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  - 
TY  - JOUR
A1  - Cisek, Richard
A1  - Tokarz, Danielle
A1  - Steup, Martin
A1  - Tetlow, Ian J.
A1  - Emes, Michael J.
A1  - Hebelstrup, Kim H.
A1  - Blennow, Andreas
A1  - Barzda, Virginijus
T1  - Second harmonic generation microscopy investigation of the crystalline ultrastructure of three barley starch lines affected by hydration
JF  - Biomedical optics express
N2  - Second harmonic generation (SHG) microscopy is employed to study changes in crystalline organization due to altered gene expression and hydration in barley starch granules. SHG intensity and susceptibility ratio values (R'(SHG)) are obtained using reduced Stokes-Mueller polarimetric microscopy. The maximum R'(SHG) values occur at moderate moisture indicating the narrowest orientation distribution of nonlinear dipoles from the cylindrical axis of glucan helices. The maximum SHG intensity occurs at the highest moisture and amylopectin content. These results support the hypothesis that SHG is caused by ordered hydrogen and hydroxyl bond networks which increase with hydration of starch granules. (C) 2015 Optical Society of America
Y1  - 2015
U6  - https://doi.org/10.1364/BOE.6.003694
SN  - 2156-7085
VL  - 6
IS  - 10
SP  - 3694
EP  - 3700
PB  - Optical Society of America
CY  - Washington
ER  -