Subject: Re: CCL:effects of temperature on hydrophobicity

From: [email-masked]
Date: Tue, 31 Aug 1999 19:30:18 +0100

Hi all CCLers

I got some answers to my question regarding the
the effects of temperature (say, an increase from
20 to 40 degrees C) on the hydrophobicity
properties of a protein?

I would like to thank Ricardo Mancera, Devapriya
Choudhury, Anil Kumar Kandalam, Robert Bywater and
Mike Gilson for their valuable answers. Here comes
a summary

Ricardo Mancera wrote

Do a literature search on Privalov, he's done a lot of work on the
temperature dependence of protein denaturation and hydrophobicity.  It
might be useful to look also for papers by Dill, Lee and Sharp.

Devapriya Choudhury wrote

Hydrophobicity, in  general, increases with temperature. This has
interesting consequences for protein folding (remember proteins are
thought to fold due to hydrophobic collapse, this should be more
pronounced at high temperature, paradoxically they unfold at high
temperatures). There is a very nice review on this aspect by Peter l.
Privalov. Check Adv. Prot. Chem.

Mike Gilson wrote

An increase in temperature is generally believed to
enhance the hydrophobic effect, based upon data on the
solvation of hydrophobic molecules (vacuum to water) as
a function of temperature.  In fact, that some proteins
denature at cold temperatures is often attributed to the
diminution of the hydrophobic effect at low temperature.

I believe the Privalov review is the following. (I didn't
find anything more recent by him in Adv. Prot. Chem.)

PRIVALOV PL, GILL SJ   STABILITY OF PROTEIN-STRUCTURE
AND HYDROPHOBIC INTERACTION ADV PROTEIN CHEM 39: 191-234
1988

I also recommend a recent analysis from Schellman, both for
the paper itself and for the references it contains:
"Temperature, Stability,and the Hydrophobic Interaction"
Biophys. J. 73:2960-64, 1997.

Anil Kumar Kandalam wrote

With an increase in temperature in the range of 20-40C,
there is change in the confirmational folding of the amino
rather an imino acid PROLINE which would maintain the protein
stable, with an increased stability of the protein as a function
of its hydrophobic microenvironment in all those proteins where
proline happens to be an essential component of the protein.
In those proteins which do not have the iminoacid proline as a
component, the activity regulation of the protein as a function
of temperature where activation of the active sites of the
protein is far more greater in comparison to deactivation.

In general, majority of the proteins after their synthesis,
fold in a cooperative fashion which demands the natural
physiological conditions as it involves nothing but the
interaction of aminoacids. Hence the temperature increase
within the physiological range would facilitate easy
folding by the increased interactions between the activated
hydrophobic aminoacids.

Robert Bywater wrote

It depends on what you mean by a hydrophobic property.
The following can all be ascribed, at least in part, to
'hydrophobic interactions' :

- protein folding
- ligand-protein interactions
- protein-protein interactions
- insertion of membrane proteins into membrane

If by hydrophobic property you mean interactions between
nonpolar surfaces that are enhanced by exclusion of water
(the 'standard' definition of 'hydrophobic interaction')
then since the latter is associated with an increase in
entropy there will be a reduction in the overall free
energy and because of delta(G) = delta(H) - T.delta(S) this
effect will increase linearly with temperature.

NB other types of interaction such as hydrogen bonding
and ion-pairing also require desolvation to take place
so this entropic contribution is by no means exclusive
to the 'hydrophobic interaction'.

__________________________

Thank you again for your contributions.

Enrique

Enrique Carredano, MSc, PhD            +46 (0)18 16 50 00 tel
Polymer and Surface Chemistry          +46 (0)18 16 50 42 direct
Amersham Pharmacia Biotech             +46 (0)18 16 63 96 fax
Bjorkg 30, 751 84 Uppsala Sweden       [email-masked]