New aspects of the alpha-helix to beta-sheet transition in stretched hard alpha-keratin fibers

Unraveling UVB effects: Catalase activity and molecular alterations in the stratum corneum

AIM

Ultraviolet B (UVB) radiation can compromise the functionality of the skin barrier through various mechanisms. We hypothesize that UVB induce photochemical alterations in the components of the outermost layer of the skin, known as the stratum corneum (SC), and modulate its antioxidative defense mechanisms. Catalase is a well-known antioxidative enzyme found in the SC where it acts to scavenge reactive oxygen species. However, a detailed characterization of acute UVB exposure on the activity of native catalase in the SC is lacking. Moreover, the effects of UVB irradiation on the molecular dynamics and organization of the SC keratin and lipid components remain unclear. Thus, the aim of this work is to characterize consequences of UVB exposure on the structural and antioxidative properties of catalase, as well as on the molecular and global properties of the SC matrix surrounding the enzyme.

EXPERIMENTS

The effect of UVB irradiation on the catalase function is investigated by chronoamperometry with a skin covered oxygen electrode, which probes the activity of native catalase in the SC matrix. Circular dichroism is used to explore changes of the catalase secondary structure, and gel electrophoresis is used to detect fragmentation of the enzyme following the UVB exposure. UVB induced alterations of the SC molecular dynamics and structural features of the SC barrier, as well as its water sorption behavior, are investigated by a complementary set of techniques, including natural abundance 13C polarization transfer solid-state NMR, wide-angle X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and dynamic vapor sorption microbalance.

FINDINGS

The findings show that UVB exposure impairs the antioxidative function of catalase by deactivating both native catalase in the SC matrix and lyophilized catalase. However, UVB radiation does not alter the secondary structure of the catalase nor induce any observable enzyme fragmentation, which otherwise could explain deactivation of its function. NMR measurements on SC samples show a subtle increase in the molecular mobility of the terminal segments of the SC lipids, accompanied by a decrease in the mobility of lipid chain trans-gauche conformers after high doses of UVB exposure. At the same time, the NMR data suggest increased rigidity of the polypeptide backbone of the keratin filaments, while the molecular mobility of amino acid residues in random coil domains of keratin remain unaffected by UVB irradiation. The FTIR data show a consistent decrease in absorbance associated with lipid bond vibrations, relative to the main protein bands. Collectively, the NMR and FTIR data suggest a small modification in the composition of fluid and solid phases of the SC lipid and protein components after UVB exposure, unrelated to the hydration capacity of the SC tissue. To conclude, UVB deactivation of catalase is anticipated to elevate oxidative stress of the SC, which, when coupled with subtle changes in the molecular characteristics of the SC, may compromise the overall skin health and elevate the likelihood of developing skin disorders.

Age-related hair denaturation related to protein carbonyls

OBJECTIVE

Hair ageing is accompanied by hair fibres becoming irregularly shaped causing them to stick out in irregular directions or have more curliness and being spread out. This is believed to be due to changes within the hair fibre structure which occur with ageing, and one of the causes of these changes could be an increase in the number of protein carbonyl groups present in the hair. The aim of this study is to investigate the internal denaturation of hair related to protein carbonyls in attempt to gain new insight into age-related changes that occur in hair.

METHODS

The degree of carbonylation of the hair structural protein as determined by fluorescent labelling and Western blotting analysis was used to investigate the primary structure of hair protein. The amount of helix, a common conformation in the secondary structure of proteins, in hair in groups of women with different ages was also analysed using infrared microscopy coupled with multivariate curve resolution (MCR). From the results of this, an image of the two-dimensional distribution of the α-helices was generated for the hair taken from each age group. Also, high-pressure differential scanning calorimetry (HPDSC) of the hair in water was performed on the hair taken from each age group to determine the peak temperature of endothermic effect and the enthalpy of denaturation.

RESULTS

We found that the amino group content in hair proteins decreased and Type II keratin, one of the subunits of intermediate filament, was more carbonylated with age. The results of the MCR indicated eight separate components, including components of the secondary structure of proteins, such as α helices and β sheets. Two-dimensional images of the hair cross-sections revealed that the presence of α helices decreased with age. In addition, data from the HPDSC showed that the enthalpy associated with the denaturing temperature also significantly decreased with age.

CONCLUSION

These results suggest that there is a negative correlation between age and structural integrity of the helix segment in intermediate filament. The results of this study also show that there is a positive correlation between age-related hair denaturation and protein carbonyls.

Maturation and Conformational Switching of a De Novo Designed Phase-Separating Polypeptide

Cellular compartments formed by biomolecular condensation are widespread features of cell biology. These organelle-like assemblies compartmentalize macromolecules dynamically within the crowded intracellular environment. However, the intermolecular interactions that produce condensed droplets may also create arrested states and potentially pathological assemblies such as fibers, aggregates, and gels through droplet maturation. Protein liquid-liquid phase separation is a metastable process, so maturation may be an intrinsic property of phase-separating proteins, where nucleation of different phases or states arises in supersaturated condensates. Here, we describe the formation of both phase-separated droplets and proteinaceous fibers driven by a de novo designed polypeptide. We characterize the formation of supramolecular fibers in vitro and in bacterial cells. We show that client proteins can be targeted to the fibers in cells using a droplet-forming construct. Finally, we explore the interplay between phase separation and fiber formation of the de novo polypeptide, showing that the droplets mature with a post-translational switch to largely β conformations, analogous to models of pathological phase separation.

Scales of non-avian reptiles and their derivatives contain corneous beta proteins coded from genes localized in the Epidermal Differentiation Complex

The evolution of modern reptiles from basic reptilian ancestors gave rise to scaled vertebrates. Scales are of different types, and their corneous layer can shed frequently during the year in lepidosaurians (lizards, snakes), 1-2 times per year in the tuatara and in some freshwater turtle, irregularly in different parts of the body in crocodilians, or simply wore superficially in marine and terrestrial turtles. Lepidosaurians possess tuberculate, non-overlapped or variably overlapped scales with inter-scale (hinge) regions. The latter are hidden underneath the outer scale surface or may be more exposed in specific body areas. Hinge regions allow stretching during growth and movement so that the skin remains mechanically functional. Crocodilian and turtles feature flat and shield scales (scutes) with narrow inter-scale regions for stretching and growth. The epidermis of non-avian reptilian hinge regions is much thinner than the exposed outer surface of scales and is less cornified. Despite the thickness of the epidermis, scales are mainly composed of variably amount of Corneous Beta Proteins (CBPs) that are coded in a gene cluster known as EDC (Epidermal Differentiation Complex). These are small proteins, 100-200 amino acid long of 8-25 kDa, rich in glycine and cysteine but also in serine, proline and valine that participate to the formation of beta-sheets in the internal part of the protein, the beta-region. This region determines the further polymerization of CBPs in filamentous proteins that, together a network of Intermediate Filament Keratins (IFKs) and other minor epidermal proteins from the EDC make the variable pliable or inflexible corneous material of reptilian scales, claws and of turtle beak. The acquisition of scales and skin derivatives with different mechanical and material properties, mainly due to the evolution of reptile CBPs, is essential for the life and different adaptations of these vertebrates.

Scaffold, mechanics and functions of nuclear lamins

Nuclear lamins are type-V intermediate filaments that are involved in many nuclear processes. In mammals, A- and B-type lamins assemble into separate physical meshwork underneath the inner nuclear membrane, the nuclear lamina, with some residual fraction localized within the nucleoplasm. Lamins are the major part of the nucleoskeleton, providing mechanical strength and flexibility to protect the genome and allow nuclear deformability, while also contributing to gene regulation via interactions with chromatin. While lamins are the evolutionary ancestors of all intermediate filament family proteins, their ultimate filamentous assembly is markedly different from their cytoplasmic counterparts. Interestingly, hundreds of genetic mutations in the lamina proteins have been causally linked with a broad range of human pathologies, termed laminopathies. These include muscular, neurological and metabolic disorders, as well as premature aging diseases. Recent technological advances have contributed to resolving the filamentous structure of lamins and the corresponding lamina organization. In this review, we revisit the multiscale lamin organization and discuss its implications on nuclear mechanics and chromatin organization within lamina-associated domains.

Alterations promoted by acid straightening and/or bleaching in hair microstructures

Human hair is a biopolymer constituted mainly of keratin intermediate filaments, lipids, pigments and water. Cosmetic treatments usually interact with the hair at the molecular level, inducing changes in its components and modifying the physicochemical and mechanical properties of the fibers. Here, the effect of acid straightening on the morphology and ultrastructure of Caucasian hair was investigated by a group of complementary experimental methods: wide-, small- and ultra-small-angle X-ray scattering; high-resolution 3D X-ray microscopy; quasi-elastic neutron scattering and inelastic neutron scattering; thermogravimetry-mass spectrometry; and differential scanning calorimetry (DSC). X-ray diffraction patterns showed that acid straightening associated with a flat iron (∼180°C) changed the cortex of the fiber, shown by denaturation of the intermediate filaments (measured by DSC). The increase in the spacing of the lipid layers and the observation of the dehydration behavior of the fiber provided indications that water may be confined between these layers, while neutron spectroscopy showed alterations in the vibration mode of the CH2 groups of the lipids and an increase of the proton (H+) mobility in the hair structure. The latter may be associated with the extremely low pH of the formulation (pH ≃ 1). Additionally, this investigation showed that bleached hair (one-time bleached) is more damaged by the action of acid straightening than virgin hair, which was shown by a threefold increase in the percentage of total porosity of the tresses. The obtained results demonstrate that the investigation approach proposed here can provide very important thermodynamic and structural information on induced changes of hair structure, and certainly can be applied for the evaluation of the action mode and efficiency of cosmetic treatments.

Studies on Chemical Composition, Structure and Potential Applications of Keratoisis Corals

The chemical composition and structure of bamboo octocoral Keratoisis spp. skeletons were investigated by using: Scanning Electron Microscopy SEM, Raman Microscopy, X-ray Diffraction XRD, Laser Ablation-Inductively Coupled Plasma LA-ICP, and amino acid analyzers. Elements discovered in the nodes (mainly organic parts of the skeleton) of bamboo corals showed a very interesting arrangement in the growth ring areas, most probably enabling the application of bamboo corals as palaeochronometers and palaeothermometers. LA-ICP results showed that these gorgonian corals had an unusually large content of bromine, larger than any other organism yet studied. The local concentration of bromine in the organic part of the growth rings of one of the studied corals grew up to 29,000 ppm of bromine. That is over 440 times more than is contained in marine water and 35 times more than Murex contains, the species which was used to make Tyrian purple in ancient times. The organic matter of corals is called gorgonin, the specific substance that both from the XRD and Raman studies seem to be very similar to the reptile and bird keratins and less similar to the mammalian keratins. The missing cross-linking by S-S bridges, absence of aromatic rings, and significant participation of β-turn organization of peptides differs gorgonin from keratins. Perhaps, the gorgonin belongs to the affined but still different substances concerning reptile and bird keratin and in relation to the more advanced version-the mammalian one. Chemical components of bamboo corals seem to have great medical potential, with the internodes as material substituting the hard tissues and the nodes as the components of medicines.

Protein-Based Biological Materials: Molecular Design and Artificial Production

Polymeric materials produced from fossil fuels have been intimately linked to the development of industrial activities in the 20th century and, consequently, to the transformation of our way of living. While this has brought many benefits, the fabrication and disposal of these materials is bringing enormous sustainable challenges. Thus, materials that are produced in a more sustainable fashion and whose degradation products are harmless to the environment are urgently needed. Natural biopolymers─which can compete with and sometimes surpass the performance of synthetic polymers─provide a great source of inspiration. They are made of natural chemicals, under benign environmental conditions, and their degradation products are harmless. Before these materials can be synthetically replicated, it is essential to elucidate their chemical design and biofabrication. For protein-based materials, this means obtaining the complete sequences of the proteinaceous building blocks, a task that historically took decades of research. Thus, we start this review with a historical perspective on early efforts to obtain the primary sequences of load-bearing proteins, followed by the latest developments in sequencing and proteomic technologies that have greatly accelerated sequencing of extracellular proteins. Next, four main classes of protein materials are presented, namely fibrous materials, bioelastomers exhibiting high reversible deformability, hard bulk materials, and biological adhesives. In each class, we focus on the design at the primary and secondary structure levels and discuss their interplays with the mechanical response. We finally discuss earlier and the latest research to artificially produce protein-based materials using biotechnology and synthetic biology, including current developments by start-up companies to scale-up the production of proteinaceous materials in an economically viable manner.

Super-resolution infrared microspectroscopy reveals heterogeneous distribution of photosensitive lipids in human hair medulla

Human hair medulla chemical composition appears mostly homogenous when mapped by FTIR microspectroscopy even when using a synchrotron radiation source (SR-μFTIR) but it is expected to be heterogeneous. We performed sub-micron chemical mapping of hair cortex and medullas using Optical Photothermal Infrared microspectroscopy (OPTIR) and a mid-infrared Quantum Cascade Laser (QCL) source covering the fingerprint and the CH stretching region. Photodamages were observed in the hair cortex at mild laser power and occurred in the hair medulla even at the lowest power settings of the IR QCL pulsed at 100 kHz rate (4 μW/μm² average power density) and visible probe laser (200 μw/μm² average power density). Photoconversion of calcium carboxylates in other molecules, possibly sodium carboxylates, was observed. Attenuation of the IR QCL power by 40% using ZnSe filter and/or high-speed measurements (1000 cm^-1/s) succeeded in almost completely eliminating the photodamages and photoconversion. OPTIR maps and images showed that the medullas were highly heterogeneous at the submicron scale. We found calcium carboxylates, aliphatic lipids and wax esters in small units, hundreds of nanometers in size. The 1470 cm^-1 CO sym stretching peak of calcium carboxylates and the CH₂asym stretching peak from aliphatic lipids proved to be the most efficient peaks to track the distribution of these molecules. OPTIR had enough sensitivity to map accurately only the strongest peaks from lipids and calcium carboxylates, weaker peaks such as the ester CO and sulfoxide SO bands were not accurately detected by OPTIR even when they were shown to be present by SR-μFTIR. Quantification of the medulla components by OPTIR is difficult due to several factors: discontinuous QCL emission, and noise. The weaker peaks such as CH₃, CO, SO are often underestimated or not detected. We demonstrate here that OPTIR can be used to measure, map and image dark, photosensitive samples using very low IR power.

Chain Sliding versus β-Sheet Formation upon Shearing Single α-Helical Coiled Coils

Coiled coils (CCs) are key building blocks of biogenic materials and determine their mechanical response to large deformations. Of particular interest is the observation that CC-based materials display a force-induced transition from α-helices to mechanically stronger β-sheets (αβT). Steered molecular dynamics simulations predict that this αβT requires a minimum, pulling speed-dependent CC length. Here, de novo designed CCs with a length between four to seven heptads are utilized to probe if the transition found in natural CCs can be mimicked with synthetic sequences. Using single-molecule force spectroscopy and molecular dynamics simulations, these CCs are mechanically loaded in shear geometry and their rupture forces and structural responses to the applied load are determined. Simulations at the highest pulling speed (0.01 nm ns^-1 ) show the appearance of β-sheet structures for the five- and six-heptad CCs and a concomitant increase in mechanical strength. The αβT is less probable at a lower pulling speed of 0.001 nm ns^-1 and is not observed in force spectroscopy experiments. For CCs loaded in shear geometry, the formation of β-sheets competes with interchain sliding. β-sheet formation is only possible in higher-order CC assemblies or in tensile-loading geometries where chain sliding and dissociation are prohibited.

Modification of protein secondary structure as an indicator of radiation-induced abscopal effect: A spectroscopic investigation

In this study, we investigate the abscopal effect induced in the brain, lung and kidney as a result of partial irradiation of experimental animals with 2 Gy γ-rays. Modifications in the protein secondary structure were used as indicator for the abscopal effect. FTIR spectroscopy and analysis of the amide I and amide II absorption bands suggested possible modifications in the protein secondary structure in the brain and kidney following irradiation. Significant shift in the amide I band was recorded only in the brain. However, the amide I/amide II band area ratio for the three organs examined varied differentially in the irradiated groups as compared with the sham-irradiated group. Employing the lorentzian model to analyze the amide I band of the FTIR spectra, we dissected the amide I band into its components, each component represents one form of the protein secondary structure. Calculation of the weight percentage contribution of each of the protein secondary structure revealed decrease in the α-helix contribution associated with equivalent increase in β-sheets and turns/random coils contributions in the brain and kidney, however the response was more evident in the brain. No change in the α-helix or β-sheets contributions was reported in the lung following irradiation. The data suggest the induction of abscopal effect in the brain and kidney rather than the lung in the form of protein conformation modification. The data also indicate that the abscopal effect is comparable to the effect of direct irradiation in both of the brain and kidney.

Promotion of glyoxylic acid penetration into human hair by glycolic acid

OBJECTIVE

Glyoxylic acid (GA) is widely used as a straight perming agent for hair care products, however, advanced GA penetration-enhancing agents are desired due to the peculiar odour and hair colour fading caused by the continuous use of GA products. Hence, it is important to develop a penetration-enhancing agent that helps minimize the GA concentration. We have found that the combined use of GA and glycolic acid (GCA) has a strong hair straightening effect.

METHODS

Straightening hair test was carried out to the evaluation of the effect of additives. Liquid chromatography-mass spectrometry (LC/MS) was performed to quantify the GA penetration amount into human hair. Attenuated total reflection (ATR) Fourier transform-infrared spectroscopy (FT-IR) and FT-IR microscope were implemented to estimate the localization of GA in the hair.

RESULTS

Straightening hair tests indicated that the hair straightening effect by GA was enhanced by the presence of GCA. LC/MS results showed that the addition of GCA enhanced the amount of GA that penetrated human hair by about four times. ATR FT-IR and FT-IR microscope measurements indicated that GA was localized more in the innermost region of hair (medulla) than the cortex and cuticle. The GA accumulated in the medulla disappeared after a hair straightener treatment at 180°C due to the chemical reaction.

CONCLUSIONS

The GA penetration-enhancing effect of GCA is worth investigating to reduce the GA concentration in products for more comfortable use.

Electrospun Silk Fibroin-CNT Composite Fibers: Characterization and Application in Mediating Fibroblast Stimulation

Electrospinning is a simple, low-cost, and highly efficient technique to generate desirable nano/microfibers from polymer solutions. Silk fibroin (SF), a biopolymer found in Bombyx mori cocoons, has attracted attention for various biomedical applications. In this study, functionalized CNT was incorporated in SF to generate biocomposite fibers by electrospinning. The electrospun (E-spun) fibers were well aligned with morphology mimicking the locally oriented ECM proteins in connective tissues. While as-spun fibers dissolved in water in just two minutes, ethanol vapor post-treatment promoted β-sheet formation leading to improved fiber stability in an aqueous environment (>14 days). The addition of a minute amount of CNT effectively improved the E-spun fiber alignment and mechanical strength while retained high biocompatibility and biodegradability. The fibers’ electrical conductivity increased by 13.7 folds and 21.8 folds, respectively, in the presence of 0.1 w% and 0.2 w% CNT in SF fibers. With aligned SF-CNT 0.1 % fibers as a cell culture matrix, we found electrical stimulation effectively activated fibroblasts from patients of pelvic organ prolapse (POP), a connective tissue disorder. The stimulation boosted the fibroblasts’ productivity of collagen III (COLIII) and collagen I (COLI) by 74 folds and 58 folds, respectively, and reduced the COLI to COLIII ratio favorable for tissue repair. The developed material and method offer a simple, direct, and effective way to remedy the dysfunctional fibroblasts of patients for personalized cell therapeutic treatment of diseases and health conditions associated with collagen disorder.

Keratin/alginate hybrid hydrogels filled with halloysite clay nanotubes for protective treatment of human hair

Keratin/alginate hydrogels filled with halloysite nanotubes (HNTs) have been tested for the protective coating of human hair. Preliminary studies have been conducted on the aqueous colloidal systems and the corresponding hydrogels obtained by using Ca²⁺ ions as crosslinkers. Firstly, we have investigated the colloidal properties of keratin/alginate/HNTs dispersions to explore the specific interactions occurring between the biomacromolecules and the nanotubes. Then, the rheological properties of the hydrogels have been studied highlighting that the keratin/alginate interactions and the subsequent addition of HNTs facilitate the biopolymer crosslinking. Finally, human hair samples have been treated with the hydrogel systems by the dipping procedure. The protection efficiency of the hydrogels has been evaluated by studying the tensile properties of hair fibers exposed to UV irradiation. In conclusion, keratin/alginate hydrogel filled with halloysite represents a promising formulation for hair protective treatments due to the peculiar structural and rheological characteristics.

Equine hoof wall: structure, properties, and bioinspired designs

The horse hoof wall exhibits exceptional impact resistance and fracture control due to its unique hierarchical structure which contains tubular, lamellar, and gradient configurations. In this study, structural characterization of the hoof wall was performed revealing features previously unknown. Prominent among them are tubule bridges, which are imaged and quantified. The hydration-dependent viscoelasticity of the hoof wall is described by a simplified Maxwell-Weichert model with two characteristic relaxation times corresponding to nanoscale and mesoscale features. Creep and relaxation tests reveal that the specific hydration gradient in the hoof keratin likely leads to reduced internal stresses that arise from spatial stiffness variations. To better understand realistic impact modes for the hoof wall in-vivo, drop tower tests were executed on hoof wall samples. Fractography revealed that the hoof wall's reinforced tubular structure dominates at lower impact energies while the intertubular lamellae are dominant at higher impact energies. Broken fibers were observed on the surface of the tubules after failure, suggesting that the physically intertwined nature of the tubule reinforcement and intertubular matrix improves the toughness of this natural fiber reinforced composite. The augmented understanding of the structure-mechanical property relationship in dynamic loading led to the design of additively manufactured bioinspired structures, which were evaluated in quasistatic and dynamic loadings. The inclusion of gradient structures and lamellae significantly reduced the damage sustained in drop tower tests, while tubules increased the energy absorption of samples tested in compact tension. The samples most similar to the hoof wall displayed remarkably consistent fracture control properties. STATEMENT OF SIGNIFICANCE: The horse hoof wall, capable of withstanding large, repeated, dynamic loads, has been touted as a candidate for impact-resistant bioinspiration. However, our understanding of this biological material and its translation into engineered designs is incomplete. In this work, new features of the horse hoof wall are quantified and the hierarchical failure mechanisms of this remarkable material under near-natural loading conditions are uncovered. A model of the hoof wall's viscoelastic response, based on studies of other keratinous materials, was developed. The role of hydration, strain rate, and impact energy on the material's response were elucidated. Finally, multi-material 3D printed designs based on the hoof's meso/microstructure were fabricated and exhibited advantageous energy absorption and fracture control relative to control samples.

Near-Infrared-Enpowered Nanomotor-Mediated Targeted Chemotherapy and Mitochondrial Phototherapy to Boost Systematic Antitumor Immunity

Phototherapy is an important strategy to inhibit tumor growth and activate antitumor immunity. However, the effect of photothermal/photodynamic therapy (PTT/PDT) is restricted by limited tumor penetration depth and unsatisfactory potentiation of antitumor immunity. Here, a near-infrared (NIR)-driven nanomotor is constructed with a mesoporous silicon nanoparticle (MSN) as the core, end-capped with Antheraea pernyi silk fibroin (ApSF) comprising arginine-glycine-aspartate (RGD) tripeptides. Upon NIR irradiation, the resulting ApSF-coated MSNs (DIMs) loading with photosensitizers (ICG derivatives, IDs) and chemotherapeutic drugs (doxorubicin, Dox) can efficiently penetrate into the internal tumor tissues and achieve effective phototherapy. Combined with chemotherapy, a triple-modal treatment (PTT, PDT, and chemotherapy) approach is developed to induce the immunogenic cell death of tumor cells and to accelerate the release of damage-associated molecular patterns. In vivo results suggest that DIMs can promote the maturation of dendritic cells and surge the number of infiltrated immune cells. Meanwhile, DIMs can polarize macrophages from M2 to M1 phenotypes and reduce the percentages of immunosuppressive Tregs, which reverse the immunosuppressive tumor microenvironment and activate systemic antitumor immunity. By achieving synergistic effects on the tumor inhibition and the antitumor immunity activation, DIMs show great promise as new nanoplatforms to treat metastatic breast cancer.

Sustainable Applications of Animal Waste Proteins

Currently, the growth of the global population leads to an increase in demand for agricultural products. Expanding the obtaining and consumption of food products results in a scale up in the amount of by-products formed, the development of processing methods for which is becoming an urgent task of modern science. Collagen and keratin make up a significant part of the animal origin protein waste, and the potential for their biotechnological application is almost inexhaustible. The specific fibrillar structure allows collagen and keratin to be in demand in bioengineering in various forms and formats, as a basis for obtaining hydrogels, nanoparticles and scaffolds for regenerative medicine and targeted drug delivery, films for the development of biodegradable packaging materials, etc. This review describes the variety of sustainable sources of collagen and keratin and the beneficial application multiformity of these proteins.

Analysis and comparison of protein secondary structures in the rachis of avian flight feathers

Avians have evolved many different modes of flying as well as various types of feathers for adapting to varied environments. However, the protein content and ratio of protein secondary structures (PSSs) in mature flight feathers are less understood. Further research is needed to understand the proportions of PSSs in feather shafts adapted to various flight modes in different avian species. Flight feathers were analyzed in chicken, mallard, sacred ibis, crested goshawk, collared scops owl, budgie, and zebra finch to investigate the PSSs that have evolved in the feather cortex and medulla by using nondestructive attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). In addition, synchrotron radiation-based, Fourier transform infrared microspectroscopy (SR-FTIRM) was utilized to measure and analyze cross-sections of the feather shafts of seven bird species at a high lateral resolution to resolve the composition of proteins distributed within the sampled area of interest. In this study, significant amounts of α-keratin and collagen components were observed in flight feather shafts, suggesting that these proteins play significant roles in the mechanical strength of flight feathers. This investigation increases our understanding of adaptations to flight by elucidating the structural and mechanistic basis of the feather composition.

Chemically characterizing the cortical cell nano-structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM-IR)

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.

Engineering with keratin: A functional material and a source of bioinspiration

Keratin is a highly multifunctional biopolymer serving various roles in nature due to its diverse material properties, wide spectrum of structural designs, and impressive performance. Keratin-based materials are mechanically robust, thermally insulating, lightweight, capable of undergoing reversible adhesion through van der Waals forces, and exhibit structural coloration and hydrophobic surfaces. Thus, they have become templates for bioinspired designs and have even been applied as a functional material for biomedical applications and environmentally sustainable fiber-reinforced composites. This review aims to highlight keratin's remarkable capabilities as a biological component, a source of design inspiration, and an engineering material. We conclude with future directions for the exploration of keratinous materials.

Fungal decomposition of chicken-feather waste in submerged and solid-state fermentation

Poultry industry is expanding rapidly and producing million tons of feather waste annually. Massive production of keratinaceous byproducts in the form of industrial wastes throughout the world necessitates its justified utilization. Chemical treatment of keratin waste is proclaimed as an eco-destructive approach by various researchers since it generates secondary pollutants. Keratinase released by a variety of microbes (bacteria and fungi) can be used for the effective treatment of keratin waste. Microbial degradation of keratin waste is an emerging and eco-friendly approach and offers dual benefits, i.e., treatment of recalcitrant pollutant (keratin) and procurement of a commercially important enzyme (keratinase). This study involves the isolation, characterization, and potential utility of fungal species for the degradation of chicken-feather waste through submerged and solid-state fermentation. The isolated fungus was identified and characterized as Aspergillus (A.) flavus. In a trial of 30 days, it was appeared that 74 and 8% feather weight was reduced through sub-merged and solid-state fermentation, respectively by A. flavus. The pH of the growth media in submerged fermentation was changed from 4.8 to 8.35. The exploited application of keratinolytic microbes is, therefore, recommended for the treatment of keratinaceous wastes to achieve dual benefits of remediation.

Vertebrate keratinization evolved into cornification mainly due to transglutaminase and sulfhydryl oxidase activities on epidermal proteins: An immunohistochemical survey

The epidermis of vertebrates forms an extended organ to protect and exchange gas, water, and organic molecules with aquatic and terrestrial environments. Herein, the processes of keratinization and cornification in aquatic and terrestrial vertebrates were compared using immunohistochemistry. Keratins with low cysteine and glycine contents form the main bulk of proteins in the anamniote epidermis, which undergoes keratinization. In contrast, specialized keratins rich in cysteine-glycine and keratin associated corneous proteins rich in cysteine, glycine, and tyrosine form the bulk of proteins of amniote soft cornification in the epidermis and hard cornification in scales, claws, beak, feathers, hairs, and horns. Transglutaminase (TGase) and sulfhydryl oxidase (SOXase) are the main enzymes involved in cornification. Their evolution was fundamental for the terrestrial adaptation of vertebrates. Immunohistochemistry results revealed that TGase and SOXase were low to absent in fish and amphibian epidermis, while they increased in the epidermis of amniotes with the evolution of the stratum corneum and skin appendages. TGase aids the formation of isopeptide bonds, while SOXase forms disulfide bonds that generate numerous cross-links between keratins and associated corneous proteins, likely increasing the mechanical resistance and durability of the amniote epidermis and its appendages. TGase is low to absent in the beta-corneous layers of sauropsids but is detected in the softer but pliable alpha-layers of sauropsids, mammalian epidermis, medulla, and inner root sheath of hairs. SOXase is present in hard and soft corneous appendages of reptiles, birds, and mammals, and determines cross-linking among corneous proteins of scales, claws, beaks, hairs, and feathers.

A new typology of human hair medullas based on lipid composition analysis by synchrotron FTIR microspectroscopy

Human hair is an organ that connects fundamental and applied research with everyday life through the cosmetic industry. Yet, the accurate compositional description of the human hair medulla is lacking due to their small size and difficulty with microextraction. Medullas are thus generally classified based on morphology. We investigated the chemical composition of the human hair medulla using synchrotron based infrared microspectroscopy. We confirmed that lipid signatures dominate the medulla infrared spectrum having 3-20 times higher lipid concentration compared to their surrounding cortex. Human hair medullas contain a mixture of non-esterified and esterified lipids, and carboxylate soaps in various proportions. We reveal the first direct spectroscopic evidence that medulla carboxylates are coordinated to calcium since they exhibit the specific calcium carboxylate signature. Using a representative sample, we observed a strong compositional variability between medullas that was unreported before. We detected calcium carboxylates in 76% of the medullas with one order of magnitude concentration variability between samples. All medullas contained esters with esterification varying by a factor of 30. Moreover, we detected the presence of crystalline calcium stearate in 9% of the medullas. We described a series of spectral markers to characterize medullas based on their lipid composition and propose to classify medullas in four to five groups. Our analysis provides a more detailed understanding of the chemical composition of human hair medullas that may impact cosmetics and biology. The origin and biological meaning of these variations must still be investigated.

Investigation of the molecular signature of greying hair shafts

OBJECTIVE

Hair greying (i.e. canitie) is a physiological process occurring with the loss of melanin production and deposition within the hair shafts. Many studies reported the oxidation as the main biological process underlying this defect of pigmentation. Even though the overall appearance and biomechanical properties of hairs are reported to be altered with greying, there is a lack of information about molecular modifications occurring in grey hair shafts. The aim of this study was thus to investigate the molecular signature and associated changes occurring in greying hair shafts by confocal Raman microspectroscopy.

METHODS

This study was conducted on pigmented, intermediate (i.e. grey) and unpigmented hairs taken from 29 volunteers. Confocal Raman microspectroscopy measurements were acquired directly on hair shafts.

RESULTS

Automatic classification of Raman spectra revealed 5 groups displaying significant differences. Hence, the analysis of the molecular signature highlighted the existence of 3 sub-groups within grey hair: light, medium and dark intermediate. Among molecular markers altered in the course of greying, this study identified for the first time a gradual modification of lipid conformation (trans/gauche ratio) and protein secondary structure (α-helix/β-sheet ratio), referring respectively to an alteration of barrier function and biomechanical properties of greying hair.

CONCLUSION

This study thus reports for the first time a highly specific molecular signature as well as molecular modifications within grey hair shaft.

Enhanced nail delivery of voriconazole-loaded nanomicelles by thioglycolic acid pretreatment: A study of protein dynamics and disulfide bond rupture

This work aimed to select an effective penetration enhancer (PE) for nail pretreatment, develop voriconazole (VOR)-loaded nanomicelles, and evaluate their ability to deliver VOR to the nail. A complete analysis of nail protein dynamics, bond rupture, and microstructure was performed. Alternative methods as electron paramagnetic resonance (EPR) and the Ellman's reagent (DTNB) assay were also evaluated. Nanomicelles were produced and characterized. The PE hydrated the hooves, following the order: urea ≈ cysteine ≈ glycolic acid < thioglycolic acid (TGA) < NaOH. SEM images and methylene blue assay showed enlarged pores and roughness of porcine hooves after incubation with NaOH and TGA. EPR was demonstrated to be the most sensitive technique. DTNB assay quantified higher thiol groups for samples treated with TGA (p < 0.05). A stratigraphic analysis with Raman spectroscopy demonstrated that hooves treated with TGA presented a higher SH/SS ratio at the edges, affecting protein secondary structure. In vitro permeation studies demonstrated significant VOR permeation (29.44 ± 6.13 µg/cm²), 10-fold higher than previous studies with lipid nanoparticles. After TGA pretreatment, VOR permeation was further enhanced (3-fold). TGA pretreatment followed by VOR-loaded nanomicelles demonstrates a promising approach for onychomycosis treatment. The novel methods for protein analysis were straightforward and helpful.

Probing Skin Barrier Recovery on Molecular Level Following Acute Wounds: An In Vivo/Ex Vivo Study on Pigs

Proper skin barrier function is paramount for our survival, and, suffering injury, there is an acute need to restore the lost barrier and prevent development of a chronic wound. We hypothesize that rapid wound closure is more important than immediate perfection of the barrier, whereas specific treatment may facilitate perfection. The aim of the current project was therefore to evaluate the quality of restored tissue down to the molecular level. We used Göttingen minipigs with a multi-technique approach correlating wound healing progression in vivo over three weeks, monitored by classical methods (e.g., histology, trans-epidermal water loss (TEWL), pH) and subsequent physicochemical characterization of barrier recovery (i.e., small and wide-angle X-ray diffraction (SWAXD), polarization transfer solid-state NMR (PTssNMR), dynamic vapor sorption (DVS), Fourier transform infrared (FTIR)), providing a unique insight into molecular aspects of healing. We conclude that although acute wounds sealed within two weeks as expected, molecular investigation of stratum corneum (SC) revealed a poorly developed keratin organization and deviations in lipid lamellae formation. A higher lipid fluidity was also observed in regenerated tissue. This may have been due to incomplete lipid conversion during barrier recovery as glycosphingolipids, normally not present in SC, were indicated by infrared FTIR spectroscopy. Evidently, a molecular approach to skin barrier recovery could be a valuable tool in future development of products targeting wound healing.

The evolving mechanical response of curly hair fibres subject to fatigue testing

Cyclic testing of human hair reveals important details about the behaviour of fibres over many cycles of loading. Phenomena which are observed under static tensile tests give important clues about the form and behaviour of hair fibres, but these do not necessarily remain constant on the inevitable march to failure. In previous work, we demonstrated that curly fibres exhibited a toe-region during tensile tests. The form of curly fibres could be altered by mechanical manipulation but the curl could be recovered upon immersion in water. In this study, where straight and curly fibres are subject to cyclic loading, this characteristic toe-region was shown to be present in the first cycle of loading (for curly fibres). As the number of cycles increased (and the curly fibres progressively became straighter), the stress-strain response of curly fibres started to resemble that of straight fibres. This observation supports our previous hypothesis, which states that the toe-region can be attributed to the presence of a hydrogen bonding mechanism, which is present in curly fibres only, and can be altered by mechanical force. Interestingly, the alteration in load-bearing pattern in curly fibres did not necessarily translate to increased endurance, demonstrating that the relationship between fatigue and strength is a complex one in hair fibres.

A bioinspired and hierarchically structured shape-memory material

Shape-memory polymeric materials lack long-range molecular order that enables more controlled and efficient actuation mechanisms. Here, we develop a hierarchical structured keratin-based system that has long-range molecular order and shape-memory properties in response to hydration. We explore the metastable reconfiguration of the keratin secondary structure, the transition from α-helix to β-sheet, as an actuation mechanism to design a high-strength shape-memory material that is biocompatible and processable through fibre spinning and three-dimensional (3D) printing. We extract keratin protofibrils from animal hair and subject them to shear stress to induce their self-organization into a nematic phase, which recapitulates the native hierarchical organization of the protein. This self-assembly process can be tuned to create materials with desired anisotropic structuring and responsiveness. Our combination of bottom-up assembly and top-down manufacturing allows for the scalable fabrication of strong and hierarchically structured shape-memory fibres and 3D-printed scaffolds with potential applications in bioengineering and smart textiles.

Structure of Keratin

Keratins, as a group of insoluble and filament-forming proteins, mainly exist in certain epithelial cells of vertebrates. Keratinous materials are made up of cells filled with keratins, while they are the toughest biological materials such as the human hair, wool and horns of mammals and feathers, claws, and beaks of birds and reptiles which usually used for protection, defense, hunting and as armor. They generally exhibit a sophisticated hierarchical structure ranging from nanoscale to centimeter-scale: polypeptide chain structures, intermediated filaments/matrix structures, and lamellar structures. Therefore, more and more attention has been paid to the investigation of the relationship between structure and properties of keratins, and a series of biomimetic materials based on keratin came into being. In this chapter, we mainly introduce the hierarchical structure, the secondary structure, and the molecular structure of keratins, including α- and β-keratin, to promote the development of novel keratin-based biomimetic materials designs.

Analysis of the Contribution of Conformation and Fibrils on Tensile Toughness and Fracture Resistance of Camel Hairs

Animal hairs, like other natural fibers, display excellent mechanical properties, especially, the tensile toughness and fracture resistance. Several structure-mechanics models have attributed mechanical superiority of hair to its unique nanocomposite structure which consists of intermediate filaments and matrix. However, the contribution of fibrils and their associated interfaces on the mechanical properties of animal hairs remains unclear. Herein, using the small- and wide-angle X-ray scattering, and an ultrahigh-speed microcamera system, it is confirmed that the conformation and fibrils (which represent both nanofibrils and microfibrils) of the keratin channel endow tensile toughness and fracture resistance to camel hairs. During the stretching process, an α-β transition occurred at the secondary structure level, leading to the formation of a tensile plateau, which improves the toughness compared with the structure without a conformation transition. Meanwhile, fibrils further toughened the camel hairs and resisted their crack propagation through confined fibrillar slippage, splitting, and pulling. These structure-property relations in natural hairs can inspire damage-tolerant polymer fiber design.

Nonlinear mechanics of lamin filaments and the meshwork topology build an emergent nuclear lamina

The nuclear lamina—a meshwork of intermediate filaments termed lamins—is primarily responsible for the mechanical stability of the nucleus in multicellular organisms. However, structural-mechanical characterization of lamin filaments assembled in situ remains elusive. Here, we apply an integrative approach combining atomic force microscopy, cryo-electron tomography, network analysis, and molecular dynamics simulations to directly measure the mechanical response of single lamin filaments in three-dimensional meshwork. Endogenous lamin filaments portray non-Hookean behavior – they deform reversibly at a few hundred picoNewtons and stiffen at nanoNewton forces. The filaments are extensible, strong and tough similar to natural silk and superior to the synthetic polymer Kevlar^®. Graph theory analysis shows that the lamin meshwork is not a random arrangement of filaments but exhibits small-world properties. Our results suggest that lamin filaments arrange to form an emergent meshwork whose topology dictates the mechanical properties of individual filaments. The quantitative insights imply a role of meshwork topology in laminopathies.

Mechanical strength of in situ assembled nuclear lamin filaments arranged in a 3D meshwork is unclear. Here, using mechanical, structural and simulation tools, the authors report the hierarchical organization of the lamin meshwork that imparts strength and toughness to lamin filaments at par with silk and Kevlar^®

Cholesterol derivatives make large part of the lipids from epidermal molts of the desert-adapted Gila monster lizard (Heloderma suspectum)

In order to understand the cutaneous water loss in the desert-adapted and venomous lizard Heloderma suspectum, the microscopic structure and lipid composition of epidermal molts have been examined using microscopic, spectroscopic and chemical analysis techniques. The molt is formed by a variably thick, superficial beta-layer, an extensive mesos-region and few alpha-cells in its lowermost layers. The beta-layer contains most corneous beta proteins while the mesos-region is much richer in lipids. The proteins in the mesos-region are more unstructured than those located in the beta-layer. Most interestingly, among other lipids, high contents of cholesteryl-β-glucoside and cholesteryl sulfate were detected, molecules absent or present in traces in other species of squamates. These cholesterol derivatives may be involved in the stabilization and compaction of the mesos-region, but present a limited permeability to water movements. The modest resistance to cutaneous water-loss of this species is compensated by adopting other physiological strategies to limit thermal damage and water transpiration as previous eco-physiological studies have indicated. The increase of steroid derivatives may also be implicated in the heat shock response, influencing the relative behavior in this desert-adapted lizard.

Tuning Chain Relaxation from an Amorphous Biopolymer Film to Crystals by Removing Air/Water Interface Limitations

A promising route to the synthesis of protein-mimetic materials that are capable of strong mechanics and complex functions is provided by intermolecular β-sheet stacking. An understanding of the assembly mechanism on β-sheet stacking at molecular-level and the related influencing factors determine the potential to design polymorphs of such biomaterials towards broad applications. Herein, we quantitatively reveal the air/water interface (AWI) parameters regulating the transformation from crowding amorphous aggregates to ordered phase and show that the polymorph diversity of β-sheet stacking is regulated by the chain relaxation-crystallization mechanism. An amorphous macroscale amyloid-like nanofilm is formed at the AWI, in which unfolded protein chains are aligned in a short-range manner to form randomly packed β-sheets. The subsequent biopolymer chain relaxation-crystallization to form nanocrystals is further triggered by removing the limitations of energy and space at the AWI.

The tripeptide GHG as an unexpected hydrogelator triggered by imidazole deprotonation

The tripeptide glycyl-histidyl-glycine (GHG) self-assembles into long, crystalline fibrils forming a strong hydrogel (G'∼ 50 kPa) above a critical concentration of 40 mM upon the deprotonation of its imidazole group. Spectroscopic data reveal a mixture of helically twisted β-sheets and monomers to coexist in the gel phase.

Porosity at Different Structural Levels in Human and Yak Belly Hair and Its Effect on Hair Dyeing

Yak belly hair was proposed as a cheap substitute for human hair for the development of hair dyes, as its chemical composition closely resembles human hair in Raman spectroscopy. The absence of melanin in yak belly hair also leads to a strong reduction of fluorescence in Raman measurements, which is advantageous for the investigation of the effectivity of hair dyes. To assess the suitability for replacing human hair, we analyzed similarities and differences of both hair types with a variety of methods: Raman spectroscopy, to obtain molecular information; small-angle X-ray scattering to determine the nanostructure, such as intermediate filament distance, distance of lipid layers and nanoporosity; optical and scanning electron microscopy of surfaces and cross sections to determine the porosity at the microstructural level; and density measurements and tensile tests to determine the macroscopic structure, macroporosity and mechanical properties. Both types of hair are similar on a molecular scale, but differ on other length scales: yak belly hair has a smaller intermediate filament distance on the nanoscale. Most striking is a higher porosity of yak belly hair on all hierarchical levels, and a lower Young’s modulus on the macroscale. In addition to the higher porosity, yak belly hair has fewer overlapping scales of keratin, which further eases the uptake of coloring. This makes, on the other hand, a comparison of coloring processes difficult, and limits the usefulness of yak belly hair as a substitute for human hair.

Comprehensive insights into microbial keratinases and their implication in various biotechnological and industrial sectors: A review

Enormous masses of keratinous wastes are annually accumulated in the environment as byproducts of poultry processing and agricultural wastes. Keratin is a recalcitrant fibrous protein, which represents the major constituent of various keratin-rich wastes, which released into the environment in the form of feathers, hair, wool, bristle, and hooves. Chemical treatment methods of these wastes resulted in developing many hazardous gases and toxins to the public health, in addition to the destruction of several amino acids. Accordingly, microbial keratinases have been drawing much interest as an eco-friendly approach to convert keratinous wastes into valuable products. Numerous keratinolytic microorganisms have been identified, which revealed the competence to hydrolyze keratins into peptides and amino acids. Several types of keratinolytic proteases have been produced that possess diverse biochemical characteristics, conferring them the versatility for implementing in multifarious applications such as detergents, leather and textile industries, animal feeding, and production of bio-fertilizers, in addition to medical and pharmaceutical treatments. This review article emphasizes the significance of keratinases and keratinase based-products via comprehensive insights into the keratin structure, diversity of keratinolytic microorganisms, and mechanisms of keratin hydrolysis. Furthermore, we discuss the biochemical properties of the produced keratinases and their feasible applications in diverse disciplines.

Self-healing silk from the sea: role of helical hierarchical structure in Pinna nobilis byssus mechanics

The byssus fibers of Mytilus mussel species have become an important role model in bioinspired materials research due to their impressive properties (e.g. high toughness, self-healing); however, Mytilids represent only a small subset of all byssus-producing bivalves. Recent studies have revealed that byssus from other species possess completely different protein composition and hierarchical structure. In this regard, Pinna nobilis byssus is especially interesting due to its very different morphology, function and its historical use for weaving lightweight golden fabrics, known as sea silk. P. nobilis byssus was recently discovered to be comprised of globular proteins organized into a helical protein superstructure. In this work, we investigate the relationships between this hierarchical structure and the mechanical properties of P. nobilis byssus threads, including energy dissipation and self-healing capacity. To achieve this, we performed in-depth mechanical characterization, as well as tensile testing coupled with in situ X-ray scattering. Our findings reveal that P. nobilis byssus, like Mytilus, possesses self-healing and energy damping behavior and that the initial elastic behavior of P. nobilis byssus is due to stretching and unraveling of the previously observed helical building blocks comprising the byssus. These findings have biological relevance for understanding the convergent evolution of mussel byssus for different species, and also for the field of bio-inspired materials.

Lateral Subunit Coupling Determines Intermediate Filament Mechanics

The cytoskeleton is a composite network of three types of protein filaments, among which intermediate filaments (IFs) are the most extensible ones. Two very important IFs are keratin and vimentin, which have similar molecular architectures but different mechanical behaviors. Here we compare the mechanical response of single keratin and vimentin filaments using optical tweezers. We show that the mechanics of vimentin strongly depends on the ionic strength of the buffer and that its force-strain curve suggests a high degree of cooperativity between subunits. Indeed, a computational model indicates that in contrast to keratin, vimentin is characterized by strong lateral subunit coupling of its charged monomers during unfolding of α helices. We conclude that cells can tune their mechanics by differential use of keratin versus vimentin.

Identification of keratinases from Fervidobacterium islandicum AW-1 using dynamic gene expression profiling

Keratin degradation is of great interest for converting agro‐industrial waste into bioactive peptides and is directly relevant for understanding the pathogenesis of superficial infections caused by dermatophytes. However, the mechanism of this process remains unclear. Here, we obtained the complete genome sequence of a feather‐degrading, extremely thermophilic bacterium, Fervidobacterium islandicum AW‐1 and performed bioinformatics‐based functional annotation. Reverse transcription PCR revealed that 57 putative protease‐encoding genes were differentially expressed in substrate‐dependent manners. Consequently, 16 candidate genes were highly expressed under starvation conditions, when keratin degradation begun. Subsequently, the dynamic expression profiles of these 16 selected genes in response to feathers, as determined via quantitative real‐time PCR, suggested that they included four metalloproteases and two peptidases including an ATP‐dependent serine protease, all of which might act as key players in feather decomposition. Furthermore, in vitro keratinolytic assays supported the notion that recombinant enzymes enhanced the decomposition of feathers in the presence of cell extracts. Therefore, our genome‐based systematic and dynamic expression profiling demonstrated that these identified metalloproteases together with two additional peptidases might be primarily associated with the decomposition of native feathers, suggesting that keratin degradation can be achieved via non‐canonical catalysis of several membrane‐associated metalloproteases in cooperation with cytosolic proteases.