Alternating-laser excitation of single molecules

Achillefs N. Kapanidis, Ted A. Laurence, Ki Lee Nam, Emmanuel Margeat, Xiangxu Kong, Shimon Weiss

Research output: Contribution to journalArticlepeer-review

282 Scopus citations


Single-molecule fluorescence spectroscopy addresses biological mechanisms and enables ultrasensitive diagnostics. We describe a new family of single-molecule fluorescence methods that uses alternating-laser excitation (ALEX) of diffusing or immobilized biomolecules to study their structure, interactions, and dynamics. This is accomplished using ratios that report on the distance between and the stoichiometry of fluorophores attached to the molecules of interest. The principle of alternation is compatible with several time scales, allowing monitoring of fast dynamics or simultaneous monitoring of a large number of individual molecules.

Original languageEnglish
Pages (from-to)523-533
Number of pages11
JournalAccounts of Chemical Research
Issue number7
StatePublished - Jul 2005
Externally publishedYes


FundersFunder number
National Institute of General Medical SciencesR01GM065382


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