title: Local site selectivity and conformational structures in the glycosidic bond scission of cellobiose.
abstract: Car-Parrinello molecular dynamics combined with metadynamics simulations were used to study the acid-catalyzed hydrolysis of cellobiose (CB) in aqueous solution. The hydrolysis was studied in two steps. Step 1 involves the proton transfer from solvent to CB and dissociation of the glycosidic bond to β-glucose and oxacarbenium ion species. Step 2 involves the formation of α-glucose from oxacarbenium and regeneration of the acid proton species. Step 1 is endothermic, while Step 2 is exothermic. The overall activation free energy of CB hydrolysis is 32.5 kcal mol(-1), and the overall reaction free energy is -5.9 kcal mol(-l), consistent with available experimental data. We observe that a stepwise mechanism generally described in the literature for Step 1 is not significantly favored relative to a concerted β-1,4' linkage dissociation process.
authors.affiliation: School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Xiao
authors.initials: X
authors.lastname: Liang
authors.forename: Alejandro
authors.initials: A
authors.lastname: Montoya
authors.forename: Brian S
authors.initials: BS
authors.lastname: Haynes
mesh_terms: D002384:Catalysis; D002475:Cellobiose / Q000737:chemistry*; D019277:Entropy; D005947:Glucose / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry*; D006868:Hydrolysis; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation
chemical_list: D006027:Glycosides; D002475:Cellobiose; D005947:Glucose