Substituting buffering agents - Did I go to far? (Sep/30/2008 )

Is it acceptable to substitute MOPS for HEPES as a buffer for a kinase assay?

I also replace 0.1% 2-mercaptoethanol with a 0.05% DTT (I lower it because DTT is a stronger reducing agent)

Do you agree with this/see any problems?

I work in a lab with limited resources - so I need to do a lot of improvisation to save some $$ - just need to know if I have gone too far because I'm having some issues with my kinase activity and I'm wondering if the buffer is responsible!

Thanks for your help