Re: Hydrophobicity (Summary so far...)

Peter Slickers (
Thu, 1 Feb 1996 18:35:37 +0100 (MET)

Simon wrote:
> Some good questions have been raised that I don't think have been
> answered yet... these include:
> Are charged residues more or less hydrophilic than uncharged residues?
> How do hydrophobicities of aliphatic and aromatic compounds compare?
I would like to answer both questions with the same arguments.

I would guess that an extended system of conjugated pi electron can make
some nice interactions with a polar molecule like water. Therefore, the
aromatic side chains should be less hydrophobic than the
aliphatic ones, and also the deprotonated aspartate with it's pi
electrons delocalized over both oxygens should be less hydrophobic
than the protonated aspartic acid.

So, an alipathic side chain like Isoleucine should be the most
hydrophobic. For the most hydrophilic side chain I would take
into account aspartate (pK 4.4), glutamate (pK 4.4) and arginine (pK 12.0).
For arginine the pK is most different from 7 and I would conclude,
that arginine is the most polar and the most hydrophilic side chain.


Peter Slickers                        
Institut fuer Molekulare Biotechnologie
Beutenbergstrasse 11, Jena                      Tel.: +49-3641-65-6202
Postfach 10 08 13, D-07708 Jena, Germany        Fax:  +49-3641-65-6210