Ionic liquids as novel solvents for the dissolution and blending of wool keratin fibers

Influence of different crosslinking treatments on the physical properties of collagen membranes.

Biophysics and Biochemistry at Low Temperatures

Advances in Composite Materials-analysis of Natural and Man-made Materials

Several thermophilic anaerobic bacteria with keratinolytic activity growing at temperatures between 50°C and 90°C were isolated from samples collected on the island of Sao Miguel in the Azores (Portugal) On the basis of morphological, physiological, and 16S rDNA studies, the isolate 2KXI was identified as a new species of the genus Thermoanaerobacter, designated Thermoanaerobacter keratinophilus This strain, which grows optimally at 70°C, pH 70, and 05% NaCl, is the first member of the genus Thermoanaerobacter that has been described for its ability to degrade native keratin Around 70% of native wool was solubilized after 10 days of incubation under anaerobic conditions The strain was shown to possess intracellular and extracellular proteases optimally active at 60°C, pH 70, and 85°C, pH 80, respectively Keratin hydrolysis was demonstrated in vitro using a sodium dodecyl sulfate gel containing feather meal The extracellular protease responsible for breaking down keratin fibers was purified to homogeneity in only one step by applying hydroxyapatite column chromatography The enzyme belongs to the serine-type proteases and has a molecular mass of 135 kDa

Isolation of Thermoanaerobacter keratinophilus sp. nov., a novel thermophilic, anaerobic bacterium with keratinolytic activity.

Graft copolymerization of vinyl monomers, mainly methyl methacrylate, in reduced, successively alkylated, or KCN-Treated wool fibers was performed in the redox LiBr–persulfate system without homopolymer. The reduction gives a striking effect in promoting the graft copolymerization. Methylation or ethylene recrosslinking of the reduced wool, especially the former, decreases the graft-on remarkably. By the KCN treatment in which the conversion of disulfide to lanthionine bonds occurs, the grafting is decreased in the bromide–persulfate system but promoted in the system with persulfate alone. Methylation or KCN treatment of wool as well as reduction brings about a great increase in the absorption of persulfate. The grafting of the lanthionine-containing wool in the redox system accompanied by the liberation of bromine might be retarded by the pronounced bromination of monomers over the inhibiting of homopolymerization, because the lanthionine bonds are more stable to bromine than the disulfide bonds. In general, disulfide bonds and the other easily oxidized components of wool may perhaps play an important role in regulating the bromination of monomers and in the graft copolymerization without homopolymer. The molecular weight of graft polymer is decreased distinctly with increasing extent of reduction of wool. From these results, the thiol groups on wool are considered to give predominantly graft centers by the radicalotropy from SO4, OH·, and/or Br·.

Graft copolymerization of vinyl monomers in wool fibers

When a small amount of persulfate is dissolved in a relatively concentrated aqueous solution of bromide salts, especially LiBr, liberation of Br2 occurs to some extent. This system was utilized for the graft copolymerization of various acrylates in wool fibers using diethylene glycol monobutylether as monomer-solubilizer. The grafting was fairly well performed at a relatively low temperature (10–40°C.) and without homopolymerization while liberating Br2. This new graft copolymerization has been attributed to the concerted action of the fiber-swelling power of bromide salts, the following redox system, and the mild bromination of some monomers by which the grafting will proceed without homopolymerization.

New method for graft polymerization of vinyl monomers in wool fibers

In order to elucidate the termination mechanism in the graft copolymerization of methyl methacrylate to unreduced and reduced wool fibers, graft copolymers were prepared by means of the LiBr–K2S2O8 redox sytem without homopolymer or with K2S2O8 only with homopolymer at 30°C. The graft polymers (PMMA) were isolated almost completely from the wool trunk by an HCI-digestion method, leaving a few amino acid residues on the end of the graft polymers. Dinitrophenylation of the isolated polymer was carried out by various methods. The spectral features were almost the same as for dinitrophenylated amino acids of the usual type such as valine, leucine, and methionine, with a maximum in ultraviolet light at 340–345 mμ. From colorimetric analysis of the number of dinitrophenylated amino acid endgroups and the measurement of the average molecular weight of the isolated polymers, the number of amino acid endgroups linked to the graft polymers was calculated to be about one and two per polymer chain in reduced and unreduced wool, respectively, independent of the reaction system, graft-on, and molecular weight of graft polymers. From these facts, it was suggested that the most of isolated polymers are the truly grafted polymers. Also, the termination reactions have been explained as follows. In the unreduced wool, the restriction of mobility of the radical end might be expected, for the confinement of growing chains in wool fibers. This would be favorable to termination by recombination rather than by the disproportionation, since the former has a lower activation energy than the latter. Thus, the formation of intra- or intermolecular crosslinks might be considered between polypeptide chains. On the other hand, in the reduced wool, the mobility of graft polymers might be considered to be greater than that of unreduced wool because of its open structure. Therefore, termination would be principally by disproportionation between graft polymer radicals.

Endgroup analysis of isolated poly(methyl methacrylate) from graft copolymers of wool.

Crosslinked structures of the permanent set wool fiber treated with boiling water at a 40% extension state and the control fiber were studied by analyzing the rubberlike force-extension curve of the swollen fiber in a mixed solution composed of equal volumes of 8M LiBr and butyl carbitol. The thiol and disulfide contents of set fibers were also determined. It was found that (1) the disulfide (SS) bonds in low-sulfur (LS) microfibril protein transform into new crosslinkages in boiling water, but the SS bonds in high-sulfur matrix protein remain intact, (2) the SS bonds in α-helical segments becomes reactive only at the extension state of fiber and produces a free thiol group, and (3) intramolecular SS bonds may exist in the α-helical segments. Discussion was also made about the closeness of the number of crosslinkage sites of SS bonds obtained from the present rubber elasticity theory and from the theoretical analysis of the amino acid sequence of the intermediate filament. The cross-linking structure model in LS protein was proposed. It was suggested further that the setting mechanism for new crosslinkage theory seems to be unsatisfactory, since the new crosslinkages do not contribute to stabilize the extended conformation of the wool chain. © 1996 John Wiley & Sons, Inc.

Crosslinking structure of keratin. VI. Number, type, and location of disulfide crosslinkages in low-sulfur protein of wool fiber and their relation to permanent set

The HCl- or papain-decomposition residues obtained from reduced wool fibers grafted with 1.5–3.0% methyl methacrylate were extractively fractionated successively with cold acetone, hot acetone, and benzene. Each fraction was examined by infrared spectroscopy. Generally, the 715 cm−1 spectral band considered to be due to vc-s-c was found in the hot acetone-soluble fraction. It was concluded that the thiol groups on wool keratin provide the main sites of grafting, as might be expected. A similar result was obtained for grafted silk fibroin fibers, the methionine residue being presumed to be related to some of the grafting sites at least. Furthermore, a sort of stereoregularity was observed in some of the graft polymer fractions, isotactic-rich material being obtained in the case of silk fibers. In the range of very low grafting, a stereoregulating effect on the structure of the polymer formed within fibers appears to be present in relation to the grafting or adsorption sites of monomers and the fine structure of fibers.

Infrared spectroscopy of graft polymers separated from graft copolymers of wool and silk with methyl methacrylate

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