Interstrand cross-linking of duplex DNA by nitrous acid: covalent structure of the dG-to-dG cross-link at the sequence 5'-CG

1992 ◽  
Vol 114 (11) ◽  
pp. 4021-4027 ◽  
Author(s):  
James J. Kirchner ◽  
Snorri T. Sigurdsson ◽  
Paul B. Hopkins
Keyword(s):  
Nitrous Acid ◽  
Cross Linking ◽  
Duplex Dna ◽  
Cross Link ◽  
Covalent Structure

EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

2016 ◽  
Vol 89 (4) ◽  
pp. 671-688 ◽  
Author(s):  
M. A. L. Verbruggen ◽  
L. van der Does ◽  
W. K. Dierkes ◽  
J. W. M. Noordermeer
Keyword(s):  
Experimental Validation ◽  
Main Chain ◽  
Sol Gel ◽  
Chain Scission ◽  
Cross Linking ◽  
Cross Link ◽  
Practical Reality ◽  
Cross Links ◽  
The Cross ◽  
Theoretical Considerations

ABSTRACT The theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

scholarly journals N 1 N 8-bis(γ-glutamyl)spermidine cross-linking in epidermal-cell envelopes. Comparison of cross-link levels in normal and psoriatic cell envelopes

1990 ◽  
Vol 271 (2) ◽  
pp. 305-308 ◽  
Author(s):  
N Martinet ◽  
S Beninati ◽  
T P Nigra ◽  
J E Folk
Keyword(s):  
Epidermal Cell ◽  
Skin Disease ◽  
Envelope Protein ◽  
Cell Envelope ◽  
Human Epidermis ◽  
Cross Linking ◽  
Cross Link ◽  
Gamma Glutamyl ◽  
Cell Envelopes ◽  
Isolated Cell

N1N8-Bis(gamma-glutamyl)spermidine was found in exhaustive proteolytic digests of isolated cell envelopes from human epidermis at levels comparable with those of epsilon-(gamma-glutamyl)lysine. Significantly higher than normal amounts of these compounds, particularly the bis(gamma-glutamyl)polyamine, were observed in envelopes from afflicted areas (scales) of psoriatic patients. These findings support the notions that N1N8-bis(gamma-glutamyl)spermidine, like epsilon-(gamma-glutamyl)lysine, functions in cell envelopes as an enzyme-generated protein cross-link and stabilizing force and that individuals with the chronic, recurrent skin disease, psoriasis, exhibit in involved epidermis abnormal cell-envelope-protein cross-linking.

scholarly journals Viscometric analysis of the gelation of Acanthamoeba extracts and purification of two gelation factors.

1980 ◽  
Vol 85 (2) ◽  
pp. 414-428 ◽  
Author(s):  
S D MacLean-Fletcher ◽  
T D Pollard
Keyword(s):  
Crude Extract ◽  
Cross Linking ◽  
Cross Link ◽  
Gelation Process ◽  
Optimum Ph ◽  
Kinetics Of ◽  
Low Shear

We have studied the kinetics of the gelation process that occurs upon warming cold extracts of Acanthamoeba using a low-shear falling ball assay. We find that the reaction has at least two steps, requires 0.5 mM ATP and 1.5 mM MgCl2, and is inhibited by micromolar Ca++. The optimum pH is 7.0 and temperature, 25 degrees-30 degrees C. The rate of the reaction is increased by cold preincubation with both MgCl2 and ATP. Nonhydrolyzable analogues of ATP will not substitute for ATP either in this "potentiation reaction" or in the gelation process. Either of two purified or any one of four partially purified Acanthamoeba proteins will cross-link purified actin to form a gel, but none can account for the dependence of the reaction in the crude extract on Mg-ATP or its regulation by Ca++. This suggests that the extract contains, in addition to actin-cross-linking proteins, factors dependent on Mg-ATP and Ca++ that regulate the gelation process.

Mechanical and structural consequences of associative dynamic cross-linking in acrylic diblock copolymers

2021 ◽  
Author(s):  
Jacob Ishibashi ◽  
Ian Pierce ◽  
Alice Chang ◽  
Aristotelis Zografos ◽  
Bassil El-Zaatari ◽  
...  
Keyword(s):  
Viscoelastic Properties ◽  
Diblock Copolymers ◽  
Microphase Separation ◽  
Network Connectivity ◽  
Ethyl Acrylate ◽  
Cross Linking ◽  
Cross Link ◽  
Block Polymers ◽  
Link Density ◽  
Cross Link Density

<p>The composition of low-T<sub>g</sub> <i>n</i>-butylacrylate-<i>block</i>-(acetoxyaceto)ethyl acrylate block polymers is investigated as a strategy to tune the properties of dynamically cross-linked vinylogous urethane vitrimers. As the proportion of the cross-linkable block is increased, the thermorheological properties, structure, and stress relaxation evolve in ways that cannot be explained by increasing cross-link density alone. Evidence is presented that network connectivity defects such as loops and dangling ends are increased by microphase separation. The thermomechanical and viscoelastic properties of block copolymer-derived vitrimers arise from the subtle interplay of microphase separation and network defects.</p><div><br></div><p></p>

Synthesis of amorphous low Tg polyesters with multiple COOH side groups and their utilization for elastomeric vitrimers based on post-polymerization cross-linking

2019 ◽  
Vol 10 (16) ◽  
pp. 2047-2056 ◽  
Author(s):  
Mikihiro Hayashi ◽  
Ryoto Yano ◽  
Akinori Takasu
Keyword(s):  
Cross Linking ◽  
Cross Link

Elastomeric vitrimer materials with tunable cross-link densities are prepared using cross-linking precursor polyesters with multiple COOH side groups in the presence of diepoxy cross-linkers and trans-esterification catalysts.

scholarly journals RanGTP induces an effector gradient of XCTK2 and importin α/β for spindle microtubule cross-linking

2019 ◽  
Author(s):  
Stephanie C. Ems-McClung ◽  
Mackenzie Emch ◽  
Stephanie Zhang ◽  
Serena Mahnoor ◽  
Lesley N. Weaver ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Spindle Assembly ◽  
Cross Linking ◽  
Tail Domain ◽  
Inhibitory Effects ◽  
Cross Link ◽  
Spindle Microtubule ◽  
Spindle Poles ◽  
Importin Α ◽  
Combined Actions

AbstractHigh RanGTP around chromatin is important for governing spindle assembly during meiosis and mitosis by releasing the inhibitory effects of importin α/β. Here we examine how the Ran gradient regulates Kinesin-14 function to control spindle organization. We show that Xenopus Kinesin-14, XCTK2, and importin α/β form an effector gradient, which is highest at the poles that diminishes toward the chromatin and is inverse of the RanGTP gradient. Importin α/β preferentially inhibit XCTK2 anti-parallel microtubule cross-linking and sliding by decreasing the microtubule affinity of the XCTK2 tail domain. This change in microtubule affinity enables RanGTP to target endogenous XCTK2 to the spindle. We propose that these combined actions of the Ran pathway are critical to promote Kinesin-14 parallel microtubule cross-linking at the spindle poles to cluster centrosomes in cancer cells. Furthermore, our work illustrates that RanGTP regulation in the spindle is not simply a switch, but rather generates effector gradients where RanGTP gradually tunes the activities of spindle assembly factors.SummaryEms-McClung et al. visualize a RanGTP effector gradient of association between XCTK2 and importin α/β in the spindle. The importins preferentially inhibit XCTK2-mediate anti-parallel microtubule cross-linking and sliding, which allows XCTK2 to cross-link parallel microtubules and help focus spindle poles.

Chemical Synthesis and Preliminary Structural Characterization of a Nitrous Acid Interstrand Cross-Linked Duplex DNA

1999 ◽  
Vol 121 (21) ◽  
pp. 5081-5082 ◽  
Author(s):  
Eric A. Harwood ◽  
Snorri Th. Sigurdsson ◽  
N. B. Fredrik Edfeldt ◽  
Brian R. Reid ◽  
Paul B. Hopkins
Keyword(s):  
Chemical Synthesis ◽  
Structural Characterization ◽  
Nitrous Acid ◽  
Duplex Dna

scholarly journals Spontaneous Cross-link of Mutated α1 Subunits during GABAA Receptor Assembly

2006 ◽  
Vol 282 (7) ◽  
pp. 4354-4363 ◽  
Author(s):  
Isabella Sarto-Jackson ◽  
Roman Furtmueller ◽  
Margot Ernst ◽  
Sigismund Huck ◽  
Werner Sieghart
Keyword(s):  
Disulfide Bonds ◽  
Early Stage ◽  
Cross Linking ◽  
Cross Link ◽  
Chloride Currents ◽  
Assembly Mechanism ◽  
Acid Type ◽  
Starting Point ◽  
Separate Pathway ◽  
Receptor Assembly

γ-Aminobutyric acid, type A (GABAA) receptor α1 subunits containing a cysteine mutation at a position in the channel mouth (H109C) surprisingly formed a spontaneous cross-link with each other in receptors composed of α1H109C, β3, and γ2 subunits. Cross-linking of two α1H109C subunits did not significantly change the affinity of [3H]muscimol or [3H]Ro15-1788 binding in α1H109Cβ3γ2 receptors, but GABA displayed a reduced potency for activating chloride currents. On reduction of the disulfide bond, however, GABA activation as well as diazepam modulation was similar in mutated and wild-type receptors, suggesting that these receptors exhibited the same subunit stoichiometry and arrangement. Disulfide bonds could not be reoxidized by copper phenanthroline after having been reduced in completely assembled receptors, suggesting that cross-linking can only occur at an early stage of assembly. The cross-link of α1H109C subunits and the subsequent transport of the resulting homodimers to the cell surface caused a reduction of the intracellular pool of α1H109C subunits and a reduced formation of completely assembled receptors. The formation of α1H109C homodimers as well as of correctly assembled GABAA receptors containing cross-linked α1H109C subunits could indicate that homodimerization of α1 subunits via contacts located in the channel mouth might be one starting point of GABAA receptor assembly. Alternatively the assembly mechanism might have started with the formation of heterodimers followed by a cross-link of mutated α1 subunits at the heterotrimeric stage. The formation of cross-linked α1H109C homodimers would then have occurred independently in a separate pathway.

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