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A model for multiexponential tryptophan fluorescence intensity decay in proteins
1Department of Biochemistry and Molecular Biology, Mayo Foundation, Rochester, Minnesota 55905.
Biophysical Journal
|December 1, 1993
Summary
This study proposes a new multiexponential model for protein fluorescence decay, explaining multiple lifetimes without needing multiple protein conformations. This energy transfer model offers a plausible alternative for analyzing fluorescence intensity decay data.
Area of Science:
- Biophysics
- Protein Dynamics
- Spectroscopy
Background:
- Tryptophan fluorescence intensity decay in proteins is often modeled using multiexponential functions.
- Multiple protein conformations are commonly invoked to explain multi-exponential decay.
- Structural constraints in some proteins challenge the multiple conformer hypothesis.
Purpose of the Study:
- To present an alternative multiexponential model for fluorescence decay.
- To explain multi-exponential decay through energy transfer to acceptors.
- To justify multiexponential modeling without invoking multiple protein conformations.
Main Methods:
- Developed a multiexponential model based on energy transfer from an excited donor to N acceptor molecules.
- Assumed specific radiative and radiationless relaxation processes.
- Neglected interactions between acceptors and back energy transfer.
Main Results:
- The model predicts 2N exponential components in the intensity decay function.
- These components are characterized by unperturbed donor lifetime and energy transfer rates.
- Applied the model to fluorescence decay data of azurin, ribonuclease T1, and thioredoxin.
Conclusions:
- A multiexponential model for fluorescence intensity decay can be justified by energy transfer mechanisms.
- This provides a plausible explanation for multi-exponential decay without multiple protein conformations.
- The model was successfully applied to several protein systems.