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Published on: February 14, 2014
Photodissociation dynamics of hydroxybenzoic acids
Yi Lin Yang1, Yuri Dyakov, Y T Lee
1Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.
The Journal of Chemical Physics
|January 26, 2011
Summary
Intramolecular hydrogen bonding in tyrosine chromophores prevents excited-state dissociation, explaining amino acid photostability under UV light. This finding offers a new mechanism for understanding ultraviolet photon interactions with biological molecules.
Area of Science:
- Photochemistry
- Biophysical Chemistry
- Molecular Dynamics
Background:
- Aromatic amino acids exhibit high UV absorption and low fluorescence.
- Ultrafast internal conversion was thought to ensure photostability.
- Recent studies suggest excited-state dissociation contradicts observed photostability.
Purpose of the Study:
- Investigate photodissociation dynamics of tyrosine chromophores.
- Explore the role of intramolecular hydrogen bonding in photostability.
- Provide an alternative mechanism for amino acid photostability.
Main Methods:
- Studied 2-, 3-, and 4-hydroxybenzoic acid photodissociation.
- Utilized multimass ion imaging techniques in a molecular beam at 193 nm.
- Performed ab initio calculations on potential energy surfaces.
Main Results:
- Dissociation from the excited state is quenched in conformers with intramolecular hydrogen bonding.
- Ab initio calculations reveal significant changes in excited and ground state potential energy surfaces.
- Intramolecular hydrogen bonding plays a crucial role in excited-state dynamics.
Conclusions:
- Intramolecular hydrogen bonding is key to the photostability of aromatic amino acids.
- This study provides a novel molecular mechanism for UV photostability.
- Findings challenge previous assumptions about ultrafast internal conversion.
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