stereospecificity and solvation

Frank Fuerst ffrank at
Sun Dec 5 14:26:43 EST 1999

hydrophile wrote in bionet.molbio.proteins:
> I know proteins exhibit stereospecific binding, but are they also
> stereospecific solutes? i.e. has anyone documented a protein being more
> soluble in one solvent isomer versus another.

A, that's what you wanted!

Well, first you would need a chiral or stereoisomeric liquid in that
proteins are soluble at all. Next, if this is a hydrophobic solvent,
you'll probably get denatured proteins, and denatured proteins in
organic solvent is not the most relevant system, is it?

Second, if you find some solvent which retains the proteins' native
structure, you'll find that though the building blocks are chiral and
of course the whole globular structure is often chiral, the surface
consists rather randomly of backbone atoms and the more hydrophilic
bunch of side chains, each in different possible rotational
configuration. Thus, averaging over the whole protein surface, you
wouldn't expect the protein to specifically interact with
stereoisomers. Thus I think your only chance is to design something
big enough to interact with the whole protein as one chiral entity,
which has a size of several tens or even hundreds of Angströms - is
that a solvent?

Or you can build something that specifically interacts with some
characteristic form on the protein surface, with a binding pocket or
similar forms - but then it's not solvation, rather specific binding.

X-Posted to bionet.biophysics where you posted your longer question,
and Follow-up-to set.

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