Research in the Imperiali group is concerned with diverse aspects of protein structure, function, and design. The lab employs a multidisciplinary approach involving synthesis, state-of-the-art spectroscopy, molecular modeling, enzymology, and molecular biology to address fundamental problems at the interface of chemistry and biology.

In one area of research Imperiali is investigating the central biological issue of protein modification. In particular, the group has focused on understanding enzyme catalyzed protein glycosylation. This objective presents a significant challenge because the substrates are densely functionalized proteins, and the opportunities for competing processes are innumerable. One of the transformations that is being studied in depth is N-linked glycosylation of asparagine mediated by the enzyme oligosaccharyl transferase. The group has developed synthetic probes and biophysical methods to gain insight on the mechanism and biochemical consequences of N-linked glycosylation. In addition, a major effort is being devoted to the cloning and overexpression of the multisubunit membrane-associated enzyme. The knowledge of the genes encoding the enzyme will allow for the manipulation of protein function through mutagenesis. Furthermore, increased supplies of the enzyme will enable structural characterization of the protein and the development of new mechanistic studies. In related studies, the group has initiated studies on the array of enzymes that comprise the dolichol pathway. This pathway provides as its ultimate product the substrate for the oligosaccharyl transferase enzyme.

A second area of research focuses on protein design. The polypeptide architecture, defined by a network of noncovalent interactions, shows remarkable versatility of structure and function. The approach to de novo protein design taken by the group is based on the assembly of "compact" supersecondary structural motifs (ca. 20-40 residues). This limited size makes the polypeptides accessible through solid phase synthesis, permits incorporation of a wide array of natural and synthetic amino acids, and allows for comprehensive solution state structure evaluation using modern spectroscopic techniques. For example, using an iterative design, synthesis, and evaluation process the group has evolved a miniature folded protein (BBA) comprising only 23 amino acids. The ultimate design enlisted a number of features including stabilized reverse turn motifs as structural nucleation elements. The group has also recently reported the development of a new stable and discretely folded b-structure motif (BBB) of only 29 amino acid residues, which folds cooperatively. Additionally, the structure of the BBA motif has been manipulated to effect the formation of discrete oligomeric structures. A key feature of the oligomerization studies has been the development of fluorescence-based methods for studying protein association phenomena. In related efforts, the group is also exploiting the modular polypeptide as a platform for selective and sensitive metal ion sensing. These fluorescent chemosensor molecules may ultimately have biomedical and environmental applications.

"Design of a Discretely Folded Mini-Protein Motif with Predominantly Β-Structure,"
Ottesen, J. J.; Imperiali, B. Nature Structural Biology, 2001, 8, 535-539.

"Synthetic Derivatives of 8-Hydroxy-2-methyl-quinoline are Powerful Prototypes for Zinc Sensors in Biological Systems," Pearce, D. P.; Jotterand, N.; Carrico, I. S.; Imperiali, B. J. Am. Chem. Soc. 2001, 123, 5160-5161.

"Oligomerization of Uniquely Folded Mini-Protein Motifs:Development of a Homotrimeric ΒΒα Peptide," Mezo, A. R.; Cheng, R. P.; Imperiali, B. J. Am. Chem. Soc. 2001, 123, 3885-3891.

"The Effect of the Outer Saccharide Residues of N-Linked Glycans on Peptide Conformation," O'Connor, S. E.; Pohlmann, J.; Imperiali, B.; Saskiawan, I.; Yamamoto, K. J. Am. Chem. Soc. 2001, 123, 6187-6188.

"Oligomeric Mini-Protein Motifs: Pivotal Role of a Single Hinge Residue in Determining Oligomeric State" McDonnell, K. A.; Imperiali, B. J. Am. Chem. Soc. 2002, 124, 428-429.

"A General Method for the Synthesis of Caged Phosphopeptides: Tools for the Exploration of Signal Transduction Pathways" Rothman, D. M.; Vázquez, M. E.; Vogel, E. M.; Imperiali, B. Org. Lett. 2002, 4, 2865-2868.

"Enantioselective Synthesis and Application of the Highly Fluorescent and Environment-Sensitive Amino Acid 6-(2-dimethylaminonaphthoyl) Alanine (DANA)" Nitz, M.; Mezo, A. R.; Ali, M. H.; Imperiali, B. Chem. Commun. 2002, 1912-1913.

"Neoglycopeptides as Inhibitors of Oligosaccharyl Transferase: Insight into Negotiating Product Inhibition" Peluso, S.; Ufret, M. de L.; O'Reilly, M. K.; Imperiali, B. Chemistry & Biology 2002, 9, 1323-1328.

"Oligosaccharyl Transferase: Gatekeeper to the Secretory Pathway" Dempski, R. E. Jr.; Imperiali, B. Curr. Op. Chem. Biol. 2002, 6, 844-850.

"Peptides to Peptidomimetics: Towards the Design of Bioavailable Inhibitors of Oligosaccharyl Transferase" Weerapana, E.; Imperiali, B. Organic and Biomol. Chem. 2003, 1, 93-99.