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Binding Affinity of Inorganic Mercury and Cadmium to Biomimetic Erythrocyte Membranes
journal contribution
posted on 2016-11-28, 00:00 authored by Mohamed Hassanin, Evan Kerek, Michael Chiu, Max Anikovskiy, Elmar J. PrennerInorganic
mercury and cadmium are becoming increasingly prevalent
due to industrial activity and have been linked to cardiovascular
disease and diabetes. The binding affinity of Hg, Cd, and their mixtures
to biomimetic erythrocyte membranes was investigated by isothermal
titration calorimetry in physiologically relevant media (100 mM NaCl,
pH 7.4, 37 °C). The thermodynamic parameters were not expressed
per mole of lipid but as metals binding to liposomes. To our knowledge,
this method is novel and provides a more intuitive approach to understand
such interactions. The results demonstrated that Hg interacted with
membranes in the following order: PC (phosphatidylcholine) > 85:15
PC/PE (phosphatidylethanolamine) > 85:15 PC/PS (phosphatidylserine),
with the binding constants ranging from 10 to 233 M–1. In contrast, Cd interacted most readily with negatively charged
PC/PS membranes but not with the remaining systems. Metal mixtures
bind less to PC/PE membranes than the individual constituents. The
large entropy contribution from these interactions suggests possible
water release and/or reorganization upon Hg and Cd binding to membranes.
ζ-Potential data indicate that the process may be electrostatically
driven. It is imperative to consider the chemical speciation of these
metals in the presence of chloride to better understand metal–lipid
interactions and their impact on biomembranes.