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41
Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling
Thursday Speaker Abstracts
Protein Structural Dynamics at Surfaces as Studied by Infrared Nanospectroscopy
Joachim Heberle
.
Freie Universität, Berlin, Germany.
Membrane proteins are the target of more than 50% of all drugs and are encoded by about 30%
of the human genome. Electrophysiological techniques, like patch-clamp, unravelled many
functional aspects of membrane proteins but suffer from structural sensitivity. We have
developed Surface Enhanced Infrared Absorption Spectroscopy (SEIRAS) to probe the structure
and function of solid-supported biomembranes and membrane proteins on the level of a
monolayer. In a new approach, we monitored the expression, insertion and folding of membrane
proteins by SEIRAS. A cell-free assay to express bacteriorhodopsin (bR) was used and insertion
and folding of the nascent polypeptide into surface-tethered lipidic nanodiscs was followed in-
situ and time-resolved by SEIRAS to resolve this complex reaction via the analysis of the amide
I vibration of the peptide backbone (C=O stretching vibration).
The structure of the native environment of bR in the purple membrane was probed by scanning
near-field IR microscopy. Mapping of the protein structure with 30 nm spatial resolution and
sensitivity to individual protein complexes by Fourier transform infrared nano-spectroscopy
(nano-FTIR) was demonstrated. The first broadband infrared spectra of purple membranes were
recorded indicating their local α-helical structure.