Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

The anomeric effect is a chemical phenomenon that refers to an observed stabilization of six-membered carbohydrate rings when they contain an electronegative substituent at the C1 position of the ring. This stereoelectronic effect influences the three-dimensional shapes of many biological molecules. It can be manifested not only in this classical manner involving interaction of the endocyclic oxygen atom (O5) found in such sugars with the C1 substituent (endo-anomeric effect) but also through a corresponding interaction of the electronegative exocyclic substituent with O5 (exo-anomeric effect). However, the underlying physical origin(s) of this phenomenon is still not clear. Here we show, using a combination of laser spectroscopy and computational analysis, that a truncated peptide motif can engage the two anomers of an isolated sugar in the gas phase, an environment lacking extraneous factors which could confound the analysis. (Anomers are isomers that differ in the orientation of the substituent at C1.) Complexes formed between the peptide and the α- or β-anomers of d-galactose are nearly identical structurally; however, the strength of the polarization of their interactions with the peptide differs greatly. Natural bond order calculations support this observation, and together they reveal the dominance of the exo- over the endo-anomeric effect. As interactions between oxygen atoms at positions C1 and C2 (O1 and O2, respectively) on the pyranose ring can alter the exo/endo ratio of a carbohydrate, our results suggest that it will be important to re-evaluate the influence, and biological effects, of substituents at position C2 in sugars.

Original publication

DOI

10.1038/nature09693

Type

Journal article

Journal

Nature

Publication Date

06/01/2011

Volume

469

Pages

76 - 79

Keywords

Amino Acid Motifs, Computer Simulation, Galactose, Gases, Isomerism, Lasers, Models, Molecular, Molecular Conformation, Oxygen, Peptides, Solvents, Spectrum Analysis