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Single-Molecule Light Microscopy

  1. Karl Otto Greulich,
  2. Volker Uhl

Published Online: 15 MAR 2010

DOI: 10.1002/9780470015902.a0002997.pub2



How to Cite

Greulich, K. O. and Uhl, V. 2010. Single-Molecule Light Microscopy. eLS. .

Author Information

  1. Leibniz Institute of Age–Research, Jena, Germany

Publication History

  1. Published Online: 15 MAR 2010


With conventional microscopy, the wavelength of visible light (∼500 nm) does not permit spatial resolution of individual molecules, but single molecules can be detected if they are themselves fluorescent (fluorophores) or are fluorescently tagged with fluorophores. Such techniques allow optical microscopy studies of quantum-mechanical phenomena, mechanical properties of macromolecules and single-molecule reaction kinetics and mechanisms. When an enzyme reaction deletes or generates fluorescence, the kinetics of one or a few of such enzyme molecules can be directly observed in the microscope. Fluorescently tagged compounds can be introduced into biologically relevant environments and their movements or molecular mode of action can be analysed. Such techniques enable further studies on various topics like the movement of motor proteins, molecular diffusion or intramolecular conformational changes. The reactions of molecules which work on DNA (deoxyribonucleic acid) can be directly seen in the microscope. Also, the addressability of the DNA molecule can be exploited to build nanostructures with nanometre accuracy.

Key concepts:

  • Single molecules can be visualized in the light microscope with high temporal resolution, when stray light and other polluting photons are separated from the informative photons.

  • Structural transitions and reactions can be observed.

  • The individuality of each molecule can be visualized.

  • DNA molecules can be used as building blocks for the construction of nanostructures.

  • Although smaller than the diffraction limit for optical microscopy, single molecules can be detected if they are fluorescent or fluorescently tagged.

  • Fluorescent molecules can be investigated to study quantum-mechanical phenomena of the mechanical properties of macromolecules, or their trajectories and properties in their specific environment can be observed.


  • spectroscopy;
  • reactions;
  • detectors;
  • fluorescence;
  • kinetics