At the lowest level of structure, most starch granules are made up of alternating amor- phous and crystalline shells which are between 100 and 400nm thick.11,12,20 These structures are termed ‘growth rings.’ Radial organization of amylopectin molecules within such structures is thought to cause optical polarization, since the visible optical polarization is in the order of the wavelength of visible light (100 to 1000nm).21 At a higher level of molecular order, x-ray diffraction investigations22–24 in association with electron microscopy20,25 indicate a periodicity of 9–10 nm within the granule. The peri- odicity is interpreted as being due to the crystalline and amorphous lamellae formed by clusters of side chains branching off from the radially arranged amylopectin mol- ecules, and appears to be a universal feature of starch granules, independent of botani- cal source. Furthermore, it suggests a common mechanism for starch deposition.26
At the lowest level of structure, most starch granules are made up of alternating amor- phous and crystalline shells which are between 100 and 400nm thick.11,12,20 These structures are termed ‘growth rings.’ Radial organization of amylopectin molecules within such structures is thought to cause optical polarization, since the visible optical polarization is in the order of the wavelength of visible light (100 to 1000nm).21 At a higher level of molecular order, x-ray diffraction investigations22–24 in association with electron microscopy20,25 indicate a periodicity of 9–10 nm within the granule. The peri- odicity is interpreted as being due to the crystalline and amorphous lamellae formed by clusters of side chains branching off from the radially arranged amylopectin mol- ecules, and appears to be a universal feature of starch granules, independent of botani- cal source. Furthermore, it suggests a common mechanism for starch deposition.26
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