Fluorescein absorption

The physical properties of the xanthene type dye stmcture in general have been considered. For example, the aggregation phenomena of xanthene dyes has been reviewed (3), as has then photochemistry (4), electron transfer (5), triplet absorption spectra (6), and photodegradation (7). For the fluoresceins in particular, spectral properties and photochemistry have been reviewed (8), and the photochemistry of rhodamines has been investigated (9). 

Fabian WMF, Schuppler S, Wolfbeis OS (1996) Effects of annulation on absorption and fluorescence characteristics of fluorescein derivatives a computational study. J Chem Soc Perkin Trans 2(5) 853-856... 

Fluorescein is excited at 494 nm, which fits to the argon-ion laser line at 488 nm, a very convenient feature for many microscopy experiments. It emits at 520 nm and the emission band is far from being sharp. The broad fluorescence emission spectrum varies with pH [18]. The advantageous photochemical properties of fluorescein are its high absorption (emax = 79,000M-1cm-1) and quantum... 

SAMSA-fluorescein is an orange solid compound. Dissolved in buffer at pH 9.0, its maximal wavelength of absorption or excitation is at 495 nm, while its emission wavelength maximum is 520 nm. The reagent and all solutions and derivatives made from it are light sensitive and should be stored in the dark. SAMSA-fluorescein is soluble in aqueous solutions above pH 6.0, but it can be dissolved in DMF to prepare a concentrated stock solution prior to adding a small amount to a buffered reaction mixture. 

In 1888, Walter studied the quenching of fluorescence, by the concentration effect, of fluorescein solutions. Nicols and Merrit observed in 1907, in solutions of eosine and resoruflne, the symmetry existing between their absorption and fluorescence spectra. In 1910, Ley and Engelhardt determined the fluorescence quantum yield of various benzene derivatives, values that were still referred to until recent years [18], The works by Lehmann and Wood, around 1910, marked the beginning of analysis based on fluorescence [4],... 

The intrinsic sensors are based on the direct recognition of the chemicals by its intrinsic optical activity, such as absorption or fluorescence in the UV/Vis/IR region. In these cases, no extra chemical is needed to generate the analytical signal. The detection can be a traditional spectrometer or coupled with fiber optics in those regions. Sensors have been developed for the detection of CO, C02 NOx, S02, H2S, NH3, non-saturated hydrocarbons, as well as solvent vapors in air using IR or NIR absorptions, or for the detection of indicator concentrations in the UV/ Vis region and fluorophores such as quinine, fluorescein, etc. 

Since the same dye molecules can serve as both donors and acceptors and the transfer efficiency depends on the spectral overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor, this efficiency also depends on the Stokes shift [53]. Involvement of these effects depends strongly on the properties of the dye. Fluoresceins and rhodamines exhibit high homo-FRET efficiency and self-quenching pyrene and perylene derivatives, high homo-FRET but little self-quenching and luminescent metal complexes may not exhibit homo-FRET at all because of their very strong Stokes shifts. 

Fast librational motions of the fluorophore within the solvation shell should also be consideredd). The estimated characteristic time for perylene in paraffin is about 1 ps, which is not detectable by time-resolved anisotropy decay measurement. An apparent value of the emission anisotropy is thus measured, which is smaller than in the absence of libration. Such an explanation is consistent with the fact that fluorescein bound to a large molecule (e.g. polyacrylamide or monoglucoronide) exhibits a larger limiting anisotropy than free fluorescein in aqueous glycerolic solutions. However, the absorption and fluorescence spectra are different for free and bound fluorescein the question then arises as to whether r0 could be an intrinsic property of the fluorophore. 

The high molar absorptivities and quantum yields of the large protein fluorophore phycoerythrin (240,000 Da) have been exploited in energy transfer assays. Phyco-erythrin has been used as both donor and acceptor, with several bound antigen molecules per phycoerythrin molecule/86,94) The usefulness of BPE is indicated in competitive assays for human IgG that use fluorescein-labeled antibody as donor to... 

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