Non-linear van't Hoff behavior in pulmonary surfactant model membranes
| Autor: | Ernanni D. Vieira, Luis G.M. Basso, Antonio J. Costa-Filho |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
1 2-Dipalmitoylphosphatidylcholine Surface Properties Enthalpy Biophysics Analytical chemistry Biochemistry Thermotropic crystal Phase Transition law.invention 03 medical and health sciences chemistry.chemical_compound Pulmonary surfactant law Phosphatidylcholine Electron paramagnetic resonance POPC Phosphatidylglycerol 030102 biochemistry & molecular biology Osmolar Concentration technology industry and agriculture Temperature Membranes Artificial Phosphatidylglycerols Pulmonary Surfactants Cell Biology Hydrogen-Ion Concentration 030104 developmental biology Membrane chemistry Models Chemical Phosphatidylcholines Thermodynamics lipids (amino acids peptides and proteins) RESSONÂNCIA PARAMAGNÉTICA |
| Zdroj: | Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual) Universidade de São Paulo (USP) instacron:USP |
| Popis: | Pulmonary surfactant exhibits phase coexistence over a wide range of surface pressure and temperature. Less is known about the effect of temperature on pulmonary surfactant models. Given the lack of studies on this issue, we used electron paramagnetic resonance (EPR) and nonlinear least-squares (NLLS) simulations to investigate the thermotropic phase behavior of the matrix that mimics the pulmonary surfactant lipid complex, i.e., the lipid mixture composed of dipalmitoyl phosphatidylcholine (DPPC), palmitoyl-oleoyl phosphatidylcholine (POPC) and palmitoyl-oleoyl phosphatidylglycerol (POPG). Irrespective of pH, the EPR spectra recorded from 5°C to 25°C in the DPPC/POPC/POPG (4:3:1) model membrane contain two spectral components corresponding to lipids in gel-like and fluid-like phases, indicating a coexistence of two domains in that range. The temperature dependence of the distribution of spin labels between the domains yielded nonlinear van't Hoff plots. The thermodynamic parameters evaluated were markedly different for DPPC and for the ternary DPPC/POPC/POPG (4:3:1) membranes and exhibited a dependence on chemical environment. While enthalpy and entropy changes for DPPC were always positive and presented a quadratic behavior with temperature, those of the ternary mixture were linearly dependent on temperature and changed from negative to positive values. Despite that, enthalpy-entropy compensation takes place in the two systems. The thermotropic process associated with the coexistence of the two domains is entropically-driven in DPPC and either entropically- or enthalpically-driven in the pulmonary surfactant membrane depending on the pH, ionic strength and temperature. The significance of these results to the structure and function of the pulmonary surfactant lipid matrix is discussed. |
| Databáze: | OpenAIRE |
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