title: Temperature- and Photocontrolled Unfolding/Folding of a Triple-Helical Azobenzene-Stapled Collagen Peptide Monitored by Infrared Spectroscopy.
abstract: The triple-helical structure of a model collagen peptide possessing azobenzene-derived clamps integrated in all three strands as side-chain-to-side-chain crosslinks is analyzed by IR spectroscopy in comparative thermal excursion experiments with the triple helix of a typical reference collagen peptide consisting of only glycine-proline-hydroxyproline repeats. By exploiting the known stabilizing effects of aqueous alcoholic solvents on the unique collagen fold, deuterated ethylene glycol/water (1:1) is used as a solvent to investigate the effect of the light-switchable trans/cis-azobenzene clamp on the stability of the triple helix in terms of H/D exchange rates and thermal unfolding. Results of this comparative analysis clearly reveal only a minor destabilization of the triple helix by the hydrophobic azobenzene moieties compared to the reference collagen peptide as reflected by a lower midpoint of the thermal unfolding and higher rates of H/D exchange. However, it also reveals that the driving force exerted by the trans-to-cis photoisomerization of the azobenzene moieties is insufficient for unfolding of the compact triple-helical collagen fold. Only temperature-dependent untightening of this fold with heating results in a reversible photomodulated unfolding and refolding of the azo-collagen peptide into the original triple helix.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438, Frankfurt, Germany.|Institute of Biophysics, Goethe University Frankfurt, Max-von-Laue-Str. 1, 60438, Frankfurt, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Lorenz
authors.affiliation: Max-Planck-Institute for Biochemistry, Am Klopferspitz 18a, 85152, Martinsried, Germany.|Institute for Systems Biology, 401 Terry Ave, North Seattle, Washington, 98109, USA.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kusebauch
authors.affiliation: Max-Planck-Institute for Biochemistry, Am Klopferspitz 18a, 85152, Martinsried, Germany. moroder@biochem.mpg.de.
authors.forename: Luis
authors.initials: L
authors.lastname: Moroder
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438, Frankfurt, Germany. wveitl@theochem.uni-frankfurt.de.
authors.forename: Josef
authors.initials: J
authors.lastname: Wachtveitl
mesh_terms: D000595:Amino Acid Sequence; D001391:Azo Compounds / Q000737:chemistry*; D003094:Collagen / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013696:Temperature
chemical_list: D001391:Azo Compounds; D010455:Peptides; D003094:Collagen; C009850:azobenzene
keywords: FTIR spectroscopy; azobenzene; collagen triple helix; photoisomerization; protein folding