MW of PVP inDenhardts?

[Greg Galloway]

Hello,
I am trying to determine what is the correct molecular weight of 
Polyvinylpyrrolidone used in Denhardts solution.  Does it really matter?  We 
have at least 3 different sizes on the shelf.  I've looked in Maniatis, the 
MGH "Red book" and a couple of other places and they all just call for PVP, 
but do not give a size preference.  Any suggestions?
Thanks,
Mark Watson