[RASMB] Holgers Mem-Prot. question

[Lustig]

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