Re: Hydrophobicity of residues

Simon Brocklehurst (
Fri, 2 Feb 1996 12:29:48 +0000 (GMT)

( wrote:

Glad you brought up the Nozaki and Tanford stuff... it's
interesting work.

One query... and one factual disagreement ;-)

Am I right in thinking the Nozaki and Tanford free-energy transfer
paper was not actually amino acid side-chains, but _model_ compounds
representing these side-chains (this needs confirming - I can't
just remember at the moment)?

>Thus tryptophan being both non-polar and having the largest
>accessible surface area would be the most hydrophobic.

>On the same scale the least hydrophobic was arginine. This is
>essentially for the same reasons : the molecule is small, with a
>small accessible surface area...


I have a problem with one aspect of your surface area arguments,
as they're written. In fact, W and R have pretty similar SA
surface areas (in extended conformations) - they're the two largest
of the 20 amino acids.

So... anyone wanting to argue for R being be regarded as the least
hydrophobic of the 20 residues needs to use a different argument I
think... any thoughts...?

-- Simon
| ,_ o Simon M. Brocklehurst,
| / //\, Oxford Centre for Molecular Sciences, Department of Biochemistry,
| \>> | University of Oxford, Oxford, UK.
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