Interaction and reaction of the hydroxyl ion with β-d-galactose and its hydrated complex: An ab initio molecular dynamics study

The interaction of OH^- with the sugar β-d-galactose is studied computationally, with Ab Initio Molecular Dynamics (AIMD) as the prime tool. The main findings are: (1) the OH^- abstracts a proton from the sugar in a barrier-less process, yielding H₂O and a Deprotonated beta-d-Galactose anion, (Dep-beta-d-G)^-. (2) This reaction can be reversed when two additional H₂O molecules are present in the sugar. (3) At 500 K, a ring-opening reaction occurs in (Dep-beta-d-G)^- within a timescale of 10 ps. The (neutral) sugar itself is stable over this timescale, and well beyond. This indicates that OH^- can catalyze the degradation of β-d-galactose. Implications of this process are briefly discussed.