(150b) Peptide Directed Assembly of Hybrid Nanoscale Objects

In nature, biological molecules form interfaces that assemble patterns of chemical functionality with exceptional precision. The role of dynamics during the assembly of biological molecules appears to be important for mineralization processes. Our work applies model sheet-forming peptides at interfaces to explore the dynamics of assembly in order to template mineral growth. The peptide molecules are rationally designed to have amphiphilic properties and a propensity for sheet like secondary structure. These designed peptides are deposited at the air water interface to explore the dynamics of their self-assembly and investigate their 2D order. To characterize the phase behavior, techniques such as Langmuir Blodgett and Brewster Angle Microscopy are used. In addition we verify out proposed sheet forming design using both Circular Dichroism and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy. Thermodynamic analysis of structure formation with increasing pressure allows us to understand the nature of self-assembly with iterative changes in the peptide sequence. Additionally, we look at the dynamics of the self-assembled state, where the organic phase switches between short- and long-range order as a function of surface pressure. This model system allows us to explore our underlying hypothesis that the time scale of the phase-transitions of the peptide at the interface defines the length-scale of the crystalline phase. This is in contrast to a system that starts with a well-ordered preformed template that defines the epitaxial growth of the mineral phase. Versions of our model peptides are modified to include histidine in order to nucleate Au nanocrystals in both the short and long range ordered organic matrix.