5.1.1.4	best crystals are obtained by mixing 2-3 microliter of the protein solution with an equal volume of crystallization buffer (0.1 M ammonium acetate/50 mM tri-sodium citrate dihydrate, pH 5.6/15% w/v polyethylene glycol 4000), equilibrated over 1 ml of the same buffer	676832	
5.1.1.4	crystal structure analysis shows that TcPRACA is a homodimer, with each monomer folded in two symmetric alpha/beta subunits separated by a deep crevice. The structure of TcPRACA in complex with a transition-state analog, pyrrole-2-carboxylic acid, reveals the presence of one reaction center per monomer, with two Cys residues optimally located to perform acid/base catalysis through a carbanion stabilization mechanism	676832