Erythrosin and light flashes induce voltage transients across bilayer membranes in the presence of transmembrane pH gradients. Fast voltage transients, which rise in less than 50 nsec and fall in approximately 500 nsec, are attributed to photo-deprotonation of dye sorbed in the glycerol region of phospholipid membranes. Six other halogenated xanthene dyes induce similar effects, which apparently resulted from triplet states of monoanionic dye. No photo-effects were observed with fluorescein.
Abstract— Voltage transients are generated across lipid bilayer membranes by light flashes as a result of photophysical processes in sorbed dyes which displace electrical charges. A theory is presented which indicates that: (i) the fraction of sorbed dye which displaces charge from one flash can be determined by the fractional reduction in the photovoltage amplitude resulting from a second and identical flash, providing the second flash occurs before dye excited by the first flash returns to its equilibrium condition. (ii) The photoeffect quantum efficiency can be determined from the fraction of dye displacing charge, the light intensity and the dyes' optical absorption cross section. Apparatus constraints required different experimental procedures for dyes with different excited state life times, which are discussed. Experimental results are presented for an azo dye, 3,3'‐bis(α‐(trimethyiammonium)methyl)azobenzenebromide (Bis‐Q), three carbocyanine dyes in the series 3,3'‐dimethyl‐2,2'‐oxacarbocyanine‐iodide (diO‐C1‐3), an amino‐pyridinium dye, 4‐(p‐(dimethyl‐amino)styryl)‐1‐rnethyl‐pyridinium‐iodide (di‐1‐ASP), and a xanthene dye, 2',4',5',7'‐tetraiodofluorescein (erythrosin), the sodium salt of which is known as F, D and C red number 3. The dyes' optical absorption cross section values are uncertain owing to solvent and orientational effects in membranes. Photoeffect quantum efficiency values obtained by calculating optical absorption cross sections from the dyes' molar extinction coefficients in aqueous solutions are: Bis‐Q (0.08), diO‐C1‐3 (0.31), diO‐C2‐3 (0.22), diO‐C5‐3 (0.08), di‐l‐ASP (0.3) and erythrosin (0.39).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.