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Energy migration and transfer rates are invariant to modeling the fluorescence relaxation by discrete and continuous distributions of lifetimes
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2004 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, ISSN 1520-6106, Vol. 108, no 9, 3092-3097 p.Article in journal (Refereed) Published
Abstract [en]

Fluorescent groups typically exhibit nonexponential photophysics when incorporated into biomolecular structures, e.g., proteins and lipid membranes. Models assuming discrete and continuous distributions of lifetimes can each accurately describe the observed relaxation. In the analyses of energy transfer and PDDEM (partial donor-donor energy migration) experiments, one frequently needs to model the nonexponential decays of noninteracting donor and acceptor groups. The present paper aims at exploring whether calculated transfer/migration rates depend on modeling the photophysics' decay by discrete or continuous distributions of lifetimes. Discrete or continuous distribution models of the decay, generated synthetically, were analyzed as well as true experimental data. Two proteins were studied. In one of the systems, we examined energy transfer from Trp (donor) to BODIPY (acceptor) in ribosomal protein S6, obtained from Thermus thermophilus. In the second system, we examined PDDEM between different BODIPY derivatives that were pairwise specifically incorporated in mutant forms of plasminogen activator inhibitor type 2. Interestingly, the rates of electronic energy migration/transfer and distances determined within pairs of interacting chromophores reveal small or negligible influence on using discrete or continuous distributions of lifetimes.

Place, publisher, year, edition, pages
2004. Vol. 108, no 9, 3092-3097 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:umu:diva-14319DOI: 10.1021/jp031096xOAI: oai:DiVA.org:umu-14319DiVA: diva2:153990
Available from: 2007-06-26 Created: 2007-06-26 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Electronic Energy Transfer within Asymmetric Pairs of Fluorophores: Partial Donor-Donor Energy Migration (PDDEM)
Open this publication in new window or tab >>Electronic Energy Transfer within Asymmetric Pairs of Fluorophores: Partial Donor-Donor Energy Migration (PDDEM)
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A kinetic model of electronic energy migration within pairs of photophysically non-identical fluorophores has been developed. The model applies to fluorescent groups that exhibit different photophysical and spectral properties when attached to different positions in a macromolecule. The energy migration within such asymmetric pairs is partially reversible, which leads to the case of partial donor-donor energy migration (PDDEM). The model of PDDEM is an extension of the recently developed donor-donor energy migration model (DDEM, F. Bergström et al, PNAS 96 (1999) 12477), and applies to quantitative measurements of energy migration rates and distances within macromolecules. One important distinction from the DDEM model is that the distances can be obtained from fluorescence lifetime measurements. A model of fluorescence depolarisation in the presence of PDDEM is also presented.

To experimentally test the PDDEM approach, different model systems were studied. The model was applied to measure distances between rhodamine and fluorescein groups within on-purpose synthesised molecules that were solubilised in lipid bilayers. Moreover, distances were measured between BODIPY groups in mutant forms of the plasminogen activator inhibitor of type 2 (PAI-2). Measurements of both the fluorescence intensity decays and the time-resolved depolarisation were performed. The obtained distances were in good agreement with independent determinations.

Finally, the PDDEM within pairs of donors is considered, for which both donors exhibit a nonexponential fluorescence decay. In this case it turns out that the fluorescence relaxation of a coupled system contains distance information even if the photophysics of the donors is identical. It is also demonstrated that the choice of relaxation model has a negligible effect on the obtained distances. The latter conclusion holds also for the case of donor-acceptor energy transfer.

Place, publisher, year, edition, pages
Umeå: Kemi, 2004. 36 p.
Keyword
Physical chemistry, fluorescence resonance energy transfer (FRET), donor-donor energy migration (DDEM), homotransfer, fluorescence relaxation, lifetimes, time-resolved fluorescence anisotropy, time-correlated single photon counting, distance measurements, protein structure, Fysikalisk kemi
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-338 (URN)91-7305-765-7 (ISBN)
Public defence
2004-11-19, KE 32, Kemihuset, Umeå University, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2004-10-19 Created: 2004-10-19 Last updated: 2010-08-05Bibliographically approved

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