Temperature‐ and Photocontrolled Unfolding/Folding of a Triple‐Helical Azobenzene‐Stapled Collagen Peptide Monitored by Infrared Spectroscopy. Issue 9 (9th March 2016)

• Record Type: Journal Article
• Authors: Lorenz, Lisa; Kusebauch, Ulrike; Moroder, Luis; Wachtveitl, Josef
• Is Part Of: Chemphyschem. Volume 17:Issue 9(2016)
• Page Start: 1314
• Page End: 1320
• Publication Date: 2016-03-09
• Subjects: azobenzene -- collagen triple helix -- FTIR spectroscopy -- photoisomerization -- protein folding; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201501103
• Languages: English
• ISSNs: 1439-4235

Abstract

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. Abstract : Smooth or crinkled : Comparative FTIR spectroscopic analysis of a model collagen peptide and its trans ‐azobenzene‐stapled analogue reveals that the driving force exerted by photoisomerization to the cis ‐azobenzene is insufficient to unfold the triple helix at lower temperatures. Only temperature‐dependent untightening of this fold results in reversible photomodulated unfolding/refolding of the collagen peptide.