Self-Association and Crystallization of Amylose

Abstract

Amylose, the linear constituent of starch, consists of α(1,4)-linked glucose monomers. Although weakly involved in the crystalline structure of starch, it can be recrystallized in a variety of allomorphic types, including those encountered in native starch (A- and B-types). Amylose can either be extracted from starch or produced in vitro by enzymatic synthesis using amylosucrase or phosphorylase. Recrystallization and self-association of amylose in aqueous solutions have been widely studied to understand both the crystallization of starch during biosynthesis and the structural changes that occur during starch processing. Depending on the chain length, concentration, and temperature, gels, spherulites, or lamellar crystals can be formed with A or B allomorphic type. Other ligand-dependent allomorphs (the various V-types) are obtained when amylose is complexed with molecules such as alcohols, lipids, or flavours. Amylose also self-associates into networks, spherulites, or axialites during in-vitro enzymatic synthesis by amylosucrase. When a highly branched acceptor like glycogen is used, dendritic nanoparticles are formed by elongation of the external chains. The recrystallization of amylose extracted from starch and the self-association of amylose during its in-vitro synthesis are described. The amylose properties are discussed in terms of polymer behaviour and model systems to investigate the structure and formation of starch granules.

Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy

“…2͑c͒, is very similar to the so-called maltese cross image of the starch granule observed in a linear polarization microscope. 182 The anisotropy value along the vertical and horizontal axes in this image is nearly 1, indicating a good radial alignment of the nanocrystallites in the starch granule. The anisotropy image shows that the nanocrystallites bend away from the radial orientation throughout the granule, and that the periphery of the granule is particularly well aligned.…”

Crystal Structure of A-amylose: A Revisit from Synchrotron Microdiffraction Analysis of Single Crystals

“…The present structure of Aamylose describes only one of the numerous allomorphs in which amylose is susceptible to crystallize as micron-sized single crystals. 44,45 Many of these are in fact crystallosolvates, where amylose single helices are co-crystallized with guest molecules that are located either within the helical cavities and/or in between the helices. These easy-to-prepare crystalline complexes are quite important for the science of starch, since they allow not only the fractionation of starch, but also the slow release of the guests over a number of days or even months.…”

Crystallite orientation maps in starch granules from polarized Raman spectroscopy (PRS) data

“…Although this allomorph is frequently 175 observed in native starch granules, spherulites (Buléon, et al, 2007) and, more recently, 176 axialites , and although the preparation of thin lamellar single crystals 177 has been reported once (Buléon, et al, 1984), the in vitro formation of large B-type single 178 crystals is still elusive. Consequently, we could not use any B-type single crystal model 179 specimen.…”