Good alkaline pH indicators?

[Saurav Misra]

Anyone using any decent pH indicator dyes with pKas (in mM to Molar salt
concs.) of 8 or higher?  We would like to check out proton pumping at
alkaline pH values in our protein, kinetically (us to ms timescales).
Ideally, the indicator would be water soluble rather than in alcohol,etc.
but the latter would be doable.

-Saurav Misra
 saurav at tgevax.life.uiuc.edu