Relaxed energetic maps of kappa-carrabiose: a DFT study.
The B3LYP density function was used with the 6-31G(d) basis set to perform relaxed energetic contour maps of the charged form of kappa-carrabiose in the gas phase and for the neutral form first in the gas phase and then by simulating the presence of water as solvent using the Onsager model. Only one starting conformation has been considered to perform all the calculations. Rigid energetic maps have been then constructed either by addition of diffuse or polarization functions to the basis set obtaining in that way 6-31+G(d)//6-31G(d), 6-31+G(d,p)//6-31G(d), and 6-311++G(d,p)//6-31G(d) energetic maps that have been carefully examined. The obtained structures corresponding to the lower energy conformers have been then fully optimized using different basis sets with the B3LYP method, a reversion in term of energy has been observed for the two first minima in the case of the charged disaccharide in the gas phase, this was attributed to the large grid of 30 degrees that could lead to the exclusion of an intermediate value corresponding to the real minimum of energy. We thus suggest that after establishing potential energy maps it is essential to proceed to full optimizations of the lower energy conformers. Calculations using the more accurate correlated method MP2 with the 6-31G(d) basis set have also been performed for conformers of the two disaccharides in the gas phase.
Yousfi
N
N
Faculté des Sciences, Laboratoire L2MSM, Université Djillali Liabes de Sidi Bel Abbes, B.P. 89, Sidi Bel Abbes 22000, Algeria.
Sekkal-Rahal
M
M
Sayede
A
A
Springborg
M
M
D002351:Carrageenan / Q000737:chemistry*; D008956:Models, Chemical; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D013816:Thermodynamics
C080061:carrabiose; D002351:Carrageenan