Monday, June 16, 2008
Room 1 (McKimmon Conference Center)
174

Interfacial Assembly of Beta-Sheet Forming Peptides

Lorraine F. Leon Gibbons, The City College & the Graduate Center of the City University of New York, New York, NY and Prof. Raymond S. Tu, City College of New york, New York, NY.

Naturally occurring biological interfaces present nano-scale patterns of chemical functionality with exceptional precision. This precision is applied in a variety of processes, such as biomineralization, where control over the spatial distribution of chemical functionality is often templated by “bottom-up” construction of amino acid based assemblies. The work presented here is based on the design, synthesis and characterization of peptides that assemble at the air-water interface. The aim of this research is to mimic the biomineralization pathways found in nature by designing peptides to template well defined chemical patterns at 2D interfaces. In doing so, we attempt to decouple the self-assembly from the nucleation and growth in an effort to verify if controlling the peptide self-assembly defines the hierarchical mineral structure formed. The peptide molecules are designed using algorithms that promote a particular secondary structure, namely β-strands. The primary structures VQVQVQVEVQVEVQVQW and VQVEVQVQVQVQVEVQW apply alternating hydrophobic and hydrophilic amino acids, defining the periodicity associated with a β-strand. Both sequences have the same number of each amino acid. However, the first sequence has a more localized negatively charged region containing glutamic acids separated by approximately 1.4 nm while the second molecule contains glutamic acids with an approximate separation of 3.5 nm. This difference in charge distribution is meant to highlight the role that electrostatic effects play on self-assembly and nucleation. The behavior of both peptides at the air-water interface has been characterized using Circular Dichroism, Langmuir Blodgett, and Brewster Angle Microscopy methods. The results obtained by the CD spectra and pressure-area isotherms confirm the overall design hypothesis. Preliminary results indicate that the supramolecular assembly of these peptides is in the form of fibrous aggregates. Transferring the peptide monolayers from the air-water interface to solid substrates will enable the use of an Atomic Force Microscope to provide more detailed look at these 2D assemblies.