Nylon membrane lot & false positive colony lift?

[graham at biodec.wustl.edu]

What we have seen here recently suggests the possibility that different 
postiviely charged nylon membrane lots (eg. Nytran, GeneScreen+, MSI 
Magnacharge) might result in different amount of "background" 
hybridization to E. coli library colony lifts. This is distinct from any 
generic background darkening of the membrane itself -rather those clones 
one would expect to be "negative" give different levels of signal 
depending on the particular set of membranes prepared. Levels do appear 
consitent within a particular batch prepared at once, but differ widely 
when different lots of the same source of membrane are used.

I find it difficult to imagine how one charged nylon surface might 
effect the hybridization of molecules bound to it differently than 
another. However, different overall nucleic acid retention efficiencies 
have been previously observed. Perhaps more proteins are bound by one 
membrane lot which leads to a higher false signal with some membrane 
lots?

Anyone seen it? If so, please e-mail me a copy of any responses 
directly. 

Thanks very much,

Jim
J. Graham PhD
Biology Department
Washington University of St. Louis