Thermodynamic and Structural Aspects of Internal Wool Lipids

Abstract

Thermotropic physicochemical techniques such as differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and electron paramagnetic resonance (EPR) were applied to liposomes made up of internal wool lipids. These vesicles can be regarded as a model of wool membranes. Differences in fluidity obtained from EPR allow us to deduce a high rigidity of the polar external section of the vesicle in contrast to the high fluidity of the hydrophobic internal section, which accounts for the thermotropic properties of the liposome. The coincidence of the thermotropic changes obtained with the EPR, FTIR, and DSC techniques allows us to infer a reversible phase transition temperature in the range of 30-40 °C, indicating a transition from a mixture of hexagonal gel-liquid crystal state to a single liquid crystal state.

Extraction and analysis of ceramides from internal wool lipids

“…In fact, the composition of IWL, similar to the ones present in the SC (1), allows for the formation of liposomes with a stable bilayer structure (6)(7)(8). Furthermore, topical application of IWL liposomes on intact and disturbed skin has been demonstrated to improve barrier skin properties (9).…”

Lipid Role in Wool Dyeing

“…Internal wool lipids have been shown to form stable liposomes (Fonollosa et al, 2000;Körner et al, 1995;Ramírez et al, 2009a) and are supposed to be arranged in the wool fiber as lipid bilayers. Raw Spanish Merino wool was Soxhlet-extracted with chloroform/methanol azeotrope (Martí et al, 2010), in order to obtain wool mostly depleted of internal lipids.…”

“…Since the polar lipids consisting mainly of ceramides and cholesterol sulfate significantly differ from PC in chemical structure and membrane behavior, the authors supposed that such a substitution should greatly affect those properties of the CMC that govern the permeability of wool to dye molecules. Indeed, it had been shown by electron paramagnetic resonance (EPR) measurements on mixed IWL/PC liposomes that the presence of PC, especially at low amounts (10 wt %), greatly fluidized the lipid bilayer at any temperature and decreased the enthalpy of the main phase transition of IWL from an ordered gel state to a liquid-crystalline fluid state (Fonollosa et al, 2000). If the dye, owing to its amphiphilic nature and some affinity to the lipid bilayer, was able to diffuse along the CMC through lipid domains, then an agent that increases their fluidity would facilitate the dye penetration deep into the wool fiber.…”

Influence of water in the lamellar rearrangement of internal wool lipids

“…Despite the considerable advances in the characterisation of the lipid composition of the cell membrane complex [2][3][4], little progress has been made in improving our understanding * Corresponding author. Tel.…”

“…of the arrangement and thermotropic behaviour of these components. However, the bilayer-forming capacity [5] and some physicochemical properties have been studied in an attempt to yield further insight into the lipid structure [6]. DSC, FTIR and EPR methodologies have been applied to IWL extracts structured in liposome vesicles as a model of a wool lipid membrane, demonstrating that the membrane is less permeable at the surface hydrophilic ends than in its hydrophobic core.…”