Condensation of Model Lipid Films by Cholesterol: Specific Ion Effects
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AuthorMartín Molina, Alberto; Castillo Santaella, Teresa del; Yang, Yan; Maldonado Valderrama, Julia
LipidCholesterolSurface pressureSurface potentialIons
Martín-Molina, A., Castillo-Santaella, D., Yang, Y., & Maldonado-Valderrama, J. (2019). Condensation of Model Lipid Films by Cholesterol: Specific Ion Effects. Coatings, 9(8), 474.
SponsorshipThis research was funded by “Ministerio de Economía y Competitividad (MINECO), Plan Nacional de Investigación, Desarrollo e Innovación Tecnológica (I + D + i)”: Grant RYC-2012-10556, Projects MAT2015-63644-C2-1-R, RTI2018-101309-B-C21 and FIS2016-80087-C2-1-P, and European Regional Development Fund (ERDF). “Universidad de Granada” CEI-BIOTIC-BS14.2015. This study was also partially supported by “Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía”, ref. SOMM17/6105/UGR and SOMM17/6109/UGR.
The condensing effect and the ability of cholesterol (CHOL) to induce ordering in lipid films is a question of relevance in biological membranes such as the milk fat globule membrane (MFGM) in which the amount of CHOL influences the phase separation and mechanical resistance to rupture of coexisting phases relevant to emulsified food systems. Here, we study the effect of different salts (NaCl, CaCl2, MgCl2, LaCl3) on monolayers made of a model mixture of lipids (DPPC:DPPS 4:1) and CHOL. To this end, we apply Langmuir Film Balance to report a combined analysis of surface pressure-area (pi-A) and surface potential-area (DV–A) isotherms along with Micro-Brewster Angle Microscopy (Micro-BAM) images of the monolayers in the presence of the different electrolytes. We show that the condensation of lipid by CHOL depends strongly on the nature of the ions by altering the shape and features of the pi-A isotherms. DV–A isotherms provide further detail on the ion specific interactions with CHOL. Our results show that the condensation of lipids in the presence of CHOL depends on the combined action of ions and CHOL, which can alter the physical state of the monolayer.