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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - BINDING FIBRES (Soluble dietary fibre: unraveling how weak bonds have a strong impact on function)

Teaser

Summary

Dietary fibres are recognized for their health promoting properties; nevertheless, many of the physicochemical mechanisms behind these effects remain poorly understood. While it is understood that dietary fibres can associate with small molecules influencing, both positively or negatively their absorption, the molecular mechanism, by which these associations take place, have yet to be elucidated. We propose a study of the binding in soluble dietary fibres at a molecular level to establish binding constants for various fibres and nutritionally relevant ligands. The interactions between fibres and target compounds may be quite weak, but still have a major impact on the bioavailability. To gain insight to the binding mechanisms at a level of detail that has not earlier been achieved, we will apply novel combinations of analytical techniques (MS, NMR, EPR) and both natural as well as synthetic probes to elucidate the associations in these complexes from macromolecular to atomic level. Glucans, xyloglucans and galactomannans will serve as model soluble fibres, representative of real food systems, allowing us to determine their binding constants with nutritionally relevant micronutrients, such as monosaccharides, bile acids, and metals. Furthermore, we will examine supramolecular interactions between fibre strands to evaluate possible contribution of several fibre strands to the micronutrient associations. At the atomic level, we will use complementary spectroscopies to identify the functional groups and atoms involved in the bonds between fibres and the ligands. The proposal describes a unique approach to quantify binding of small molecules by dietary fibres, which can be translated to polysaccharide interactions with ligands in a broad range of biological systems and disciplines. The findings from this study may further allow us to predictably utilize fibres in functional foods, which can have far-reaching consequences in human nutrition, and thereby also public health.

Work performed

The first years of the project have focused on the method development to study biomolecular interactions between dietary fibres and small molecules. We have successfully synthesised different kinds of probes, which can be used to study the existence and strength of interactions, and to provide complementary information about the possible binding mechanisms. These include creation of a well-defined fibre substrates with molecular structures that are characterised in detail with complementary analytical techniques (MS, SEC, DLS). In all sub-projects the initial setup of the method has been established, and the methods can be used to study different kinds of fibres and ligands in the coming years to enable the creation of structure-function relationships. Furthermore, the methods can further be diversified to cover fibre mixtures and multiple ligands in the same system, simultaneously adding to the applicability of the same technologies for a range of applications.

Final results

The project utilises previously unexplored analytical techniques for the study of molecular interactions between fibres and ligands. Analytical tools like direct mass spectrometry, electron paramagnetic resonance, and other methods for biomolecular interactions are commonly used for proteins, but seldom for carbohydrate polymers like dietary fibres. The major advantage of stretching the methods out to utilize them for polysaccharides lies in the fact that these methods can provide much more detailed information about the nature of the interaction and identify the functional groups involved, rather than merely confirming the existence of an interaction.