Wedge gels (try #2)

[John J Welch]

Dear Net:

	I am interested in sequencing/footprinting on relatively small
DNA sequences.  A 20% denaturing PAGE gel will accomodate almost the entire
sequence, but the smallest fragments usually get very spread-out and the
very smallest  zip right off the end of the gel.  One person suggested 
pouring a gel of variable thickness to create an electrical field gradient.
Large pieces would migrate faster, small pieces would migrate slower, relative
to their mobilities in a standard "flat" gel.  This makes sense to me, and
I have seen examples of such gels.  After checking searching the archives 
for this group, I have seen nothing on this topic except a reference to 
thermal gradient gels which may yield similar results.  

	I would like to see if anyone has had experience with E-field 
gradient gels, or if anyone can give pointers to literature on the subject.
According to the person who recommended this technique, his lab used to 
home-make the spacers out of nylon plastic sheets using a lathe.  Can 
anyone recommend a commercial supplier?  

	Thanks in advance for information.  Please respond by Email to
	
	welch at sc3101.med.buffalo.edu

	Or reply via this newsgroup.

	
Sincerely,


John Welch
Roswell Park Cancer Institute