Morphology and molecular mobility of fibrous hard alpha-keratins by 1H, 13C, and 129Xe NMR

Integrative measurement analysis via machine learning descriptor selection for investigating physical properties of biopolymers in hairs

Integrative measurement analysis of complex subjects, such as polymers is a major challenge to obtain comprehensive understanding of the properties. In this study, we describe analytical strategies to extract and selectively associate compositional information measured by multiple analytical techniques, aiming to reveal their relationships with physical properties of biopolymers derived from hair. Hair samples were analyzed by multiple techniques, including solid-state nuclear magnetic resonance (NMR), time-domain NMR, Fourier transform infrared spectroscopy, and thermogravimetric and differential thermal analysis. The measured data were processed by different processing techniques, such as spectral differentiation and deconvolution, and then converted into a variety of “measurement descriptors” with different compositional information. The descriptors were associated with the mechanical properties of hair by constructing prediction models using machine learning algorithms. Herein, the stepwise model refinement via selection of adopted descriptors based on importance evaluation identified the most contributive descriptors, which provided an integrative interpretation about the compositional factors, such as α-helix keratins in cortex; and bounded water and thermal resistant components in cuticle. These results demonstrated the efficacy of the present strategy to generate and select descriptors from manifold measured data for investigating the nature of sophisticated subjects, such as hair.

Valorisation of waste chicken feathers: Optimisation of keratin extraction from waste chicken feathers by sodium bisulphite, sodium dodecyl sulphate and urea

Extraction of keratin from keratinous waste materials, such as chicken feathers, has been identified as the favourable approach in beneficiation of this biomass. The chemical extractions of keratin by reducing agents are usually preferred because the process is much faster than its counterpart, oxidation extraction. One such reduction extraction is the use of a mixture of sodium bisulphite, sodium dodecyl sulphate and urea. There are at least five factors that may affect the keratin extraction process and its final properties when using this extraction. Even though this extraction method is often used, the effects of its independent variables have not been studied; as a result, the effects of independent variables cannot be fully linked to the extraction process and final keratin properties. Therefore, this study aimed to optimise the extraction of keratin from waste chicken feathers using sodium bisulphite, sodium dodecyl sulphate and urea. The optimisation was statistically performed using Response Surface Methodology (RSM) linked with Box-Behnken Design. After screening the independent variable using one factor at a time method, the concentration of sodium bisulphite, concentration of sodium dodecyl sulphate, reaction temperature and reaction time were chosen for the study. Twenty-nine experiments were statistically designed and executed, and their results were used to analyse the effects of all the independent variables in order to optimise the extraction process. The reaction temperature was found to be the most significant factor, while the concentration of sodium dodecyl sulphate was the most insignificant factor of this extraction process. Independent variables significance order was reaction temperature > reaction time > concentration of NaHSO₃ > concentration of NaC₁₂H₂₅SO₄. The designed reduced cubic model was significant and was used to predict the protein yield from the keratin extraction using sodium bisulphite.

Removal of chromium from wastewater by swine hair residues applied as a putative biofilter

Swine production chain generates residues with potential application in environmental processes. This study aimed at the use of swine hair as a potential biofilter for hexavalent chromium (Cr(VI)) removal from wastewater of tannery industry. The hair was pretreated using H₂O₂ in alkaline medium, and statistical analysis was carried out to evaluate the hair degradation, as well the Cr(VI) removal by the potential pretreated biofilter. The results showed 99% of Cr(VI) removal in 105 min of treatment in large pH range (1-10). Treated and untreated effluents were submitted to cytotoxicity study using vegetable and animal cells, demonstrating a significant reduction on toxicity to both cells. Therefore, swine hair demonstrated to be a promising residue for heavy metal removal on the perspective of an environmentally friendly technique.

The structure of the "amorphous" matrix of keratins

Various keratin fibers, particularly human hairs, were investigated by transmission electron microscopy, TEM, solid-state ¹H NMR and Transient Electro-Thermal Technique, TET. The results converge to suggest that the matrix of keratin fiber cortex, far from being amorphous, has a well-defined nano-scale grainy structure, the size of these grains being around 2-4nm. The size of the grains appears to strongly depend on the chemical treatment of the fiber, on the temperature and on the relative humidity of the environment, as well as on the physiological factors at the level of fiber production in follicle. By suggesting an organization at the nano-scale of the protein chains in these grains, likely to be Keratin Associated Proteins, the results challenge the view of matrix as a homogeneous glassy material. Moreover, they indicate the potential of further investigating the purpose of this structure that appears to reflect not only chemical treatments of keratins but also biological processes at the level of the follicle.

Sex-related chemical differences in keratin from fingernail plates: a solid-state carbon-13 NMR study

The carbon-13 solid-state NMR reveals chemical differences in fingernail keratin between young, healthy males and females.

Solid state NMR of isotope labelled murine fur: a powerful tool to study atomic level keratin structure and treatment effects

We have prepared mouse fur extensively ¹³C,¹⁵N-labelled in all amino acid types enabling application of 2D solid state NMR techniques which establish covalent and spatial proximities within, and in favorable cases between, residues. ¹³C double quantum-single quantum correlation and proton driven spin diffusion techniques are particularly useful for resolving certain amino acid types. Unlike 1D experiments on isotopically normal material, the 2D methods allow the chemical shifts of entire spin systems of numerous residue types to be determined, particularly those with one or more distinctively shifted atoms such as Gly, Ser, Thr, Tyr, Phe, Val, Leu, Ile and Pro. Also the partial resolution of the amide signals into two signal envelopes comprising of α-helical, and β-sheet/random coil components, enables resolution of otherwise overlapped α-carbon signals into two distinct cross peak families corresponding to these respective secondary structural regions. The increase in resolution conferred by extensive labelling offers new opportunities to study the chemical fate and structural environments of specific atom and amino acid types under the influence of commercial processes, and therapeutic or cosmetic treatments.

Nondisruptive Dissolution of Hyperpolarized (129)Xe into Viscous Aqueous and Organic Liquid Crystalline Environments

Studies of hyperpolarized xenon-129 (hp-(129)Xe) in media such as liquid crystals and cell suspensions are in demand for applications ranging from biomedical imaging to materials engineering but have been hindered by the inability to bubble Xe through the desired media as a result of viscosity or perturbations caused by bubbles. Herein a device is reported that can be reliably used to dissolve hp-(129)Xe into viscous aqueous and organic samples without bubbling. This method is robust, requires small sample volumes (<60 μL), is compatible with existing NMR hardware, and is made from readily available materials. Experiments show that Xe can be introduced into viscous and aligned media without disrupting molecular order. We detected dissolved xenon in an aqueous liquid crystal that is disrupted by the shear forces of bubbling, and we observed liquid-crystal phase transitions in (MBBA). This tool allows an entirely new class of samples to be investigated by hyperpolarized-gas NMR spectroscopy.