Immunoassay excitation wavelength

Lanthanides also have potential as DEFRET energy donors. Selvin et al. have reported the use of carbostyril-124 complexes (53) with europium and terbium as sensitizers for cyanine dyes (e.g., (54)) in a variety of immunoassays and DNA hybridization assays.138-140 The advantage of this is that the long lifetime of the lanthanide excited state means than it can transfer its excitation energy to the acceptor over a long distance (up to 100 A) sensitized emission from the acceptor, which occurs at a wavelength where there is minimal interference from residual lanthanide emission, is then measured. 

Relatively few probes have been widely applied to FlAs. Fluorescein and rho-damine, their derivatives, and to some extent phycoerythrin have dominated immunoassays that are based on steady-state measurements. Dansyl, umbelliferone, coumarins, and pyrenes are among others that have been used. Several more commonly used dyes are shown in Figure 14.2. Shorter-wavelength dyes tend to be less useful since they excite at wavelengths where endogenous chromophores, fluorophores, and... 

FIA Fluorescence immunoassay uses a fluorescent tag on the antibody or antigen. Fluorescent labels absorb light of one wavelength and reemit it at another wavelength. The label is excited by UV and emits visible light. Common fluorescent labels are fluorescein, Texas red, and GFP (green fluorescent protein). 

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