"Hole" in the middle of Southern bands?(More for less)

Euan R. Taylor etaylor at ccu.umanitoba.ca
Mon Sep 20 17:12:42 EST 1993

In <1993Sep13.141945.1 at mcvax4.d48.lilly.com> dallas at mcvax4.d48.lilly.com writes:

>In article <GERLACHJ.54.747688503 at QUCDN.QueensU.CA>, GERLACHJ at QUCDN.QueensU.CA (Jim Gerlach) writes:
>> In article <26nbu3$q7n at rigel.fccc.edu> hardy at mighty.fccc.edu (Randy Hardy) writes:
>>>From: hardy at mighty.fccc.edu (Randy Hardy)
>>>Subject: "Hole" in the middle of Southern bands?
>>>Date: 9 Sep 93 13:43:31 GMT
>>> Here's a weird problem: recently we have started seeing empty centers to
>>>intense bands in our PCR-Southerns (amplify, blot, probe with internal
>>>fragment, autorad).  Previous months of blotting never showed this.  Now
>>>past 2 weeks, several blots have it.  Sometimes only in certain lanes of a
>>>single blot, sometimes all.  Sometimes appears as a clear area in the lane
>>>(2 sides of band are hot), other times it's a "doughnut".  Anyone else
>>>ever seen this and/or opinions as to what's causing it.  BTW, We're using
>>>a StrataGene pressure blotter (have been for past year).  Thanks in
>> We sometimes see this as well and it is *NOT* caused by air bubbles. In our 
>> hands it only occurs in bands that could be considered as "overloaded".

I seem to remember seeing this in a plasmid blot and also a couple oftimes
in gels of radiolabelled primers. I assumed it was due to the radiation
level being sufficient to bleach the film. I dnt know exactly how that
would hapen. Inot convinced by the idea of overloading because the path
length of 32P is enough to blacken a good centimetre diameter of film in a
really strong signal, and the blank patches I have seen were very local
and discreet bands, course I also dont understand why path length wouldn't
make for a largely blurred and spread out pale area.
Any more ideas anyone?

Usual disclaimers. These are my own opinions and probably nobody else's.
etaylor at ccu.umanitoba.ca
"All great truths begin life as blasphemies"  George Bernard Shaw 

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