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<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Origin from OriginLab is a comprehensive fitting and layout program
for windows that can handle this and other equations with minor modifications
(e.g. setting the “var” to “double”). It uses an Origin
specified C source code and supports other programming features, such as X-Function,
LabTalk, Labview, scripting etc. Though a license is also expensive. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Best wishes<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Titus<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Von:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
rasmb-bounces@server1.bbri.org [mailto:rasmb-bounces@server1.bbri.org] <b>Im
Auftrag von </b>Arthur Rowe<br>
<b>Gesendet:</b> Tuesday, February 03, 2009 10:40 AM<br>
<b>An:</b> RASMB<br>
<b>Betreff:</b> [RASMB] The INVEQ function<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>This function for fitting monomer-dimer equilibria with both
thermodynamic (BM) and mass interaction parameters (Ka) floated is simple in
the extreme. Yet it makes no concessions to the art of approximation: it may
have only a single second virial term (BM) for both monomer and dimer, but it
is trivial to expand the function to cover separate coefficients for monomer
and for dimer, or to incorporate a third virial term (CM). Equally, there is a
simple mod to make it fit heterologous (equimolar) interaction, so long as the
2 sigma values are not too disparate (say from 3:1 to 1:3).<br>
<br>
But let's start with the basic INVEQ function, inveq5a. Which deals with the
situation when BM(1) = BM(2) is an adequate approximation, which it often is:<br>
<br>
function inveq5a(c_reference,sigma,r_reference,BM,Ka,E:real);<br>
<br>
description<br>
'fits non-ideal single solute data using the inverse equation',<br>
'float baseline offset E, BM, Ka and c_reference. Set r_initial & sigma
inactive';<br>
<br>
var<br>
aq,b,c,alpha,sigmaw:real;<br>
<br>
begin<br>
<br>
aq:=2*Ka*(x+E);<br>
b:=-(4*Ka*(x+E)+1);<br>
c:=2*Ka*(x+E);<br>
<br>
alpha:=(-1)*(b+((b*b-4*aq*c)^0.5))/(2*aq);<br>
<br>
sigmaw:=sigma*(alpha*2 + (1-alpha));<br>
<br>
y:=((ln((x+E)/(c_reference+E))+0.5*(sigmaw/(1+2*BM*(x+E)))*r_reference^2)/(0.5*(sigmaw/(1+2*BM*(x+E)))))^0.5;<br>
<br>
end;<br>
<br>
Yes, that's it. I am not sure that I could justify a major SEMINAR on it's
application! Of course what you get out in the way of ease of use does depend a
bit on what you paste this function into. I use pro Fit™ on Mac OS-X,
which has loads of lovely features, lovingly incorporated by the mathematical
physicists and engineers who are it's authors and principal users. You need to
be a MATLAB** user, I think, to get anything similar under Windows. BUT:
someone who is a Grafit user - a nice but not at all sophisticated Windows package
- had no problems feeding the above algorithm in, and it ran just fine, albeit
with a much simpler GUI and none of the fancy full statistics you can do as
routine in pro Fit™.<br>
<br>
Final comment: I cannot of course guarantee that there are no fitting engines
out there which will gum up when presented with the above function. But why
should they - it is not a transcendental equation, and the only really horrible
parameter correlation is between sigma and E, and you fix that by fixing E. <br>
<br>
Regards to all<br>
<br>
Arthur<br>
<br>
**but a single copy of MATLAB will set you back more than the total cost of a
Mac Mini + KB + mouse + display + single copy of pro Fit™. AND you will
have to learn MATLAB programming. But you <i>will</i> end up with what it take
to get a decent GUI, and full capabilities for multi-algorithm fitting and
advanced error stats. Just like in pro Fit™ . . . . . <br>
<br>
<br>
*******************************************************************************<br>
Arthur J Rowe<br>
Professor of Biomolecular Technology / Director NCMH Business Centre<br>
School of Biosciences<br>
University of Nottingham<br>
Sutton Bonington<br>
Leics LE12 5RD<br>
<br>
TEL: 0115 9516156<br>
FAX: 0115 0516157<br>
*******************************************************************************<o:p></o:p></p>
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