Plused Field Gel Electrophoresis - (Dec/13/2005 )

hi. I have some doubts regarding pulsed field gel electrophoresis. What is the main concept presented here? Also, what is the purpose of zigzaging the current?
Hope someone can answer my questions. Thanks!

Here is a very cool link which explain everything
http://www.nal.usda.gov/pgdic/Probe/v2n3/puls.html

Basically this process allows the separation of very high molecular weight DNA, I use it to type the Neisseria meningitidis in my lab and it's quite good to discriminate among variants and mutants of a given strain

Pesji