title: Coacervation of α-elastin studied by ultrafast nonlinear infrared spectroscopy.
abstract: Elastin is the main protein to confer elasticity to biological tissues, through the formation of a hierarchical network of fibres. α-Elastin, a soluble form of the protein, is widely used in studies of the biosynthesis of human elastic tissue and exhibits coacervation in solution. This process involves the association of α-elastin molecules through a liquid-liquid phase transition, which is reversible unless the temperature is driven sufficiently high to induce the formation of insoluble aggregates. The thermodynamics of this process have attracted interest over many years and in the present work we used ultrafast nonlinear infrared spectroscopy of the amide I protein backbone vibration to resolve the secondary structural changes occurring during coacervation and probe the protein dynamics on a picosecond time scale. Four classes of carbonyl oscillators with distinct absorption peaks were revealed and, through narrowband excitation, vibrational and anisotropy decays could be distinguished. Analysis of the vibrational lifetimes and anisotropy decay times of these bands characterized the conformational changes and revealed the structural bases of the coacervation process.
authors.affiliation: LENS, European Laboratory for Nonlinear Spectroscopies, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Florence, Italy and Department of Physics, University of Siegen, Walter-Flex Str. 3, D-57068 Siegen, Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Ragnoni
authors.affiliation: School of Physics and Astronomy, University of Exeter, Exeter EX4 4QJ, UK. f.palombo@exeter.ac.uk.
authors.forename: Francesca
authors.identifier: http://orcid.org/0000-0001-6355-2601
authors.initials: F
authors.lastname: Palombo
authors.affiliation: School of Physics and Astronomy, University of Exeter, Exeter EX4 4QJ, UK. f.palombo@exeter.ac.uk.
authors.forename: Ellen
authors.initials: E
authors.lastname: Green
authors.affiliation: School of Physics and Astronomy, University of Exeter, Exeter EX4 4QJ, UK. f.palombo@exeter.ac.uk.
authors.forename: C Peter
authors.initials: CP
authors.lastname: Winlove
authors.affiliation: LENS, European Laboratory for Nonlinear Spectroscopies, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Florence, Italy and Department of Chemistry, University of Florence, via della Lastruccia 3-13, I-50019 Sesto Fiorentino, Florence, Italy and INO, National Institute of Optics, Largo Enrico Fermi 6, I-50125 Florence, Italy.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Di Donato
authors.affiliation: LENS, European Laboratory for Nonlinear Spectroscopies, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Florence, Italy and INO, National Institute of Optics, Largo Enrico Fermi 6, I-50125 Florence, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Lapini
mesh_terms: D016880:Anisotropy; D004549:Elastin / Q000737:chemistry*; D006801:Humans; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014732:Vibration
chemical_list: D004549:Elastin