Manganese negatively impacts the properties of biomimetic lipid membranes
Kevin Sule and Elmar Prenner 1 University of Calgary, Canada
The prevalence of metals from daily anthropogenic activities has become widespread since the industrial revolution due to a multitude of applications in modern times (1). Lipids are a potential binding target of these metals, which can alter lipid-lipid interactions. This work investigated the interaction of the essential trace element manganese (Mn) with commercially available lipid extracts of mammalian and bacterial origin. Metal speciation modelling using Visual Minteq software showed that Mn mainly forms cationic species (Mn 2+ ) under physiological conditions (2). This study utilized a spectroscopic approach in determining Mn – induced changes to membrane fluidity and generation of lipid peroxidation byproducts. For membrane fluidity measurements, the dye laurdan was used. Laurdan is a solvent sensitive fluorophore that detects changes in membrane phase properties and can be used to assess metal- induced changes to membrane fluidity (3, 4). In brief, GP values are normalized between +1 to -1, with more positive GP values indicative of more rigid membranes and vice versa. Furthermore, thin layer chromatography (TLC) was used to assess changes in lipid profile when subjected to Mn – induced lipid peroxidation. Earlier studies have determined that Mn 2+ specifically targets anionic phospholipids and caused an increase in membrane rigidity (5). Complex lipid extracts, containing zwitterionic and anionic lipids, displayed and overall increase in membrane rigidity in the presence of Mn 2+ . On the contrary, Mn 2+ was able cause oxidative damage through lipid peroxidation of complex biological extracts, generating cleaved phospholipids and lipid peroxide by products. Collectively, interaction of divalent metals with biological membranes could have negative consequences associated with disrupting membrane biophysical properties. References 1. Sule, K., Umbsaar, J., and Prenner, E. J. (2020) Mechanisms of Co, Ni, and Mn toxicity: From exposure and homeostasis to their interactions with and impact on lipids and biomembranes. 2. Biochim. Biophys. Acta - Biomembr. 1862 , 183250 Gustafsson, J. P. (2016) Visual MINTEQ Chemical Equilibrium Software Parasassi, T., Krasnowska, E. K., Bagatolli, L., and Gratton, E. (1998) Laurdan and Prodan as Polarity-Sensitive Fluorescent Membrane Probes. 3. J. Fluoresc. 8 , 365–373 Sanchez, S. A., Tricerri, M. A., Gunther, G., and Gratton, E. (2007) Laurdan Generalized Polarization : from cuvette to microscope. Mod. Res. Educ. Top. Microsc. Sule, K., and Prenner, E. J. (2022) Lipid headgroup and side chain architecture determine manganese-induced dose dependent membrane rigidification and liposome size increase. Eur. Biophys. J. 51 , 205–223
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