Microscopic Studies on the Structure and Composition of Keratin Fibers1

The mechanism of bilateral staining of the cortex of wool fibers by basic dyes has been investigated in detail. Merino wool fibers were treated with formic acid and pronase, and their behavior in staining with basic dyes such as methylene blue and janus green was examined using light and electron microscopy. Formic acid is known to remove intercellular cement, one of the nonkeratinous proteins, from the cell membrane complex, while pronase removes all nonkeratinous proteins. Bilateral staining was still distinctly observed after cuticle removal, but not for wool fibers treated with pronase, for fiber fragments obtained by treatment with formic acid with stirring, or for cortical cell particles recovered after fibrillation of the cortex in formic acid. The microfibril-matrix structure of the cortex remained unchanged, however, even after treatment with formic acid and with pronase. These results imply that bilateral staining with basic dyes occurs because of the difference in the network structure of nonkeratinous proteins, especially the intercellular cement of the cell membrane complex between the orthocortex and paracortex.The cortex of fine wool fibers consists of two major segments, the orthocortex and the paracortex, and the bilateral arrangement of these two cortices is closely associated with the crimped structure of wool fibers [2,3,12]. Since its discovery by Horio and Kondo [9] and Mercer [ 18], many researchers have studied the differences in the responses of each component of the bilateral cortex to various dyes and metal ions [2]. These differences have been interpreted in terms of differences in the fine structure or the reactivity between orthocortex and paracortex [2,4,9,10,14,18,19,21 ]. There are several possible differences between the two cortices, however, and their behavior in staining is different with ,dyes and metal ions [2]. The detailed mechanism of bilateral staining of the cortex is still open for discussion to some extent. The pioneer works by Horio et al. [9,10] were done with ionic dyes. The staining mechanism with dyes is relatively simple compared to that with metal ions, which is specific to individual ions. A possible interpretation is that the content of charged groups is different for the orthocortex and paracortex. Wool fibers are composed of a number of ceU components, however, and the accessibility of dye molecules to the charged groups is different for different cell components. There is insufficient experimental evidence to explain why large dye molecules can produce a remarkable contrast in staining between the two cortical components.In a previous paper [ 11 ], we reported on the amino acid composition of the isolated orthocortical and paracortical cells. The results showed that there is little difference in the relative content of the charged groups except for cystine. During the course of this study, we also found that bilateral staining does not occur alter fibrillation of the cortex. These results suggest that the nonkeratinous materials [2,24], which may be remove...

Section: Summary Of Prior Investigatiorimentioning

confidence: 88%

Section: Summary Of Prior Investigatiorimentioning

confidence: 99%

Mechanism of Bilateral Staining of Merino Wool Fibers with Basic Dyes

Sakabe

Ito

Miyamoto

et al. 1986

“…For example, Menkart and Sokol [28] have recently described enhanced swelling of fibers following reduction. This was known to occur following oxidation [17,19,27].…”

Section: Methodsmentioning

confidence: 99%

Wool Shrinkproofing Studies

Williams

1963

Potassium perrnanganate in water confers shrink resistance on wool fabric, the degree of initial shrink resistance increasing with addition of inorganic salts. On extended severe washing, fabrics treated in higher salt concentrations felt at a greater rate, once the initial period of shrink resistance has passed, than do fabrics treated in low salt concentrations. On the basis of these observations a theory of felting shrinkage is proposed which defines felting behavior of treated wool in terms of cuticle and cortex modification. Cortex modification need only be in the outer layers.Shrink resistance conferred by cuticle modification is characterized by an initial period during which no felting shrinkage takes place, followed by felting at a rate similar to that of untreated wool. Permanganate in saturated salt is an example of such a cuticle treatment.Shrink resistance conferred by outer cortex modification is not achieved by a shrink resist induction period, but by a reduced rate of felting shrinkage. Examples of shrinkproofing treatments resulting in outer cortex modification are: permanganate in water; dry, acid, and alkaline chlorinations; and the additional shrink resistance, following permanganate oxidation, conferred by residue times in bisulfite beyond that necessary to clear manganese dioxide.In permanganate treatments followed by reductive clearing, the major portion of shrink resistance is imparted during the oxidation stage for treatments in saturated salt, and during the clearing stage for treaments in water.

“…Hence the precise component producing the detected x-rays cannot be determined. In the STEM, the very thin sections required for maximum resolution of components give very low intensities of x-rays because of the much smaller specimen volumes.The merino wool fiber consists of an inner cortex and a peripheral region known as the cuticle [3,15].The cortex can be differentiated into orthocortical and paracortical cells on the basis of the denser staining of the orthocortex by basic dyes, acid dyes, and phosphotungstic acid, and by salts of lead, mercury, silver and gold [2,5,10,12,16,21 ]. Several attempts have been made to determine the origin in the intact wool fiber of various proteins isolated as soluble extracts [3,6].…”

mentioning

confidence: 99%

“…The cortex can be differentiated into orthocortical and paracortical cells on the basis of the denser staining of the orthocortex by basic dyes, acid dyes, and phosphotungstic acid, and by salts of lead, mercury, silver and gold [2,5,10,12,16,21 ]. Several attempts have been made to determine the origin in the intact wool fiber of various proteins isolated as soluble extracts [3,6].…”

mentioning

confidence: 99%

Using Electron Microscopy and X-Ray Microanalysis to Study Wool Morphology and Composition

Carr

Holt

Drennan

1986

Energy dispersive x-ray analysis has been used in combination with scanning electron microscopy and scanning transmission electron microscopy to investigate the distribution of both cystine and tyrosine in the morphological components of wool fiber. The technique has also been used to show that the zirconium in Zirpro treated wool is deposited evenly throughout the fiber.The technique [8] of scanning electron microscopy (SEM) with an energy dispersive x-ray microanalysis system (EDS) involves irradiating a sample with a fine beam of electrons. When the electron beam impinges on the specimen, the primary electrons can be reflected or, alternatively, can produce secondary electrons or x-rays. The primary and secondary electrons produce the image of the sample, whereas the characteristic xrays can be used to determine the nature and concentration of the elements present in the specimen. In scanning transmission electron microscopy (STEM), the x-rays produced by the electron beam can be analyzed to give the same information, but the image of the specimen is formed by the transmitted electrons.In any study of biological materials using electron microscopy with EDS, a compromise has to be made with regard to specimen thickness. Infinitely thick specimens, which can be studied with the SEM, give the maximum amount of x-rays, but in a heterogeneous specimen, the distribution of components within the specimen is unresolved in the electron image. Hence the precise component producing the detected x-rays cannot be determined. In the STEM, the very thin sections required for maximum resolution of components give very low intensities of x-rays because of the much smaller specimen volumes.The merino wool fiber consists of an inner cortex and a peripheral region known as the cuticle [3,15].The cortex can be differentiated into orthocortical and paracortical cells on the basis of the denser staining of the orthocortex by basic dyes, acid dyes, and phosphotungstic acid, and by salts of lead, mercury, silver and gold [2,5,10,12,16,21 ]. Several attempts have been made to determine the origin in the intact wool fiber of various proteins isolated as soluble extracts [3,6]. These studies involve disruption of the wool fiber by ultrasonication or by repeated freeze-thawing in formic acid [ 11 ], separation of the cortical cells by centrifugation in an organic medium of appropriate density, and protein and amino acid analyses of the separated cell fractions. One possible disadvantage of this technique is that the severity of the procedures required to disrupt the wool 6ber may lead to degradation of the proteins or loss of material from the cells into the solvent.K,assenbeck et al. [ 13] have attempted to overcome these problems by using SEM and EDS to determine the sulfur distribution in intact wool fiber sections. Sulfur content was found to vary from 4.3% to 2.9% across the fiber, and the high and low sulfur regions were assigned to paracortex and orthocortex, respectively, on the basis of results obtained by other workers from stud...