title: Vibrational spectra of the ground and the singlet excited ππ* state of 6,7-dimethyl-8-ribityllumazine.
abstract: 6,7-Dimethyl-8-ribityllumazine serves as fluorophore in lumazine proteins (LumP) of luminescent bacteria. The molecule exhibits several characteristic vibrational absorption bands between 1300 and 1750 cm(-1) in its electronic ground state. The IR-absorption pattern of the singlet excited ππ* state was monitored via ultrafast infrared spectroscopy after photoexcitation at 404 nm. The comparison of experimentally observed band shifts for a number of isotopologues allows for a clear assignment of several absorption bands--most importantly the two carbonyl bands. This assignment is confirmed by normal-mode calculations by means of either density functional theory (DFT) calculations for the ground state or the configuration interaction singles (CIS) method for the excited singlet state. A good agreement between experiment and calculation is obtained for models including explicitly a first solvation shell. The results provide a basis for further investigations of lumazine protein and demonstrate the necessity of proper accounting for explicit hydrogen bonding in case of strongly polar molecular systems.
authors.affiliation: Lehrstuhl für BioMolekulare Optik, Fakultät für Physik and Munich Center for Integrated Protein Science CIPSM, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, 80538 München, Germany.
authors.forename: Wolfgang J
authors.initials: WJ
authors.lastname: Schreier
authors.forename: Igor
authors.initials: I
authors.lastname: Pugliesi
authors.forename: Florian O
authors.initials: FO
authors.lastname: Koller
authors.forename: Tobias E
authors.initials: TE
authors.lastname: Schrader
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Zinth
authors.forename: Markus
authors.initials: M
authors.lastname: Braun
authors.forename: Sylwia
authors.initials: S
authors.lastname: Kacprzak
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
authors.forename: Werner
authors.initials: W
authors.lastname: Römisch-Margl
authors.forename: Adelbert
authors.initials: A
authors.lastname: Bacher
authors.forename: Boris
authors.initials: B
authors.lastname: Illarionov
authors.forename: Markus
authors.initials: M
authors.lastname: Fischer
mesh_terms: D006860:Hydrogen Bonding; D011621:Pteridines / Q000737:chemistry*; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D014732:Vibration
chemical_list: D011621:Pteridines; D012997:Solvents; C008297:lumazine; C001061:6,7-dimethyl-8-ribityllumazine