The ability to change conformations in response to environmental perturbations is a central feature of many natural proteins. There has been a good deal of interest in using natural stimuli-responsive peptides sequences, as well as rationally engineered sequences, in a variety of important biotechnology applications including: biomaterials, nanodevices, biosensors, bioseparations, tissue engineering, and drug delivery. A classic example of this approach is the elastin-like peptide that is sensitive to changes in temperature, pH, or ionic strength. This peptide has recently been reported in several high-impact applications including targeted drug delivery, environmental bioremediation, and one-step protein purification.

Directed evolution is a powerful technique for the engineering of proteins and peptides with novel phenotypes, but the evolution of peptides to exhibit conformational changes in response to prescribed stimuli is especially challenging. We are developing new methods for the directed evolution of novel peptides that are responsive to unique environmental cues. These methods require a means to detect the occurrence of a conformational change in an attached peptide sequence. One system that we are currently exploring for this process involves a well-known fluorescein-binding single chain antibody fragment (scFv). It has previously been shown that the artificial linker of a scFv can have a dramatic impact on the binding affinity of the scFv. And, it has also been demonstrated that an elastin-like peptide inserted in the linker region of the anti-fluorescein scFv can be used to create a temperature responsive antibody. We are using this system in conjunction with a unique plasmid display technique and affinity chromatography to evolve new peptides that undergo conformational changes in response to novel environmental stimuli. Proof of principle experimental results of this approach will be presented as well as the results of preliminary attempts to isolate new environmentally responsive peptides. The potential impact of these new molecules will also be highlighted.

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