TY - JOUR A1 - Cisek, Richard A1 - Tokarz, Danielle A1 - Kontenis, Lukas A1 - Barzda, Virginijus A1 - Steup, Martin T1 - Polarimetric second harmonic generation microscopy BT - an analytical tool for starch bioengineering JF - Starch-Starke N2 - Second harmonic generation (SHG) is a nonlinear optical process that inherently generates signal in non-centrosymmetric materials, such as starch granules, and therefore can be used for label-free imaging. Both intensity and polarization of SHG are determined by material properties that are characterized by the nonlinear susceptibility tensor, ((2)). Examination of the tensor is performed for each focal volume of the image by measuring the outgoing polarization state of the SHG signal for a set of incoming laser beam polarizations. Mapping of nonlinear properties expressed as the susceptibility ratio reveals structural features including the organization of crystalline material within a single starch granule, and the distribution of structural properties in a population of granules. Isolated granules, as well as in situ starch, can be analyzed using polarimetric SHG microscopy. Due to the fast sample preparation and short imaging times, polarimetric SHG microscopy allows for a quick assessment of starch structure and permits rapid feedback for bioengineering applications. This article presents the basics of SHG theory and microscopy applications for starch-containing materials. Quantification of ultrastructural features within individual starch granules is described. New results obtained by polarization resolved SHG microscopy of starch granules are presented for various maize genotypes revealing heterogeneity within a single starch particle and between various granules. KW - Determination of crystallinity KW - Determination of hydration KW - Label-free imaging KW - Nonlinear optical microscopy KW - Structural determination Y1 - 2017 U6 - https://doi.org/10.1002/star.201700031 SN - 0038-9056 SN - 1521-379X VL - 70 IS - 1-2 PB - Wiley-VCH CY - Weinheim ER -