title: Disentangling Peptide Configurations via Two-Dimensional Electronic Spectroscopy: Ab Initio Simulations Beyond the Frenkel Exciton Hamiltonian.
abstract: Two-dimensional (2D) optical spectroscopy techniques based on ultrashort laser pulses have been recently extended to the optical domain in the ultraviolet (UV) spectral region. UV-active aromatic side chains can thus be used as local highly specific markers for tracking dynamics and structural rearrangements of proteins. Here we demonstrate that 2D electronic spectra of a model proteic system, a tetrapeptide with two aromatic side chains, contain enough structural information to distinguish between two different configurations with distant and vicinal side chains. For accurate simulations of the 2DUV spectra in solution, we combine a quantum mechanics/molecular mechanics approach based on wave function methods, accounting for interchromophores coupling and environmental effects, with nonlinear response theory. The proposed methodology reveals effects, such as charge transfer between vicinal aromatic residues that remain concealed in conventional exciton Hamiltonian approaches. Possible experimental setups are discussed, including multicolor experiments and signal manipulation techniques for limiting undesired background contributions and enhancing 2DUV signatures of specific electronic couplings.
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università di Bologna , V. F. Selmi 2, 40126 Bologna, Italy.
authors.forename: Artur
authors.initials: A
authors.lastname: Nenov
authors.affiliation: Laboratoire de Chimie, Ecole Normale Supérieure de Lyon, 46, allée d'Italie 69364 Lyon, France ; Dipartimento di Chimica "G. Ciamician", Università di Bologna , V. F. Selmi 2, 40126 Bologna, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Rivalta
authors.affiliation: IFN-CNR, Dipartimento di Fisica, Politecnico di Milano , Piazza L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697-2025, United States.
authors.forename: Shaul
authors.initials: S
authors.lastname: Mukamel
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università di Bologna , V. F. Selmi 2, 40126 Bologna, Italy ; Laboratoire de Chimie, Ecole Normale Supérieure de Lyon, 46, allée d'Italie 69364 Lyon, France.
authors.forename: Marco
authors.initials: M
authors.lastname: Garavelli