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From: jack correia <jcorreia@fiona.umsmed.edu>
To : rasmb@bbri.harvard.edu
Date: Mon, 01 Jun 1998 11:41:04 -0500
Re: dc_dt README file correction
rasmber's,
Walter's s/D method was originally described in an abstract where the
equation reported is correct (Stafford, 1996 Biophys J 70, A231). It also
appears in more detail in an article Preston Hensley & Walter have on
antibody-antigen interactions, available at a web I believe (Walter?). To
my knowledge (others?) it has been used only once otherwise, on a His
tagged human kinesin construct K332 (Rosenfeld et al (1996)JBC 271, 30212),
where is was compared with Svedberg. Both methods gave identical results,
about 3% smaller than the actual MW. This construct irreversibly
aggregated during sed equilibrium experiments and thus Svedberg or the s/D
methods were essential.
This methods fails if any aggregation or asociation occurs where there is
a mixture of species and thus a larger apparent Diffusion coefficient.
Walter say you must be 2 orders of magnitude above K for this to work with
reversible association. Multiple gaussian fits may work if the species are
noninteracting and well separable such that good estimates of D can be made.
--------------------------------------------------------
Dr. John J. "Jack" Correia
Department of Biochemistry
University of Mississippi Medical Center
2500 North State St.
Jackson, MS 39126
(601) 984-1522
fax (601) 984-1501
email: jcorreia@fiona.umsmed.edu
homepage: http://fiona.umsmed.edu/~biochem/correia.html
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