An X-ray free-electron laser structure of human carbonic anhydrase II is presented at 1.7 Å resolution and compared with structures derived using other methods.

Ultrahigh-resolution crystallographic structures of human carbonic anhydrase II (hCA II) cryocooled under CO₂ pressures of 7.0 and 2.5 atm are presented. The structures reveal new intermediate solvent states of hCA II that provide crystallographic snapshots during restoration of the proton-transfer water network in the active site.

Carbonic anhydrase II microcrystals suitable for XFEL data collection diffracted to 1.7 Å resolution and were indexed in space group P2₁, with unit-cell parameters a = 42.2, b = 41.2, c = 72.0 Å, β = 104.2°.

X-ray crystal structures of carbonic anhydrase II (CA II) in complex with nicotinic acid and ferulic acid are presented. Previously deposited structures of CA II in complex with carboxylic acid-based compounds are compared and the general mechanisms of CA inhibition are discussed.