Ultrafast Excited-State Deactivation of the Bacterial Pigment Violacein

J Phys Chem B. 2017 Aug 24;121(33):7855-7861. doi: 10.1021/acs.jpcb.7b05769. Epub 2017 Aug 9.

Abstract

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 × 10-4, and femtosecond transient absorption measurements reveal excited-state lifetimes of 3.2 ± 0.2 and 4.5 ± 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 about an interring bond leads to a conical intersection with the ground state.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Fluorescence
  • Indoles / chemistry*
  • Molecular Structure
  • Oxalobacteraceae / chemistry*
  • Quantum Theory*

Substances

  • Indoles
  • violacein