Three-dimensional structures of the clinical drugs brinzolamide (BZM, left) and
dorzolamide (DZM, right) as observed in the hCA II active site. The red arrow
shows the amino groups of the drugs: in BZM, the nitrogen atom (in blue)
is not protonated and thus not charged; in DZM, the nitrogen atom
has accepted an extra proton and thus is positively charged.