Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Crosslinking shopping experience:
1. Compare - without doubt the biggest advantage that the Crosslinking offers shoppers today is the ability to compare thousands of Crosslinking at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Crosslinking? Wrong! If the Crosslinking is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Crosslinking then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Crosslinking? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Crosslinking and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Crosslinking wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Crosslinking then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Crosslinking site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Crosslinking, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Crosslinking, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
is an example of cross-linking.
Cross-links are covalent bonds linking one polymer chain to another. They are the characteristic property of thermosetting polymer materials. In biology, cross-linking has applications in forming polyacrylamide gels for
gel electrophoresis and in
protein studies. Crosslinking inhibits close packing of the polymer chains, preventing the formation of crystalline regions. The restricted molecular mobility of a crosslinked structure limits the extension of the polymer material under loading.
Cross-links are formed by
chemical reactions that are initiated by heat and/or pressure, or by the mixing of an unpolymerized or partially polymerized resin with specific chemicals called
crosslinking reagents. Cross-linking can be induced in materials that are normally thermoplastic through exposure to radiation.
In most cases, cross-linking is irreversible, and the resulting thermosetting material will degrade or burn if heated, without melting. Once a substance is cross-linked, the product is very hard or impossible to recycle. In some cases, though, if the cross-link bonds are sufficiently different, chemically, from the bonds forming the polymers, the process can be reversed.
Permanent wave solutions, for example, break and re-form naturally occurring cross-links (disulfide bonds) between protein chains in hair.
The chemical process of vulcanization is a type of cross-linking and it changes the property of
rubber to the hard, durable material we associate with car and bike tires.This process is often called sulphur curing, and the term
vulcanization comes from Vulcan (mythology), the
Roman mythology god of fire. However, this is a slow process, taking around 8 hours. A typical car tire is cured for 15 minutes at 150°C. However, the time can be reduced by the addition of accelerators such as 2-benzothiazolethiol or tetramethylthiuram disulphide. Both of these contain a sulphur atom in the molecule that initiates the reaction of the sulphur chains with the rubber. Accelerator (chemistry) increase the rate of cure by catalysing the addition of sulphur chains to the rubber molecules.
Cross-links can be made also by purely physical means. For example,
electron beams are used to cross-link the C type of PEX. Other types of cross-linked polyethylene are made by addition of peroxide during extruding (type A) or by addition of a cross-linking agent (eg.
vinylsilane) and a catalyst during extruding and then performing a post-extrusion curing.
Crosslinker use in protein study
A variety of crosslinkers are used to analyze
subunit structure of proteins,
protein interactions and various parameters of protein function. Subunit structure is deduced since crosslinkers only bind surface amino 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 captured and analyzed.
Examples of some common crosslinkers are the
imidoester crosslinker dimethyl suberimidate, the
NHS-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 caboxyls into amine-reactive isourea intermediates that bind to lysine residues or other available primary amines.
In-vivo crosslinking of protein complexes using photo-reactive amino acid analogs was introduced in 2005 by researchers from the Max Planck Institute Suchanek, M., Radzikowska, A., and Thiele, C. (2005) Photo-leucine and photo-methionine allow identification of protein-protein interactions in living cells. Nature Methods. 2, 261 – 268. In this method, cells are grown with photoreactive
diazirine analogs to
leucine and
methionine, which are incorporated into proteins. Upon exposure to ultraviolet light, the diazirines are activated and bind to interacting proteins that are within a few
angstroms of the photo-reactive amino acid analog.
Crosslinker for keratoconus treatment
Cross linking by means of photosensitizers (Riboflavin) and
UV light has entered clinical application for the treatment of
keratoconus . Keratoconus is a disease of the cornea that makes the cornea become weak and may gradually bulge outward. Approximately half of the keratoconus patients have significant visual problems beyond corrective lenses. The only resolution to keratoconus has been corneal transplantation, with a long healing period and unpredictable refractive error. Today, Corneal Cross Linking is used to increase the biomechanical stability of cornea to avoid corneal transplantation.
See also
References
is an example of cross-linking.
Cross-links are
covalent bonds linking one polymer chain to another. They are the characteristic property of thermosetting polymer materials. In biology, cross-linking has applications in forming
polyacrylamide gels for
gel electrophoresis and in protein studies. Crosslinking inhibits close packing of the polymer chains, preventing the formation of crystalline regions. The restricted molecular mobility of a crosslinked structure limits the extension of the polymer material under loading.
Cross-links are formed by
chemical reactions that are initiated by heat and/or pressure, or by the mixing of an unpolymerized or partially polymerized
resin with specific chemicals called
crosslinking reagents. Cross-linking can be induced in materials that are normally
thermoplastic through exposure to radiation.
In most cases, cross-linking is irreversible, and the resulting thermosetting material will degrade or burn if heated, without melting. Once a substance is cross-linked, the product is very hard or impossible to recycle. In some cases, though, if the cross-link bonds are sufficiently different, chemically, from the bonds forming the polymers, the process can be reversed. Permanent wave solutions, for example, break and re-form naturally occurring cross-links (
disulfide bonds) between protein chains in hair.
The chemical process of vulcanization is a type of cross-linking and it changes the property of rubber to the hard, durable material we associate with car and bike
tires.This process is often called sulphur curing, and the term
vulcanization comes from Vulcan (mythology), the Roman mythology god of fire. However, this is a slow process, taking around 8 hours. A typical car tire is cured for 15 minutes at 150°C. However, the time can be reduced by the addition of accelerators such as 2-benzothiazolethiol or tetramethylthiuram disulphide. Both of these contain a sulphur atom in the molecule that initiates the reaction of the sulphur chains with the rubber. Accelerator (chemistry) increase the rate of cure by catalysing the addition of sulphur chains to the rubber molecules.
Cross-links can be made also by purely physical means. For example,
electron beams are used to cross-link the C type of
PEX. Other types of cross-linked polyethylene are made by addition of peroxide during extruding (type A) or by addition of a cross-linking agent (eg.
vinylsilane) and a catalyst during extruding and then performing a post-extrusion curing.
Crosslinker use in protein study
A variety of crosslinkers are used to analyze subunit structure of
proteins, protein interactions and various parameters of protein function. Subunit structure is deduced since crosslinkers only bind surface amino 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 captured and analyzed.
Examples of some common crosslinkers are the
imidoester crosslinker dimethyl suberimidate, the
NHS-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 caboxyls into amine-reactive isourea intermediates that bind to lysine residues or other available primary amines.
In-vivo crosslinking of protein complexes using photo-reactive amino acid analogs was introduced in 2005 by researchers from the Max Planck Institute Suchanek, M., Radzikowska, A., and Thiele, C. (2005) Photo-leucine and photo-methionine allow identification of protein-protein interactions in living cells. Nature Methods. 2, 261 – 268. In this method, cells are grown with photoreactive
diazirine analogs to leucine and methionine, which are incorporated into proteins. Upon exposure to ultraviolet light, the diazirines are activated and bind to interacting proteins that are within a few
angstroms of the photo-reactive amino acid analog.
Crosslinker for keratoconus treatment
Cross linking by means of photosensitizers (
Riboflavin) and
UV light has entered clinical application for the treatment of
keratoconus . Keratoconus is a disease of the cornea that makes the cornea become weak and may gradually bulge outward. Approximately half of the keratoconus patients have significant visual problems beyond corrective lenses. The only resolution to keratoconus has been corneal transplantation, with a long healing period and unpredictable refractive error. Today, Corneal Cross Linking is used to increase the biomechanical stability of cornea to avoid corneal transplantation.
See also
References
