The thermodynamics of simple biomembrane mimetic systems

Abstract

Insight into the forces governing a system is essential for understanding its behavior and function. Thermodynamic investigations provide a wealth of information that is not, or is hardly, available from other methods. This article reviews thermodynamic approaches and assays to measure collective properties such as heat adsorption / emission and volume variations. These methods can be successfully applied to the study of lipid vesicles (liposomes) and biological membranes. With respect to instrumentation, differential scanning calorimetry, pressure perturbation calorimetry, isothermal titration calorimetry, dilatometry, and acoustic techniques aimed at measuring the isothermal and adiabatic processes, two- and three-dimensional compressibilities are considered. Applications of these techniques to lipid systems include the measurement of different thermodynamic parameters and a detailed characterization of thermotropic, barotropic, and lyotropic phase behavior. The membrane binding and / or partitioning of solutes (proteins, peptides, drugs, surfactants, ions, etc.) can also be quantified and modeled. Many thermodynamic assays are available for studying the effect of proteins and other additives on membranes, characterizing non-ideal mixing, domain formation, bilayer stability, curvature strain, permeability, solubilization, and fusion. Studies of membrane proteins in lipid environments elucidate lipid–protein interactions in membranes. Finally, a plethora of relaxation phenomena toward equilibrium thermodynamic structures can be also investigated. The systems are described in terms of enthalpic and entropic forces, equilibrium constants, heat capacities, partial volume changes, volume and area compressibility, and so on, also shedding light on the stability of the structures and the molecular origin and mechanism of the structural changes.

Eugenol Induces Phenotypic Alterations and Increases the Oxidative Burst in Cryptococcus

“…The first 1 mL injection was discarded to eliminate diffusion effects of material from the syringe to the calorimetric chamber. The injection time was 2 s and the interval between the injections was 240 s ( Abraham et al, 2005 ; Raudino et al, 2011 ).…”

Impact of poly(ethylene glycol) functionalized lipids on ordering and fluidity of colloid supported lipid bilayers

“…Such an increase in the FWHM has been related to defects within the pure membrane. 57 Here these are presumably due to the compositional differences between the head groups and tails of the anchors and DPPC. It has been reported [59][60][61] that such compositional can cause coexistence of gel like and liquid like phases.…”

“…2a). 56,57 The transitions are signalled by a characteristic peak from which we can determine an excess enthalpy, transition temperature and full width half maximum (FWHM). The latter can be taken as a qualitative measure of the cooperativity of melting of the hydrocarbon chains during the melting transition.…”

Mitochondrial Complex I activity is inhibited by changes in the abundance of phosphatidylinositol and phosphatidylserine in wheat plants exposed to high temperatures

“…Membrane lipids undergo phase transition at specific transition temperature T m , changing the physical state of the bilayer (Marsh 2010, Raudino et al 2011). In order maintain the metabolic reactions that are dependent on membrane architecture, plants modify their membrane lipid composition in response to temperature to preserve membrane integrity and lipo-protein interactions (Chen et al 1982, Neidleman 1987, Hazel 1995, Vanlerberghe 2013).…”