of real networks.

In(NO3)3 catalyzed curing reaction of benzoxazine

2020 ◽  
Vol 32 (6) ◽  
pp. 702-709 ◽  
Author(s):  
Xin Zhang ◽  
Weihong Hu ◽  
Li Pei ◽  
Sipei Zhao ◽  
Congyun Zhang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Char Yield ◽  
Curing Temperature ◽  
Cross Linking ◽  
Bridge Structure ◽  
Curing Reaction ◽  
Thermoset Resin ◽  
Coordination Bonding ◽  
First Time ◽  
Thermal Stability Of

Benzoxazine is a new kind of thermoset resin with excellent properties, but it suffers from high curing temperature and low char yield in the presence of catalyst without halogen. In(NO3)3 was herein used for the first time to efficiently catalyze the curing reaction of benzoxazine and to elevate the char yield at 800°C. The reaction of benzoxazine was catalyzed by In(NO3)3 after stirring at 35°C for 300 min, and the initial curing temperature decreased to 151°C. Polybenzoxazine/In(NO3)3 showed higher thermal stability and char yield at 800°C (increased by 7.5%) compared with those of polybenzoxazine. The possible pathway of coordination bonding between In3+ and benzoxazine was proposed. In the cross-linking process, two different structures, that is, the N, O-acetal bridge structure and arylamine Mannich bridge structure formed at 35°C, both existed, which ultimately affected the thermal stability of the cured product.

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