From: Cole, James L <jim_cole@merck.com>
  To  : 'lkott@lanet.lv' <lkott@lanet.lv>
  Date: Wed, 18 Oct 2000 11:49:07 -0400

RE: 3 mm centerpieces

Laila:

We used the 3mm centerpieces a while ago in some equilibrium work  using
absorption optics. (Cole, J. L. (1996) Biochemistry  35, 15601-15610).  It
works fine, but you  need to take into account the shorter optical
pathlength of these cells when fitting data. For example, If you are using
NONLIN then the concentration factors must be adjusted for the optical
pathlength for   globally fitting data to association models. There are also
some problems that were discussed several years ago on the RASMB which
relate to the use of interference optics with shorter pathlengths. At high
fringe gradients, you can have  problems with Wiener skewing if the light
isn't focussed at the 2/3 plane.  The optics gurus out there  may want to
comment on this.
Also, if you want to go to really short pathlengths, you can make
"centerpieces" out of rubber gasket material Emory Braswell, Marc Lewis and
Preston Hensley and probably others have done this,  but I  have never
tried.
Hope this helps.

Jim
----------------------------------------------------------------------------
--------------------------
James L. Cole, Research Fellow
WP 16-201
Merck Research Laboratories
West Point, PA 19486
Phone: (215) 652-5876                               FAX: (215) 652-0994
Email:  jim_cole@merck.com

> ----------
> From: 	Laila Kott[SMTP:kottl@chem.umass.edu]
> Reply To: 	lkott@lanet.lv
> Sent: 	Wednesday, October 18, 2000 10:27 AM
> To: 	rasmb@alpha.bbri.org
> Subject: 	3 mm centerpieces
> 
> Hi All,
> Can some suggest an article where 3mm centerpieces were used in
> equilibrium
> sedimentation experiments?  I need to shorten my pathlength, and was
> wondering if I need to change anything else in my setup.
> 
> Thanks,
> Laila
> 
> 
>