Sulfuric acid Terms Links

In structural terms, djenkolic has two units of L-cysteine joined through a CH2 group linked to sulfur atoms. It has also been found in seeds of Albizzia lophanta and Parkia speciosa32 and, as noted earlier, is the source of CS2 in Mimosa pudica (Section 11.1.2.2.2). An enzyme in A. lophanta seeds converted djenkolic acid to an unstable material with a leek-like odor, methylene dithiol 39.92 This was presumably an elimination of aminoacrylic acid 28 via intermediates 37 and 38 (Scheme 13). The methylene dithiol decomposed to H2S and possibly, thioformaldehyde, CH2S the latter might be a source for polysulfides. 

Figure 37-1. Network density ft in amount of network chains per unit volume vulcanizate as a function of the vulcanization time for the vulcanization of natural rubber with 2 phr sulfur, 5 phr zinc oxide, 1 phr 2>mercaptobenzthiazole, and 1 phr stearic acid at 140 C. Cl, main cross-linking reaction Cii, long-term crosslinking A chain degradation. (After D. A. Smith.)...

Except for a small amount of the amino acid methionine, the sulfur in wool occurs in the form of the amino acid cystine. Only approximately 82% of clean wool consists of keratinous proteins, which are characterized by a high concentration of cystine. Approximately 17% of the fiber is protein material of relatively low cystine content (<3%) this has been termed nonkeratinous. As a result of the lower cystine content, the nonkeratinous proteins have a lower concentration of disulfide cross-links compared with the keratinous proteins in the fiber. The nonkeratinous material is, therefore, more labile and less resistant to chemical attack than the keratinous proteins. The nonkeratinous proteins are located primarily in the cell membrane complex between the cortical cells and in the endocuticle (Fig. 3). Approximately 13% of the total nonkeratinous material is also located within the cortical cells, where its distribution differs between the cells of the ortho- and paracortex. 

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