Deciphering Post-Translationally Modified Peptides with Arrayed Synthetic Receptors

With support from the Chemical Measurement and Imaging (CMI) program and partial co-funding from the Chemistry of Life Processes (CLP) and the Chemical Structures, Dynamics, and Mechanisms-B (CSDM-B) programs in the Division of Chemistry, Professor Zhong's group and their collaborators at the University of California-Riverside are developing and extending ways of characterizing chemical modifications occurring in proteins and peptides after they are synthesized. Such “post-translational modifications” (PTMs) greatly expand the structural and functional diversity of proteins. Interaction among PTMs (“crosstalk”) is also crucial for regulation of protein function and biological processes. However, identification and detection of PTMs pose significant challenges, because multiple types and numbers of PTMs often coexist on a single peptide or protein and these are not easily separable. Some modifications produce only small changes to the properties, making their sensing difficult. The Zhong group is developing innovative tools for the analysis of important classes of PTMs in peptides, aiming to enhance our understanding of protein modifications and their functional implications. The research will be integrated with on campus and outreach activities aiming to increase minority participation in STEM fields, to improve the retention rates of underserved minorities in STEM fields, and to provide teaching opportunities to students interested in education as a career goal. It will provide interdisciplinary research training to graduate students and undergraduates in areas that bridge chemistry, biology, and materials science. The Zhong group is developing flexible synthetic receptor hosts paired with indicator dyes to study PTM crosstalk and identify isomeric peptides, two challenging tasks not readily addressed by current measurement technologies. Employing multiple orthogonal recognition mechanisms, arrays formed between the self-folding cavitands with upper and lower rim functionality and their fluorescent guests can selectively recognize different PTM peptide targets. The developed arrays can then be employed to investigate how PTMs affect the function of kinases, enzymes responsible for adding phosphate groups to proteins, and to study PTM crosstalk, where nearby modifications influence the properties of a target modification. Additionally, the arrays can be used to detect the subtle structural differences among isomeric peptides and measure the activities of isomerases. By leveraging multiple different self-folding deep cavitands in an arrayed format, the work aims to advance our understanding of PTM functions and regulation, through improvements in PTM detection and by enabling the discovery of hosts with high affinity and selectivity for diverse PTM types. 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.