[Crumbs]

Hello,

I'd like to ask a question that is really bugging me. I read about the salting-in and-out effects, yet I do not understand the salting-in effect well. I read something about the fact that the sult increases the ionic strength and so forth, but I do not understand how this influences the solubility of the protein.. why does it increase?

I do understand that salting-out is caused by the salt "taking" the water molecules, therefore not letting the protein use the water, and therefore it percipitates.

Anyone who could explain the matter opf salting in, please do, i would greatly appreciate it.

Jonathan

[Albert]

Adding a salt, its ions neutralize the electric charges on the surface of the proteins and act against their aggregation.

Reducing the concentration of salt (this means increasing ionic force) the effect will be an excess of charges that, after having saturated the protein, competes with the protein for what concerns water.

[Borek]

Reducing the concentration of salt (this means increasing ionic force)

What do you mean by ionic force - ionic strength?

[Crumbs]

Ok, so if I understand correctly, in salting-in, the salt is added and and therefore neutralizes the electric charges on the protein. Because the proteins don't have charges, they don't bind, and so they are dissolved with the water.

If so, why, after adding more and more salt, the solubility of the proteins decrease? Is it because the salt starts to compete with the proteins for the water molecules?

Thanks a lot for your help.

[Albert]

What do you mean by ionic force - ionic strength?

Of course, sorry it's an italianism  

[Albert]

Is it because the salt starts to compete with the proteins for the water molecules?

Yes. Let me add that Hofmeister's series tells you which are the best salts to be used.

[Crumbs]

thanks a lot

[Borek]

No problem

However, to quote you:

Reducing the concentration of salt (this means increasing ionic force)

Ionic strength - almost always and almost by definition - is directly proportional to concentration of salt. Thus decreasing concentration you may only decrease ionic strength.

See ionic strength definition.

[Albert]

Ok, I apologize but I was in a hurry and I didn't read my message before posting it.