Proteins leather

Albumen has the largest number of acid and basic groups. It is the most soluble of the proteins present in a hide. The albumen is not a fibrous material, however, and therefore has no value in the leather. Keratin is the protein of the hair and the outermost surface of the hide. Unless the hair is desired for the final product it is removed by chemical and/or physical means. The elastin has Htde acid- or base-binding capacity and is the least soluble of the proteins present. The lack of reactivity of the elastin is a detriment for most leather manufacture. The presence of elastin in the leather greatly limits the softness of the leather. 

The differences in the amino acid chemistry of the hide coUagen and the hair keratin are the basis of the lime-sulfide unhairing system. Hair contains the amino acid cystine. This sulfur-containing amino acid cross-links the polypeptide chains of mature hair proteins. In modem production of bovine leathers the quantity of sulfide, as Na2S or NaSH, is normally 2—4% based on the weight of the hides. The lime is essentially an unhmited supply of alkah buffered to pH 12—12.5. The sulfide breaks the polypeptide S—S cross-links by reduction. Unhairing without sulfide may take several days or weeks. The keratin can be easily hydrolyzed once there is a breakdown in the hair fiber stmcture and the hair can be removed mechanically. The coUagen hydrolysis is not affected by the presence of the sulfides (1—4,7). 

The mechanism of the tarmage is accepted to be largely one of replacement of the bound water molecules by the phenoHc groups of the tannin and subsequent formation of hydrogen bonds with the peptide bonds of the protein. The effect of this bonding is to make the leather almost completely biorefractive. 

OxazoHdines, formed by reaction of alkanolamines with aldehydes, ate useful as leather tanning agents and ate effective curing agents for proteins, phenoHc resins, moisture-cure urethanes, etc. They also find use as antimicrobial agents. 

Many enzymes have been the subject of protein engineering studies, including several that are important in medicine and industry, eg, lysozyme, trypsin, and cytochrome P450. SubtiHsin, a bacterial serine protease used in detergents, foods, and the manufacture of leather goods, has been particularly well studied (68). This emphasis is in part owing to the wealth of stmctural and mechanistic information that is available for this enzyme. 

Acylated Protein Hydrolysates. These surfactants are prepared by acylation of proteia hydrolysates with fatty acids or acid chlorides. The hydrolysates are variable ia composition, depending on the degree of hydrolysis. CoUagen from leather (qv) processiag is a common proteia source. Acylated proteia hydrolysates (Maypoa, by laotex Chemical Company) are mild surfactants recommended for personal-care products (see Cosmetics). 

Leather Tanning and Textiles. Although chromium (VT) compounds are the most important commercially, the bulk of the appHcations in the textile and tanning industries depend on the abiUty of Cr(III) to form stable complexes with proteins, ceUulosic materials, dyestuffs, and various synthetic polymers. The chemistry is complex and not well understood in many cases, but a common denominator is the coordinating abiUty of chromium (ITT) (see LEATHER Textiles). 

Formaldehyde has been rated as a possible carcinogen by the United States Occupational Safety and Health Act (OSHA) rules and should be handled with due caution. It is also a strong lacrymator and choking respiratory irritant. It irritates the skin, eyes, and mucous membranes [76]. Since it is used for tanning leather, it is obvious that fonnaldehyde has a high potential for reactions with proteins. Formaldehyde gas is flammable and most formalin solutions contain significant amounts of methanol, which is also volatile, toxic, and flammable. 

Proteins, Nitrated. Proteinaceous or albuminoid materials (glue, bones, hides, leather, hair, feathers, etc) can be nitrated in a two-stage process to yield expl yel oils. Thus, glue is treated first with 3.6 pts by wt of 66°Be sulfuric acid and 2.7 pts of 36°Be nitric acid. The resultant oil is sepd from the heavier spent acid and nitrated further with 3 pts of oleum and 2.6 pts of 36°BS nitric acid. Both nitrations are conducted at 15—20°, and never above 40°. The resulting oily expl can be used alone or mixed with other materials... 

Chromium is also important in converting animal hides into leather. In the tanning process, hides are treated with basic solutions of Cr(HI) salts, which causes cross-linking of collagen proteins. The hides toughen and become pliable and resistant to biological decay. 

Leather is the material made from animal skin by the process of tanning, which entails chemically altering the composition of the skin so as to make it durable and resistant to decay. Leather is therefore not a protein but a protein derivative. Although the tanning process alters the composition of skin, leather retains the fibrous structure and utilitarian functionality that make skin suitable for multifarious applications. Shelter, clothing, and decorative objects made from leather are, unlike skin or hide, stable to physical, chemical, and biological decay under dry or wet conditions (O Flaherty et al. 1965 ... 

All the tannins readily react with proteins, forming insoluble, stable compounds when they react with collagen, the main constituent of animal skin, they form leather, a material that is resistant to hydrolysis, oxidation, and biological attack and therefore stable to weathering and resistant to decomposition. Since tannins from different plant sources have different chemical compositions, each tannin used for tanning skin produces a leather having slightly different properties and color. Tannins that have... 

The first acid dye, Orange I (1.53 Cl Acid Orange 20), was discovered in 1876. All but a handful of the acid dyes developed since then were evaluated initially with wool dyeing in mind. In terms of adaptability to the coloration of other substrates, however, acid dyes have proved pre-eminent. This is the main reason for their number and variety. As well as the dyeing and printing of nylon and protein fibres, acid dyes are important for the coloration of leather, paper, jute, wood and anodised aluminium. Most of the permitted dyes for food and... 

We know that cellulose (chief component of the cell walls of a plant), proteins essential constituents of living cells, rubber, leather and natural fibres like silk, wool, etc. are all polymers and these are known as natural polymers. 

In the development of the protein-fatty acid condensates it was possible to combine the renewable resources fatty acids (from vegetable oil) and protein, which can be obtained from both animal waste (leather) as well as from many plants, to construct a surfactant structure with a hydrophobic (fatty acid) and a hydrophilic (protein) part (Fig. 4.12). This was carried out by reacting protein hydrolysate with fatty acid chloride under Schotten-Baumann conditions using water as solvent. Products are obtained that have an excellent skin compatibility and, additionally, a good cleaning effect (particularly on the skin) and, in combination with other surfactants, lead to an increase in performance. For instance, even small additions of the acylated protein hydrolysate improve the skin compatibility. An... 

Wool, leather, and silk are natural materials that are made of proteins. Your fingernails, hair, and skin are composed of different proteins. Proteins carry out many important functions in your body, such as speeding up chemical reactions (enzymes), transporting oxygen in your Wood (hemoglobin), and regulating your body responses (hormones). 

Uses. As broad-spectrum antimicrobial cold sterilant/disinfectant for hospital equipment as tanning agent for leather as tissue fixative as cross-linking agent for proteins as preservative in cosmetics as therapeutic agent for warts, hyperhidrosis, and dermal mycotic infections in X ray processing solutions and film emulsion as a disinfectant in the beauty industry... 

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