[RASMB] Holgers Mem-Prot. question

[Ewa Folta-Stogniew]

How about running SEC with LS/RI/UV detection using
computed ext. coeff. It does work nicely (not always-
depends how well is the sample equilibrated) and the
apparent dn/dc (and amount of detergent present on the
peptide chain) can be determined from RI and UV
traces.

Please see slides 38-48 at:

http://info.med.yale.edu/wmkeck/biophysics/Final_10_25_02a_Wyatt.pdf

Also in published form at:
http://info.med.yale.edu/wmkeck/biophysics/reprints/Yernool_et_al_2003.pdf

Ewa




--- Lustig <ariel.lustig at unibas.ch> wrote:
>
----------------------------------------------------------------------------------
> The older archived RASMB emails can be found at:
> http://rasmb-email.bbri.org/rasmb_archives
> and current archives at
> http://rasmb-email.bbri.org/pipermail/rasmb/
> Search All the Archives at:
> http://rasmb-email.bbri.org/rasmb_search.html
>
----------------------------------------------------------------------------------
> 
> Dear Holger and colleagues ,
> I join Jo's  opinion that the determination of the
> concentration of a 
> mem-prot MP
> in detergent  solution is quasi  impossible with
> conventional methods.
> Lets return to the roots!
> It took me  years to learn that it is impossible  to
> determine  with 
> pycnometrical
>   methods (density-meter) detergents micelles or
> MP-complexes , first of 
> all because
> the lack of the concentration knowledge. In such  a
> solution  we have 3 
> sorts of
> particles  1 . under Cmc detergent, 2. over CMc 
> detergent micelles(empty), 
> 3. and
> MP-complexes.
> With  SV and schlieren or interference optic =dn/dc
> you are  able to see with
> OG  or DM two sedimenting peaks  the
> "empty"=detergent micelles -only and
> the MP-complexes, that one can  indicate also by
> absorption optics. S' is 
> also pressure dependent.
> Important in this case is
> that the detergent micelles have  a density over  1
> (not  like Octyl Poe, 
> ro = about 1)
> The under Cmc  can not be measured in this  system.
> As I learned recently , the ratio  of bound 
> micelles  is labile=unstable.
> I have submitted  to BBA  a short  paper  and will
> speak  about this  next 
> in the
> Oxford-meeting.
> I do not prepare  myself  MP solutions but measure 
> them and am happy  if 
> the OD
> fits  to the cell thickness .
> Meanwhile no answer for you    ariel
> 
> _______________________________________________
> RASMB mailing list
> RASMB at rasmb-email.bbri.org
> http://rasmb-email.bbri.org/mailman/listinfo/rasmb




__________________________________
Do you Yahoo!?
Yahoo! Finance: Get your refund fast by filing online.
http://taxes.yahoo.com/filing.html