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Second Harmonic Generation Mediated by Aligned Water in Starch Granules.
MedLine Citation:
PMID:  25427055     Owner:  NLM     Status:  Publisher    
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 starch crystalline allomorphs originates from the anisotropic organization of hydroxide and hydrogen bonds mediated by aligned water found within the crystals. 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 SHG PIPO 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 hydroxyl and hydrogen bond network. The polarization SHG imaging results of potato starch granules, representing crystalline starch allomorph B, were compared to 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 the ordered hydroxide and hydrogen bond network.
Richard Cisek; Danielle Tokarz; Serguei Krouglov; Martin Steup; Michael J Emes; Ian J Tetlow; Virginijus Barzda
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-11-26
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  J Phys Chem B     Publication Date:  2014 Nov 
Date Detail:
Created Date:  2014-11-26     Completed Date:  -     Revised Date:  2014-11-27    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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