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Atomic-scale dynamical structures of fatty acid bilayers observed by ultrafast electron crystallography

Chen, Songye and Seidel, Marco T. and Zewail, Ahmed H. (2005) Atomic-scale dynamical structures of fatty acid bilayers observed by ultrafast electron crystallography. Proceedings of the National Academy of Sciences of the United States of America, 102 (25). pp. 8854-8859. ISSN 0027-8424. PMCID PMC1150297. http://resolver.caltech.edu/CaltechAUTHORS:CHEpnas05b

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Abstract

The structure and dynamics of a biological model bilayer are reported with atomic-scale resolution by using ultrafast electron crystallography. The bilayer was deposited as a Langmuir-Blodgett structure of arachidic (eicosanoic) fatty acids with the two chains containing 40 carbon atoms (50 Å), on a hydrophobic substrate, the hydrogen terminated silicon(111) surface. We determined the structure of the 2D assembly, establishing the orientation of the chains and the subunit cell of the CH2 distances: a0 = 4.7 Å, b0 = 8.0 Å, and c0 = 2.54 Å. For structural dynamics, the diffraction frames were taken every 1 picosecond after a femtosecond temperature jump. The observed motions, with sub-Å resolution and monolayer sensitivity, clearly indicate the coherent anisotropic expansion of the bilayer solely along the aliphatic chains, followed by nonequilibrium contraction and restructuring at longer times. This motion is indicative of a nonlinear behavior among the anharmonically coupled bonds on the ultrashort time scale and energy redistribution and diffusion on the longer time scale. The ability to observe such atomic motions of complex structures and at interfaces is a significant leap forward for the determination of macromolecular dynamical structures by using ultrafast electron crystallography.


Item Type:Article
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http://www.pnas.org/content/102/25/8854.longPublisherArticle
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1150297/PubMed CentralArticle
Additional Information:© 2005 National Academy of Sciences. Freely available online through the PNAS open access option. Contributed by Ahmed H. Zewail, May 13, 2005. We thank Prof. J. Heath for the use of his facilities and Drs. Y. Luo and H. Yu for the preparation of the LB bilayer. This work was supported by the National Science Foundation.
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Subject Keywords:dynamics, ultrafast electron diffraction, Langmuir-Blodgett films
PubMed Central ID:PMC1150297
Record Number:CaltechAUTHORS:CHEpnas05b
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:CHEpnas05b
Alternative URL:http://dx.doi.org/10.1073/pnas.0504022102
Official Citation:Songye Chen, Marco T. Seidel, and Ahmed H. Zewail Atomic-scale dynamical structures of fatty acid bilayers observed by ultrafast electron crystallography PNAS 2005 102 (25) 8854-8859; published ahead of print June 14, 2005, doi:10.1073/pnas.0504022102
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:492
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:11 Jul 2005
Last Modified:11 Aug 2016 22:09

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