Characterization of nanofibers formed by self-assembly of {beta}-peptide oligomers using small angle x-ray scattering
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706-1322 (United States)
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706-1322 (United States)
- Departments of Chemistry and Bioengineering, Rice University, 6100 Main Street, Houston, Texas 77005 (United States)
Helical oligomers of {beta}-peptides represent a particularly promising type of building block for directed assembly of organic nanostructures because the helical secondary structure can be designed to be very stable and because control of the {beta}-amino acid sequence can lead to precise patterning of chemical functional groups over the helix surfaces. In this paper, we report the use of small angle x-ray scattering measurements (SAXS) to characterize nanostructures formed by the directed assembly of {beta}-peptide A with sequence H{sub 2}N-{beta}{sup 3}hTyr-{beta}{sup 3}hLys-{beta}{sup 3}hPhe-ACHC-{beta}{sup 3}hPhe-ACHC-{beta}{sup 3}hPhe-{beta}{sup 3}hLys-ACHC-ACHC-{beta}{sup 3}hPhe-{beta}{sup 3}hLys-CONH{sub 2}. Whereas prior cryo-TEM studies have revealed the presence of nanofibers in aqueous solutions of {beta}-peptide A, SAXS measurements from the nanofibers were not well-fit by a form factor model describing solid nanofibers. An improved fit to the scattering data at high q was obtained by using a form factor model describing a cylinder with a hollow center and radial polydispersity. When combined with a structure factor calculated from the polymer reference interaction site model (PRISM) theory, the scattered intensity of x-rays measured over the entire q range was well described by the model. Analysis of our SAXS data suggests a model in which individual {beta}-peptides assemble to form long cylindrical nanofibers with a hollow core radius of 15 A (polydispersity of 21%) and a shell thickness of 20 A. This model is supported by negative stain transmission electron microscopy.
- OSTI ID:
- 21106225
- Journal Information:
- Journal of Chemical Physics, Vol. 129, Issue 9; Other Information: DOI: 10.1063/1.2955745; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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