Spec problems - Trying to measure protein conc. (Dec/04/2002 )

When i go to measure protein concentration, i keep getting negative 260 and 280 numbers. Then i decided to just try using water as a blank and then a titration of just BSA and i still keep getting negative numbers. Anyone know why or what it means? how can i have a negative abs?

are u using urea in any of your steps cos i have encountered such a problem with 6M urea u can also take a fluoresence scan of yor protein some materails that may interfere with 280 abs do not do so with fluoresence.

You can use a new measure kit from Biorad, it is special for 2-D running, it is compactble to urea.