Structural heterogeneity in the collision complex between organic dyes and tryptophan in aqueous solution
Qinfang Sun1, Rong Lu, Anchi Yu
1Department of Chemistry, Renmin University of China, Beijing, People's Republic of China.
The Journal of Physical Chemistry. B
|December 14, 2011
Summary
Photoinduced electron transfer (PET) kinetics in aqueous solutions reveal significant structural heterogeneity in fluorophore-tryptophan complexes. This finding impacts PET-based fluorescence correlation spectroscopy studies.
Area of Science:
- Photochemistry
- Biophysical Chemistry
- Spectroscopy
Background:
- Heterogeneity in photoinduced electron transfer (PET) kinetics is well-studied in biopolymers.
- PET kinetics between fluorophores and quenchers in aqueous solutions remain less explored.
Purpose of the Study:
- To investigate the structural heterogeneity of collision complexes formed between common fluorophores and tryptophan in aqueous solutions.
- To explore photoinduced electron transfer (PET) kinetics in these complexes using femtosecond transient absorption spectroscopy.
Main Methods:
- Femtosecond transient absorption spectroscopy was employed.
- The decay of the first excited electronic state of four fluorophores (TMR, RhB, Alexa546, Atto655) was measured with and without 50 mM tryptophan.
- Charge separation rates in collision complexes were derived.
Main Results:
- All four studied fluorophores exhibited two distinct charge separation rates in 50 mM tryptophan solutions.
- This indicates significant structural heterogeneity within the collision complexes of fluorophores and tryptophan.
- Results align with previous molecular dynamics simulations.
Conclusions:
- The study demonstrates substantial structural heterogeneity in fluorophore-tryptophan collision complexes in aqueous solution.
- Derived PET kinetic parameters are crucial for PET-based fluorescence correlation spectroscopy applications involving these fluorophores in biopolymers.
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