(550e) Rational Design of Peptides for DNA Separations

We have designed a peptide with switchable surface activity, where the folded form (α-helical) of the peptide is amphiphilic and the unfolded form is not. We hypothesize that we can control the secondary structure of the peptide, and, thus, control its surface activity. The primary structure of a peptide is designed in such a way that upon folding the hydrophobic and hydrophilic domains become spatially disjoint, leading to amphiphilic behavior. The ensemble average population of folded states depends on binding to a specific sequence of DNA. The secondary structure has been characterized by using circular dichroism spectropolarimetry, and we show that the peptide has a transient secondary structure as a function of binding. The dynamic behavior of the peptide is characterized by pendant drop/bubble method and modeled accordingly. Here, we hypothesize that only folded peptide adsorbs at the air/water interface, and the dynamic surface tension due to α-helical peptide adsorption is predicted by a diffusive transport model that accounts for peptide folding dynamics and the kinetics of adsorption.