Ultrafast Excited-State Deactivation of the Bacterial Pigment Violacein
- Beckstead, Ashley A. [ Montana State University: Chemistry & Biochemistry ]
- Zhang, Yuyuan [ Ohio State Univ, Dept Chem & Biochem, 100 West 18th Ave, Columbus, OH 43210 USA ]
- Hilmer, Jonathan K. [ Montana State University: Chemistry & Biochemistry ] [ Montana State Univ, Univ Informat Technol, POB 173240, Bozeman, MT 59717 USA ]
- Smith, Heidi J. [ Montana State University: Center for Biofilm Engineering ]
- Bermel, Emily [ Montana State University: Center for Biofilm Engineering ] [ Univ Minnesota, Dept Biomed Engn, Minneapolis, MN 55455 USA ]
- Foreman, Christine M. [ Montana State University: Chemical & Biological Engineering ]
- Kohler, Bern [ Montana State University: Chemistry & Biochemistry ] [ Ohio State Univ, Dept Chem & Biochem, 100 West 18th Ave, Columbus, OH 43210 USA ]
The photophysical properties of the natural pigment violacein extracted from an Antarctic organism adapted to high exposure levels of UV radiation were measured in a combined steady-state and time-resolved spectroscopic study for the first time. In the low-viscosity solvents methanol and acetone, violacein exhibits low fluorescence quantum yields on the order of 1 x 10(-4), and femtosecond transient absorption measurements reveal excited-state lifetimes of 3.2 +/- 0.2 and 4.6 +/- 0.2 ps in methanol and acetone, respectively. As solvent viscosity is increased, both the fluorescence quantum yield and excited-state lifetime of this intensely colored pigment increase dramatically, and stimulated emission decays 30-fold more slowly in glycerol than in methanol at room temperature. Excited-state deactivation is suggested to occur via a molecular-rotor mechanism in which torsion interring bond leads to a conical intersection with the ground state.