Kinetic Evidence Suggests Spinodal Phase Separation in Stratum Corneum Models by IR Spectroscopy

Although lipid structure in models for the stratum corneum (SC), the main barrier to skin permeability, has been extensively studied, only limited data are extant concerning the kinetic mechanism for the formation of domains, lamellar phases, and lipid packing motifs. Such information would be of su...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2014-04, Vol.118 (16), p.4378-4387
Main Authors: Mendelsohn, Richard, Selevany, Ibrahim, Moore, David J, Mack Correa, M. Catherine, Mao, Guangru, Walters, Russel M, Flach, Carol R
Format: Article
Language:English
Subjects:
Animals
Barriers
Cattle
Ceramides - chemistry
Chains
Cholesterol - chemistry
Formations
Hydrogen Bonding
Infrared spectroscopy
Kinetics
Lamellar structure
Lipids
Models, Molecular
Molecular Structure
Phase separation
Skin - chemistry
Spectrophotometry, Infrared
Stearic Acids - chemistry
Swine
Temperature
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Summary:Although lipid structure in models for the stratum corneum (SC), the main barrier to skin permeability, has been extensively studied, only limited data are extant concerning the kinetic mechanism for the formation of domains, lamellar phases, and lipid packing motifs. Such information would be of substantial interest in the characterization of the effects of disease states which disrupt the barrier. Kinetic IR spectroscopy measurements probed the temporal sequence of molecular events producing ordered structures in a three-component SC model of equimolar ceramide[NS] (cer[NS]), perdeuterated stearic acid-d 35 (SA-d 35), and cholesterol. Samples, heated above T m, were quenched to 31 °C, and then spectra were recorded at ∼15 min intervals for a total of 20–150 h. IR provides unique molecular structure information about headgroup H-bonding, lipid packing, and lipid chain order. The following sequence for phase separation was observed: (1) Formation of ceramide amide H-bonds from disordered forms to ordered structures (0.5–4 h); (2) appearance of ordered ceramide chains with some orthorhombically packed structures (0.5–8 h); and (3) phase separation of large orthorhombic domains of SA-d 35 (4–10 h). A spinodal decomposition mechanism, defined by continuous composition changes during the phase separation, suggests a qualitative description for these events.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp501003c