Absorption of the green fluorescent protein chromophore anion in the gas phase studied by a combination of FTICR mass spectrometry with laser-induced photodissociation spectroscopy

Abstract: The optical absorption of the green fluorescent protein chromophore anion (HBDI−) in the gas phase has been addressed by a number of experimental and theoretical studies; however, there is no consensus on its spectral characteristics yet. In this report, the intrinsic absorption of HBDI− was probed by photo-induced dissociation (“action”) spectroscopy using discrete lines of a continuous-wave (CW) laser source. The observed spectral profile of dissociation efficiency revealed a pronounced dependence on the laser irradiance. Dissociation at high irradiance is governed by multiple-photon absorption processes whose efficiency peaks between 476 and 488nm. At very low irradiance (<0.4mWcm−2) dissociation of gas-phase HBDI− is mostly promoted by single-photon transitions and suggests an intrinsic absorption maximum of gas-phase HBDI− <476nm, blue-shifted compared to earlier results obtained with pulsed lasers. [Copyright &y& Elsevier]