Thanks Artem and Frank (Was: Re: Ammonium Sulfate)

Dr. Artem Evdokimov eudokima at mail.ncifcrf.gov
Thu Aug 9 17:00:41 EST 2001


Hi,

> These are the two I was thinking of but wasn't sure if they are
> sufficiently meaningful. Light-scattering - what exactly does it
> measure - size? or is it sensitive enough for conformation?

Static light scattering would be able to tell you the gyration radius
(or radii) - what it may be able to do is to tell you if two samples
that look the same according to other techniques are actually somewhat
different. Dynamic light scattering can detect aggregates, but I doubt
that it would give you much information beyond that.
In combinaiton with the experimentally measured refraction coefficient,
static LS gives nice m.w. (usually within 1-2 kDa), so if you get weird
m.w. that'd be an indication of something.

> Although this is third time I come accross such proteins, this time it
> is actually plain ole actin. That it is soluble after denaturation/dialysis is
> well-known; that it does not polymerize after this is also well-known.
> I played with salts, Ca, Mg, ATP and the result is ~ same everywhere.
> I was just thinking maybe it gets trapped into some conformation that
> is "better" G-actin (in a sense that it is always soluble no matter what)
> than a real G-actin.

Try surface residue mutations, a-la Derewenda et. al. ?

> Kinda fascinating problem since this is the most abundant cellular
> protein in many species and the one for which, apparently, there are
> special "custom-made" chaperons. The question is - why such a
> complexity for a simple idea of a reversible polymerizing agent?

Well maybe actin isn't just a reversible polymerizing agent ?

Cheers !

Artem
-- 
|Dr. Artem Evdokimov   Protein Engineering |
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