Alexa

E. Graf, M. Alexa, Planta Med. 1985, 428 [14-(umbelliferon-7-0-yl)driman-3a,8a-diol]. 

Fig. 4.13 Compounds 357 and 358 from Castanospermum and Alexa. Compounds 359-364, diterpenes from Scoparia dulcis...

Castanospermum, an Australian genus that consists of the single species C australe A. Cunn. C. Fraser ex Hook., and Alexa, a genus of eight or so species from South America (Kaplan, 1995) both belong to the tribe Sophoreae of Papilionoi-deae. Other, related genera will be commented upon below. 

The LANCE cAMP assay is a competitive assay in which cAMP produced by the cells competes with fluorescent-labeled acceptor cAMP for a cryptate tagged donor antibody. The principal of the assay is shown in Fig. 6. On the left strepta-vidin conjugated Europium binds to biotinylated cAMP. An antibody labeled with the fluorescent dye Alexa binds to the cAMP, bringing the donor and acceptor into close proximity, and energy transfer occurs. When the cell releases cAMP, it competes with the biotin-labeled cAMP for the antibody, and a signal decrease is observed. In the TR-FRET assay the antibody is directly labeled with either Eu or Tb. In this format an increase in cAMP also causes a decrease in signal. 

The number of new NIR fluorophores that can be used in biological systems has grown substantially in recent years as a consequence of extensive research efforts to improve the properties of available dyes. A brief overview of the various types of long-wavelength (above 600 nm) fluorophores including phycobiliproteins, BODIPY, and Alexa Fluor dyes (Life Technologies), Cy dyes (GE Healthcare),... 

The excitation and emission maxima of Alexa Fluor 647, 680, and 750 (the numbers indicate approximate absorption maxima in nanometers), and the molar absorptivities are in the same range as those for Cy5, Cy5.5, and Cy7, but Alexa Fluor dyes are reported to have major advantages in terms of their photostability,... 

While open-chain cyanines such as Cy5, Cy5.5, or Alexa 647 typically exhibit small fluorescence lifetime changes upon binding to biomolecules, squaraine dyes, in general, demonstrate pronounced lifetime changes upon binding to large-molecular-weight analytes [17, 18], which can be used for FLT-based assays. 

Recently, SETA BioMedicals has developed a new near-infrared squaraine-based label Seta-633, which can be used to study the interaction between low-molecular-weight analytes and proteins using fluorescence lifetime as the readout parameter [19]. This label exhibits lower quantum yields and shorter fluorescence lifetimes when free in solution, but these values substantially increase upon interaction with proteins, which is contrary to tracers like Cy5 or Alexa 647. It was demonstrated in a model assay that a biotinylated Seta-633 binds to anti-biotin with high specificity. Importantly, the lifetime of Seta-633-biotin increases about 2.76 fold upon binding to a specific antibody (anti-biotin, MW =160 kDa), while the titration with BSA or nonspecific antibody does not result in a noticeable change in lifetime (Fig. 13). The label is compatible with readily available light sources (635 nm or 640 nm lasers) and filter sets (as for Cy5 or Alexa 647) and its... 

RPE-Alexa 610, or RPE-DyLight 594 RPE-Alexa 647 or RPE-DyLight 594 RPE-DyLight 649 DyLight 649,... 

Fig. 1 Glycan array analysis of codakine as measured by fluorescence intensity (glycan array v3.0 at Consortium for Functional Glycomics). Purified codakine from white clams was purified with Alexa Fluor 488 Protein Labeling Kit (Molecular Probes , Invitrogen) and tested on glycan array v3.0 at Consortium for Functional Glycomics.

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