Long-Lifetime Metal—Ligand Complexes

  • Joseph R. Lakowicz


Throughout the previous chapters, we described fluorophores with decay times ranging from 1 to 20 ns. While this timescale is useful for many biophysical measurements, there are numerous instances where longer decay times are desirable. For instance, one may wish to measure rotational motions of large proteins or membrane-bound proteins. In such cases the overall rotational correlation times can easily be longer than 200 ns, and they can exceed 1 μs for larger macromolecular assemblies. Rotational motions on this timescale are not measurable using fluorophores which display nanosecond lifetimes. Processes on the microsecond or even the millisecond timescale have occasionally been measured using phosphorescence.1–4 However, relatively few probes display useful phosphorescence in room-temperature aqueous solutions. Also, it is usually necessary to perform phosphorescence measurements in the complete absence of oxygen. Hence, there is a clear need for probes which display microsecond lifetimes. In this chapter we describe a family of metal—ligand probes which display decay times ranging from 100 ns to 10μs. The long lifetimes of the metal—ligand probes allow the use of gated detection, which can be employed to suppress interfering autofluorescence from biological samples and can thus provide increased sensitivity.5 Finally, the metal—ligand probes display high chemical and photochemical stability. Because of these favorable properties, we expect metal—ligand probes to have numerous uses in biophysical chemistry, clinical chemistry, and DNA diagnostics.


Human Serum Albumin Decay Time Rotational Correlation Time Intensity Decay Fluorescence Polarization Immunoassay 
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Copyright information

© Springer Science+Business Media New York 1999

Authors and Affiliations

  • Joseph R. Lakowicz
    • 1
  1. 1.University of Maryland School of MedicineBaltimoreUSA

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