Monodispersity aids

bill lodi at dino.qci.bioch.bcm.tmc.edu
Tue Aug 15 11:16:38 EST 1995


 I only received two responses to my question about additives to
help with aggregation problems, but the responses seem consistent
so here they are. Thanks again to my respondents.
___

#1

You're right in thinking that it's a long shot, but there have been a few 
cases where non-specific (amd specific) aggregation could be perturbed 
by additives.  Historically, the ones that have worked (that I know of, 
anyway) are beta-octylglucoside, spermidine, t-butanol and glycerol, all 
at concentrations of 2-10%.   The solubility and aggregation behavior of 
a macromolecule can change profoundly when specific ligands bind to, e.g.,
the active site, so if your protein is an enzyme you may want to see what 
an inhibited complex does.


#2

	What works is protein dependent, but things to try are;

glycerol
other polyols
pH
changes in salt concentration
and changes in salts
detergents (tween, BOG, etc)
TFE (but it is pricey!)

	Don't overlook protein purity, but I assume that you have
tried that.  In particular, you may want to check isoelectric
focussing gels for partially degraded or phosphorylated proteins.

	I don't know of a magic bullet and I don't consider myself an
expert in light scattering machines (we borrow time on someone
else's).

___
    
   Of the above, it seems the suggested concentration of BOG might 
be a little high.  When I asked about glycerol some months ago, I
received a couple of replies which said it was necessary for some
crystals, and in general seemed to be a nucleation inhibitor(good
for production xtallizations, bad for first xtal).  One person also
said use of glycerol in xtallizations was considered sexy.  This
could provide a useful morale boost when nothing is working.

W. E. Meador




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