Hofmeister series

The Hofmeister series ( Hofmeister series or lyotropic also series) describes the different precipitating effects of salts. The chemist Franz Hofmeister examined 1888 proteinfällende effect of salts and thus the dissolved ions in water. He found empirically ion sequences, which characterizes the strength of influence on the biomolecules dissolved in water.

Lyotropic series

The Hofmeister series is used for the classification of the chaotropic effect of ions on macromolecules in aqueous solution and is given below for anions and cations:

Given in the Hofmeister series takes the chaotropic effect of the said ions (and thus, these ions containing salts) from left to right. The further to the left ( antichao or cosmotropic ) ions act as a precipitant. They reinforce the hydrophobic effects in aqueous protein solutions, thereby promoting protein aggregation via hydrophobic interactions, resulting in the loss of proteins from the solution. The one uses for salting. The further to the right ( chaotropic ) ions reduce hydrophobic effects and thereby lead to the denaturation of proteins, since the characteristic spatial structures of biomolecules are significantly influenced by hydrophobic effects. Therefore, increasing the chaotropic salts, by reducing the hydrophobic interaction, the solubility of hydrophobic molecules into water and is referred to as salting.

For example, water and oils do not mix. The liquids are kept separate as a result of the hydrophobic effect. This effect reducing chaotropic salts. They disrupt the hydrophobic forces that hold the proteins in their tertiary or quaternary structure and denature them. Chaotropic salts pick up the strict separation of water and fat, they "stabilize" hydrophobic particles or hydrophobic moieties in water. NMR relaxation studies demonstrated that accumulate such as large chaotropic anions such as bromide ( Br ), and iodide (I- ) to hydrophobic particles or groups of molecules occur and so polar sites on their surface, which is then the total molecular system water makes up more soluble and the salting- causes. Theory is not completely understood the Hofmeister series; the main effects are based on a very complex interplay of interactions between the ions, the solvent water and the dissolved organic molecules. It is striking that the chaotropic effect in monoatomic anions increases with the ionic radius, whereas it decreases with monatomic cations. Experiments have also found that the Hofmeister series is valid not only in water-dissolved macromolecules, but even with small particles, or non-polar moieties, the ion impact on the hydrophobic effect, describes ( see, e.g., Ref 4 )

Applications

Chemists use in practice as chaotropic salts often perchlorates, thiocyanates or barium salts. As an application of knowledge from the Hofmeister series protein purification is to be mentioned, as these findings in biochemical analysis, namely, the hydrophobic interaction play an important role. In medicine, the Hofmeister series are also available for Diuresewirkung important.

Salting out of glycerol with sodium chloride is used in soap manufacture and thus in addition to the precipitation of gypsum tofu with one of the oldest industrial applications of the precipitation.

Bioengineered recombinant proteins are occasionally concentrated by precipitation with ammonium sulfate. In biochemistry guanidinium thiocyanate is used for denaturing solubilizing of hydrophobic proteins, such as in the purification of DNA or RNA.

From salt effects are also hopes approaches to the treatment of protein misfolding diseases such as Alzheimer 's disease, amyotrophic lateral sclerosis, the BSE and similar diseases where aggregates of proteins are important. They managed to dissolve clumps of protein, for example, by the addition of certain salts. In a study of the same problem, it was found that anti-chaotropic salts (eg, ammonium sulfate), which were used for the precipitation of proteins in a solution that can subsequently lead to denaturation of high molecular weight metalloproteins in the same solution.