Protein conformational changes induced in human stratum corneum by organic sulfoxides: An infrared spectroscopic investigation

Abstract

Formation of the antiparallel‐chain β‐sheet protein conformation is induced in in vitro human stratum corneum by three homologous organic sulfoxides known to enhance skin permeability: dimethylsulfoxide (Me₂SO), hexylmethylsulfoxide (HxMeSO), and decylmethylsulfoxide (DecMeSO). Me₂SO and HxMeSO apparently function by displacing water molecules bound to polar protein side‐chains, whereas DecMeSO probably interacts hydrophobically with the protein. The conformational transition does not result from lipid removal. The β‐sheet protein, most likely formed in normally α‐helical portions of the intracellular keratin filaments, is reconverted to α‐helix upon rehydration of the tissue. Though neat Me₂SO produces the most β‐sheet of all treatments examined, the sequence of ability to promote β‐sheet formation at the 1M level is HxMeSO > DecMeSO > Me₂SO. Spectroscopic evidence is presented regarding the dependence of β‐sheet formation on sulfoxide concentration, treatment duration, pH, and tissue hydration. The relationship of this conformational change to the enhancement of skin permeability is briefly discussed. The result of sulfoxide treatment is different from results of sodium dodecylsulfate and heat treatments of stratum corneum.