Regensburg 2013 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 2: Proteins

BP 2.2: Vortrag

Montag, 11. März 2013, 10:00–10:15, H44

Peptide with a trigger: The aggregation and refolding of pH sensitive peptide GALA in solution and at interfaces — •Denise Schach, Christoph Globisch, Adrian Fuchs, Clemens K. Weiss, Christine Peter, Mischa Bonn, and Tobias Weidner — Max-Planck-Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz

GALA is a 30 amino acid synthetic peptide consisting mainly of the Glu-Ala-Leu-Ala repeat motif. Originally it was designed to act as a shuttle across lipid membranes in drug or gene delivery systems. Importantly, structure and function can be triggered by pH. The triggering mechanism relies on the conversion from a random coil to an amphipathic α-helix when decreasing the pH from 7 to 5. The helix formation is driven by protonation, i.e. neutralization, of the Glu side at pH 5, which makes a folded structure energetically more favorable. The repetition of hydrophobic and hydrophilic residues is responsible for the amphipathic peptide properties in the helical state. In its amphipathic state, GALA is also likely to aggregate. Near a lipid membrane the aggregation leads to cell penetration, pore formation and membrane leakage. To better understand the fundamental mechanisms of refolding and aggregation in bulk solution and at interfaces, we probe structural details with Fourier-transform infrared spectroscopy and sum frequency generation. Moreover, we apply Brewster angle microscopy and light scattering to follow aggregation. The interpretation of the experiments is complemented by molecular dynamics simulations of GALA refolding and aggregation.