The diketo acid (DKA) class of HIV-1 integrase inhibitors are thought to function by chelating divalent metal ions within the enzyme catalytic center. However, differences in mutations conferring resistance among sub-families of DKA inhibitors suggest that multiple binding orientations may exist. In order to facilitate identification of DKA-binding sites, biotin-tagged biphenyl ketone-containing 2, 4-dioxobutanoic acids were prepared as DKA photoaffinity ...