The chemical fingerprint of hair melanosomes by infrared nano-spectroscopy

Abstract

In situ characterization of the chemical and structural properties of black and white sheep hair was performed with a spatial resolution of 25 nm using infrared nano-spectroscopy. Comparing data sets from two types of hair allowed us to isolate the keratin FTIR fingerprint and so mark off chemical properties of the hair's melanosomes. From a polarization sensitive analysis of the nano-FTIR spectra, we showed that keratin intermediate filaments (IFs) present anisotropic molecular ordering. In stark contrast with white hair which does not contain melanosomes, in black hair, we spatially resolved single melanosomes and achieved unprecedented assignment of the vibrational modes of pheomelanin and eumelanin. The in situ experiment presented here avoids harsh chemical extractive methods used in previous studies. Our findings offer a basis for a better understanding of the keratin chemical and structural packing in different hair phenotypes as well as the involvement of melanosomes in hair color and biological functionality.

Nanoscale Molecular Characterization of Hair Cuticle Cells Using Integrated Atomic Force Microscopy–Infrared Laser Spectroscopy

“…32 Some of the bands in Table II have been assigned to these oxidation products and provide a measure of the total cystine content. 24,33–37…”

“…32 Some of the bands in Table II have been assigned to these oxidation products and provide a measure of the total cystine content. 24,[33][34][35][36][37] The intensity ratio (as used previously for profiles in Figs. 4 and 5) of selected cystine-related bands to selected amide III bands is plotted as a function of positions 1 to 20 in Fig.…”

Super-resolution mid-infrared spectro-microscopy of biological applications through tapping mode and peak force tapping mode atomic force microscope

“…The hyperspectral data cube was further processed by the multivariate analysis, enabling the identification of either subsurface melanin or a thin slice of melanin granule. Likewise, melanosomes from sheep hairs were examined using s-SNOM [102]. IR signatures of two pigments -eumelanin and pheomelanin, were successfully extracted from individual nanoscale melanosomes in situ, which avoids the harsh treatment used in traditional chemical extractive methods.…”

Nanoscale Molecular Characterisation of Hair Cuticles using Integrated AFM-IR

“…32 Some of the bands in Table 3 have been assigned to these oxidation products and provide a measure of the total cystine content. 23,[33][34][35][36][37] Table 3: Approximate band origins and their assignments in the cystine and Amide-III spectral region.…”