|Willett, Julious - J l|
Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 6/13/2007
Publication Date: 8/23/2007
Citation: Schnupf, U., Momany, F.A., Willett, J.L., Bosma, W. 2007. DFT STUDIES OF DP-3 AMYLOSE FRAGMENTS. Meeting Abstract. xx. Interpretive Summary:
Technical Abstract: This study extends our work on mono- and disaccharides to structures with three glucose residues by two alpha-[1-4] bridges, denoted herein as DP-3's. DFT optimization studies of DP-3 fragments have been carried out at the B3LYP/6-311++G** level of theory. Different hydroxymethyl conformations (gg, gt, tg) were chosen on each of the three residue sites. Calculation of this type of sequence of single residue conformational changes allows one to determine the influence of hydroxymethyl variation on the bridge Phi-Psi values, as a function of position in the DP-3 sequence. The exocyclic hydroxyl groups were considered in either the all clockwise or "c" form, or the all reverse-clockwise or "r" form. Energy differences between conformations are examined in order to assess the stability of different hydroxyl/hydroxymethyl configurations and to identify the sources of energy that dictate amylose polymer formation. In addition, DP-3 is the smallest amylose fragment that allows the study of boat/skew conformations placed as the middle residue. The search for low energy boat/skew forms within an amylose fragment is important in the collection of conformational tools of starch materials. A comparison with alpha-maltose and DP-4 amylose fragments show that the energy differences between conformers become more pronounced as one proceeds to larger fragments.