RNase Band in old plasmid stored at -40 - (Mar/23/2012 )

Hi all
I isolated plasmid PET21 by alkaline lysis method treated it with RNase and used required amount then stored the remaining plasmid at -40C two year back in 2011. But yesterday I again needed that pet and i check that it was there intact band but there was again RNase band present even though i treated it with RNase because i labeled it at that time. I want to perform restriction of this plasmid can any one tell why it is so? should I use it after RNase treatment again?

It might not be RNA. It could be degraded DNA from over lysis or rough handling during lysis. But this should not affect your plasmid digestion or its downstream utility (except perhaps to overestimate its concentration).

Speaking for myself, I think I would find it hard to have done this two years ago in 2011.

I meant in 2010 . thank you for ur suggestion .