[RASMB] Weak association?

[Thomas Jowitt]

Hi Andrew

If your sedimentation coefficient is constant throughout that concentration range then it would appear that there is no association. This is a decent sedimentation coefficient for a monomeric species. The fact that you are not observing any non-ideality in your sample either is not that surprising as your molecule is very spherical and at the low concentrations of 0.3mg/ml you wouldn't really expect that much.  

If you need independent verification of the mass, then run it on your light scattering system.

Thanks

Tom J

-----Original Message-----
From: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org] On Behalf Of Leech, AP
Sent: 02 February 2009 14:22
To: RASMB
Subject: [RASMB] Weak association?

Hello all,

I have done some SV runs at various concentrations 0.3-10 mg/ml on
a protein (~14 ka) and the sedimentation coefficient appears to
remain constant (about 1.58). I had expected it to drop slightly at
higher concentrations, and so I suspect a weak self association.
Buffer is NaCl/Tris.

Is it reasonable to try and estimate an association coefficient
from this sort of data, and what is the best way to do it? (Even
a lower limit would be acceptable, as the intent is to show that
dimerisation is not significant).

I'm working my way through Gilbert & Gilbert at the moment (Meth.
Enzymol vol 27, p273) but is there perhaps something more in the
"global analysis" line?

All comments appreciated,

Andrew

--
Dr Andrew Leech                   *  Laboratory Manager
Technology Facility               *  Molecular Interactions Laboratory
Department of Biology (Area 15)   *  Tel   : +44 (0)1904 328723
University of York                *  Fax   : +44 (0)1904 328804
PO Box 373,  York  YO10 5YW       *  Email : apl3 at york.ac.uk
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