Resolution Loss after 150 bp

Steve Steve
Mon Jun 2 08:02:54 EST 1997

In article <5luspj$eg3 at>, a.wilton at wrote:

> Dear Sequencers,
> We are suffering a loss of resolution on some of our gels from about 
> 150 bp on.  On Genescan gels these means markers are not visible after 
> 150 bp and on sequencing gels basecalling is not good.  The problem is 
> intermittent but regular.  It seems that our usual sudden loss of 
> resolution at about 550 bp has just moved down the gel.
> It has been suggested that it may be a build up junk on some plates.  
> Does anybody know?  Has anybody had the problem and been able to fix 
> it?  Is our usual loss of resolution at 550 bp normal or is that 
> avoidable too?
> Thanks
> Alan Wilton
> a.wilton at

Alan, I work For PE Applied Biosystems as a Field service Engineer in LA
working on the sequencers. If the problem is on a 377 I had a similar
experience when I worked at CalTech doing DNA sequencing. The solution was
to soak the plates in 3N HCL for 20 min. Then rinse well in diWater. Then
Wash the plates as normal. We found this immediatly solved the problem. If
this doesn't correct the problem, switch to new plates. This should work
on the 370/373 as well. If it is a 373 check the PMT and make sure that
the lowest baseline in the plate check is higher than 800 on the y axis in
the plate check window. feel free to email me if you have any further
Steve Marsh
marshsr at

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