PEG solutions contain fragments of all sizes - it is the average size
(however defined by the manufacturer) that is 1000. So technically it
is incorrect to claim that you have PEG1000 molecules bound to your
protein, it is most likely much shorter fragments that can penetrate the
channels in protein crystals.
It's not a lot of work to generate monomer libraries for peg fragments
of different length (and some are available from standard monomer
libs).
I always wondered why PEG is not defined in the standard libraries as a
polymer - perhaps because it is rarely needed. Or is it?
Ed.
On Thu, 2010-08-12 at 08:16 +0000, Klaus Sengstack wrote:
> Hi everybody,
>
> I just solved the structures of an enzyme an some variants. In the
> active site cavity of each variant I found one or two fragments of
> PEG1000 bound. I used PEG1000 in the crystallization condition. Among
> the enzyme variants the number of non-hydrogen atoms of these PEG
> fragments varies between 7 and 19 atoms. Now I want to deposit the
> structures in the pdb and my question is, if I have to define each
> fragment as a single ligand (what would be a lot of work) or can I
> define them as PEG1000 molecules? Thanks.
>
> K.S.
>
>
--
"I'd jump in myself, if I weren't so good at whistling."
Julian, King of Lemurs
