A new twist on PIFE: photoisomerisation-related fluorescence enhancement

Evelyn Ploetz, Benjamin Ambrose, Anders Barth, Richard Börner, Felix Erichson, Achillefs N. Kapanidis, Harold D. Kim, Marcia Levitus, Timothy M. Lohman, Abhishek Mazumder, David S. Rueda, Fabio D. Steffen, Thorben Cordes, Steven W. Magennis, Eitan Lerner

Research output: Contribution to journalReview articlepeer-review


PIFE was first used as an acronym for protein-induced fluorescence enhancement, which refers to the increase in fluorescence observed upon the interaction of a fluorophore, such as a cyanine, with a protein. This fluorescence enhancement is due to changes in the rate of cis/trans photoisomerisation. It is clear now that this mechanism is generally applicable to interactions with any biomolecule. In this review, we propose that PIFE is thereby renamed according to its fundamental working principle as photoisomerisation-related fluorescence enhancement, keeping the PIFE acronym intact. We discuss the photochemistry of cyanine fluorophores, the mechanism of PIFE, its advantages and limitations, and recent approaches to turning PIFE into a quantitative assay. We provide an overview of its current applications to different biomolecules and discuss potential future uses, including the study of protein-protein interactions, protein-ligand interactions and conformational changes in biomolecules.

Original languageAmerican English
Article number012001
JournalMethods and Applications in Fluorescence
Issue number1
StatePublished - 1 Jan 2024


  • PIFE
  • biophysics
  • fluorescence spectroscopy
  • photoisomerisation
  • single-molecule

All Science Journal Classification (ASJC) codes

  • Instrumentation
  • Atomic and Molecular Physics, and Optics
  • Spectroscopy
  • General Materials Science


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