[RASMB] pressure induced dissociation

[Judith Kornblatt]

I suggest you look at "Pressure Effects in Ultracentrifugation of 
Interacting Systems" in Methods in Enzymology, vol 27D, 306-345 (1973). 
I apologize, but I don't know the names of the author(s). There is a 
pressure gradient across an ultracentrifuge cell and hydrostatic 
pressure is known to dissociate many oligomeric systems. Whether or not 
one would see any effects with ultracentrifugation depends on whether or 
not the system is already slightly dissociated or close to it and how 
great the volume change is for dissociation. I work with a dimeric 
enzyme (enolase) that is dissociated by pressure. I've calculated that, 
if I start with the enzyme already 50% dissociated and centrifuge at 42 
000 rpm, than the % monomeric enzyme would vary from 50% at the meniscus 
to perhaps 70% at the bottom of the cell. I must admit, however, that i 
haven't looked closely at my data to see if this is happening.  If I 
were to start with fully dimeric enzyme, the pressure gradient across 
the cell would not be enough to produce any measurable dissociation.

Judith Kornblatt
Professor Emeritus
Department of Chemistry and Biochemistry
Concordia University
Montreal, QUebec


smcbryan wrote:
> All, 
> Would anyone/everyone care to comment on these results:
> http://www.ncbi.nlm.nih.gov/pmc/articles/PMC389292/pdf/pnas00083-0121.pdf
> and perhaps generalize on how/if they present a common or uncommon
> phenomenon in centrifugation. 
> Is this something that we should look out for, or is it very specific to
> this particular complex?
> thanks, 
> steve
>
>