assigning protonation states



 Dear CClers
 
I'm looking for some program able to automatically (and reliably) assign protonation states at Phisiological pH to small organic molecules, preferably saved as mol2 files. As I can expect my boss ranting if he's to shed any money for it, any freeware alternative would be more than welcome. Any suggestion? many thanks
    luca
 --
 Real programmers don't comment!
 It was hard to write, It should be hard to read!