関: destabilization、destabilize、labilization

WordNet

the action of destabilizing; making something less stable (especially of a government or country or economy) (同)destabilisation
an event that causes a loss of equilibrium (as of a ship or aircraft)
become unstable; "The economy destabilized rapidly" (同)destabilise
make unstable; "Terrorism destabilized the government" (同)destabilise

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/21 23:43:23」(JST)

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A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules. This has an effect on the stability of the native state of other molecules in the solution, mainly macromolecules (proteins, nucleic acids) by weakening the hydrophobic effect. For example, a chaotropic agent reduces the amount of order in the structure of a protein formed by water molecules, both in the bulk and the hydration shells around hydrophobic amino acids, and may cause its denaturation (biochemistry).

Conversely, an antichaotropic agent is a molecule in an aqueous solution that will increase the hydrophobic effects within the solution. Antichaotropic salts like ammonium sulphate can be used to precipitate substances from the impure mixture. This is used in protein purification processes, to remove undesired proteins from solution.

Overview

A chaotropic agent is a substance which disrupts the structure of, and denatures, macromolecules such as proteins and nucleic acids (e.g. DNA and RNA). Chaotropic solutes increase the entropy of the system by interfering with intramolecular interactions mediated by non-covalent forces such as hydrogen bonds, van der Waals forces, and hydrophobic effects. Macromolecular structure and function is dependent on the net effect of these forces (see protein folding), therefore it follows that an increase in chaotropic solutes in a biological system will denature macromolecules, reduce enzymatic activity and induce stress on a cell (i.e., a cell will have to synthesize stress protectants). Tertiary protein folding is dependent on hydrophobic forces from amino acids throughout the sequence of the protein. Chaotropic solutes decrease the net hydrophobic effect of hydrophobic regions because of a disordering of water molecules adjacent to the protein. This solubilises the hydrophobic region in the solution, thereby denaturing the protein. This is also directly applicable to the hydrophobic region in lipid bilayers; if a critical concentration of a chaotropic solute is reached (in the hydrophobic region of the bilayer) then membrane integrity will be compromised, and the cell will lyse.^[1]

Chaotropic salts that dissociate in solution exert chaotropic effects via different mechanisms. Whereas chaotropic compounds such as ethanol interfere with non-covalent intramolecular forces as outlined above, salts can have chaotropic properties by shielding charges and preventing the stabilization of salt bridges. Hydrogen bonding is stronger in non-polar media, so salts, which increase the chemical polarity of the solvent, can also destabilize hydrogen bonding. Mechanistically this is because there are insufficient water molecules to effectively solvate the ions. This can result in ion-dipole interactions between the salts and hydrogen bonding species which are more favorable than normal hydrogen bonds.^[2]

Examples of Chaotropic agent

Chaotropic agents include:

Butanol
Ethanol
Guanidinium chloride
Lithium perchlorate
Lithium acetate
Magnesium chloride
Phenol
Propanol
Sodium dodecyl sulfate
Thiourea
Urea

References

^ Bhaganna, Prashanth; Volkers, Rita J. M.; Bell, Andrew N. W.; Kluge, Kathrin; Timson, David J.; McGrath, John W.; Ruijssenaars, Harald J.; Hallsworth, John E. (2010). "Hydrophobic substances induce water stress in microbial cells". Microbial Biotechnology 3 (6): 701–716. doi:10.1111/j.1751-7915.2010.00203.x. PMID 21255365.
^ Collins, K.D. (1997). "Charge density-dependent strength of hydration and biological structure". Biophysical Journal 72 (1): 65–76. doi:10.1016/S0006-3495(97)78647-8. PMC 1184297. PMID 8994593.

English Journal

Direct-reversible binding of small molecules to G protein βγ subunits.

Seneviratne AM, Burroughs M, Giralt E, Smrcka AV.SourceDepartment of Pharmacology and Physiology, 601 Elmwood Ave., Rochester, NY 14642, USA; Department of Pathology, 601 Elmwood Ave., Rochester, NY 14642, USA.
Biochimica et biophysica acta.Biochim Biophys Acta.2011 Sep;1814(9):1210-8. Epub 2011 May 18.
Heterotrimeric guanine nucleotide-binding proteins (G proteins) composed of three subunits α, β, γ mediate activation of multiple intracellular signaling cascades initiated by G protein-coupled receptors (GPCRs). Previously our laboratory identified small molecules that bind to Gβγ and interfer
PMID 21621014

Single dilution Avidity-Blocking ELISA as an alternative to the Bovine Viral Diarrhea Virus neutralization test.

Franco Mahecha OL, Ogas Castells ML, Combessies G, Lavoria MA, Wilda M, Mansilla FC, Seki C, Grigera PR, Capozzo AV.SourceInstituto de Ciencia y Tecnologia Dr. Cesar Milstein, Saladillo 2468, 1440, Ciudad Autonoma de Buenos Aires, Argentina.
Journal of virological methods.J Virol Methods.2011 Aug;175(2):228-35. Epub 2011 May 19.
This study describes the development and validation of a blocking ELISA that measures avidity of BVDV-specific immunoglobulins (Igs) as an alternative to the classic virus neutralization test. The assay comprises a recombinant soluble E2 glycoprotein as target antigen, a neutralizing serum as detect
PMID 21621555