title: pH-Responsive Aminoproline-Containing Collagen Triple Helices.
abstract: (4S)- and (4R)-configured aminoproline (Amp) residues were used as pH-responsive probes to tune the thermal stability of collagen triple helices in acidic and basic environments. The different steric and stereoelectronic properties of amino versus ammonium groups lead to a switch of the ring pucker of Amp upon changing the pH. The choice of the position of Amp within collagen model peptides (CMPs) as well as the absolute configuration at C(4) of the pH-responsive probe allows for tuning of the stability of Amp-containing collagen triple helices over a broad range. Comparative quantum chemical calculations on the steric and stereoelectronic effects of amino and ammonium groups versus fluorine, hydroxy, chlorine, and methyl substituents support the experimental findings. The research also shows that substitution of the naturally occurring hydroxy group in collagen by electron-withdrawing groups with a larger hydration shell than that of the hydroxy group is not tolerated.
authors.affiliation: Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland.
authors.forename: Jasmine
authors.initials: J
authors.lastname: Egli
authors.affiliation: Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland.
authors.forename: Christiane
authors.initials: C
authors.lastname: Siebler
authors.affiliation: Chair of Theoretical Chemistry, Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, 81377, Munich, Germany.|Center of Integrated Protein Science (CIPSM) at the Department of Chemistry, University of Munich (LMU), Butenandtstr. 5-13, 81377, Munich, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Maryasin
authors.affiliation: Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland.
authors.forename: Roman S
authors.initials: RS
authors.lastname: Erdmann
authors.affiliation: Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland.
authors.forename: Cedric
authors.initials: C
authors.lastname: Bergande
authors.affiliation: Chair of Theoretical Chemistry, Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, 81377, Munich, Germany.|Center of Integrated Protein Science (CIPSM) at the Department of Chemistry, University of Munich (LMU), Butenandtstr. 5-13, 81377, Munich, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Ochsenfeld
authors.affiliation: Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland.
authors.forename: Helma
authors.identifier: http://orcid.org/0000-0002-3075-5741
authors.initials: H
authors.lastname: Wennemers
keywords: conformation analysis; density functional calculations; helical structures; protein folding; protein structures