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Re: [ccp4bb]: questions on dimers in crystal packing

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On Tue, 15 Apr 2003, Rongjin Guan wrote:

> Sorry this is not a ccp4 question.
> Can anybody give some hints on the following questions?
>             1. Can one molecule form more than 1 kind of dimers
>                in different crystallization conditions?

I have never seen one, but that doesn't mean much. If it would
occur that would mean that you have an association-dissociation
equilibrium at crystallization conditions, i.o.w. your dimer is
very instable.

>             2. If the answer is "yes", is there any possibilities
>                that there is a dynamic equilibruim between them, and
>                what we see in the crystal structure is the main
>                dimeric form or the favorite dimer form?

not necessarily. One would see the form that best combines high
concentration with low solubility, i.e. maximizes the quotient

>             3. what are the main factors controling the dimer formation?

attractive and repulsive forces of the atoms of the monomers,
complementarity of surfaces.

>             4. Can the dimer formed in crystals reflect the situation in
>                body
>                if it is known to function as dimers biologically?

it can, and mostly it does. That it really does so in the
particular case we are working on is what we all hope for.

 Dr. Manfred Buehner             Phone:  +49-931-888-4100
 Physiologische Chemie           FAX:    +49-931-888-4150
 Theodor-Boveri-Institut fuer Biowissenschaften
 Biozentrum der Universitaet Wuerzburg
 Am Hubland,  D-97074 WUERZBURG,  Germany
 Email:  buehner@biozentrum.uni-wuerzburg.de