English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
All categories

Fixatives can either cross-link proteins or coagulate them.What is the difference?.Guide me please if possible ,to diagrams that illusterate the two events.Does crosslinking implies denaturation of the protein or the story is something else?

2007-02-23 04:20:21 · 3 answers · asked by Ahmed S 1 in Science & Mathematics Chemistry

3 answers

Cross-links are covalent bonds linking one polymer chain to another. 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 various chemicals; 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.

Coagulation (a form of protein denaturation) is the alteration of a protein shape through some form of external stress (for example, by applying heat, acid or alkali), in such a way that it will no longer be able to carry out its cellular function. Denatured proteins can exhibit a wide range of characteristics, from loss of solubility to communal aggregation. Denaturation can affect secondary, tertiary or quatanary protein structure.

In quaternary structure denaturation, protein sub-units are dissociated and/or the spatial arrangement of protein subunits is disrupted.
Tertiary structure denaturation involves the disruption of:
Covalent interactions between amino acid side chains (such as disulfide bridges between cysteine groups)
Noncovalent dipole-dipole interactions between polar amino acid side chains (and the surrounding solvent)
Van der Waals (induced dipole) interactions between nonpolar amino acid side chains.
In secondary structure denaturation, proteins lose all regular repeating patterns such as alpha-helixes and beta-pleated sheets, and adopt a random coil configuration.
Primary structure, such as the sequence of amino acids held together by covalent peptide bonds, is not disrupted by denaturation.

2007-02-23 04:34:33 · answer #1 · answered by Suedoenimm 3 · 0 0

Crosslinking involves the formation of covalent bonds between protein molecules. Coaguation is generally just the non-specific clumping together of proteins that have been denatured.

I think if you googled some of the specific fixatives like glutarladehyde or formaldehyde, you'll probably be able to find something about how those crosslinking fixatives actually work.

2007-02-23 04:31:37 · answer #2 · answered by hcbiochem 7 · 0 0

protein coagulation occurs when the protein denatures. Like in the egg white, it is at first(in liquid-like state) in a form of colloidal suspension. Upon heating, the proteins denatures and the globular proteins form a sheet like structure. Also, when you drink milk, the acidity in your stomach cause the the proteins to denature and cause coagulation. When milk is left in the open, bacteria land on it and act on the milk and thus produce acidic substance. The acidic substance causes the denaturing of the protein and thus coagulation.

2016-05-24 02:36:13 · answer #3 · answered by Anonymous · 0 0

fedest.com, questions and answers