title: Density functional conformational study of 2-O-sulfated 3,6 anhydro-α-D-galactose and of neo-κ- and ι-carrabiose molecules in gas phase and water.
abstract: We examined the conformational preferences of the 2-O-sulfated-3,6-α-D-anhydrogalactose (compound I) and two 1,3 linked disaccharides constituting-κ or ι-carrageenans using density functional and ab initio methods in gas phase and aqueous solution. Systematic modifications of two torsion angles leading to 324 and 144 starting geometries for the compound I and each disaccharide were used to generate adiabatic maps using B3LYP/6-31G(d). The lower energy conformers were then fully optimized using B3LYP, B3PW91 and MP2 with several basis sets. Overall, we discuss the impact of full relaxation on the energy and structure of the dominant conformations, present the performance comparison with previous molecular mechanics calculations if available, and determine whether our results are impacted, when polarization and diffuse functions are added to the 6-31G(d) basis set, or when the MP2 level of theory is used.
authors.affiliation: L2MSM, Faculté des Sciences, Université Djillali Liabes de Sidi Bel Abbes, B.P. 89, 22000, Sidi Bel Abbes, Algeria.
authors.forename: Noreya
authors.initials: N
authors.lastname: Bestaoui-Berrekhchi-Berrahma
authors.forename: Philippe
authors.initials: P
authors.lastname: Derreumaux
authors.forename: Majda
authors.initials: M
authors.lastname: Sekkal-Rahal
authors.forename: Michael
authors.initials: M
authors.lastname: Springborg
authors.forename: Adlane
authors.initials: A
authors.lastname: Sayede
authors.forename: Noureddine
authors.initials: N
authors.lastname: Yousfi
authors.forename: Abd-Ed-Daim
authors.initials: AE
authors.lastname: Kadoun
mesh_terms: D002236:Carbohydrate Conformation; D002351:Carrageenan / Q000737:chemistry*; D005690:Galactose / Q000031:analogs & derivatives*; D005740:Gases; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D013816:Thermodynamics; D014867:Water
chemical_list: D005740:Gases; D014867:Water; C080061:carrabiose; D002351:Carrageenan; D005690:Galactose