From: Hans T.H. Beernink <hbeernin@protein.med.uvm.edu>
  To  : RASMB <RASMB@BBRI.HARVARD.EDU>
  Date: Tue, 21 Jan 1997 11:37:14 -0500 (EST)

XL-I noise revisited

Just to clarify a few issues from my previous message (and an apology for 
the lack of detail)-

The phenomenon that we see using the Rayleigh optical system appears to be
sytematic.  It's not random, and it's very reproducible within the same run. 
As I said previously, it's most visible in the residual plots from
equilibrium curve fits, appearing as a regular oscillation about the ideal
fit. The fluctuation is about +/- 0.02-0.05 on the residuals, with 6-10 full
cycles over the entire radius of the short column. Closer inspection 
reveals that each cycle is composed of a number of smaller cycles of 
correspondingly smaller magnitude. 

It seems to be independent of how the laser is set up (either using the
automatic setup function or manually), and absorbance scans during the same
run appear 'normal'. I don't think the software could be the cause, 
unless there's an error in the FFT.  We're using Beckman's XLA/I v3.01g.


Again, thanks.

Hans


_____________________________________________________________________________
Hans T.H. Beernink, Department of Biochemistry, University of Vermont

hbeernin@protein.med.uvm.edu			FAX (802)862-8229 
hbeernin@zoo.uvm.edu				Tel.(802)656-8244