--
Pr. Nadir T. Mrabet
Cellular & Molecular Biochemistry
INSERM U-724
Nancy University, School of Medicine
9, Avenue de la Foret de Haye, BP 184
54505 Vandoeuvre-les-Nancy Cedex
France
Phone: +33 (0)3.83.68.32.73
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Hi,
Salt bridges (or ion pairs) can be long-range (up to 7-8 Ang). They obey
Coulomb's law.
In contrast, H-bonds are short-range and are further anisotropic.
For those with general interest in electrostatics, I suggest to go back
to the
1978 paper of Max Perutz:
Electrostatic Effects in Proteins
Science (1978) 201 (4362), 1187-1191.
Nadir Mrabet
Jayashankar wrote:
> Dear Fransico,
>
> *Salt bridges are close range electrostatic interaction which depend
> on conformer population.
>
> *S.Jayashankar
> Research Student
> Institute for Biophysical Chemistry
> Hannover Medical School
> Germany.
>
>
> On Thu, Oct 16, 2008 at 8:21 AM, Chavas Leo <[log in to unmask]
> <mailto:[log in to unmask]>> wrote:
>
> Dear Francisco --
>
> On 15 Oct 2008, at 17:05, Francisco J. Enguita wrote:
>>
>> how
>>
>> can you define a salt-bridge within a protein structure ?
>>
>
> According to Wikipedia:
> a salt bridge in proteins is "a relatively weak ionic bond between
> positively and negatively charged side-chains of proteins."
>
> Now, at far as I understand (based on "Structure and Mechanism in
> Protein Science - Alan Fersht), you have a salt bridge when two
> groups are making an hydrogen bond that is favored by
> electrostatic interaction, electrostatic energies being weak in
> water. To quote the author of the book, let say you have the
> following equilibrium:
>
> E-NH3+ ------- OH2 + OH2 ------- -O2C-S <==> E-NH3+
> ------- -O2C-S + H2O ------- H2O
>
> The right-hand side equation would be more "favorable", as the
> electrostatic interaction will be more stable than in the
> left-hand side where both ions would be in contact with water
> molecules.
>
> HTH
>
> Kind regards.
>
> -- Leo --
> ------------------------------------------------------------
> Chavas Leonard, Ph.D. @ home
> Research Associate
> Marie Curie Actions Fellow
> ------------------------------------------------------------
> Faculty of Life Sciences
> The University of Manchester
> The Michael Smith Building
> Oxford Road
> Manchester Lancashire
> M13 9PT
> ------------------------------------------------------------
> Tel: +44(0)161-275-1586
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> <mailto:[log in to unmask]>
> http://personalpages.manchester.ac.uk/staff/leonard.chavas/
>
>
>
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