Mesoscale Structural Control in 2D Peptide Assemblies

Emory University, Atlanta GA

Investigators

Abstract

The meso-scale (circa 100-1000 nm) is above the nano-scale, in which molecules and macromolecules (polymers) fit, but below of the macroscale of everyday objects. The construction of defined structures within the meso-scale range is a problem of significant scientific and technological interest because it is key to the ultimate realization of "bottom-up" fabrication. This process employs structurally- and functionally-defined nano-scale building blocks for the creation of meso-scale objects of defined size, composition, pattern, and morphology, which in turn represent ideal platforms for the creation of functional devices including sensors, actuators, and tranducers. However, the physical principles for construction of synthetic materials on the meso-scale are not well developed in practice. In contrast, biological systems, e.g., cells, assemble multiple nano-scale components into exquisitely-defined, functionally-complex meso-scale machines. Researchers in the laboratory of Prof. Vincent Conticello at Emory University are developing principles derived from the study of biological systems to create structurally-homogeneous, meso-scale 2D assemblies from synthetic peptides. These principles are generalizable to the field of soft materials. The structurally-defined 2D assemblies represent prototypes for the creation of functional devices. Concepts and principles from this project are being utilized in the development of a new course as part of the undergraduate curriculum reform in the Department of Chemistry at Emory University. The reform emphasizes the integration of traditional disciplines into themes using a blended pedagogical approach. The new introductory course focuses on macromolecular structure and function, which is a topic rarely covered at the undergraduate level. Two-dimensional crystalline or quasi-crystalline protein assemblies present in living systems display a range of essential biochemical functions including as molecular sieves and barrier materials, photochemical energy transducers, selective transporters, and signal transduction and amplification agents. The native protein assemblies provide inspiration for the types of critical functions that could potentially be encoded within synthetic 2D protein arrays, if their structure could be controlled across length-scales. This proposal investigates methods to create structurally-defined and programmable meso-scale 2D assemblies from synthetic peptides. Peptides offer a number of advantages for the controlled fabrication of 2D assemblies; most importantly, the sequence-specificity of peptides makes possible molecular-level programming of hierarchical order and enhances the capacity for rational control of the assembly . However, thus far meso-scale structural control has been fortuitous and, this far extensive structural polymorphism was observed for assemblies of synthetic peptide. Researchers in the Conticello laboratory are defining methods to control the mechanism of assembly and identify conditions that promote meso-scale structural order. Three complementary approaches are being investigated: (1) controlled nucleation of "living" supramolecular assemblies, (2) selective formation of heteromeric assemblies, and (3) implementation of principles based on geometrical frustration. Each of these practices has the potential to generate structurally-homogeneous meso-scale 2D peptide assemblies, which in turn serve as structural prototypes for the types of functional 2D materials employed in devices. Hence this work addresses the opportunity implicit in the "meso-scale challenge". This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.