Wool Cuticle Research Articles

Structure and Performance of Cuticles Isolated from Wool Fibers Using Different Approaches

ABSTRACT Wool cuticles have a complex hierarchical structure and inherent resistance to general chemicals and enzymes. However, data on the structure and properties of the cuticle, which informs its processing and utilization remains scant. In this paper, we successfully isolated flaky cuticles using the ultrasonic technique from wool residues after keratin extraction with combined L-cysteine and urea (Cuticle-L + U). We then characterized and analyzed the chemical structure and thermal stability of the cuticle-L + U and compared it with the raw wool and wool cuticle isolated with the formic acid method (cuticle-FA). Our data show that the cuticle-L + U has a lower disulfide bond content compared to either raw wool or cuticle-FA. The solid-state 13C NMR spectra demonstrated that the raw wool had a higher content of α-helix structures (61.57%), while cuticle-FA (80.08%) and cuticle-L + U (52.32%) had more β-sheet or disorder structures. Differential scanning calorimetry (DSC) analysis indicated that both the cuticle-L + U and cuticle-FA have lower α-helical crystallinity compared to the raw wool, which further proved that the cuticle mainly consists of β-sheet and random coil structure. In addition, TG analysis and SDS-PAGE showed higher thermal stability and insolubility with the cuticle-L + U compared with cuticle-FA.

Investigation of effects of protease enzyme produced by Bacillus subtilis 168 E6-5 and commercial enzyme on physical properties of woolen fabric

Wool is one of the most important fibers in textile industry, and has been commonly used for producing value added products due to its properties of lightness, warmth, softness, and smoothness. However, the special scale structure in wool cuticle can cause felting shrinkage of wool fabrics. Proteases have been widely used to modify the surface of wool to prevent wool felting, due to their ability to catalyze the hydrolysis of peptide bonds in wool scales. Although the treatment of wool with proteases was considered as an environmentally friendly technique to provide wool fabrics with shrink resistance properties, proteases exhibited low efficacy in removing the cuticle scales because of the highly cross-linked barriers. In this study, wool fabric was treated with protease enzyme obtained from novel isolated bacteria and commercial protease enzyme, and the results were compared. The tear strength, pilling changes in ΔE values, whiteness and yellowness values of wool were controlled. Results showed that treatment with Bacillus subtilis 168 E6-5 protease enzyme yielded improvements in the physical properties of wool fabric compared with commercial enzyme.

The structure and properties of wool treated with a reversed-phase microemulsion containing aqueous alkali

In order to limit modification to the surface of wool fibers and decrease pollution caused by conventional chemical treatments using chlorine, a water-in-oil-type reversed-phase microemulsion with decamethylcyclopentasiloxane as the external phase was prepared containing very small amounts of an aqueous solution of alkali. The edges of the wool cuticle scales were modified by the alkali in aqueous solution contained in the reversed-phase microemulsion. The external phase decamethylcyclopentasiloxane can be recycled after application. In this paper, the solubility of water in the reversed-phase microemulsion and its stability were first studied and then it was applied in the treatment of wool. The results showed that surfactant sodium alcohol ether sulfate/NaOH aqueous solution was quite stable. Felting shrinkage of treated wool was reduced and the initial dyeing speed was higher than that for untreated wool. The corroded scales of treated wool were observed by scanning electron microscopy and the bromine Allwörden reaction with bromine water was reduced or eliminated after treatment. This adsorbable organohalogen-free modification should be useful in improving the manufacturing properties of wool, such as hydrophilicity, and as a pretreatment for wool printing.

Biodegradation of wool waste and keratinase production in scale-up fermenter with different strategies by Stenotrophomonas maltophilia BBE11-1

A keratin-degrading strain Stenotrophomonas maltophilia BBE11-1 was grown in a 3-L batch fermenter containing wool waste as the main medium and cell growth rate was determined as the key factor to affect keratinase yield. Three strategies of temperature-shift procedure, two-stage DO control and fed-batch process were used to change growth rate. And a 62.2% improvement of keratinase yield was achieved. With the glucose fed-batch procedure in 30-L fermenter, keratinase production was significantly improved up to 117.7% (1728 U/ml) as compared with initial data (793.8 U/ml) in a 3-L fermenter and with much shortened fermentation time within 18 h. Significant structure changes and high levels of free amino acids from wool decomposition indicated the possible applications for wool waste management and fertilizer industry. The remarkable digestion of wool cuticle also suggested its potential utilization in textile industry.

Enzyme Assisted Ultrasound Scouring of Raw Wool Fibres

Scouring of raw wool is a chemical treatment that needs a high amount of detergents, alkalis and water. Effluents produced by this treatment are extremely polluted with chemicals and impurities washed out from the fibers. It is well known that the ultrasound washing can remove effectively different substances from the textile surfaces even without surfactants due to the cavitations occurring at certain parameters of the ultrasound field. On the other side water treatments of wool combined with mechanical agitation provoked felting which can impair the quality of wool materials. Felting itself depends not only on the parameters of water treatments but also on the structure of wool cuticle. Partial hydrolysis of the cuticle with some proteases can decrease considerably the wool felting. The aim of this work is to study the possibility of applying the ultrasound at the process of raw wool scouring and the influence of proteases on the felting properties of wool at these conditions. It has been found out that ultrasound environment applied does not impair the specific activity of enzyme auxiliaries used and leads to increasing of their effect on the surface of wool fibers. Thus the scouring process studied could be used for developing of a technology producing lower amount and less polluted effluents.

The Proteome of the Wool Cuticle

The cuticle is responsible for important wool fiber characteristics such as handle and abrasion resistance, which impact on the fiber's performance in both interior and apparel textiles. The cuticle proteome, however, is not well understood due to the difficulty in isolating pure wool cuticle and its significant resistance to protein extraction, which is attributed to the presence of extensive disulfide and isopeptide cross-linking. We investigated the proteome of highly pure Merino wool cuticle using a combined strategy of chemical and enzymatic digestion and identified 108 proteins, including proteins responsible for a variety of cellular processes. The majority of identified proteins belonged to keratin and nonkeratin protein families known to play an important role in molecular assembly and cellular structure. Keratin-associated, intermediate filament and cytoskeletal keratin proteins were identified as the most prominent keratinous cuticular constituents, while histones, tubulins, and desmosomes were the key nonkeratin structural proteins. We conclude that a variety of proteins contribute to cuticle structure and fiber characteristics, and that the keratinous protein families of IFPs and KAPs represent the most important cuticular constituents.

Higher sequence coverage and improved confidence in the identification of cysteine-rich proteins from the wool cuticle using combined chemical and enzymatic digestion

Keratin-associated proteins (KAPs) are important constituents of the wool cuticle, comprised of the endo-, exocuticle and a-layers, which contribute significantly to the fibre's molecular and mechanical characteristics. Relatively little is known about the distribution of specific KAPs across these layers, and correct protein identification of individual KAPs is difficult due to extensive homology and identity among individual KAPs. We here present evidence that, by specifically exploiting the high-cysteine content of KAPs in the wool cuticle, using 2-nitro-5-thiocyanobenzoic acid (NTCB) cleavage in combination with tryptic digestion, a larger number of KAPs can be identified than with standard trypsin-only digests. A total of 27 KAPs were identified, six of which could only be identified using NTCB. Furthermore, NTCB-mediated cleavage of cuticle proteins generated unique peptides critical for unambiguous identification of two KAPs, as well as significantly increasing the overall sequence coverage of most identified KAPs. Interestingly, some of the peptides found to be unique to particular KAPs could only be found in either the exo- or endocuticle. We conclude that for the analysis of high sulphur proteomes, specific targeting of cysteine residues using chemical agents such as NTCB can provide critical information for unambiguous protein identification.

A morphology-related study on photodegradation of protein fibres

The wool fibre has a complex morphology, consisting of an outer layer of cuticle scales surrounding an inner cortex. These two components are hard to separate effectively except by using harsh chemical treatments, making it difficult to determine the susceptibility of the different components of the fibre to photoyellowing. An approach to this problem based on mechanical fibre modification is described. To expose the inner cortex of wool to different degrees, clean wool fibres were converted into ‘powders’ of various fineness via mechanical chopping, air-jet milling, ball milling or their combination. Four types of powdered wool (samples A, B, C and D) were produced with reducing particle size distributions and an increasing level of surface damage as observed using SEM. Sample A contained essentially intact short fibre snippets and sample D contained a large amount of exposed cortical materials. Samples B and C contained a mixture of short fibre snippets and cortical materials. Solid wool discs were then compressed from the corresponding powder samples in a polished stainless steel die to enable colour measurement and UV irradiation studies. ATR-FTIR studies on powder discs demonstrated a small shift in the amide I band from 1644 cm −1 for disc A to 1654 cm −1 for disc D due to the different structures of the wool cuticle and cortex, in agreement with previous studies. Similarly an increase in the intensity ratio of the amide I to amide II band (1540 cm −1) was observed for disc D, which contains a higher fraction of cortical material at the surface of the disc. Discs prepared from sample D appeared the lightest in colour before exposure and had the slowest photoyellowing rate, whereas discs made from powders A–C with a higher level of cuticle coverage were more yellow before exposure and experienced a faster rate of photoyellowing. This suggests that the yellow chromophores of wool may be more prevalent in cuticle scales, and that wool photoyellowing occurs to a greater extent in the cuticle than in the cortex. Photo-induced chemiluminescence measurements showed that sample D had a higher chemiluminescence intensity after exposure to UVA radiation and a faster decay rate than samples A and B. Thus one of the roles of the wool cuticle may be to protect the cortex by quenching of free radical oxidation during exposure to the UV wavelengths present in sunlight.

Characterization of the exocuticle a‐layer proteins of wool

The outermost protein layer of wool cuticle cells is known as the exocuticle a-layer. This layer is a resistant barrier to the degradation of the fibre and, as a result, little is known of its proteinaceous composition. Merino wool fibres were subjected to both proteolytic and chemical digestion and the resulting material was found by transmission electron microscopy to be highly enriched in a-layer. Amino acid analysis revealed a high cysteine and glycine content, with a close, but not exact, match to the Allwörden membrane. Subsequent digestion of the a-layer preparation by 2-nitro-5-thiocyano-benzoic acid produced a large number of short peptides, and analysis by mass spectrometry revealed peptides with strong homologies to cuticular ultra-high sulphur proteins of sheep wool and cuticular ultra-high and high-sulphur proteins of human hair, thus supporting other evidence for the presence of these sulphur-rich proteins in the a-layer.

Chemical modification of proteases for wool cuticle scale removal

Over the last few decades several enzymatic processes to improve properties of wool fabrics like felting tendency, shrink resistance, dyeing ability and handling characteristics have been described. Previous investigations into the use of proteases to hydrolyse the cuticles at the surface of wool fibres, resulted in high strength and weight losses. Therefore restriction of the enzyme activity to the wool surface or control of enzyme diffusion to the cortex cells is required.To change the diffusion behaviour of proteases in wool fibres, the soluble polymer PEG was covalently attached to a protease from Bacillus lentus. Modified enzymes with different molecular weights were compared. These modified enzymes retained up to 80% of their activity in the standard assay while hydrolysis of wool fibres was successfully restricted to cuticles, resulting in a 90% decrease in weight losses compared to non-modified enzymes.

Partial Release of Covalently Bound 18-Methyleicosanoic Acid from Wool Cuticle with Primary Alcohols

The stability of the bond of 18-methyleicosanoic acid (18-MEA) from untreated and chlorinated wool towards transesterification by alcohols was investigated. The extraction of untreated wool top with methanol not only dissolves the readily solvent-extractable lipids, but also the methyl esters of palmitic acid and 18-MEA from the cuticle proteolipids. About 10% of the total amount of 18-MEA is released by a 100 h Soxhlet-extraction with methanol from untreated top. With methanol replaced by ethanol, the ethyl esters of 18-MEA were detected. Transesterification of the 18-MEA proteolipids with the secondary alcohol 2-propanol was not observed. The treatment of wool with formic acid resulted in the removal of the soluble cell membrane lipids from the fibre but not in the release of 18-MEA. However, the removal of cell membrane compounds by solvents was shown to increase the accessibility of the 18-MEA-proteolipid regions for transesterification, and the influence of industrial chlorination is even more pronounced. These findings support the view that a significant part of the 18-MEA is bound to membrane domains of cuticular membrane proteins. The major portion of 18-MEA-containing proteolipids, however, is localized in areas of the fibre which are not accessible after modification of the cell membrane complex with solvents or by industrial chlorination.

The analysis of Merino wool cuticle and cortical cells by Fourier transform Raman spectroscopy.

Wool fibers are comprised of proteins known as alpha-keratins and have a complex morphological structure. The major components of this structure, the cuticle and cortical cells, differ in the conformations of their chains as well as their amino acid compositions. High quality Fourier transform Raman spectra of cortical and cuticle cells isolated from fine Merino wool fibers have been obtained. Raman spectroscopy has been shown to be sensitive to the differences in both secondary structure and amino acid composition. The cortical cells were found to be higher in alpha-helical content as compared to the cuticle cells, which had an increased disordered content. Specific information, consistent with amino acid analysis results, regarding cystine, tyrosine, tryptophan, and phenylalnine residues, were obtained for both the cortical and cuticle cells. In addition, the Raman spectra provided information about free thiol groups, amino acids residues with amide group side chains, and residues with protonated carboxyl group side chains. Middle ir transmission spectra of these isolated cells were also obtained. In comparison to the Raman data, the middle ir spectra were found to be not as rich in information.

A Bam HI polymorphism in ovine wool cuticle keratin sequences

A Bam HI polymorphism in ovine wool cuticle keratin sequences

Examination of Proteins from Wool Cuticle by Two-Dimensional Gel Electrophoresis

Examination of Proteins from Wool Cuticle by Two-Dimensional Gel Electrophoresis

Membrane from wool cuticle cells

Membrane from wool cuticle cells

5] Complete enzymatic hydrolysis of wool and its morphological components

Publisher Summary Enzymatic hydrolysis helps in assessment of the nutritional value of proteins in food science, the gentle and limited alteration of cells and cellular organelles in cell biology, to the chemical analysis of protein structure in biochemistry. Complete enzymatic hydrolysis of proteins allows quantitative recovery of amino acids that are unstable in acid or alkali, both primary amino acids and many of the co– and posttranslationally modified secondary amino acids. This chapter deals with the enzymatic hydrolysis of wool, wool cuticle, and its morphological subunits with respect to the distribution of diagnostic components in the fiber. Since, wool is subjected to drastic chemical treatments during industrial processing, therefore in some cases specific degradation of definite morphological components, such as exocuticle and nonkeratinous proteins is also observed. Keratins and nonkeratinous proteins have been defined on the basis of relative resistance to digestion by proteolytic enzymes and results from microscopic studies. The procedure for complete enzymatic hydrolysis of keratins is improved for application to wool keratins. Diagnostic components can be quantitated, permitting a correlation between morphological and chemical changes in the fiber to be made.

Observations by Light and Electron Microscopy on Wool Cuticle Fractions Obtained by Ultrasonics

The “cuticle material” produced by the action of ultrasonic vibrations on wool fibers has been examined by microscopic techniques. It was found that despite prior laboratory cleaning of virgin wool with solvents the contamination of the wool fiber surface by dust particles, keratinized flakes derived from the skin epidermis, and bacteria was extremely high. Ultrasonic treatments in aqueous solution remove most of these contaminants but are insufficient for releasing much cuticle material. The study has indicated that stringent measures must be taken to remove contaminating particles from the fiber surface prior to ultrasonic release of cuticle material for chemical study. Although an anionic detergent was tested and found to remove most contaminants, a cleaning procedure has not been devised which could be regarded as completely effective.