Silk, water-soluble

Films or membranes of silkworm silk have been produced by air-drying aqueous solutions prepared from the concentrated salts, followed by dialysis (11,28). The films, which are water soluble, generally contain silk in the silk I conformation with a significant content of random coil. Many different treatments have been used to modify these films to decrease their water solubiUty by converting silk I to silk II in a process found usehil for enzyme entrapment (28). Silk membranes have also been cast from fibroin solutions and characterized for permeation properties. Oxygen and water vapor transmission rates were dependent on the exposure conditions to methanol to faciUtate the conversion to silk II (29). Thin monolayer films have been formed from solubilized silkworm silk using Langmuir techniques to faciUtate stmctural characterization of the protein (30). ResolubiLized silkworm cocoon silk has been spun into fibers (31), as have recombinant silkworm silks (32). 

The alkaline solutions can remove water-soluble polymers in the spinning mix and inert products such as titanium dioxide. Basic treatments can also hydroly2e a certain amount of the polyester itself. For some silk-like appHcations or for producing fine denier fabrics, this basic treatment can produce a 10—30% weight loss of polyester (190,196). Certain polyesters such as anionically modified polyester can undergo more rapid weight loss than regular polyester (189). 

A series of water-soluble fiber-reactive xanthene dyes has been prepared from the reaction of benzoxanthenedicarboxylic acid anhydride disulfonic acid with, for example, 3-aminophenyl- 3-hydroxyethyl sulfone to yield dyes, with high brilliance and good fastness properties for dyeing of or printing on leather, wool, silk, or cellulosic fibers (53). 

Cationic (Basic) Dyes. These water-soluble cationic dyes are applied to paper, polyacrylonitrile (e g. Dralon), modified nylons, and modified polyesters. Their original use was for silk, wool, and tannin-mordanted cotton when brightness of shade was more important than fastness to light and washing. Basic dyes are water-soluble and yield colored cations in solution. For this reason they are frequently referred to as cationic dyes. The principal chemical classes are diazahemi-cyanine, triarylmethane, cyanine, hemicyanine, thiazine, oxazine, and acridine. Some basic dyes show biological activity and are used in medicine as antiseptics. 

Acid Dyes. These water-soluble anionic dyes are applied to nylon, wool, silk, and modified acrylics. They are also used to some extent for paper, leather, ink-jet printing, food, and cosmetics. 

The B. mori silk fiber is made up of two kinds of protein. One is called sericin, a water-soluble protein responsible for the gum-like, sticky coating covering the fiber, and the other is referred to as fibroin, the core filament of silk. The inner part of silk fiber is composed of two monofilaments called brins (Figure la) (Poza et al., 2002 Shao and Vollrath, 2002). 

Textiles Acid dyes are characterized by the presence of one or more water soluble anionic groups which is typically a sulphonic acid. These dyes are applied to nitrogenous materials such as wool, silk, nylon or modified acrylics. They are not fast to cotton. 

Different proteins have different physical properties. Some—such as casein in milk, ovalbumin in egg whites, and hemoglobin in blood—are water-soluble. Others—such as keratin in hair, fibroin in spider silk, and collagen in connective tissue—are flexible solids. 

Many commercial dyes contain one or more sulfonic acid groups to confer water solubility to the dye and assist in binding the dye to the polar fibres in the textile (cotton, nylon, silk, wool, etc.). An example is Congo Red (12) (Figure 3). This is red in alkaline solution thus, the sodium salt will dye cotton red, but it is very sensitive to acids and on acidification the colour changes from red to blue, and so this compound is also used as a type of indicator. Vat dyes, known as sulfur dyes, can be prepared by heating various organic compounds, e.g. amines, aminophenols, and nitrophenols, with sodium polysulfide. 

Many dyes used in the clothing industry contain sulfonic acid groups which impart water solubility and help to make the dye become fast to the fabric. The dye becomes fast by attaching itself to polar sites in the fibres of, for instance, cotton, wool or silk. Many azo dyes, like Congo Red (see Introduction, p. 5), contain one or more sulfonic acid groups. Another example is Orange II (7), synthesised by coupling p-naphthol (8) with diazotised sulfanilic acid (9) (Scheme 2). 

Biological Degradation. Microbial (enzymatic) attack can occur on silk, but it is the water-soluble sericin, that is the more readily depolymerised. 

Beilstein Handbook Reference) acid eosin BRN 0063410 Bromeosin Bromoeosin C.l. 45380 2 C.l. Solvent Red 43 CCRIS 4904 Cl 45380 2 D C Red no. 21 D and C Red No. 21 D C Red No. 21 2-(3,6-Dihydroxy-2,4,5,7-tetrabromoxanthen-9-yl)-benzoic acid 3,6-Dihydroxy-2,4,5,7-tetrabromospiro-(xanthene-9,3 -phthalide) EINECS 239-138-3 Eosin Eosin A Eosin acid Eosin 3J Eosin 4J extra Eosin A extra Eosin B Eosin C Eosin DH Eosin G Eosin G Extra Eosin GGF Eosin JJS Eosin KS Eosin yellowish Eosin Y spirit soluble Eosine acid Fluorescein, 2, 4, 5 ,7 -tetrabromo- Japan Red 223 Japan Red No. 223 NSC 244436 Red No. 223 Solvent Red 43 Spira(isobenzofuran-1(3H),9 -(9H)-xanthen)-3-one, 2, 4, 5, 7 -tetrabromo-3 ,6 -di-hydroxy- Water soluble eosin. The alkali salts of tetrabromo-fluoresceine, dyes wool and silk yellowish red used as a microscopic stain and a fluorescent tracer dye red writing ink cosmetic products and a colorant for motor fuel. Red solid. 

PHYSICAL PROPERTIES Properties vary depending upon the specific soluble thallium compound, (thallium acetate) silk-white crystals or hygroscopic, colorless monoclinic crystals from ethanol soluble in water and alcohol MP (131°C, 268°F) DN (3.68 g/cm ). (thallium iodide) yellow, crystalline powder metallic at high pressures becomes gray on exposure to light becomes red at 170°C (338°F) almost insoluble in water soluble in potassium iodide solution and aqua regia insoluble in alcohol MP (440°C, 824°F) BP (824°C, 1515°F) DN (7.09 g/cm") SG (7.1) HV (104.7 kJ/mol at 1097K) VD (NA) VP (unknown). 

Two other papers from this laboratory should also be mentioned. Ambrose, Elliott, and Temple (1951) have studied the infrared spectrum of a single crystal of diketopeperazine and obtained excellent confirmation of the structure worked out by Corey (1938) for this molecule by X-ray methods. Of particular interest is the conclusion that the three bonds of the nitrogen atom are coplanar in this molecule. The other publication (Ambrose, Bamford, Elliott, and Hanby, 1951) concerns the spectra of silk rendered soluble in water by treatment in a concentrated solution of lithium bromide. The soluble silk appears to be in the a (folded) configuration and becomes insoluble when it (or part of it) goes over to the 3 (extended) configuration. 

Goldrecovery is proposed using animal fibrous proteins such as egg shell membrane, chicken feathers, wool, silk, elastin, and other stable water soluble fibers with high surface area. 

Luteolln (3, 4, 5,7-tetrahydroxyflavone C. I. 75590, natural yellow 2). Formula see flavones. CisHioO, Mr 286.23, fine yellow crystals with silk-like luster, mp. 329 °C (decomp.), poorly soluble in water, soluble in alkalis to give deep yellow solutions. The bitter-tasting L. has anticonvulsant activity. L. occurs in leaves, flowers, and stems of dyer s weld Reseda luteola), in the flowers of the yellow foxglove (Digitalis lutea thus also the name digitoflavone for L.), and in other... 

Elliott and Bradbury (1962) disagreed with some of the deductions made by Krimm (1962) from spectra published by their laboratory. For instance, the enhanced intensity at 1520 cm in the spectrum of water-soluble silk, to which he referred and attributed to a random coil form, could be seen in their spectra only when the water-soluble silk had been altered by treatment which produces the j8-form (Ambrose et ai, 1951). In the spectrum of lithium bromide soluble silk (where there was no ) -band... 

The amide I band has been examined by Elliott et al. (1950) in native and denatured insulin, by Elliott et al. (1957) in lysozyme, and by Ambrose et al. (1951) in water-soluble silk. The band at 3200 cm" has also been investigated. Beer et al. (1959) have given a comprehensive list of proteins studied up to 1959, along with characteristic absorption bands. Bamford et al. (1956) have reviewed work done up to 1956 in the region between 5000 and 4500 cm (combination band of the N—H stretching frequency and that of the amide I or amide II band). The infrared dichroic properties of crystals of hemoglobin and ribonuclease have been observed in this region (Elliott and Ambrose, 1951 Elliott, 1952). 

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