RUI: Learning the Rules that Govern the Folding and Stability of Coiled Coils

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The objective of this project is to explore factors that regulate the polymerization of short peptides into a-helical polymeric structures. An improved understanding of such biopolymer processes will contribute to the advancement of a number of different active fields of research, including: (1) elucidating general protein folding rules and how they relate to polymerization; (2) understanding how such processes can lead to misfolding and aggregation; and (3) designing novel biomaterials. The ability of these helical polymers to form depends on designed staggered interactions between helical peptides, whose structure is based on the well-known coiled-coil structural motif. The peptide sequence will be mutated to test the role of the hydrophobic interaction in polymer assembly and structure. Mutations will also be made to test regulation of polymerization by metal binding and a novel photosensitive switch capable of inducing local structural changes. One particular sequence variant made for this project was discovered to form polymers containing either a-helical or b-strand conformations. The investigator will test the role of glutamines in influencing the propensity to form these two polymer structures. Circular dichroism and Fourier transform infrared spectroscopy will be used to quantify secondary structure content and stability of the polymers. The size and shape of the polymers will be tracked by analytical ultracentrifugation, atomic force microscopy, and dynamic light scattering.Although focusing on basic research questions, this project will also impact a different project in the lab whose goal is to create bio-electronic materials, involving faculty at Haverford and at U. Pennsylvania. The work described here will be driven primarily by undergraduates, since Haverford College is an undergraduate institution. Students fulfill major course credit by writing a thesis proposal and a final thesis paper, presenting their work at group meetings and to the Department as a whole, while carrying out their experiments. Elements of this research program have been developed by the investigator for a junior laboratory course to be taught to chemistry and biology majors, and ideas relevant to biomaterial design are being developed for inclusion in a junior-level lecture course in chemical biology and biochemistry. The investigator has a long-standing commitment to improving access to research for under-represented groups. In addition to a long-term commitment to an existing outreach program for science and writing for K-12 students from Philadelphia, The PI regularly reserved space in his research lab over the summer for at least one student self-identified as belonging to an under-represented group. In a newer direction, the investigator has also hosted a high school teacher and student from Philadelphia to work in his lab this past summer, in which they learned to synthesize and purify peptides critical for the goals of this project.