Redox properties of the calcium chelator Fura-2 in mimetic biomembranes

Gulaboski, Rubin and Pereira, Carlos M. and Cordeiro, M Natália D S and Silva, A. Fernando and Hoth, Markus and Bogeski, Ivan (2008) Redox properties of the calcium chelator Fura-2 in mimetic biomembranes. Cell Calcium, 43 (6). pp. 615-621. ISSN 01434160

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Fura-2 is one of the most commonly used fluorescent dyes to analyze the cytosolic Ca2+ concentration ([Ca2+]i) of living cells. Fura-2-
dependent measurements of [Ca2+]i are susceptible to changes of pH, reactive oxygen species concentration and membrane potential. Fura-2
is often loaded over the lipophilic cell membrane into the cytosol of a cell in its esterified form (Fura-2/AM) which is then cleaved by
endogenous esterases. We have analyzed the electrochemical properties of Fura-2/AM and Fura-2 salt by cyclic voltammetry (“three-phase”
and “thin-film” electrode methods). Using Fura-2/AM as a redox facilitator, we were able to mimic the transport of various ions across a
lipophilic barrier. We show that Fura-2/AM in this biomimetic set-up can be reversibly oxidized in a single electrochemical step. Its redox
reaction was highly proton sensitive in buffers with pH≤6. At physiological pH of around 7.0, the oxidation of Fura-2/AM was coupled
to an uptake of mono-anions across the liquid–liquid interface. The voltage-dependence of the redox cycle was sensitive to the free Ca2+
concentration, either after de-esterification of Fura-2/AM, or when Fura-2 salt was used. The complex between Fura-2 and Ca2+ ions is ionic
(complexation occurs via the dissociated negative groups of Fura forms), while the redox transformations in Fura-2 occurs at the nitrogen
atoms of the amino groups. Our results suggest that redox transformations of the Fura-2 forms do not affect the binding ability toward Ca2+
ions and thus do not interfere with [Ca2+]i measurements.

Item Type: Article
Uncontrolled Keywords: FURA 2, azo dyes, voltammetry, facilicated ion transfer, liquid-liquid interfacem Ca2+ binding
Subjects: Natural sciences > Chemical sciences
Divisions: Faculty of Agriculture
Depositing User: Rubin Gulaboski
Date Deposited: 31 Oct 2012 13:11
Last Modified: 05 Nov 2012 10:46

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