Lamellar subcomponents of the cuticular cell membrane complex of mammalian keratin fibres show friction and hardness contrast by AFM

Abstract

SummaryThere is a substantial body of information indicating that 18-methyleicosanoic acid (18-MEA) is covalently linked to the outer surface of all mammalian keratin fibres and also forms the outer β-layer of the cuticular cell membrane complex (CCMC) which separates the cuticle cells from each other. Low cohesive forces are expected between the lipid-containing outer β-layer and the δ-layer of the CCMC, thus providing a weak point for cuticular delamination and presenting a fresh layer of 18-MEA to the newly exposed surface.We have used lateral force microscopy and force modulation atomic force microscopy (AFM) to examine human hair fibres in which the non-covalently linked fatty acids have been removed. Examination of the lateral force images of new cuticle surfaces revealed by the attrition of overlying cuticle layers showed three separate zones of clearly defined frictional contrast. These are thought to correspond with the δ-layer, the proteinaceous epicuticle and outer β-layers of the CCMC. The δ-layer was found to have a thickness of 16 nm (SD = 1 nm, n = 25), comparable to the 18.0 nm thickness measured from transverse crosssections of fibres with transmission electron microscopy. Force modulation AFM showed that the outer β-layer was softer than the epicuticle and the δ-layer. The frictional contrast was removed following treatment with methanolic KOH (0.1 mol dm −3 ) at 25 °C for 30 min, suggesting the hydrolysis of the thioester linkage and removal of 18-MEA from the surface.

The influence of hair bleach on the ultrastructure of human hair with special reference to hair damage

“…1 [1][2][3] . The structure of the cuticle CMC (cell membrane complex), which originates from the cell membrane, has the role of connecting cuticle cells with each other and provides a penetration route for moisture to reach the i nner part of the hair 4) .…”

Temperature-dependent dielectric properties of slightly hydrated horn keratin

“…The nature of keratin has been the subject of numerous investigations involving host of experimental techniques such as mechanical properties [4], dynamic mechanical loss [5], differential scanning calorimetry (DSC) [6,7], conventional and advanced microscopic techniques like optical microscopy, scanning electron microscopy [8], transmission electron microscopy and atomic force microscopy [9], spectroscopic techniques like nuclear magnetic resonance (NMR) [10], Fourier transform infrared (FTIR) and Raman spectroscopy [11,12], NIR spectroscopy [13], ellipsometry [14,15], structural techniques like conventional X-ray diffraction [16,17] and that employing synchrotron radiation [18,19] and various electric and dielectric techniques [20][21][22][23][24][25][26]. Mechanical [27][28][29], electrical [20][21][22][23][24][25][26] and thermal [6,7] properties of keratin have been found to strongly depend on the amount of moisture in the sample and hence it is important to understand the exact nature of bound water in keratin.…”

Effect of the covalently linked fatty acid 18-MEA on the nanotribology of hair’s outermost surface

“…Being local probe techniques, it is not surprising that AFM and LFM have been readily used to investigate Wbres and, in particular, the surface architecture and sub-lamellar structure of keratin Wbres (O'Connor et al, 1995;Smith, 1997Smith, , 1998Smith and Swift, 2002;Swift and Smith, 2000). Longitudinal striations (h D 10 nm, w D 290-390 nm) running in the direction of the longaxis on the freely exposed outer cuticle surfaces of original undamaged hairs have been observed in AFM images Smith, 2000, 2001).…”