Accurate Vertical Electron Detachment Energies and Multiphoton Resonant Photoelectron Spectra of Biochromophore Anions in Aqueous Solution.

We introduce a new methodology for calculating vertical electron detachment energies (VDEs) of biologically relevant chromophores in their deprotonated anionic forms in aqueous solution. It combines a large-scale mixed DFT/EFP/MD approach with the high-level multireference perturbation theory XMCQDPT2 and the Effective Fragment Potential (EFP) method. The methodology includes a multiscale flexible treatment of inner (∼1000 water molecules) and outer (∼18000 water molecules) water shells around a charged solute, capturing both the effects of specific solvation and the properties of bulk water.

Wavelength dependent mechanism of phenolate photooxidation in aqueous solution.

Phenolate photooxidation is integral to a range of biological processes, yet the mechanism of electron ejection has been disputed. Here, we combine femtosecond transient absorption spectroscopy, liquid-microjet photoelectron spectroscopy and high-level quantum chemistry calculations to investigate the photooxidation dynamics of aqueous phenolate following excitation at a range of wavelengths, from the onset of the S-S absorption band to the peak of the S-S band. We find that for ≥ 266 nm, electron ejection occurs from the S state into the continuum associated with the contact pair in which the PhO˙ radical is in its ground electronic state.

Liquid-microjet photoelectron spectroscopy of the green fluorescent protein chromophore.

Green fluorescent protein (GFP), the most widely used fluorescent protein for in vivo monitoring of biological processes, is known to undergo photooxidation reactions. However, the most fundamental property underpinning photooxidation, the electron detachment energy, has only been measured for the deprotonated GFP chromophore in the gas phase. Here, we use multiphoton ultraviolet photoelectron spectroscopy in a liquid-microjet and high-level quantum chemistry calculations to determine the electron detachment energy of the GFP chromophore in aqueous solution.

Mode-Specific Vibrational Autodetachment Following Excitation of Electronic Resonances by Electrons and Photons.

Electronic resonances commonly decay via internal conversion to vibrationally hot anions and subsequent statistical electron emission. We observed vibrational structure in such an emission from the nitrobenzene anion, in both the 2D electron energy loss and 2D photoelectron spectroscopy of the neutral and anion, respectively. The emission peaks could be correlated with calculated nonadiabatic coupling elements for vibrational modes to the electronic continuum from a nonvalence dipole-bound state.

Comparison of Targeted Mass Spectrometry Techniques with an Immunoassay: A Case Study for HSP90α.

Purpose: The objective of this study is to better understand factors governing the variability and sensitivity in SRM and PRM, compared to immunoassay.

Experimental Design: A 2D-LC-MS/MS-based SRM and PRM assay is developed for quantitative measurements of HSP90α in serum. Forty-three control sera are compared by SRM, PRM, and ELISA following the manufacturer's instructions.