Zhuo, Zong-YanZong-YanZhuoLiao, Chien-ShengChien-ShengLiaoHuang, Chen-HanChen-HanHuangYu, Jiun-YannJiun-YannYuTzeng, Yu-YiYu-YiTzengLo, WenWenLoCHEN-YUAN DONGChui, Hsiang-ChenHsiang-ChenChuiHuang, Yu-ChanYu-ChanHuangHSI-MEI LAISHI-WEI CHU2019-12-262019-12-262010-07https://scholars.lib.ntu.edu.tw/handle/123456789/441789https://www.scopus.com/pages/publications/77953615568?origin=resultslistWe present a new method, second harmonic generation (SHG) imaging for the study of starch structure. SHG imaging can provide the structural organization and molecular orientation information of bio-tissues without centrosymmetry. In recent years, SHG has proven its capability in the study of crystallized bio-molecules such as collagen and myosin. Starch, the most important food source and a promising future energy candidate, has, for a decade, been shown to exhibit strong SHG response. By comparing SHG intensity from different starch species, we first identified that the SHG-active molecule is amylopectin, which accounts for the crystallinity in starch granules. With the aid of SHG polarization anisotropy, we extracted the complete χ (2) tensor of amylopectin, which reflects the underlying molecular details. Through χ (2) tensor analysis, three-dimensional orientation and packing symmetry of amylopectin are determined. The helical angle of the double-helix in amylopectin is also deduced from the tensor, and the value corresponds well to previous X-ray studies, further verifying amylopectin as SHG source. It is noteworthy that the nm-sized structure of amylopectin inside a starch granule can be determined by this far-field optical method with 1-μm excitation wavelength. Since SHG is a relatively new tool for plant research, a detailed understanding of SHG in starch structure will be useful for future high-resolution imaging and quantitative analyses for food/energy applications.AmylopectinMolecular orientationNonlinear opticsPolarization anisotropyTensor analysisThree-dimensional imaging[SDGs]SDG7journal article10.1016/j.jsb.2010.02.0202-s2.0-77953615568https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953615568&doi=10.1016%2fj.jsb.2010.02.020&partnerID=40&md5=30e7bd3e3b98391c8a37e278fe8cf922