Chelates energy transfer

Rare-earth chelates, energy transfer, 203 Rare-earth, energy levels of, 25 Recombination luminescence, 160 Redox potential excited state, 111 of PS I and PS II, 282 Redox reactions, 218... 

Dorn, 1. T., Neumaier, K. R. and Tampe, R. (1998) Molecular recognition of histidine-tagged molecules by metal-chelating lipids monitored by fluorescence energy transfer and correlation spectroscopy. ]. Am. Chem. Soc 120, 2753. 

An eel of an europium (III) chelate was reported before (60 ). The complex was not involved in the electrolysis. Excited organic compounds formed electrochemically underwent an intermolecular energy transfer to the emitting Eu compound. Interestingly, in the absence of the redox-active organic compounds an eel of the europium chelate was not observed 2+... 

Lanthanide chelates also can be used in FRET applications with other fluorescent probes and labels (Figure 9.51). In this application, the time-resolved (TR) nature of lanthanide luminescent measurements can be combined with the ability to tune the emission characteristics through energy transfer to an organic fluor (Comley, 2006). TR-FRET, as it is called, is a powerful method to develop rapid assays with low background fluorescence and high sensitivity, which can equal the detection capability of enzyme assays (Selvin, 2000). 

Figure 9.51 Time-resolved FRET assay systems involve energy transfer between the lanthanide chelate and an organic dye that are brought together as two labeled molecules bind to an analyte. In this illustration, an antibody labeled with a lanthanide chelate is used along with a Cy5-labeled antibody to detect a protein target in solution. Excitation of the lanthanide label results in energy transfer and excitation of the cyanine dye only if they are held within close enough proximity to allow efficient FRET to occur. Under these conditions, excitation of the lanthanide chelate results in cyanine dye emission, which will not occur if the labeled antibodies have not bound to a target.

Li, M., and Selvin, P.R. (1997) Amine-reactive forms of a luminescent DTPA chelate of terbium and europium Attachment to DNA and energy transfer measurements. Bioconjugate Chem. 8(2), 127-132. 

Pei et al. [412] reported an alternating fluorene copolymer 331 with 2,2 -bipyridyl in a side chain that emitted at 422 nm. Treating this polymer with Eu3+ chelates formed the polymeric complexes 332-334. Their emission was governed by intramolecular Forster energy transfer, whose efficiency depends on the structure of the ligands and the Eu3+ content (Scheme 2.49) [412], The most effective energy transfer manifested itself in a single red emission band at 612 nm for the complex 332 with a maximum intensity achieved at —25 mol% content of Eu3+. 

Xiao, M. Selvin, P. R. Quantum yields of luminescent lanthanide chelates and far-red dyes measured by resonance energy transfer. J. Am. Chem. Soc. 2001,123, 7067-7073. 

Sato, S. Wada, M. Relations between intramolecular energy transfer efliciences and triplet energies in rare earth beta-diketone chelates. Bull. Chem. Soc. Japan 1970, 43,1955. 

Figure 6.16 Energy transfer pathway in rare earth chelates.

---