Chen CS, Yu YP, Hsu CH, Zou W, Fang JM, Wu SH. Evaluation of the regioselective delactonization of tri-sialic acid lactone by in-solution molecular dynamics simulation.
Carbohydr Res 2012;
354:87-93. [PMID:
22572126 DOI:
10.1016/j.carres.2012.02.022]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 02/18/2012] [Accepted: 02/22/2012] [Indexed: 11/29/2022]
Abstract
An approximate model for the delactonization of tri-sialic acid lactone is presented with two water-layers that led to neutral hydrolysis of δ-lactone. The hydrolytic reactivity was studied with a 10-ns in-solution molecular dynamics simulation. The initial step of this hydrolysis involves a reactant water nucleophile complex via a proton transfer with another water molecule. Therefore, the probability of water molecules localized at the hydrolytic center correlates to the hydrolysis of δ-lactone. The stepwise delactonization of α2,8-(NeuAc)(3) lactone results/resulted from water concentration discrepancy near the carbonyl carbon of lactones in two water oxygen···carbonyl carbon shells, and the distances of OC···O(water) layers were 2.8 Å and 5.1 Å. Based on in-solution molecular dynamics study, the motion of water molecules over the re-face of the carbonyl groups was used for the quantitative description of the residence probability, p, whose value is 0.11 for lactone I and 0.33 for lactone II. The geometric criteria used to determine the residence statistics are (1) the distance of water-oxygen···carbonyl carbon in less than 5.1 Å and (2) the cone angle, θ, of carbonyl OC···O(water) in the range of 85-115°. As expected, a higher residence probability at lactone II led to its faster hydrolysis. Both the radial g(r) and angular p(θ) pair distribution functions of water oxygen and carbonyl groups of lactones ensure a better surrounding hydration encounter for lactone II. In contrast, water molecules around lactone I are deduced due to a steric hindrance by the turn structure of α2,8-(NeuAc)(3) lactone.
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