AMBER Archive (2009)

Subject: Re: [AMBER] Ki and G

From: Marek Maly (
Date: Tue Sep 15 2009 - 06:58:07 CDT

Dear prof. Case and Thomas,

thank you very much for the final explanation and sorry for my
confusion which was primarily caused by two possible names of the
relevant quantity (H-TS) which is called either Gibbs free "energy"
or free "enthalpy" and also with the fact that enthalpy (but not "free
appears in the given formula.

Best regards,


Dne Mon, 14 Sep 2009 22:24:05 +0200 case <>

> On Mon, Sep 14, 2009, Marek Maly wrote:
> This page confirms what I said earlier: the term "free energy" might mean
> either Gibbs free energy (G) or Helmholtz free energy (A), depending on
> context.
>> I think that much more important and
>> little surprising is the fact, that binding constant,
>> (which is the experimental measure of the strength of the
>> inter-molecular
>> interaction) is related only to enthalpic part (dH)
>> of the free energy of binding and do not reflect whole free energy of
>> binding (dH-TdS).
> The above is not correct -- equilibrium (binding) constants are related
> to free
> energies, not just to enthalpies.
> But this whole subject is not really well-suited to discussion on a
> mailing list. For example, what Thomas wrote looks perfectly correct to
> me, but used a somewhat unfamiliar term ("free enthalpy") that may have
> caused confusion. Your assertion above, that a binding constant "is the
> experimental measure of the strength of inter-molecular interaction", is
> itself subject to mis-interpretation. It is better to refer to
> textbooks,
> where both words and mathematics can be carefully constructed, and the
> thread of the discussion is not fragmented into a bunch of separate
> emails from a variety of authors and viewpoints.
> ...dac
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