One of the key features required for the exceptional properties of this durable biopolymer is the extensive covalent cross-linking between domains of its monomer molecule tropoelastin. Here, using bovine elastin, we investigated the different types of cross-links in mature elastin to gain insight into its structure.
We purified and proteolytically cleaved elastin from a single tissue sample into soluble cross-linked and non-cross-linked peptides that we studied by high-resolution MS. This analysis enabled the elucidation of cross-links and other elastin modifications. We found that the lysine residues within the tropoelastin sequence were simultaneously unmodified and involved in various types of cross-links with different other domains.
The Lys-Pro domains were almost exclusively linked via lysinonorleucine, whereas Lys-Ala domains were found to be cross-linked via lysinonorleucine, allysine aldol, and desmosine. Unexpectedly, we identified a high number of intramolecular cross-links between lysine residues in close proximity. For permission for commercial use of this work, please see paragraphs 4.
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Compromised collagen in the cornea, a condition known as keratoconus , can be treated with clinical crosslinking. In biological context crosslinking could play a role in atheroscelerosis through AGEs which have been implicated to induce crosslinking of collagen which may lead to vascular stiffening. The interactions or mere proximity of proteins can be studied by the clever use of crosslinking agents. For example, protein A and protein B may be very close to each other in a cell, and a chemical crosslinker  could be used to probe the protein—protein interaction between these two proteins by linking them together, disrupting the cell, and looking for the crosslinked proteins.
A variety of crosslinkers are used to analyze subunit structure of proteins , protein interactions , and various parameters of protein function by using differing crosslinkers, often with diverse spacer arm lengths. Subunit structure is deduced, since crosslinkers bind only surface residues in relatively close proximity in the native state.
Protein interactions are often too weak or transient to be easily detected, but by crosslinking, the interactions can be stabilized, captured, and analyzed. Examples of some common crosslinkers are the imidoester crosslinker dimethyl suberimidate, the N-Hydroxysuccinimide -ester crosslinker BS3 and formaldehyde. Each of these crosslinkers induces nucleophilic attack of the amino group of lysine and subsequent covalent bonding via the crosslinker. The zero-length carbodiimide crosslinker EDC functions by converting carboxyls into amine-reactive isourea intermediates that bind to lysine residues or other available primary amines.
In-vitro cross-linking method, termed PICUP photo-induced cross-linking of unmodified proteins , was developed in In-vivo crosslinking of protein complexes using photo-reactive amino acid analogs was introduced in by researchers from the Max Planck Institute of Molecular Cell Biology and Genetics. Synthetically crosslinked polymers have many uses, including those in the biological sciences, such as applications in forming polyacrylamide gels for gel electrophoresis.
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Synthetic rubber used for tires is made by crosslinking rubber through the process of vulcanization. This crosslinking makes them more elastic. Hard-shell kayaks are also often manufactured with crosslinked polymers. Other examples of polymers that can be crosslinked are ethylene-vinyl acetate —as used in solar panel manufacturing  — and polyethylene. Alkyd enamels, the dominant type of commercial oil-based paint, cure by oxidative crosslinking after exposure to air.https://rikonn.biz/wp-content/2020-09-16/cellular-line-bumper-satin-iphone.php
What is cross-linking?
In many hydraulic fracturing treatments, a delayed gel-cross-linker fluid is used to carry out fracture treatment of the rock. The earliest examples of crosslinking, linking long chains of polymers together to increase strength and mass, involved tires. Rubber was vulcanized with sulfur under heat, which created a link between latex models. Novel uses for crosslinking can be found in regenerative medicine, where bio-scaffolds are crosslinked to improve their mechanical properties.
Crosslinking is often measured by swelling tests.
Cross-Linked Information Resources (CLIR)
The crosslinked sample is placed into a good solvent at a specific temperature, and either the change in mass or the change in volume is measured. The more crosslinking, the less swelling is attainable. Based on the degree of swelling, the Flory Interaction Parameter which relates the solvent interaction with the sample , and the density of the solvent, the theoretical degree of crosslinking can be calculated according to Flory's Network Theory.
In ASTM D, the sample is weighed, then placed in a solvent for 24 hours, weighed again while swollen, then dried and weighed a final time. In another ASTM standard, F, the sample is placed in an instrument that measures the height change in the sample, allowing the user to measure the volume change. From Wikipedia, the free encyclopedia. Bond that links one polymer chain to another. Several terms redirect here.
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IUPAC definition. A small region in a macromolecule from which at least four chains emanate, and formed by reactions involving sites or groups on existing macromolecules or by interactions between existing macromolecules. Notes 1. In the majority of cases, a crosslink is a covalent structure but the term is also used to describe sites of weaker chemical interactions, portions of crystallites, and even physical interactions and entanglements.