Skip to main content

Research Repository

Advanced Search

A Hückel Model for the Excited-State Dynamics of a Protein Chromophore Developed Using Photoelectron Imaging

Anstöter, Cate S.; Verlet, Jan R.R.

A Hückel Model for the Excited-State Dynamics of a Protein Chromophore Developed Using Photoelectron Imaging Thumbnail


Authors

Cate S. Anstöter



Abstract

Chemistry can be described as the movement of nuclei within molecules and the concomitant instantaneous change in electronic structure. This idea underpins the central chemical concepts of potential energy surfaces and reaction coordinates. To experimentally capture such chemical change therefore requires methods that can probe both the nuclear and electronic structure simultaneously and on the time scale of atomic motion. In this Account, we show how time-resolved photoelectron imaging can do exactly this and how it can be used to build a detailed and intuitive understanding of the electronic structure and excited-state dynamics of chromophores. The chromophore of the photoactive yellow protein (PYP) is used as a case study. This chromophore contains a para-substituted phenolate anion, where the substituent, R, can be viewed as an acrolein derivative. It is shown that the measured photoelectron angular distribution can be directly related to the electronic structure of the para-substituted phenolate anion. By incrementally considering differing R groups, it is also shown that these photoelectron angular distributions are exquisitely sensitive to the conformational flexibility of R and that when R contains a π-system the excited states of the chromophore can be viewed as a linear combination of the π* molecular orbitals on the phenolate (πPh*) and the R substituent (πR*). Such Hückel treatment shows that the S1 state of the PYP chromophore has predominantly πR* character and that it is essentially the same as the chromophore of the green fluorescent protein (GFP). The S1 excited-state dynamics of the PYP chromophore probed by time-resolved photoelectron imaging clearly reveals both structural (nuclear) dynamics through the energy spectrum and electronic dynamics through the photoelectron angular distributions. Both motions can be accurately assigned using quantum chemical calculations, and these are consistent with the intuitive Hückel treatment presented. The photoactive protein chromophores considered here are examples of where a chemists’ intuitive Hückel view for ground-state chemistry appears to be transferable to the prediction of photochemical excited-state reactivity. While elegant and insightful, such models have limitations, including nonadiabatic dynamics, which is present in a related PYP chromophore, where a fraction of the S1 state population forms a nonvalence (dipole-bound) state of the anion.

Citation

Anstöter, C. S., & Verlet, J. R. (2022). A Hückel Model for the Excited-State Dynamics of a Protein Chromophore Developed Using Photoelectron Imaging. Accounts of Chemical Research, 55(9), 1205-1213. https://doi.org/10.1021/acs.accounts.1c00780

Journal Article Type Article
Online Publication Date Feb 16, 2022
Publication Date May 3, 2022
Deposit Date Mar 15, 2022
Publicly Available Date Mar 28, 2024
Journal Accounts of Chemical Research
Print ISSN 0001-4842
Electronic ISSN 1520-4898
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 55
Issue 9
Pages 1205-1213
DOI https://doi.org/10.1021/acs.accounts.1c00780

Files





You might also like



Downloadable Citations