[RASMB] observation boundaries for the fluorescence detector

[Cole, James]

Dear Titus
The meniscus in this data set is at  5.8 cm. If you are using  the Beckman-Coulter or Spin Analytics  2-sector cells, a nearly  filled channel  should have the meniscus at around 5.9-6.0 cm. The window holder/ screw-ring block the fluorescence detector at the bottom of the  cell, causing the downward slope. It has nothing to do with fluorescence quenching. In our system, the drop off begins at about 7 cm. In  your data it seems to occur at about 6.9 cm. So, it does seem possible that the radii are shifted low in this data. This is strange because in the fluorescence system  the detector movement is is controlled by stepper motor and is stable.
Regards,
Jim Cole

On 11/2/09 1:54 PM, "Titus M. Franzmann" <tmfr at umich.edu> wrote:

Hi,
What are the optical sedimentation observation boundaries for the fluorescence detector? I do not have access to the system currently. A friend sent me his data. I have the impression that in this particular run the entire signal is shifted toward smaller radii. My impression was always, that the cell gets illuminated to about 7.1 cm before the bottom gets visible due to the dye quenching. My suspicion is that the radial calibration is off on this machine.
Thanks for your help
Best,
Titus

Titus M. Franzmann


University of Michigan
Molecular, Cellular,
   Developmental and Biology (MCDB)
4140 Nat. Sci. Bldg
830 North University
Ann Arbor, Mi, 48109
USA

Tel: +1 (734) 647 2291
eMail: tmfr at umich.edu
web: walter lab website <http://www.mcdb.lsa.umich.edu/labs/walter/>



----------------------------------------
James Cole
Associate Professor, Department of Molecular and Cell Biology
Head, National Analytical Ultracentrifugation Facility
University of Connecticut
91 North Eagleville Road
Storrs, Connecticut 06269
Tel: (860) 486-4333
Fax: (860) 486-4331
email: james.cole at uconn.edu