[RASMB] a lot

[Lustig]

Dear John Steckert and RASMB colleagues,
if one goes over the  classical  literature using interference cells , one 
should be aware that in this double sector system in both sectors have to 
be the same solution except that  one of 
them   contains   particles  (protein ) one like to determine.  The 
solutions have to be  dialyzed and as "solvent" the outside 
dialyzing  solution should be used.
Detergent  solutions  are hard  to  dialyze for many reasons. Detergent 
micelles are of  high  Mw,
remain often  on /in  the membrane and many other reasons......
Depending  on the detergent  concentration , usually  in refraction index 
systems  ,Schlieren and  interference you will detect with   SV two 
moving  boundaries, one  of the over CMC micelles and one of the  complex 
detergent/protein. Only in the  case that the  buffer  has the equal density
( like e.g. OPOe ), the "empty " micelles can't migrate . Not always  must 
be seen 2   bondaries, it depends on  size,   density  and shape - dfferences.
Crucial is the  situation using SE, there will be a mix!!
Using absorption  optics, the  micelles  are  >>optically transparent<< 
even so at high micelle concentration  you have a certain refraction 
influence  at the radial position  of the  emtey once.
I mentioned only  the  optically transparency and not the most  crucial 
problem >>gravitational transparency<< this one  can read  in my 
Publication-list N° 15 and 10 given in the net.
http://www.biozentrum.unibas.ch/personal/jseelig/AUC/news.html
You will ask how we determine not dialyzed membrane protein samples using 
the abs. optical
system of the  XLA?  With the Segal program (without knowing the "baseline 
absorbance") we achieved nice results. (I refer to the same net address) .

To your second  question.
Usually  only  with schlieren  optics you can rise  the  concentration 
over1-4mg/mL We produce  our self 2, 3 and 4 mm thick cells, (Beckman has 
also 3mm cells) so we are  able to rise the  conc.  several times.
To literature  it is  worth  to  go back to Beckmans 
technical  manuals  for model  E.

yours...ariel

Lustig Ariel
Biozentrum der Universität Basel
Klingelbergstr. 70
CH 4056 Basel
Switzerland
Dept. of Biophysical Chemistry /
Analytical Ultracentrifuge Lab.TEL....+61 2672187
Fax +61 2672189
E-mail Ariel.Lustig at unibas.ch