title: Second Harmonic Generation Mediated by Aligned Water in Starch Granules.
abstract: The origin of second harmonic generation (SHG) in starch granules was investigated using ab initio quantum mechanical modeling and experimentally examined using polarization-in, polarization-out (PIPO) second harmonic generation microscopy. Ab initio calculations revealed that the largest contribution to the SHG signal from A- and B-type allomorphs of starch originates from the anisotropic organization of hydroxide and hydrogen bonds mediated by aligned water found in the polymers. The hypothesis was experimentally tested by imaging maize starch granules under various hydration and heat treatment conditions that alter the hydrogen bond network. The highest SHG intensity was found in fully hydrated starch granules, and heat treatment diminished the SHG intensity. The PIPO SHG imaging showed that dried starch granules have a much higher nonlinear optical susceptibility component ratio than fully hydrated granules. In contrast, deuterated starch granules showed a smaller susceptibility component ratio demonstrating that SHG is highly sensitive to the organization of the hydroxyl and hydrogen bond network. The polarization SHG imaging results of potato starch granules, representing starch allomorph B, were compared to those of maize starch granules representing allomorph A. The results showed that the amount of aligned water was higher in the maize granules. Nonlinear microscopy of starch granules provides evidence that varying hydration conditions leads to significant changes in the nonlinear susceptibility ratio as well as the SHG intensity, supporting the hypothesis from ab initio calculations that the dominant contribution to SHG is due to the ordered hydroxide and hydrogen bond network.
authors.affiliation: Department of Chemical and Physical Sciences, Department of Physics, and Institute for Optical Sciences, University of Toronto , 3359 Mississauga Road North, Mississauga, Ontario Canada L5L 1C6.
authors.forename: Richard
authors.initials: R
authors.lastname: Cisek
authors.affiliation: Department of Chemical and Physical Sciences, Department of Physics, and Institute for Optical Sciences, University of Toronto , 3359 Mississauga Road North, Mississauga, Ontario Canada L5L 1C6.
authors.forename: Danielle
authors.initials: D
authors.lastname: Tokarz
authors.affiliation: Department of Chemical and Physical Sciences, Department of Physics, and Institute for Optical Sciences, University of Toronto , 3359 Mississauga Road North, Mississauga, Ontario Canada L5L 1C6.
authors.forename: Serguei
authors.initials: S
authors.lastname: Krouglov
authors.affiliation: Department of Plant Physiology, Institute of Biochemistry and Biology, University of Potsdam , Karl-Liebknecht-Strasse 24-25 Building 20, 14476 Potsdam, Germany.|Department of Molecular and Cellular Biology, College of Biological Science, Summerlee Science Complex, University of Guelph , 50 Stone Road East, Guelph, Ontario Canada N1G 2W1.
authors.forename: Martin
authors.initials: M
authors.lastname: Steup
authors.affiliation: Department of Molecular and Cellular Biology, College of Biological Science, Summerlee Science Complex, University of Guelph , 50 Stone Road East, Guelph, Ontario Canada N1G 2W1.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Emes
authors.affiliation: Department of Molecular and Cellular Biology, College of Biological Science, Summerlee Science Complex, University of Guelph , 50 Stone Road East, Guelph, Ontario Canada N1G 2W1.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Tetlow
authors.affiliation: Department of Chemical and Physical Sciences, Department of Physics, and Institute for Optical Sciences, University of Toronto , 3359 Mississauga Road North, Mississauga, Ontario Canada L5L 1C6.
authors.forename: Virginijus
authors.initials: V
authors.lastname: Barzda
mesh_terms: D006860:Hydrogen Bonding; D011198:Solanum tuberosum / Q000737:chemistry; D013213:Starch / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry
chemical_list: D014867:Water; D013213:Starch