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Epitaxial Nucleation on Rationally Designed Peptide Functionalized Interface

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Final rept. Feb 2008-Feb 2011

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Over the course of the grant period we have applied a set of rationally designed interfacially confined peptides to explore the cooperative relationship between self-assembly and hybrid materials processing. This research report highlights our ability to apply the dynamics of surface active peptides to simultaneously control structure at two length scales, 1 the length scale associated with a fibrous peptide supramolecular assembly and 2 the length scale associated with a nucleating nano-crystalline structure. To understand the supramolecular assembly of interfacially confined peptides, we have designed a set of four amphiphilic -sheet forming peptides and explored the role of electrostatics on phase behavior. We characterize the phase behavior by using Langmuir techniques, Brewster Angle Microscopy, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy, and circular dichroism spectroscopy. We find that peptides with an alternating binary sequence transition at high pressures from discrete circular domains to fibrous domains. The qualitative behavior is independent of surface pressure but dependent on molecular areas. In addition, thermodynamic models are employed to specifically quantify differences in electrostatics by obtaining parameters for the critical aggregation area, limiting molecular area, and the dimensionless ratio of line tension to dipole density. Using these parameters, we are able to relate localized charge distribution to phase transitions. Additionally, Histidine-containing peptides are designed to examine the nucleation and growth of gold nanocrystals to the interface as a function of surface pressure. We show that peptides at low surface pressure yield large single crystalline gold domains, whereas peptides at high surface pressures yield much smaller polycrystalline gold domains.

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  • Biochemistry

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