Structural characterisation of native and hydrolysed starches and their polymers

In the case of starch, it is possible to recrystallise amylose either from solution [10, 54, 43], or during in vitro enzymatic synthesis [55, 56], in the different crystalline forms present in native or processed starches. We thus obtained a 3D structure [10, 54] of one of the polymorphs at a resolution never before obtained for a polymer (0.13nm) and, using high-resolution solid state NMR on labelled amylose crystals [56], fine measurements of the distances between carbon atoms within the structure of another polymorph.

All these results can be interpreted in terms of self-association and typical entanglement/crystallisation behaviour of biopolymers, with strong homologies between in vivo biosynthesis and in vitro experiments on the one hand, and between starch and synthetic polymers on the other [37]. Finally, hybrid materials based on mixtures of carboxymethylcellulose or amylose can be prepared with carbon nanotubes, making it possible to select their optical or conductive properties without modifying their mechanical properties, with a view to designing biosensors [40, 11, 0].

The development of comprehensive, rapid and simple methods using the A4F-MALLS coupling (Fractionation by crossing two flows and Multiangular Light Scattering) and HDC-SEC-MALLS-QELS (Hydrodynamic Chromatography and Steric Exclusion Chromatography and Light Scattering in static and dynamic modes), has made it possible to study the structure of highly branched macromolecules, such as amylopectin. Thanks to their high throughput and high resolution, interpretations are easier and more reliable. The molecular structure and variability of a series of cassava starches has thus been compared with maize starches, making it possible to reduce the environmental impact of the plant on the structure of its starch.