Absorption of fluorescein

Niven, R.W. Byron, P.R. Solute absorption from the airways of the isolated rat lung. 2. Effect of surfactants on absorption of fluorescein. Pharm. Res. 1990, 7, 8-13. 

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... 

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],... 

These compounds are readily prepared by the reaction of fluorescein isothiocyanate with the polypeptide in a DMSO/water mixture and fluorescein-polyacrylate conjugate (6) is prepared by the reaction of fluoresceinamine with polyacrylic acid by using the mixed anhydride method [150]. In all cases, the absorption and emission maxima were similar at 490 and 525 nm, respectively, and reflect the photophysical properties of fluorescein itself. 

The main fluorescent pH indicator probes are based on fluorescein and therefore it is important to understand the pH-dependent ionic equilibria of it and its derivatives, hi aqueous solutions above pH 9 the phenolic and carboxylic acid functional groups in the molecule are almost totally ionised (Figure 3.14). Upon acidification of the dianion, firstly, protonation of the phenolic group occurs (pK 6.4) to yield the monoanion followed by the carboxylic acid (pA < 5), giving the neutral species of fluorescein. On further acidification the fluorescein cation pK 2.1) is generated. In strongly acidic environments fluorescein is non-fluorescent, only the mono-anion and di-anions are fluorescent, with quantum yields of 0.37 and 0.93, respectively. The pH-dependent absorption spectrum of fluorescein exhibits a blue-shift and... 

Fig. 11. New absorption spectrum (solid line) appearing reversibly on irradiation of fluorescein in boric acid glass. The dotted line shows the normal absorption spectrum. After G. N. Lewis et al., J. Am. Ckem. Soc., to, 3005 (1941).

Hoogstraate, A., et al. 1996. In-vivo buccal delivery of fluorescein isothiocyanate-dextran 4400 with glycodeoxycholate as an absorption enhancer in pigs. J Pharm Sci 85 457. 

A liquid prism was created on a PDMS chip for detection based on absorption and refractive index shift. The liquid prism was formed by filling a hollow triangular-shaped chamber with a liquid sample. Excitation and emission were arranged at the minimum deviation configuration. At a low concentration of fluorescein (< 100 pM), excitation light from an optical fiber was absorbed by the molecule, but there was no shift in the excitation maximum. In this absorption-only mode, the LOD of fluorescein was 6 pM. At higher concentration (i.e., 100-1000 pM), there is an additional shift in the excitation maximum This leads to a much sharper decrease in the measured intensity, which is more than can be accounted for simply by the absorption effect [714]. 

---