Lambda DNA prep

[Chi-kuang Wen]

Thanks John for posting your lambda DNA prep by using DE-52.  I got 
several questions regarding the preparation of DE-52 in your
protocol.

1. Why the MgCl2 is important in the preparation of DE-52 after the HCl wash?
   I understand that HCl washing is an important step in "precycling" of
   DE-52, a DEAE-cellulose, but do not know the function of MgCl2 in the 
   following step.  As a standard "precycling" procedure of DEAE-cellulose,
   the DEAE-cellulose is washed by HCl and then by NaOH, and the resulting 
   counter-ion will be OH-, and the salt conc will be 0.5M of NaCl.  To remove
   the salt which will interfere with the binding capacity of DEAE, low-salt
buffer is applied to the resin.

2.  Is it a procedure modified from an article published from 
    Nucleic Acids Research several years ago?  Anyway, your procedure is
    more improved in the aspect of ion-exchange.

Thnaks again.

Chi_Kuang