Monodispersity aids

bill lodi at
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.


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.


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

other polyols
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

   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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