Resistance of Keratin to Pronase

The effect of the cooling rate on freezing of a wool-water system is studied using Dsc at cooling rates (CR) that vary from 1.25 to 40 K/min. By means of centrifugation, an equilibrium quantity of interstitial water in the fibers ( Ws) is determined to be 0.48 g/g of wool. Two samples with different water contents are used: sample A is more than Ws, i.e., Wc = 0.54, and sample B is 0.43 g/g of wool. Characteristic shape changes in a broad exotherm ranging from temperatures of about 230 to 260 K are observed in DSC curves. A freezing mechanism of interstitial water is proposed on the basis of supercooling. The swollen wool is assumed to be a dispersion system consisting of domains defined as structurally favored sites, permitting water migration for ice crystal growth. The shape change with CR can be explained by differences in the freezing temperature of water of different volumes in the domains. Kissinger's equation is applicable to this crystallization process. Values of activation energy for both A and B samples are nearly the same, about -115 kJ/mol. Activation energy is considered to be the sum of the two terms for crystallization and migration of water, and the latter value is presumed to be about 49 kJ/mol. The important finding is that ice crystals in sample A cooled at 1.25 K/min contain an amount of water corresponding to about 38.2% of the so-called "nonfreezing water" Wu, which remains unfrozen at a CR above 5 K/min.

Section: Location Of Interstitial Water 'mentioning

confidence: 99%

Effect of Cooling Rate on Freezing of Wool-Water Mixtures

Takahashi

Mitomo

Arai

et al. 2003

“…These proteins are considered to originate from the endocuticle, the nuclear remnants, the intermacrofibrillar materials, and the intercellular cement of the cell membrane complex [9,27,36]. In order to obtain a wool sample with no nonkeratinous proteins, the wool fibers were treated with pronase.…”

Section: Proteinsmentioning

confidence: 99%

States of Water Sorbed on Wool as Studied by Differential Scanning Calorimetry

Sakabe

Ito

Miyamoto

et al. 1987

The states of water sorbed on Merino wool fibers, their histological components, and chemically modified wool fibers were investigated by differential scanning calorimetry (DSC) in order to elucidate the amount of bound water on wool fibers, the differences between the histological components of wool fibers, and the effect of polar groups on the states of water sorbed on wool fibers. For the sake of comparison, the states of water sorbed on cotton and silk were also examined. There may exist three different kinds of water sorbed on wool fibers, i.e., free water, freezing bound water, and nonfreezing bound water. The amount of bound water on wool fibers is larger than that on cotton yam and silk. The amount of bound water on cortical cells is about two times higher than that on cuticular cells. The amount of bound water on nonkeratinous cell components is about three times higher than that on keratinous cell components. The cell membrane complex plays an important role in water penetrating to wool fibers, but its contribution to the amount of bound water is negligible. The contribution of polar groups in wool fibers to the amount of bound water is not specific at high water contents, indicating that the peptide groups of the main chain play a significant role as water binding sites at high water contents.Many of excellent properties of wool as a textile fiber are more or less associated with the specific interactions of wool proteins with water. The ability to bind and absorb large amounts of water is one of the characteristics of wool fibers [ 13]. A relatively large number of .papers have examined the interaction of wool fibers with water using water vapor sorption isotherms [5, 14, 30, 32, 331 and basic calorimetric techniques [4, 20, 26]. Workers have established that part of the water sorbed on natural polymers such as keratin proteins and cellulose and silk fibroin has properties that are markedly different from free water. Many different works have substantiated this consideration [8, 10, 18; 19, 21, 22, 24, 34].On the other hand, wool consists of several histological components that are very different in chemical and physical properties [2,13,36]. It is important to elucidate the differences between these histological components and the functions of individual cell components. Numerous efforts have been devoted to this problem [2,11,12,36]. The accessibility of water molecules to individual histological components of wool has also been studied extensively from various points of view [6,7,23,27,28,29,36], but no study has reported so far on the states of water sorbed on the individual histological components of wool fibers.Recently, Nakamura et al. [22] pointed out that there are three different kinds of sorbed water on polymer: free water, freezing bound water, and nonfreezing bound water, based on the studies using differential scanning calorimetry (DSC). Recent developments in microcalorimetry by DSC enable us to evaluate the contents of free and bound water on polymers [22]. It is of interest to exam...

“…In older to clarify this discrepancy, we examined the staining behavior of the fibers treated with pronase, which is known to digest the nonkeratinous proteins in the fiber [7,24]. Figure 4 shows the staining results on pronasetreated wool fibers.…”

Section: Summary Of Prior Investigatiorimentioning

confidence: 99%

Mechanism of Bilateral Staining of Merino Wool Fibers with Basic Dyes

Sakabe

Ito

Miyamoto

et al. 1986

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...