These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: The crystal structure of the alpha-cellobiose.2 NaI.2 H(2)O complex in the context of related structures and conformational analysis.
    Author: Peralta-Inga Z, Johnson GP, Dowd MK, Rendleman JA, Stevens ED, French AD.
    Journal: Carbohydr Res; 2002 Apr 30; 337(9):851-61. PubMed ID: 11996839.
    Abstract:
    The crystal structure of beta-D-glucopyranosyl-(1-->4)-alpha-D-glucopyranose (alpha-cellobiose) in a complex with water and NaI was determined with Mo K(alpha) radiation at 150 K to R=0.027. The space group is P2(1) and unit cell dimensions are a=9.0188, b=12.2536, c=10.9016 A, beta=97.162 degrees. There are no direct hydrogen bonds among cellobiose molecules, and the usual intramolecular hydrogen bond between O-3 and O-5' is replaced by a bridge involving Na+, O-3, O-5', and O-6'. Both Na+ have sixfold coordination. One I(-) accepts six donor hydroxyl groups and three C-H***I(-) hydrogen bonds. The other accepts three hydroxyls, one Na+, and five C-H***I(-) hydrogen bonds. Linkage torsion angles phi(O-5) and psi(C-5) are -73.6 and -105.3 degrees, respectively (phi(H)=47.1 degrees and psi(H)=14.6 degrees ), probably induced by the Na+ bridge. This conformation is in a separate cluster in phi,psi space from most similar linkages. Both C-6-O-H and C-6'-O-H are gg, while the C-6'-O-H groups from molecules not in the cluster have gt conformations. Hybrid molecular mechanics/quantum mechanics calculations show <1.2 kcal/mol strain for any of the small-molecule structures. Extrapolation of the NaI cellobiose geometry to a cellulose molecule gives a left-handed helix with 2.9 residues per turn. The energy map and small-molecule crystal structures imply that cellulose helices having 2.5 and 3.0 residues per turn are left-handed.
    [Abstract] [Full Text] [Related] [New Search]