Conversely, an antichaotropic agent (kosmotropic) is a molecule in an aqueous solution that will increase the hydrophobic effects within the solution.[1] Antichaotropic salts such as 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.
Overviewedit
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 intermolecular 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.[2]
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.[3]
^Moelbert, S; Normand, B; De Los Rios, P (2004). "Kosmotropes and chaotropes: modelling preferential exclusion, binding and aggregate stability". Biophysical Chemistry. 112 (1): 45–57. arXiv:cond-mat/0305204. doi:10.1016/j.bpc.2004.06.012. PMID 15501575. S2CID 9870865.
^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. PMC3815343. PMID 21255365.
chaotropic, agent, chaotropic, agent, molecule, water, solution, that, disrupt, hydrogen, bonding, network, between, water, molecules, exerts, chaotropic, activity, this, effect, stability, native, state, other, molecules, solution, mainly, macromolecules, pro. A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules i e exerts chaotropic activity 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 Conversely an antichaotropic agent kosmotropic is a molecule in an aqueous solution that will increase the hydrophobic effects within the solution 1 Antichaotropic salts such as 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 editA 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 intermolecular 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 2 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 3 Common chaotropic agents include n butanol ethanol guanidinium chloride lithium perchlorate lithium acetate magnesium chloride phenol 2 propanol sodium dodecyl sulfate thiourea and urea citation needed See also editBoom method Chaotropic activity Denaturation biochemistry DNA separation by silica adsorption Hofmeister series Kosmotropic Minicolumn purificationReferences edit Moelbert S Normand B De Los Rios P 2004 Kosmotropes and chaotropes modelling preferential exclusion binding and aggregate stability Biophysical Chemistry 112 1 45 57 arXiv cond mat 0305204 doi 10 1016 j bpc 2004 06 012 PMID 15501575 S2CID 9870865 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 PMC 3815343 PMID 21255365 Collins K D 1997 Charge density dependent strength of hydration and biological structure Biophysical Journal 72 1 65 76 Bibcode 1997BpJ 72 65C doi 10 1016 S0006 3495 97 78647 8 PMC 1184297 PMID 8994593 Retrieved from https en wikipedia org w index php title Chaotropic agent amp oldid 1064873688, wikipedia, wiki, book, books, library,
