Combined high-resolution neutron and X-ray analysis of inhibited elastase confirms the active-site oxyanion hole but rules against a low-barrier hydrogen bond.
Tamada T, Kinoshita T, Kurihara K, Adachi M, Ohhara T, Imai K, Kuroki R, Tada T. J Am Chem Soc. 2009 Aug 12; 131(31):11033-40.