Smart trick for marking replicas?

[Jarkko Kortesmaa]

Dear netters,

I have marked the position of replica filters on the plate by stabbing 
through the filter into the plate agar as suggested in Current Protocols. 

Finding the needle holes after hybrization and marking them on the film 
is time-consuming and not very convenient. Also, this method usually is 
so inaccurate that distinguishing between two plaques near each other for 
sure may be impossible, which means further screening/other extra analysis. 

In Clontech´s library manual, they recommended stabbing the filter with a
needle attached to a radioactive ink containing syringe. This way, the
positions of the holes should be seen directly on the film. IMHO, sounds 
VERY messy. Has anyone tried this? How active must the ink be? 

Do you have a clever method for this?
  
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Jarkko Kortesmaa		Dept. of Biochemistry and Biocenter Oulu
jkortes at paju.oulu.fi		University of Oulu
				Finland					
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