PROJECT SUMMARY Mucin glycoproteins are the essential component of mucus and the epithelial cellular glycocalyx. Mucins are essential for life in creatures from jellyfish to humans and play roles in hydration, lubrication, nutrient absorption, and host defense against pathogens. Mucin glycosylation is regulated by complex enzymatic pathways subject to flux, resulting in heterogeneous and variable glycan patterns that vary between tissues and species, and that evolve in response to diet and disease. The Kramer Lab is developing synthetic mucins, or synMUCs, that harness the chemical and biophysical properties of native mucins but have molecularly tunable structures. Polymerization of glycosylated amino acid N-carboxyanhydrides affords high molecular weight polypeptides with the native peptide and glycan linkages. Compared to short peptides, polysaccharides, or traditional polymers bearing attached sugars, synMUCs are the most authentic mucin mimics to date. The synMUCs will be applied in engineered models of the glycocalyx and secreted mucus. These models will find broad future application in studies of epithelial biology with application in cancer, drug delivery, immunity, and infection. Since mucins are on the front lines of cellular defense, diverse viruses have evolved strategies to adhere to their glycans, alter them, and even use them to enter host cells for replication. Virus-mucin binding can have outcomes on viral diffusion, tissue specificity, and replication but molecular details are lacking due to mucin heterogeneity. We will chemoenzymatically modify our synMUCs to display virus-binding sialic acid glycans. Viral binding preferences for various sialic acid structures in different densities and from varied peptide backbone compositions will be defined. The sialic-acid-bearing-synMUCs will be utilized to probe how mucins in the glycocalyx vs mucus regulate adhesion, cell entry and replication, tissue tropism and viral gene evolution. This knowledge will shed light on fundamental aspects of the viral life cycle and may assist in improving human health though development of new antiviral therapeutics and disease transmission prevention strategies. Additionally, scientific citizenship and mentoring are a priority and active involvement in supporting equity, diversity and inclusion of underrepresented groups in STEM will be a focus for the duration of the project and beyond.