Oxidation of Human Hair

Wolfram and co-workers [12, 60] have studied the oxidation of human hair with and without pigment. They have also studied the oxidation of... 

In spite of the importance of bleaches in oxidation dyeing, very few technical improvements apart from formulation aspects have occurred recently in this field. The selective adsorption of metal ions [21], especially of iron(n) salts [22], on melanin has been proposed for gentler bleaching of human hair. This process has achieved no more acceptance than the use of peroxocarboxylic acids or their precursors, which are important as bleaching intensifiers in textile bleaching. 

Brenner, L., Squires, P. L., Garry M., and Tumosa, C. S. (1985). A measurement of human hair oxidation by Fourier transform infrared spectroscopy /. Forensic Sci. 30, 420-426. 

As a consequence of their tendency to form lamellar phases or rod shaped micelles at low concentration, cationic surfactants are frequently employed as the primary surfactants to thicken high salt formulas [72,73]. The viscoelastic nature of certain cationic surfactant solutions has been employed in a novel way to allow for a solution of sodium hypochlorite not to be easily diluted and therefore to remain at a higher concentration for the purpose of oxidizing clogs of human hair which form in drains [73 ]. Low concentrations of cetyl trimethyl ammonium chloride in combination with two hydro tropes form viscoelastic solutions with the values of viscosity and Tau/Go shown in Table 6.6. 

Matusiewicz, H., Suszka, A., Ciszewski, A. Efficiency of wet oxidation with pressurized sample digestion for trace analysis of human hair material. Acta Chim. Hung. 128, 849-859 (1991)... 

Alpha keratin is found in sheep wool. The springy nature of wool is based on its composition of alpha helices that are coiled around and cross-linked to each other through cystine residues. Chemical reduction of the cystine in keratin to form cysteines breaks the cross-links. Subsequent oxidation of the cysteines allows new cross-links to form. This simple chemical reaction sequence is used in beauty shops and home permanent products to restructure the curl of human hair—the reducing agent accounts for the characteristic odor of these products. Beta keratin is found in bird feathers and human fingernails. The more brittle, flat structure of these body parts is determined by beta keratin being composed of beta sheets almost exclusively. 

Menkes syndrome is a genetic disorder of kinked hair in which the sul-phydryl groups of human hair are only partly converted to disulfide bonds (about 50% oxidized). Mercer [135] suggested that this disease is linked to a copper deficiency caused by a mutation in a protein involved in copper transport. 

In spite of the fact that research on permanent waving has decreased over the past several decades, significant findings have been made within the past 10 years. For example, Wortmann and Kure [1,2] have developed a model and recently extended it to show that the bending stiffness of reduced and oxidized fibers controls the permanent waving behavior of human hair and that the cuticle plays a role in permanent waving. Further, they have shown not only that the cuticle functions as a barrier to reduction but also that its stiffness may contribute to fiber set. 

The objectives of this chapter are to describe bleach product compositions and their formulation and to review the chemistry of both chemical and photochemical bleaching (i.e., the oxidative degradation of hair pigments and the accompanying oxidative degradation of the proteins of human hair) and to describe the chemical nature of bleached hair. 

Reactions of the Proteins of Human Hair with Bleaches Chemical Oxidation of the Disulfide Bond... 

Since the bleaching of human hair is carried out in an aqueous alkaline oxidizing medium, hydrolysis of the cystine oxide intermediates (Figure... 

To summarize, sulfonic acid is the principal established end product of the oxidative cleavage of the disulhde bond from the chemical bleaching of human hair with current hair bleach products [3,9]. The mercaptan content of bleached hair is lower than that of unbleached hair [4], The intermediate oxidation products of cystine (i.e., the disulhde monoxide, dioxide, trioxide, and tetroxide) do not exist as signihcant end products of hair bleaching using today s commercial bleach products [3,6,9]. Nevertheless, evidence has been presented demonstrating low levels of cystine oxides in bleached hair [2],... 

In step 4, p-phenylenediamine adds to the indophenol in a 1,4 manner [25, 33], producing the trinuclear species (XXVIII), which is then oxidized to the trinuclear green pigment (XXI). Several routes exist for formation of polymeric indophenols, and all are analogous to steps 4 and 5. Repetition of these steps will result in the formation of higher polymers. Because most oxidation dyes contain both p-phenylenediamine and resorcinol, the formation of these tri- and polynuclear pigments is important in the oxidative dyeing of human hair. 

More recently, Robbins and Crawford [8] provided additional evidence that the cortex and not the cuticle is responsible for the tensile properties of human hair and that severe damage can occur in the cuticle that cannot be detected by tensile property evaluation. This work involved selective oxidation of the cuticle with m-diperisophthalic acid. This treatment produces extensive cuticular damage that is detectable microscopically, but this damage could not be detected by either wet or dry tensile property evaluation. These results are consistent with the fact that wet extension of hair fibers to 30% can damage the cuticle [9] yet on relaxation in water, tensile recovery occurs producing virtually identical elongation-recovery curves in a before and after type of evaluation. This basic procedure is commonly used throughout the industry. 

Oxidative bleaching of human hair on live heads provides similar results for the tensile properties. Robbins examined both the wet and dry tensile properties of frosted and nonfrosted hair fibers from the same person (Table 8-3). Except for the resilience ratio, the loss in dry tensile proper-... 

The oxidative polymerization of 5,6-dihydroxyindole (1) and related tyrosine-derived metabolites is a central, most elusive process in the biosynthesis of eumelanins, which are the characteristic pigments responsible for the dark color of human skin, hair, and eyes. Despite the intense experimental research for more than a century,36 the eumelanin structure remains uncharacterized because of the lack of defined physicochemical properties and the low solubility, which often prevents successful investigations by modem spectroscopic techniques. The starting step of the oxidative process is a one-electron oxidation of 5,6-dihydroxyindole generating the semiquinone 1-SQ (Scheme 2.7). 

The lack of zinc can also be a problem in biological systems and is responsible for disease states. For example, nitric oxide-dependent apoptosis can be induced in motor neurons by zinc-deficient SOD, and in some cases of amyotrophic lateral sclerosis, zinc-deficient SOD may participate in this type of oxidative mechanism involving nitric oxide.969 One form of hereditary human hair loss or alopecia was mapped to a specific gene and a mutation found in affected individuals. The gene encodes a single zinc finger transcription factor protein with restricted expression in the brain and skin.970 Zinc has been implicated in Alzheimer s via beta amyloid formation, and a role has been attributed for the cerebral zinc metabolism in the neuropathogenesis of Alzheimer s disease.971... 

The use of primary intermediates as sole dye precursors severely limits the range of shades some couplers are therefore sometimes added. They do not themselves develop a significant color effect as such but if present in primary intermediates they modify the resulting colors. The usual couplers are 1,3-diami-nobenzene (blue), 3-aminophenols (red), and resorcinol (yellow-green). This technique is mostly used for human hair (see Section 5.4.2), the oxidation steps being performed at around pH 9.5 with hydrogen peroxide. 

Bleaching of natural hair color can be done as a single cosmetic application but is also part of oxidative hair coloring. Bleaching, blonding, and lightening of human... 

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