[RASMB] a hiccup in radial space

[Chad Brautigam]

Dear All,

Whilst checking the data from the first speed of a sedimentation  
equilibrium run, I noticed a troubling discontinuity in the data.  It  
appears in all three cells, and it is not exactly subtle.  The jump in  
the data can be as much as 0.1 OD, and it always occurs betwixt 7.05  
and 7.06 in radial space.  The anomaly occurs at both 280 and 250 nm.   
I attach a graph of three successive scans from the same cell, spaced  
four hours apart, for your delectation.  The data were collected in  
stepping mode, with 20 replicates.

While I suspect that the heavily glycosylated protein in these samples  
might behave nonideally, I suspect that the real problem here is  
instrumentation, maybe a sticky rail.  But, before calling my service  
rep, I thought I'd tap the collective wisdom of the AUC hive mind.

And a further question:  do y'all think that these data can still be  
analyzed if I simply exclude the affected region from the analysis?   
I'm running in the 6-hole centerpieces, so that means I'd be  
eliminating about half of the data from the outer holes.  Alas.

Thanks for any insight you can provide.

Best,
Chad




======================================
Chad A. Brautigam, Ph.D.
Assistant Professor
Department of Biochemistry
The University of Texas
Southwestern Medical Center at Dallas
Department of Biochemistry
5323 Harry Hines Blvd.
Rm. ND10.214G
Dallas, TX 75390-8816
Office:  214-645-6384
Fax:  214-645-6353
Email:  chad.brautigam at utsouthwestern.edu

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