Room-Temperature Self-Healable and Remoldable Cross-linked Polymer Based on the Dynamic Exchange of Disulfide Bonds

2014 ◽  
Vol 26 (6) ◽  
pp. 2038-2046 ◽  
Author(s):  
Zhou Qiao Lei ◽  
Hong Ping Xiang ◽  
Yong Jian Yuan ◽  
Min Zhi Rong ◽  
Ming Qiu Zhang
Keyword(s):  
Disulfide Bonds ◽  
Room Temperature ◽  
Dynamic Exchange

scholarly journals Self-Healing Photocurable Epoxy/thiol-ene Systems Using an Aromatic Epoxy Resin

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Ricardo Acosta Ortiz ◽  
Omar Acosta Berlanga ◽  
Aída Esmeralda García Valdez ◽  
Rafael Aguirre Flores ◽  
José Guadalupe Télles Padilla ◽  
...  
Keyword(s):  
Disulfide Bonds ◽  
Epoxy Resins ◽  
Room Temperature ◽  
Gel Permeation Chromatography ◽  
Mechanical Analysis ◽  
Hypervalent Iodine ◽  
Self Healing ◽  
Healing Efficiency ◽  
Kinetics Of ◽  
Epoxy Groups

A rapid and efficient method to obtain self-healing epoxy resins is discussed. This method is based on the use of a thiol-disulfide oligomer obtained by partial oxidation of a multifunctional thiol using a hypervalent iodine (III) compound as oxidant. The oligomer was characterized by Fourier transform infrared spectroscopy (FTIR), Raman and nuclear magnetic resonance spectroscopies, and gel permeation chromatography (GPC). The oligomer was a joint component of the thiol-ene system along with a tetra-allyl-functionalized curing agent. The kinetics of the photopolymerization of diglycidylether of bisphenol A (DGEBA) revealed that conversions of the epoxy groups as high as 80% were achieved in only 15 minutes by increasing the concentration of the thiol-ene system in the formulation. The disulfide bonds introduced in the copolymer using the thiol-disulfide oligomer allowed the repairing of the test specimens in as little as 10 minutes when the specimens were heated at 80°C or for 500 minutes at room temperature. The analysis of the mechanical properties using dynamic mechanical analysis (DMA) showed that the specimens displayed a healing efficiency up to 111% compared with the unhealed specimens, depending on the amount of polythioethers present in the copolymer.

Programmable actuation of liquid crystal elastomers via “living” exchange reaction

Soft Matter ◽  
2019 ◽  
Vol 15 (13) ◽  
pp. 2811-2816 ◽  
Author(s):  
Zhijian Wang ◽  
Qiguang He ◽  
Yang Wang ◽  
Shengqiang Cai
Keyword(s):  
Liquid Crystal ◽  
Exchange Reaction ◽  
Disulfide Bonds ◽  
Room Temperature ◽  
Programming Method ◽  
Liquid Crystal Elastomers

We report a facile room-temperature mechanical programming method of liquid crystal elastomers via the “living” exchange reaction of disulfide bonds.

Accelerating dynamic exchange and self-healing using mechanical forces in crosslinked polymers

2020 ◽  
Vol 7 (6) ◽  
pp. 1581-1587 ◽  
Author(s):  
Nethmi De Alwis Watuthanthrige ◽  
Ballal Ahammed ◽  
Madison T. Dolan ◽  
Qinghua Fang ◽  
Jian Wu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Mechanical Forces ◽  
Self Healing ◽  
Ambient Conditions ◽  
Crosslinked Polymers ◽  
Dynamic Exchange

Surprisingly, a few seconds–minutes of compression at room temperature can increase the rate of dynamic bond exchange as measured by better self-healing, even for thermoresponsive dynamic bonds which do not exchange under ambient conditions.

A user's guide to the thiol-thioester exchange in organic media: scope, limitations, and applications in material science

2018 ◽  
Vol 9 (36) ◽  
pp. 4523-4534 ◽  
Author(s):  
Brady T. Worrell ◽  
Sudheendran Mavila ◽  
Chen Wang ◽  
Taylor M. Kontour ◽  
Chern-Hooi Lim ◽  
...  
Keyword(s):  
Material Science ◽  
Room Temperature ◽  
Organic Media ◽  
Crosslinked Polymers ◽  
Thioester Exchange ◽  
Dynamic Exchange

The dynamic exchange of thiols and thioesters in organic media was explored, leading to room temperature plasticity in crosslinked polymers.

The structure of the Pfp1 protease from the hyperthermophilic archaeonThermococcus thioreducensin two crystal forms

2017 ◽  
Vol 73 (9) ◽  
pp. 749-756 ◽  
Author(s):  
Steven B. Larson ◽  
Alexander McPherson
Keyword(s):  
Active Site ◽  
Disulfide Bonds ◽  
Room Temperature ◽  
Search Model ◽  
Molecular Replacement ◽  
Pyrococcus Horikoshii ◽  
Crystal Forms ◽  
X Ray ◽  
Laboratory Source ◽  
Intermolecular Disulfide Bonds

The Pfp1 protease, a cysteine protease of unknown specificity from the hyperthermophilic archaeonThermococcus thioreducens, was crystallized in two distinctive crystal forms: from concentrated citrate in one case and PEG in the other. X-ray data were collected from both crystal forms at room temperature to about 1.9 Å resolution using a laboratory source and detector, and the structures were solved by molecular replacement using the Pfp1 protease fromPyrococcus horikoshiias the search model. In theT. thioreducensprotease structures, Cys18 residues on adjacent molecules in the asymmetric units form intermolecular disulfide bonds, thereby yielding hexamers composed of three cross-linked, quasi-dyad-related dimers with crystallographically exact threefold axes and exhibiting almost exact 32 symmetry. The corresponding residue inP. horikoshiiPfp1 is Tyr18. An individual active site containing Cys100 and His101 also includes a Glu74 residue contributed by a quasi-twofold-related, non-cross-linked subunit. Two catalytic triads are therefore closely juxtaposed about the quasi-twofold axis at the interface of these subunits, and are relatively sequestered within the hexamer cavity. The cysteine in the active site is observed to be oxidized in both of the crystal forms that were studied.

scholarly journals Anopheles gambiae TEP1 forms a complex with the coiled-coil domain of LRIM1/APL1C following a conformational change in the thioester domain

2019 ◽  
Author(s):  
Marni Williams ◽  
Alicia Contet ◽  
Elena A. Levashina ◽  
Richard H. G. Baxter
Keyword(s):  
Immune Response ◽  
Anopheles Gambiae ◽  
Conformational Change ◽  
Disulfide Bonds ◽  
Room Temperature ◽  
Coiled Coil ◽  
Sub Saharan Africa ◽  
Coiled Coil Domain ◽  
Wide Range ◽  
The Stability

AbstractThe complement-like protein thioester-containing protein 1 (TEP1) is a key factor in the immune response of the malaria vector Anopheles gambiae to pathogens. Multiple allelic variants of TEP1 have been identified in laboratory strains and in the field, and are correlated with distinct immunophenotypes. TEP1 is tightly regulated by conformational changes induced by cleavage in a protease-sensitive region. Cleaved TEP1 forms a soluble complex with a heterodimer of two leucine-rich repeat proteins, LRIM1 and APL1C, and precipitates in the absence of this complex. The molecular structure and oligomeric state of the TEP1/LRIM1/APL1C complex is unclear. We have analyzed the stability of the cleaved form of four TEP1 alleles. Soluble TEP1 forms exhibit significant variation in stability from hours to days at room temperature. Stability is correlated with allelic variation within two specific loops in direct proximity to the thioester bond. The variable loops are part of an interface between the TED and MG8 domains TEP1 that protect the thioester from hydrolysis. Engineering specific disulfide bonds to prevent separation of the TED-MG8 interface stabilizes the cleaved form of TEP1 for months at room temperature. The C-terminal coiled-coil domain of the LRIM1/APL1C complex is sufficient to stabilize the cleaved form of TEP1 in solution but cleaved forms of disulfide-stabilized TEP1 do not interact with LRIM1/APL1C. This implies that formation of the TEP1cut/LRIM1/APL1C complex is dependent on the same conformational change that induces the precipitation of cleaved TEP1.Author SummaryThe mosquito Anopheles gambiae is the principal vector for malaria in Sub-Saharan Africa. A mosquito’s own immune system affects how readily it transmits disease. A protein in A. gambiae called TEP1 is responsible for targeting malaria parasites that traverse the mosquito’s midgut. TEP1 has multiple alleles and some are associated with a stronger immune response to malaria than others. How genetic variability in TEP1 is linked to phenotypic diversity is not understood. We show that the variation between TEP1 alleles affects the stability of the protein in solution. We also show that the different TEP1 alleles have a wide range in stability of the protein, from hours to days. Engineering disulfide bonds into TEP1 can increase this stability to months. TEP1 activity in vivo is maintained by a complex of two leucine-rich proteins called LRIM1 and APL1C, which binds TEP1 through its C-terminal coiled-coil domain. We found that LRIM1/APL1C does not bind disulfide-stabilized TEP1, suggesting that LRIM1/APL1C binds to activated TEP1. This research advances our molecular understanding of a key immune response that affects the capacity of A. gambiae mosquitoes to transmit malaria.

scholarly journals Zn Complex of Diaminedithiol Tetradentate Ligand as a Stable Precursor for 99mTc-Labeled Compounds

Molecules ◽  
2020 ◽  
Vol 25 (2) ◽  
pp. 254
Author(s):  
Shinobu Oshikiri ◽  
Tomoya Uehara ◽  
Hiroyuki Suzuki ◽  
Miho Koike-Satake ◽  
Akihiro Hino ◽  
...  
Keyword(s):  
Disulfide Bonds ◽  
Room Temperature ◽  
Ethylenediaminetetraacetic Acid ◽  
Simple Procedure ◽  
Tetradentate Ligand ◽  
Labeled Compounds ◽  
Igg Antibody ◽  
One Pot ◽  
Radiochemical Yields

The diaminedithiol (N2S2) tetradentate ligand constitutes a useful chelating molecule for preparing 99mTc-labeled compounds of high in vivo stability in high radiochemical yields. However, since the thiol groups in the N2S2 ligand are easy to be oxidized to disulfide bonds, they need to be protected with an appropriate protecting group, which hinders the broad applications of the N2S2 ligand for radiopharmaceuticals. In this study, a Zn chelate of N2S2 was evaluated as a precursor for purification-free 99mTc-labeled N2S2 under the mild and simple procedure. Zn-N2S2 was prepared by reacting Zn acetate with N2S2, and the Zn-N2S2 remained stable under aerobic conditions at room temperature. 99mTc-N2S2 was obtained over 90% radiochemical yields at room temperature by a one-pot reaction, consisting of Zn-N2S2 (10−5 M), 99mTcO4−, ethylenediaminetetraacetic acid (EDTA), and a reducing agent (Sn2+) at pH = 5.5 to 7.5. 99mTc-N2S2 was also obtained over 90% radiochemical yields when the reaction was conducted in the presence of an equimolar amount of IgG antibody. These findings indicate the Zn complex of N2S2 ligand constitutes a stable and useful precursor to prepare 99mTc-labeled N2S2 compounds in high yields under the mild and simple procedure.

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Hepatocyte Alterations in Guinea Pigs FED Polychlorinated Biphenyls (PCBs), Dibenzodioxins (PCDD), AND DIBENZOFURANS (PCDF)

1982 ◽  
Vol 40 ◽  
pp. 56-57
Author(s):  
J. N. Turner ◽  
D. N. Collins
Keyword(s):  
Guinea Pigs ◽  
Room Temperature ◽  
Dose Group ◽  
Methyl Cellulose ◽  
Uranyl Acetate ◽  
Target Organ ◽  
Office Building ◽  
Lead Citrate ◽  
Control Groups ◽  
Cooling Fluid

A fire involving an electric service transformer and its cooling fluid, a mixture of PCBs and chlorinated benzenes, contaminated an office building with a fine soot. Chemical analysis showed PCDDs and PCDFs including the highly toxic tetra isomers. Guinea pigs were chosen as an experimental animal to test the soot's toxicity because of their sensitivity to these compounds, and the liver was examined because it is a target organ. The soot was suspended in 0.75% methyl cellulose and administered in a single dose by gavage at levels of 1,10,100, and 500mgm soot/kgm body weight. Each dose group was composed of 6 males and 6 females. Control groups included 12 (6 male, 6 female) animals fed activated carbon in methyl cellulose, 6 males fed methyl cellulose, and 16 males and 10 females untreated. The guinea pigs were sacrificed at 42 days by suffocation in CO2. Liver samples were immediately immersed and minced in 2% gluteraldehyde in cacadylate buffer at pH 7.4 and 4°C. After overnight fixation, samples were postfixed in 1% OsO4 in cacodylate for 1 hr at room temperature, embedded in epon, sectioned and stained with uranyl acetate and lead citrate.

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