Structures of Biomolecules
in the gas phase
-JPSGroup-
Sugars and oligosaccharides
Introduction
Carbohydrates constitute
one of the four major classes of biomolecules, along with proteins, nucleic
acids and lipids. They can be found as polysaccharides, or bound to proteins
and/or lipids, or as part of the structural framework of the nucleic acids
- but they are not normally found in the gas phase! They make up most of
the organic matter on Earth and have multiple functions in living systems:
They serve as energy stores, fuels, and metabolic intermediates, they are
parts of cell walls and play a key role in molecular recognition at the
cell’s surface.
Current research projects 
A model monosaccharide,
phenyl-b-D-glucopyranoside,
has been investigated spectroscopically and with ab initio computation.
Comparison with ab initio predictions of unsubstituted b-D-glucopyranose
indicates that the addition of a phenyl substituent at position 1 on the
pyranoside ring has very little effect on the low energy region of the
conformational landscape.
|
-
Figure 1. Low-lying conformers
of phenyl-b-D-glucopyranoside. Relative energies are in kJ/mol.
|
3 conformers are observed.
Assuming all three conformers have the same oscillator strength, these
intensities then correspond to population percentages of 68:25:7 %, for
A:B:X.
|
-
Figure 2.
|
The IR spectra allow
an unambiguous assignment of species ‘X’ to the trans conformer ttttTg+.
Species ‘A’ and ‘B’ correspond
to the two gauche
conformers, and are tentatively assign to the ttttG+g- and ttttG-g+ conformers
respectively. The liquid-phase population of 50:50:0 % for gauche:gauche:trans
does not reflect our gas-phase population of 68:25:7%, which encourages
the investigation of the water clusters...
|
-
Figure 3.
|
Near future 
An investigation of phenylgalactose
will be the second step toward the investigation of lactose (Gal-Glc).
Collaborations 
Professor
George Fleet (Dyson Perrins Laboratory for Organic Chemistry, Oxford)
Professor
Raymond Dwek, Dr.
Mark Wormald (Oxford Glycobiology Institute)
References
Sugars in the gas phase: the
spectroscopy and structure of jet-cooled Phenyl b-D-Glucopyranoside,
F.O. Talbot and J.P. Simons, Phys. Chem. Chem. Phys., 2002, 4,
3562-3565.
Neurotransmitters
| Sugars | Amino acids, peptides
| Protonated species | Circular
Dichroism spectroscopy
Last updated 08/10/2002
by
Lavina Snoek