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Title: Effects of hydrocarbon chains saturation degree on molecular interaction between phospholipids and cholesterol in mixed monolayers
Authors: Hao, Changchun
Zhang, Lei
Zhang, Qing
Xu, Guoqing
Sun, Runguang
Keywords: Attractive and repulsive;Compressibility;Gibbs energy;Excess molecular area;Monolayers
Issue Date: Oct-2017
Publisher: NISCAIR-CSIR, India
Abstract: Monolayers of three mixed systems of cholesterol (Chol) with 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-choline (POPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were investigated at the air/water interface. Based on the isotherms of monolayers, the molecular interaction and miscibility have been evaluated in terms of the excess mean molecular area (A(ex)) and excess Gibbs free energy (G(ex)). The excess molecular area (A(ex)) of DOPC/Chol monolayers was negative at Xchol = 0.2, and 0.6, indicating it was attractive interaction. The repulsive interaction was observed at Xchol = 0.4. In the range of Xchol = 0.8, the A (ex) was negative at the surface pressure of 5, 10 and 15 mN/m, positive at 20, 25 and 30 mN/m. In the POPC/Chol monolayers, the value of A (ex) was negative for all the studied mixed monolayers except for 30 mN/m at Xchol = 0.8. The thermodynamic behavior in DPPC/Chol monolayers was more complex. The A (ex) was negative only at Xchol = 0.2 and lower pressure at Xchol = 0.4, and 0.6. The stability of mixed monolayers was assessed by the parameter of excess Gibbs energy. For the three binary monolayers, the maximum appeared at the points of Xchol = 0.6, Xchol = 0.4 and Xchol = 0.2 for DOPC/Chol, POPC/Chol and DPPC/Chol, respectively. The results of the analysis for elasticity modulus showed the saturated DPPC monolayer was more elastic than unsaturated PCs. The different unsaturation chains of PCs could determine the different compressibility behavior. These results can help to understand the thermodynamic behavior of membranes made of mixtures of PCs with different chains and cholesterol.
Page(s): 186-190
ISSN: 0975-0959 (Online); 0301-1208 (Print)
Appears in Collections:IJBB Vol.54(5) [October 2017]

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