Chemically characterizing the cortical cell nano-structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM-IR) / A. P. Fellows in INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Vol. 44, N° 1 (02/2022)  

[article]  inINTERNATIONAL JOURNAL OF COSMETIC SCIENCE > Vol. 44, N° 1 (02/2022) . - p. 42-55 Titre : Chemically characterizing the cortical cell nano-structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM-IR) Type de document : document électronique Auteurs : A. P. Fellows, Auteur ; M. T. L. Casford, Auteur ; P. B. Davies, Auteur Année de publication : 2022 Article en page(s) : p. 42-55 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse spectrale Caractérisation Cellules corticales Cheveux -- analyse Microscopie à force atomique Nanostructures Index. décimale : 668.5 Parfums et cosmétiques Résumé : - Objective : The use of conventional microscopy and vibrational spectroscopy in the optical region to investigate the chemical nature of hair fibres on a nanometre scale is frustrated by the diffraction limit of light, prohibiting the spectral elucidation of nanoscale sub-structures that contribute to the bulk properties of hair. The aim of this work was to overcome this limitation and gain unprecedented chemical resolution of cortical cell nano-structure of hair. - Methods : The hybrid technique of AFM-IR, combining atomic force microscopy with an IR laser, circumvents the diffraction limit of light and achieves nanoscale chemical resolution down to the AFM tip radius. In this work, AFM-IR was employed on ultra-thin microtomed cross-sections of human hair fibres to spectrally distinguish and characterize the specific protein structures and environments within the nanoscale components of cortical cells. - Results : At first, a topographical and chemical distinction between the macrofibrils and the surrounding intermacrofibillar matrix was achieved based on 2.5 × 2.5 μm maps of cortical cell cross-sections. It was found that the intermacrofibrillar matrix has a large protein content and specific cysteine-related residues, whereas the macrofibrils showed bigger contributions from aliphatic amino acid residues and acidic-/ester-containing species (e.g. lipids). Localized spectra recorded at a spatial resolution of the order of the AFM tip radius enabled the chemical composition of each region to be determined following deconvolution of the Amide-I and Amide-II bands. This provided specific evidence for a greater proportion of α-helices in the macrofibrils and correspondingly larger contributions of β-sheet secondary structures in the intermacrofibrillar matrix, as inferred in earlier studies. Analysis of the parallel and antiparallel β-sheet structures, and of selected dominant amino acid residues, yielded further novel composition and conformation results for both regions. - Conclusion : In this work, we overcome the diffraction limit of light using atomic force microscopy integrated with IR laser spectroscopy (AFM-IR) to characterize sub-micron features of the hair cortex at ultra-high spatial resolution. The resulting spectral analysis shows clear distinctions in the Amide bands in the macrofibrils and surrounding intermacrofibrillar matrix, yielding novel insight into the molecular structure and intermolecular stabilization interactions of the constituent proteins within each cortical component. Note de contenu : - Sample preparation - AFM-IR analysis - Spectral analysis - Table 1 : Assignments of the bands observed in Figure 2 based on data reported in the literature - Table 2 : Contributions in the Amide-I and Amide-II spectral regions obtained by second-derivative peak fitting for each of the spectra shown - Table 3 : Summary of the contributing residues and secondary structures present in the hair cortex indicating the regions of greater band contributions DOI : https://doi.org/10.1111/ics.12753 En ligne : https://drive.google.com/file/d/1HoX77-CB6ZECCPsdUFJmdOi-fqSTdByF/view?usp=shari [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=37259 [article]

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