title: Unraveling solvent-driven equilibria between alpha- and 3(10)-helices through an integrated spin labeling and computational approach.
abstract: In this work we present an effective and flexible computational approach, which is the result of an ongoing development in our groups, allowing the complete a priori simulation of the ESR spectra of complex systems in solution. The usefulness and reliability of the method are demonstrated on the very demanding playground represented by the tuning of the equilibrium between 3(10)- and alpha-helices of polypeptides by different solvents. The starting point is the good agreement between computed and X-ray diffraction structures for the 3(10)-helix adopted by the double spin-labelled heptapeptide Fmoc-(Aib-Aib-TOAC)2-Aib-OMe. Next, density functional computations, including dispersion interactions and bulk solvent effects, suggest another energy minimum corresponding to an alpha-helix in polar solvents, which, eventually, becomes the most stable structure. Computation of magnetic and diffusion tensors provides the basic ingredients for the building of complete spectra by methods rooted in the Stochastic Liouville Equation (SLE). The remarkable agreement between computed and experimental spectra at different temperatures allowed us to identify helical structures in the various solvents. The generality of the computational strategy and its implementation in effective and user-friendly computer codes pave the route toward systematic applications in the field of biomolecules and other complex systems.
authors: Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, I-35131 Padova, Italy.
authors: Silvia
authors: S
authors: Carlotto
authors: Paola
authors: P
authors: Cimino
authors: Mirco
authors: M
authors: Zerbetto
authors: Lorenzo
authors: L
authors: Franco
authors: Carlo
authors: C
authors: Corvaja
authors: Marco
authors: M
authors: Crisma
authors: Fernando
authors: F
authors: Formaggio
authors: Claudio
authors: C
authors: Toniolo
authors: Antonino
authors: A
authors: Polimeno
authors: Vincenzo
authors: V
authors: Barone
mesh_terms: D003198:Computer Simulation; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013113:Spin Labels
chemical_list: D010455:Peptides; D013113:Spin Labels