Absorption and Fluorescence Spectra of Halogen Derivatives of Fluorescein

Erythrosin and pH gradient induced photo-voltages in bilayer membranes

“…The results described above indicate that the fast photo-voltage transients reported here are associated with pK3, which in dioxane/water is 5.9 [29]. At pH values above pK3, erythrosin is a divalent anion, while below pK3 it is monovalent [12,29]. Photo-voltages observed on the 5-psec apparatus with 10 pM dye, pH ~5.5 inside, 3 outside, in 10 mM NaC1, has fast-part amplitudes (in mV) of: erythrosin (1.7), ethyl eosin (1.3), rose bengal (1.2), eosin Y (0.6), phloxine B (0.5), 4',5'-dibromofluorescein (0.3) and T,7'-dichlorofluorescein (0.1).…”

“…The slow part is seen in part F, and with reduced amplitude in D in membranes. The results described above indicate that the fast photo-voltage transients reported here are associated with pK3, which in dioxane/water is 5.9 [29]. At pH values above pK3, erythrosin is a divalent anion, while below pK3 it is monovalent [12,29].…”

“…The value of pK2 in pure water, determined spectrophotometrically [27] is 3.7. In dioxane/water (2:3) pK2 is 4.5 [29], so the pK,, values may be expected to vary with different sorption sites Traces recorded with PE membrane, pH ~5.5 inside, 3 outside, in 1 mM NaCI. The dashed "'RC "' trace shows the resistance-capacitance discharge of the membrane through a 109 ~ shunt resistor [15].…”

Ionization and tautomerism of methyl fluorescein and related dyes

“…It should be mentioned, however, that the detailed ionization scheme of the mother compound, fluorescein, in water [4,6,[19][20][21][22][23] and non-aqueous solvents was already studied in full and reported in a set of publications [24][25][26][27][28][29].…”