Terbium fluorescence

Yuan, J. Wang, G. Majima, K. Matsumoto, K. Synthesis of a terbium fluorescent chelate and its application to time-resolved fluoroimmunoassay. Anal. Chem. 2001, 73(8), 1869-1876. 

Wang, G., J. Yuan, K. Matsumoto, et al. 2001. Homogeneous time-resolved fluoroimmunoassay of bensulfuron-methyl by using terbium fluorescence energy transfer. Talanta 55 1119-1125. 

M. Amin, K. Harrington and R. Vonwandmszka, Determination of Steroids in Urine by MLC with Detection by Sensitized Terbium Fluorescence, Anal Chem., 65 2346 (1993). 

Ye ZQ, Tan MQ, Wang GL et al (2005) Development of functionalized terbium fluorescent nanoparticles for antibody labeling and time-resolved fluoroimmunoassay application. Talanta 65 206-210... 

The interaction between DNA and Tb in the solid state has been investigated using the terbium fluorescence (Yonuschot and Mushrush, 1975). The fluorescence at 491 and 545 nm upon excitation at 307 nm was monitored as a function... 

Flumequine is shown to form a complex compound with terbium(III), whose fluorescence spectmm has one band with a maximum at 545 nm (emission of terbium(III)), it corresponds to the transition. The... 

Another popular assay format for kinase assays is the Lanthascreen. This format is a variation on the LANCE assay, but employs Tb as the cryptate. In this format N-terminally fluorescently tagged peptide substrate (acceptor) is phosphorylated by the kinase. Next, a phophospecific antibody which is labeled with terbium binds specifically to the phosphorylated product, placing the donor and acceptor in close proximity, generating a signal [25]. 

Different lanthanide metals also produce different emission spectrums and different intensities of luminescence at their emission maximums. Therefore, the relative sensitivity of time-resolved fluorescence also is dependent on the particular lanthanide element complexed in the chelate. The most popular metals along with the order of brightness for lanthanide chelate fluorescence are europium(III) > terbium(III) > samarium(III) > dysprosium(III). For instance, Huhtinen et al. (2005) found that lanthanide chelate nanoparticles used in the detection of human prostate antigen produced relative signals for detection using europium, terbium, samarium, and dysprosium of approximately 1.0 0.67 0.16 0.01, respectively. The emission... 

Organic fluorescent dyes with the appropriate spectral properties also can be paired with lanthanide chelates in FRET systems. For instance, many rhodamine dyes and the cyanine dye Cy5 have ideal excitation wavelengths for receiving energy from a nearby europium chelate. The LeadSeeker assay system from GE Healthcare incorporates various Cy5-labeled antibodies for developing specific analyte assays. In addition, if using a terbium chelate as the donor, then a Cy3 fluorescent dye can be used in assays as the acceptor. 

When used with europium or terbium ions, a carbostyril-based lanthanide chelate can be excited at 340 nm and provide sharp characteristic emission bands for transfer of energy to the appropriate acceptor fluor. Similar to the TMT chelator described previously, luminescence from terbium FRET signals well with Cy3 dyes and luminescence from europium can be used with APC or Cy5 dyes. Other fluorescent dyes that have similar excitation and emission ranges to these also can be used as acceptors in TR-FRET assays. For instance, terbium chelates can... 

Hemmila, 1988) (see Chapter 9, Section 9). The most commonly used lanthanides for this purpose are europium (Eu3+), terbium (Tb3+), and samarium (Sm3+). Proteins modified with DTTA and complexed with lanthanide metal ions form the basis for unique fluorescent probes possessing long lived signals upon excitation. 

In 2000, most European countries switched from their traditional currencies to the euro. Lanthanide luminescence is used as a means of preventing counterfeit euro banknotes from passing into the money chain. Excitation of euro banknotes with ultraviolet light results in fluorescence in the red, green and blue regions due to complexes of europium (Eu3+), terbium (Tb3+) and thulium (Tm3+), respectively, that are present in the banknotes. 

The fluorescence lifetime can be measured by time-resolved methods after excitation of the fluorophore with a light pulse of brief duration. The lifetime is then measured as the elapsed time for the fluorescence emission intensity to decay to 1/e of the initial intensity. Commonly used fluorophores have lifetimes of a few nanoseconds, whereas the longer-lived chelates of europium(III) and terbium(III) have lifetimes of about 10-1000 /tsec (Table 14.1). Chapter 10 (this volume) describes the advantages of phase-modulation fluorometers for sensing applications, as a method to measure the fluorescence lifetime. Phase-modulation immunoassays have been reported (see Section 14.5.4.3.), and they are in fact based on lifetime changes. 

Figure 14.8. Enzymatically-amplified TR-FIA ofa-fetoprotein (AFP), using streptavidin-alkaline phosphatase conjugate (SA-ALP) and 5-lluorosalicyl phosphate (FSAP) to generate 5 fluorosalicylic acid (FSA). The FSA comhines with terbium-EDTA to form a bright, fluorescent complex. (Adapted from Ref. 83 with permission.) (01992, American Chemical Society).

Time-resolved approaches for multi-analyte immunoassays have been described recently. Simultaneous determination of LH, follicle stimulating hormone (FSH), hCG, and prolactin (PRL) in a multisite manual strip format has been reported. 88 Four microtiter wells are attached to a plastic strip, two-by-two and back-to-back, such that the wells can be read on a microtiter plate reader. In a quadruple-label format, the simultaneous quantitative determination of four analytes in dried blood spots can be done using europium, samarium, dysprosium, and terbium. 89 In this approach, thyroid-stimulating hormone, 17-a-hydroxyprogesterone, immunoreactive trypsin, and creatine kinase MM (CK-MM) isoenzyme are determined from dried blood samples spotted on filter paper in a microtiter well coated with a mixture of antibodies. Dissociative fluorescence enhancement of the four ions using cofluorescence-based enhancement solutions enables the time-resolved fluorescence of each ion to be measured through four narrow-band interference filters. 

T. K. Christopoulos and E. P. Diamandis, Enzymatically amplified time-resolved fluorescence immunoassay with terbium chelates, Anal. Chem. 64, 342-346 (1992). 

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