HELP!! - ExoIII-mung bean digests

[Shin-ichiro HIRAGA]

I think of some points.
1. Purity of the plasmid DNA. Is it almost completely pure covalently-closed circular 
DNA? No contamination of host DNA of open-cicular DNA?
2. ExoIII digests DNA more processively at lower temp such as 30-C or 23-C. At 23-C, 
if sufficient enzymes are supplied, ExoIII digest DNA in very synchronous manner 
(apparently, of course).
3. ExoIII digest 3' end of " DOUBLE - STRAND " DNA. So, high temp or DMSO might 
greatly inhibit ExoIII.

Good luck.