Cross-Linking Polymerization in Two-Dimensional Assemblies:  Effect of the Reactive Group Site

1999 ◽  
Vol 32 (17) ◽  
pp. 5519-5524 ◽  
Author(s):  
Sanchao Liu ◽  
David F. O'Brien
Keyword(s):  
Cross Linking ◽  
Two Dimensional ◽  
Reactive Group

scholarly journals Transformation Between 2D and 3D Covalent Organic Frameworks via Reversible [2+2] Cycloaddition

2020 ◽  
Author(s):  
Thaksen Jadhav ◽  
Yuan Fang ◽  
Cheng-Hao Liu ◽  
Afshin Dadvand ◽  
Ehsan Hamzehpoor ◽  
...  
Keyword(s):  
Band Structure ◽  
Absorption Edge ◽  
Room Temperature ◽  
Three Dimensional ◽  
Cross Linking ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Doping Behavior ◽  
2D Polymers ◽  
2D And 3D

We report the first transformation between crystalline vinylene-linked two-dimensional (2D) polymers and crystalline cyclobutane-linked three-dimensional (3D) polymers. Specifically, absorption-edge irradiation of the 2D poly(arylenevinylene) covalent organic frameworks (COFs) results in topological [2+2] cycloaddition cross-linking the π-stacked layers in 3D COFs. The reaction is reversible and heating to 200°C leads to a cycloreversion while retaining the COF crystallinity. The resulting difference in connectivity is manifested in the change of mechanical and electronic properties, including exfoliation, blue-shifted UV-Vis absorption, altered luminescence, modified band structure and different acid-doping behavior. The Li-impregnated 2D and 3D COFs show a significant ion conductivity of 1.8×10<sup>−4</sup> S/cm and 3.5×10<sup>−5</sup> S/cm, respectively. Even higher room temperature proton conductivity of 1.7×10<sup>-2</sup> S/cm and 2.2×10<sup>-3</sup> S/cm was found for H<sub>2</sub>SO<sub>4</sub>-treated 2D and 3D COFs, respectively.

Autophosphorylation of the 16 kDa and 70 kDa antigens (Hsp 16·3 and Hsp 70) of Mycobacterium tuberculosis

Microbiology ◽  
2004 ◽  
Vol 150 (7) ◽  
pp. 2135-2141 ◽  
Author(s):  
Rachel Preneta ◽  
K. G. Papavinasasundaram ◽  
Alain J. Cozzone ◽  
Bertrand Duclos
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Calcium Ions ◽  
Expression System ◽  
Cross Linking ◽  
Molecular Characteristics ◽  
Two Dimensional ◽  
Hsp 70 ◽  
E Coli ◽  
Environmental Variations ◽  
Vertebrate Eye

Several antigens of Mycobacterium tuberculosis, identified by monoclonal antibodies, have been previously cloned and are being exploited in the development of improved vaccines and diagnostic reagents. In this study, the molecular characteristics of two of these antigens, the immunodominant proteins Hsp 16·3 and Hsp 70, were analysed in further detail by assessing their capacity to undergo protein phosphorylation, a chemical modification frequently used by organisms to adjust to environmental variations. Hsp 16·3 was overproduced in an Escherichia coli expression system and purified to homogeneity. Upon incubation in the presence of radioactive ATP, it was shown to possess autophosphorylation activity. Two-dimensional analysis of its phosphoamino acid content revealed that it was modified exclusively at serine residues. In addition, cross-linking experiments demonstrated that it could tightly bind to ATP. Purified Hsp 70 was also shown to autophosphorylate but phosphorylation occurred exclusively at threonine residues. This reaction was found to be strongly stimulated by calcium ions. These data indicate that both structural and functional similarities exist between Hsp 16·3 (Acr) and α-crystallin, a eukaryotic protein which plays an important role in maintaining the transparency of the vertebrate eye, and that the functional properties of Hsp 70 from M. tuberculosis are similar to those of other bacterial members of the Hsp 70 family, particularly the E. coli homologue DnaK.

scholarly journals N,N,N′-Trimethyl-N′′-(4-nitrophenyl)-N′-phenylguanidine

2014 ◽  
Vol 70 (5) ◽  
pp. o516-o517 ◽  
Author(s):  
Ioannis Tiritiris ◽  
Wolfgang Frey ◽  
Willi Kantlehner
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Phenyl Ring ◽  
Cross Linking ◽  
Planar Geometry ◽  
Two Dimensional ◽  
Single Bond ◽  
Compound C ◽  
Dimensional Network ◽  
Bond Character

The C—N bond lengths in the guanidine unit of the title compound, C16H18N4O2, are 1.298 (2), 1.353 (2) and 1.401 (3) Å, indicating double- and single-bond character. The N—C—N angles are 115.81 (16), 118.90 (18) and 125.16 (18)°, showing a deviation of the CN3plane from an ideal trigonal–planar geometry. In the crystal, C—H...O hydrogen bonds are observed between the methyl- and aromatic-H atoms and nitro-O atoms. One H atom of the phenyl ring and of the NMe2group associate with the O atoms of the nitro group, giving chains along thea-andb-axis directions. Cross-linking of these two chains results in a two-dimensional network alongbc.

Photoelectrochemical properties of size-quantized semiconductor photoelectrodes prepared by two-dimensional cross-linking of monodisperse CdS nanoparticles

2000 ◽  
Vol 45 (20) ◽  
pp. 3269-3276 ◽  
Author(s):  
Tsukasa Torimoto ◽  
Naohiro Tsumura ◽  
Hiroshi Nakamura ◽  
Susumu Kuwabata ◽  
Takao Sakata ◽  
...  
Keyword(s):  
Cds Nanoparticles ◽  
Cross Linking ◽  
Photoelectrochemical Properties ◽  
Two Dimensional

scholarly journals Preliminary Characterization of Genipin-Cross-Linked Silk Sericin/Poly(vinyl alcohol) Films as Two-Dimensional Wound Dressings for the Healing of Superficial Wounds

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Tippawan Siritientong ◽  
Juthamas Ratanavaraporn ◽  
Teerapol Srichana ◽  
Pornanong Aramwit
Keyword(s):  
Vinyl Alcohol ◽  
Light Transmission ◽  
Transmission Rate ◽  
Wound Dressings ◽  
Poly Vinyl Alcohol ◽  
Cross Linking ◽  
Two Dimensional ◽  
Silk Sericin ◽  
Superficial Skin

The genipin-cross-linked silk sericin/poly(vinyl alcohol) (PVA) films were developed aiming to be applied as two-dimensional wound dressings for the treatment of superficial wounds. The effects of genipin cross-linking concentration on the physical and biological properties of the films were investigated. The genipin-cross-linked silk sericin/PVA films showed the increased surface density, tensile strength, and percentage of elongation, but decreased percentage of light transmission, water vapor transmission rate, and water swelling, compared to the non-cross-linked films. This explained that the cross-linking bonds between genipin and silk sericin would reduce the mobility of molecular chains within the films, resulting in the more rigid molecular structure. Silk sericin was released from the genipin-cross-linked films in a sustained manner. In addition, either L929 mouse fibroblast or HaCat keratinocyte cells showed high percentage of viability when cultured on the silk sericin/PVA films cross-linked with 0.075 and 0.1% w/v genipin. Thein vivosafety test performed according to ISO 10993-6 confirmed that the genipin-cross-linked silk sericin/PVA films were safe for the medical usages. The efficacy of the films for the treatment of superficial skin wounds will be further investigatedin vivoand clinically. The genipin-cross-linked silk sericin/PVA films would be promising choices of two-dimensional wound dressings for the treatment of superficial wounds.

scholarly journals Transformation Between 2D and 3D Covalent Organic Frameworks via Reversible [2+2] Cycloaddition

2020 ◽  
Author(s):  
Thaksen Jadhav ◽  
Yuan Fang ◽  
Cheng-Hao Liu ◽  
Afshin Dadvand ◽  
Ehsan Hamzehpoor ◽  
...  
Keyword(s):  
Band Structure ◽  
Absorption Edge ◽  
Room Temperature ◽  
Three Dimensional ◽  
Cross Linking ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Doping Behavior ◽  
2D Polymers ◽  
2D And 3D

We report the first transformation between crystalline vinylene-linked two-dimensional (2D) polymers and crystalline cyclobutane-linked three-dimensional (3D) polymers. Specifically, absorption-edge irradiation of the 2D poly(arylenevinylene) covalent organic frameworks (COFs) results in topological [2+2] cycloaddition cross-linking the π-stacked layers in 3D COFs. The reaction is reversible and heating to 200°C leads to a cycloreversion while retaining the COF crystallinity. The resulting difference in connectivity is manifested in the change of mechanical and electronic properties, including exfoliation, blue-shifted UV-Vis absorption, altered luminescence, modified band structure and different acid-doping behavior. The Li-impregnated 2D and 3D COFs show a significant ion conductivity of 1.8×10<sup>−4</sup> S/cm and 3.5×10<sup>−5</sup> S/cm, respectively. Even higher room temperature proton conductivity of 1.7×10<sup>-2</sup> S/cm and 2.2×10<sup>-3</sup> S/cm was found for H<sub>2</sub>SO<sub>4</sub>-treated 2D and 3D COFs, respectively.

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