Electronic Structure Of Chromophores Research Articles

Tuning the Protein-Induced Absorption Shifts of Retinal in Engineered Rhodopsin Mimics.

Rational design of light-capturing properties requires understanding the molecular and electronic structure of chromophores in their native chemical or biological environment. We employ here large-scale quantum chemical calculations to study the light-capturing properties of retinal in recently designed human cellular retinol binding protein II (hCRBPII) variants (Wang et al. Science, 2012, 338, 1340-1343). Our calculations show that these proteins absorb across a large part of the visible spectrum by combined polarization and electrostatic effects. These effects stabilize the ground or excited state energy levels of the retinal by perturbing the Schiff-base or β-ionone moieties of the chromophore, which in turn modulates the amount of charge transfer within the molecule. Based on the predicted tuning principles, we design putative in silico mutations that further shift the absorption properties of retinal in hCRBPII towards the ultraviolet and infrared regions of the spectrum.

Gas-Phase Studies of Chromophore Molecules in an Electrostatic Storage Ring

The use of an electrostatic storage ring for the study of chromophore ions in the gas phase is demonstrated. In this way the intrinsic photophysics and photochemistry of “naked” chromophore ions without the “disturbance” of a solvation shell is elucidated. The ring is combined with an electrospray ion source which enables the production of large molecular ions. Experiments described here involve absorption spectroscopy of protein chromophores and measurements of lifetimes for dissociation processes and excited states of nucleotide and protoporphyrin ions. Comparisons with solution phase experiments allow us to address the perturbation of a solvent or a protein environment on the electronic structure of chromophores.