<br><font size=2 face="Arial">It has been a while since I did these measurements, but if I recall correctly, the literature I was following suggested that the relavent vbar was that of the detergent above the CMC. I am pretty sure that all the measurements that I did were above the CMC. As you suggest Fumio, the concentrations were all from dry weight into solution (gm/mL). It is likely I made a more concentrated stock (10gm/100mL?) and diluted from there for the measurements. Not only did the graphs from the density vs. concentration measurements give a straight line, they were quite flat. While the graphs were flat, I did use a vbar value extrapolated to the CMC for each detergent I did this for.</font>
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<br><font size=2 face="Arial">You could probably get the concentration from the number of fringes, but to do this I think you would need to know the refractive index increment for the detergents in micelles. I don't have a good idea on how to get this value.</font>
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<br><font size=2 face="Arial">John</font>
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<td><font size=1 face="sans-serif"><b>Fumio Arisaka <farisaka@bio.titech.ac.jp></b></font>
<br><font size=1 face="sans-serif">Sent by: rasmb-admin@rasmb-email.bbri.org</font>
<p><font size=1 face="sans-serif">11/24/2003 01:42 AM</font>
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<td><font size=1 face="Arial"> </font>
<br><font size=1 face="sans-serif"> To: rasmb@rasmb-email.bbri.org</font>
<br><font size=1 face="sans-serif"> cc: </font>
<br><font size=1 face="sans-serif"> Subject: [RASMB] Re: vbar of DM +OG</font></table>
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<br><font size=3 face="Arial"><br>
Dear John and Ariel,<br>
<br>
Thank you very much for the information from both of you.<br>
<br>
Actually, I have a question. Ariel, why are the values obtained by Anton Paar density<br>
meter designated as "not hydrated"? It may be an elementary question, but both states in <br>
the density meter and ultracentrifuge cell are hydrated, arn't they? <br>
<br>
Another question to both of you is that as Ariel pointed out, the micelle formation<br>
of OG and DM may make the measurement difficult. In your measurement, as the<br>
concentration of the solute increases, the fraction of OG or DM in the micelle would <br>
increase with respect to the free ones. Does the graph of rho vs. c still give a straight line?<br>
(Actually, I do not know the cmc of these reagents and the range of concentration<br>
that you used.) We have recently purchased an Anton Paar DMA5000. Could you give<br>
any advice concerning precaution of the measurement if we measure it ourselves? <br>
I suppose the concentrations are estimated from the dry weight of OG or DM or<br>
can you get the concentration from the number of fringe?<br>
<br>
Thank you in advance. Fumio<br>
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Dear Fumio and dear colleagues,<br>
the Vbar of OG is 0.867 not hydrated and hydrated mesured in sucrose or similar<br>
densifiers 0.924 (mesured in the model E)<br>
That of DM is 0.813 (measured in the A. Paar desity-meter) and the hydrated<br>
one is 0.885 (measured in model E).In my next ? paper will be the reference?<br>
<br>
OG reference under N$B!<(B15 of Lustig A, Engel A, Tsiotis G, Landau EM, Baschong W.<br>
" Molecular weight<br>
determination of membrane proteins by sedimentation equilibrium at the<br>
sucrose or nycodenz-adjusted density of the hydrated detergent micelle."<br>
Biochim Biophys Acta. 2000 Apr 5;1464(2):199-206.<br>
<br>
Yours ....ariel<br>
<br>
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Fumio-</font><font size=3 face="Arial"> <br>
</font><font size=2 face="Arial"><br>
Partial specific volume of octylglucoside is 0.859 (Reynolds & McCaslin (1985), Methods in Enzymology, 117:41-53)</font><font size=3 face="Arial"> <br>
</font><font size=2 face="Arial"><br>
Partial specific volume of decylmaltoside is 0.795. I determined this for my thesis work using density measurments at several detergent concentrations using a Mettler/Paar density meter (DMA 01 C).</font><font size=3 face="Arial"> <br>
</font><font size=2 face="Arial"><br>
Regards,</font><font size=3 face="Arial"> <br>
</font><font size=2 face="Arial"><br>
John Harlan</font><font size=3 face="Arial"> <br>
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<br>
At 15:10 03/11/22 +0100, Lustig wrote:<br>
</font>
<br><font size=3 face="Arial">Dear John Harlan , Fumio and colleagues,<br>
I'm not astonished that you =John report on a bit different Vbar values as I have done.<br>
The deviation of detergent micelles densities stem from several reasons.<br>
We have to understand that a detergent solution is mixture of underand over CMC.<br>
This equilibrium of particles may differ by concentrationand used buffer/water.<br>
In density-meters you need to know the realconcentration of micelles and this<br>
is quasi impossible for the Vbar determination, where you have tocross<br>
the under CMC range.<br>
In AUC you can determine the micelles density with schlieren and interference<br>
in densifiers between sedimentation and floatation, but thisdensities are hydrated once.<br>
with a water shell so they are 40-50% off.<br>
Different producers of detergents reports on different subunits fora micelle so<br>
also the density variegates.<br>
The reference of Shire (15 of the BBA paper I sent to Fumio) gives alsodifferent values<br>
as the Meth.of Enzymology.if not to trust in my own measurements.<br>
<br>
Yours....ariel</font>
<p><font size=3 face="Arial">***********************************************************<br>
Fumio Arisaka, Ph.D.<br>
Department of Biomolecular Engineering<br>
Graduate School of Bioscience and Biotechnology<br>
Tokyo Institute of Technology<br>
5249 Nagatsuta, Midori-ku<br>
Yokohama 226-8501 JAPAN<br>
Tel/Fax:+81-45-924-5713<br>
E-mail: farisaka@bio.titech.ac.jp<br>
URL </font><a href=http://www.farisaka.bio.titech.ac.jp/><font size=3 color=blue face="Arial"><u>http</u></font></a><font size=3 face="Arial">://www.farisaka.bio.titech</font><a href=http://www.farisaka.bio.titech.ac.jp/><font size=3 color=blue face="Arial"><u>.ac.jp/</u></font></a><font size=3 face="Arial">$B!!!!(B<br>
$B!!!!!!(B </font><a href=http://edpex104.bcasj.or.jp/pricps2004/><font size=3 color=blue face="Arial"><u>http</u></font></a><font size=3 face="Arial">://edpex104.bcasj.or.jp</font><a href=http://edpex104.bcasj.or.jp/pricps2004/><font size=3 color=blue face="Arial"><u>/pricps2004/</u></font></a>
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