AW: [RASMB] Interpreting SV and SE data

[Eric Salgado]

Titus,

    My ranges are from 5 uM to 1 mM ( viscosity at the higher end 
doesn't seem to be a problem).

Titus M. Franzmann wrote:
> Hi Eric, 
> may I ask what the concentration range is you cover in your experiments?
> Best regards
> Titus
>
> -----Ursprüngliche Nachricht-----
> Von: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org] Im
> Auftrag von Eric Salgado
> Gesendet: Donnerstag, 29. Mai 2008 19:55
> An: rasmb at server1.bbri.org
> Betreff: [RASMB] Interpreting SV and SE data
>
> Hello all,
>    I have a system for which I've done SV experiments at multiple 
> concentrations that, on  increasing the concentration, reveals a peak 
> that starts at an s value of about 2, shifts to a plateau between 2.4 
> and 2.6, then steadily increases at 2.6. I should point out that all of 
> these peaks are very broad.
>    The c(MW) analysis describes a monomer at low concentrations; dimer 
> at intermediate concentrations;  something between  dimer and trimer at 
> high concentrations;  and finally, as  an aggregate  starts to form at 
> very high concentrations, a trimer peak is resolved. This trimer peak 
> correlates to our crystal structure, but it appears as if, because of 
> the apparently low association constant and fast kinetics involved with 
> the trimer formation, this fact is masked in the SV data.
>    In order to hopefully rid of this ambiguity, I performed SE 
> experiments in the concentration regime that did not form an aggregate 
> (and therefore apparently only a small amount of trimer), but find that, 
> as far as a species analysis goes, both a model with monomer-dimer or 
> monomer-dimer-trimer present are statistically equal. That being said, 
> the statistics are lower for the later model, while the fit and 
> residuals for both are equally good.
>    With all of this in hand, how can I determine the best SE model to 
> use, and can I say with certainty that the trimer exists in solution 
> from these data?
>
> I know this is a lot, but I would appreciate any help I can get  with 
> this problem.
>
> Thank you in advance,
>
> Eric Salgado
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