Long-Range Energy Transfer in Protein Megamolecules

Elijah L. Taylor, Kevin J. Metcalf, Benedetta Carlotti, Cheng Tsung Lai, Justin A. Modica, George C. Schatz*, Milan Mrksich, Theodore Goodson

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

In this investigation, we report evidence for energy transfer in new protein-based megamolecules with tunable distances between donor and acceptor fluorescent proteins. The megamolecules used in this work are monodisperse oligomers, with molecular weights of ∼100-300 kDa and lengths of ∼5-20 nm, and are precisely defined structures of fusion protein building blocks and covalent cross-linkers. Such structures are promising because the study of energy transfer in protein complexes is usually difficult in this long length regime due to synthetic limitations. We incorporated fluorescent proteins into the megamolecule structure and varied the separation distance between donor and acceptor by changing the length of the cross-linker in dimer conjugates and inserting nonfluorescent spacer proteins to create oligomers. Two-photon absorption measurements demonstrated strong coupling between donor and acceptor dipoles in the megamolecules. For the dimer systems, no effect of the cross-linker length on energy transfer efficiency was observed with the steady-state fluorescence investigation. However, for the same dimer conjugates, energy transfer rates decreased upon increasing cross-linker length, as evaluated by fluorescence up-conversion. Molecular dynamics simulations were used to rationalize the results, providing quantitative agreement between measured and calculated energy transfer lengths for steady-state results, and showing that the differences between the time-resolved and steady-state measurements arise from the long time scale for large-scale fluctuations in the megamolecule structure. Our results show an increase in energy transfer length with increasing megamolecule size. This is evidence for long-range energy transfer in large protein megamolecules.

Original languageEnglish (US)
Pages (from-to)15731-15743
Number of pages13
JournalJournal of the American Chemical Society
Volume140
Issue number46
DOIs
StatePublished - Nov 21 2018

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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  • Cite this

    Taylor, E. L., Metcalf, K. J., Carlotti, B., Lai, C. T., Modica, J. A., Schatz, G. C., Mrksich, M., & Goodson, T. (2018). Long-Range Energy Transfer in Protein Megamolecules. Journal of the American Chemical Society, 140(46), 15731-15743. https://doi.org/10.1021/jacs.8b08208