[RASMB] a hiccup in radial space

[claus urbanke]

Dear Chad, dear  all,

there might be another source of the hiccup. It seems as if at least two 
of the scans (red and green) are sort of parallel shifted on th OD axis. 
It might be a (faulty) effect of the high voltage regulation of the PM - 
of the sort you have if you try to gather intensity data from samples in 
reference and sample channel. By the way, if my impression is correct it 
shoulf show up in the residuals of the fit.

Best wishes

Claus

Prof. Dr. Claus Urbanke
Medizinische Hochschule
Abtlg. Strukturanalyse OE 8830
Carl-Neuberg Str. 1
D-30625 Hannover
Tel.: +49 511 532 9372
FAX:  +49 511 532 5966



Chad Brautigam schrieb:
> 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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