Document Detail

Molecular self-assembly into one-dimensional nanostructures.
MedLine Citation:
PMID:  18754628     Owner:  NLM     Status:  MEDLINE    
Self-assembly of small molecules into one-dimensional nanostructures offers many potential applications in electronically and biologically active materials. The recent advances discussed in this Account demonstrate how researchers can use the fundamental principles of supramolecular chemistry to craft the size, shape, and internal structure of nanoscale objects. In each system described here, we used atomic force microscopy (AFM) and transmission electron microscopy (TEM) to study the assembly morphology. Circular dichroism, nuclear magnetic resonance, infrared, and optical spectroscopy provided additional information about the self-assembly behavior in solution at the molecular level. Dendron rod-coil molecules self-assemble into flat or helical ribbons. They can incorporate electronically conductive groups and can be mineralized with inorganic semiconductors. To understand the relative importance of each segment in forming the supramolecular structure, we synthetically modified the dendron, rod, and coil portions. The self-assembly depended on the generation number of the dendron, the number of hydrogen-bonding functions, and the length of the rod and coil segments. We formed chiral helices using a dendron-rod-coil molecule prepared from an enantiomerically enriched coil. Because helical nanostructures are important targets for use in biomaterials, nonlinear optics, and stereoselective catalysis, researchers would like to precisely control their shape and size. Tripeptide-containing peptide lipid molecules assemble into straight or twisted nanofibers in organic solvents. As seen by AFM, the sterics of bulky end groups can tune the helical pitch of these peptide lipid nanofibers in organic solvents. Furthermore, we demonstrated the potential for pitch control using trans-to-cis photoisomerization of a terminal azobenzene group. Other molecules called peptide amphiphiles (PAs) are known to assemble in water into cylindrical nanostructures that appear as nanofiber bundles. Surprisingly, TEM of a PA substituted by a nitrobenzyl group revealed assembly into quadruple helical fibers with a braided morphology. Upon photocleavage of this the nitrobenzyl group, the helices transform into single cylindrical nanofibers. Finally, inspired by the tobacco mosaic virus, we used a dumbbell-shaped, oligo(phenylene ethynylene) template to control the length of a PA nanofiber self-assembly (<10 nm). AFM showed complete disappearance of long nanofibers in the presence of this rigid-rod template. Results from quick-freeze/deep-etch TEM and dynamic light scattering demonstrated the templating behavior in aqueous solution. This strategy could provide a general method to control size the length of nonspherical supramolecular nanostructures.
Liam C Palmer; Samuel I Stupp
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Accounts of chemical research     Volume:  41     ISSN:  1520-4898     ISO Abbreviation:  Acc. Chem. Res.     Publication Date:  2008 Dec 
Date Detail:
Created Date:  2009-02-20     Completed Date:  2009-03-18     Revised Date:  2014-09-24    
Medline Journal Info:
Nlm Unique ID:  0157313     Medline TA:  Acc Chem Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1674-84     Citation Subset:  IM    
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MeSH Terms
Anthracenes / chemistry
Microscopy, Atomic Force
Microscopy, Electron, Transmission
Nanostructures / chemistry*,  radiation effects
Peptides / chemistry
Grant Support
5 R01 DE015920-04/DE/NIDCR NIH HHS; 5 R01 EB003806-05/EB/NIBIB NIH HHS; 5 U54 CA119341-03/CA/NCI NIH HHS; R01 DE015920/DE/NIDCR NIH HHS; R01 DE015920-04/DE/NIDCR NIH HHS; R01 EB003806/EB/NIBIB NIH HHS; R01 EB003806-04/EB/NIBIB NIH HHS; U54 CA119341/CA/NCI NIH HHS; U54 CA119341-03/CA/NCI NIH HHS
Reg. No./Substance:
0/Anthracenes; 0/Peptides; 0/dendron

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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