Replica exchange molecular dynamics simulations reveal the structural and molecular properties of levan-type fructo-oligosaccharides of various chain lengths

摘要

Background Levan and levan-type fructo-oligosaccharides (LFOs) have various potential applications in pharmaceutical and food industries due to their beneficial properties such as their low intrinsic viscosity and high water solubility. Previous studies showed that they exhibited prebiotic effects, anti-inflammatory and anti-tumor activities against Sarcoma-180 tumor cells of human. Despite their various potential applications, the structural and molecular properties of LFOs of various chain lengths are not well understood. Results We employed the replica-exchange molecular dynamics simulations method (REMD) in AMBER14 to elucidate structural and molecular properties of LFOs with chain lengths of 5 (LFO₅), 10 (LFO₁₀) and 15 (LFO₁₅) residues in two models of generalized Born implicit solvent (GB_HCT and GB_OBC1). For LFO₁₀ and LFO₁₅, four distinct conformations (helix-like, partial helix, zig-zag and random structures) were characterized by their upper-middle and lower-middle torsions. For LFO₅, two distinct conformations (partial helix and random structures) were characterized by their middle torsion and molecular angle of residues 1, 3 and 5. To determine hydrogen bonds important for the formation of helix-like structures of LFO₁₀ and LFO₁₅, occurrence frequencies of hydrogen bonds were analyzed, and the O6_(i)--H3O_(i+1) hydrogen bond was found with the highest frequency, suggesting its importance in helix formation. Among three dihedral angles between two fructosyl units [? (O5’-C2’-O6-C6), ψ (C2’-O6-C6-C5) and ω (O6-C6-C5-C4)], dihedral angle distributions showed that ω was the most flexible dihedral angle and probably responsible for conformational differences of LFOs. Conclusions Our study provides important insights into the structural and molecular properties of LFOs, which tend to form helical structures as the chain length increases from 5 to 15 residues. This information could be beneficial for the selection of LFOs with appropriate lengths and properties for pharmaceutical and biological applications.