MM3 Potential energy surfaces of β-4-linked mannobiose and mannotriose at different dielectric constants

Carlos A Stortz

doi:10.3998/ark.5550190.0006.c03

Abstract

The adiabatic potential energy surface (PES) of β-4-linked mannobiose was obtained using the MM3 force field at e=3 and e=80, and plotted as contour maps and as 2D graphs representing the energy vs. the ψ angle. The surfaces of the corresponding trisaccharide were also obtained and represented by a single 3D contour map for which the energy is plotted against the two ψ glycosidic angles. The PES of the disaccharide contains a low-energy well comprising two different minima, and three more minima in different locations. No major change was observed by changing the dielectric constant. For the trisaccharide, four main minima were observed, located within one minimum-energy region. The minima have a geometry close to that experimentally obtained for mannobiose, mannotriose and mannan I in solid state, but differ from that expected in aqueous solutions. The flexibility of the glycosidic linkage increases at higher dielectric constant, whereas it decreases for the linkage closer to the reducing end when passing from the dito the trisaccharide.

Highlights

In order to understand the industrial and biological functions of carbohydrates, a deep knowledge of their shapes is very important
The adiabatic potential energy surface (PES) of β-4-linked mannobiose was obtained using the MM3 force field at ε=3 and ε=80, and plotted as contour maps and as 2D graphs representing the energy vs. the ψ angle
The minima have a geometry close to that experimentally obtained for mannobiose, mannotriose and mannan I in solid state, but differ from that expected in aqueous solutions

Summary

Introduction

In order to understand the industrial and biological functions of carbohydrates, a deep knowledge of their shapes is very important. The minima are named by a two-letter code according to the minimum energy region (A or B) of the Man”→Man’ linkage (first letter) and the Man’→Man linkage (second letter).[12,13,14,15] Table 3 shows the flexibility measurements carried out using the data obtained for the di- and trisaccharides under study.

Results

Conclusion