International Research Fellowship Program: Preparation of a Polypeptide-Based Dendrimer Library for the Development and Design of Artificial Enzymes

Liang Catherine O, Berkeley CA

Investigators

Abstract

0401973 Liang The International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-two-month research fellowship by Dr. Catherine O. Liang to work with Dr. Jean-Louis Reymond at University of Berne in Switzerland. In light of the complexity and sophistication of naturally occurring systems, rational enzyme design is a challenging and daunting task. Current technology has not yet developed a way to design an amino acid sequence that folds predictably into a desired conformation resulting in a molecule capable of a specific function. Scientists have had to turn to modification of naturally occurring enzyme frameworks through techniques such as site-directed mutagenesis and chemical modification of the active site. In response to the challenges of developing a large, sophisticated, 3-dimensional enzyme mimic, novel peptide-based dendrimer libraries are being investigated. Dendrimers are highly branched, well-controlled, monodisperse macromolecules and offer a globular morphology similar to naturally occurring enzymes. Their characteristic branching and well-defined interior provides a 'pre-folded' architecture amenable to the mimicry of peptide-based biomolecules. Preparation of target structures is carried out through solid-phase peptide synthesis. Unlike many approaches that focus on a singular target, the issue of diversity is addressed through a combinatorial strategy to generate multitudes of different library members. A complementary approach focusing on the preparation of targeted libraries like the catalytic triad chymotrypsin - His, Asp, Ser - for instance, is included. The combination of the branched, hierarchical structure of dendrimers and amino acid repeat units opens up possibilities towards biomimetic applications. Dendrimers are screened for activity in sensing or "artificial nose" processes through identification of substrate selective macromolecules. In addition, the unique nanoenvironment created by the amino-acid residues is evaluated for catalytic activity. Potential aldolase, which catalyze carbon-carbon bond forming reactions, and esterase mimics are screened in fluorogenic assays with dye-labeled substrates. Clearly many possibilities of exploration into peptide-based dendrimers have yet to be uncovered.