In addition to its annual lectures, ChBE hosts a weekly seminar throughout the year with invited lecturers who are prominent in their fields. Unless otherwise noted, all seminars are held on Wednesdays in the Molecular Science and Engineering Building ("M" Building) in G011 (Cherry Logan Emerson Lecture Theater) at 4:00 p.m. Refreshments are served at 3:30 p.m. in the Emerson-Lewis Reception Salon.

January 25
Dr. Amy Karlsson
Researcher, Engineering Cellular Protein Research Group
School of Chemical and Biomolecular Engineering
Cornell University
Improving Nature’s Design: Engineering Peptides and Proteins for Enhanced Fitness and Function

Abstract
The fitness and function of proteins and peptides can be engineered using either rational design or directed evolution approaches. Rational design uses information about a protein or peptide’s structure and function to make informed decisions on the amino acids to target for mutation, while directed evolution involves making random changes in sequence and then screening for a desired property. In this seminar, I will describe my work in rational design and directed evolution to engineer proteins and peptides with biological applications. My PhD research utilized rational design to engineer non-natural antimicrobial β-peptides that exhibit antifungal activity against the human pathogen Candida albicans. Through this work, we developed a deeper understanding of the properties of β-peptides that contribute to their toxicity towards fungal cells and fungal biofilms. My postdoctoral research employs directed evolution to engineer antibodies that fold and function inside cells, where the reducing environment prevents formation of the disulfide bonds normally required for proper antibody folding. We have developed a bacterial inner membrane display system that harnesses the cytoplasmic folding quality control mechanisms of the Escherichia coli twin-arginine translocation pathway to display only proteins that are well folded. We used this method to display a combinatorial library of single-chain variable fragment antibodies (scFvs) and screened for binding to a target protein antigen. Our approach isolated scFvs with dramatic improvements in both antigen-binding and intracellular solubility. Together, rational design and directed evolution create a powerful set of tools for engineering proteins and peptides to have the improved fitness characteristics and biological activity required for a broad range of applications.