Electrostatic control of photoisomerization pathways in proteins
Matthew G Romei1, Chi-Yun Lin1, Irimpan I Mathews2
1Department of Chemistry, Stanford University, Stanford, CA 94305, USA. sboxer@stanford.edu.
Science (New York, N.Y.)
|January 4, 2020
Summary
Photoexcitation drives bond rotation in proteins, crucial for vision and technology. This study quantifies how electrostatic effects, not just sterics, control this photoisomerization in Dronpa2, guiding future protein design.
Area of Science:
- Biochemistry
- Photochemistry
- Molecular Biology
Background:
- Photoisomerization of chromophores is fundamental to biological processes like vision and technological applications.
- The interplay between steric and electrostatic effects in controlling photoisomerization pathways is a key area of research.
- Green fluorescent protein variants are valuable tools for studying photochemistry and developing molecular devices.
Purpose of the Study:
- To quantitatively assess the contributions of steric and electrostatic effects on photoisomerization in a photoswitchable protein.
- To investigate how altering electrostatic properties of the green fluorescent protein chromophore influences its photoisomerization pathway.
- To develop a generalized framework for protein design based on electrostatic control of photoisomerization.
Main Methods:
- Systematic modification of the electrostatic properties of the Dronpa2 green fluorescent protein chromophore using amber suppression.
- Introduction of electron-donating and electron-withdrawing groups to the phenolate ring of the chromophore.
- Analysis of absorption spectra (color), fluorescence quantum yield, and isomerization energy barriers.
Main Results:
- Electrostatic effects were shown to quantitatively bias the pathway of chromophore photoisomerization.
- Changes in electron-donating and withdrawing groups significantly altered the absorption and fluorescence properties.
- Energy barriers for ground- and excited-state isomerization were modulated by the introduced electrostatic modifications.
Conclusions:
- Electrostatic interactions play a critical, quantifiable role in directing photoisomerization pathways, complementing steric effects.
- The findings provide a generalized framework to guide the rational design of photoactive proteins and molecular devices.
- Understanding and controlling photoisomerization through electrostatics opens new avenues in optogenetics and super-resolution microscopy.
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