Hello Deepak, What pH are your crystals at? Also, you need to check whether your atomic arrangement has reasonable geometry for hydrogen bonding in addition to the interatomic distances.
ho ------------------------------ Date: Mon, 29 Mar 2010 12:11:59 +0800 From: Deepak Oswal <deepos...@gmail.com> Subject: activation of thiol group Dear colleagues: We have a 1.4 Angstrom structure of an enzyme showing a water molecule enclosed in a triangular pocket formed by the hydroxyl oxygens of 2 serine residues and a sulfhydryl group of an essential cysteine. The water molecule is forming a 2.8 Angstrom hydrogen bond with each of the hydroxyl groups of the 2 serines and a 2.9 Angstrom hydrogen bond with the sulfhydryl group of the cysteine. Is it possible for such a water molecule to lower the pKa of the cysteine and activate the thiol group? I would appreciate any comments or suggestions or information on any literature that I need to look up :> Sincerely, Deepak