Oxidation of wool: Alkali-solubility test for determining the extent of oxidation

Harris, Milton; Smith, Arthur L.

doi:10.6028/jres.017.027

Cited by 74 publications

(20 citation statements)

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“…The cystine analyses were made by the Sullivan method [10], sulfur analyses by the oxygen-bomb method [11], alkali-solubilities by the method of Harris and Smith [12], and serine analyses by the method of Nicolet and Shinn [13].…”

Section: Analytical Proceduresmentioning

confidence: 99%

Nature of the reaction of wool with alkali

Mizell¹,

Harris²

1943

J. RES. NATL. BUR. STAN.

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The course of the reaction of the cystine in wool with alkali has been reinvestigated. The earlier findings that one sulfur atom is split from each molecule of cystine a re confi rmed. Of the residual noncystine s ulfur in the alka li-tregted wool, mbre than 25 percent has bee n accounted for as lanthionine. No signifi cant amounts of s ulfhydryl groups are in the t reated wools. The res ults lead to the conclusion that the alkali cleavage of the dis ulfide group does not consist prim a rily in a hydrolytic rupture between the s ulfur atoms with the formation of a s ulfhydryl compound and a s ulfenic acid, as postulated earlier; rather, they are more consistent with a mechanism recently advanced by N icolet and Shinn, which involves a rupture between s ulfur and carbon to yield dehydroalanine and a -C H 2 -S-SH residue. An atom of s ulfur is then eliminated from the latter and the sulfhydryl group thus formed reacts with dehyclroalanine to form lantilionine.

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Section: Analytical Proceduresmentioning

confidence: 99%

Nature of the reaction of wool with alkali

Mizell¹,

Harris²

1943

J. RES. NATL. BUR. STAN.

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“…Alkali-solubility was measured by the method of Harris and Smith [19]. Samples were treated with 0.1 N sodium hydroxide solution for 1 hr at 65 0 C, and the percentage loss in weight was determined.…”

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confidence: 99%

Role of cystine in the structure of the fibrous protein, wool

Patterson¹,

Geiger²,

Mizell³

et al. 1941

J. RES. NATL. BUR. STAN.

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A number of the important physical and chemical properties of wool are closely associated with the presence of disulfi de cross-linkages between the polypeptide chains of the protein. This conclusion results from a study of the behavior of wool before and after alteration of the mode of linkage of the sulfur by a series of highly specific reactions.The cystine in wool can be readily reduced to cysteine with thioglycolic acid. Strongly alkaline solutions of the reagent have been shown by previous investigators t o dissolve the protein and destroy its fibro us structure. It is now shown that wool can be reduced with thioglycolic acid over a wide range of pH, and that when the reduction is carried out in neutral or acid solution, the fib rous structure of the wool is not destroyed when the disulfide groups are reduced to sulfhydryl groups. T he sulfhydryl groups of fibers reduced in this way react readily with alkyl halides to form thioether groups.Thus reaction of reduced wool with alkyl monohalides, such as methyl iodide, results in permanent rupture of disulfide linkages, and the fibers are greatly increased in extensibility and decreased in strength. Alkylation with aliphatic dihalides, such as methylene iodide or trilnethylene dibromide, introduces hydrocarbon chains between pairs of sulfur atoms of cystine molecules in the fibers. Such fibers are very similar to untreated fibers in physical properties.Wool in which the disulfide linkages have been broken by reduction, or by reduction and alkylation with alkyl monohalides, possesses much higher alkalisolubility t han untreated wool, while wool in which the disulfide cross-linkages have been replaced by new covalent cross-linkages through reduction followed by alkylation with dihalides possesses m uch lower alkali-solubility. Since th!' susceptibility of wool to degradation by alkalies is one of its greatest disadvantages, p rocesses that would make it stable toward alkalies should also enhance its durability. CONTENTS

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“…Nevertheless, even when the sulfur cross-links have been broken as in the present product, the material is not digested by enzymes. Moreover, the scale material was found to be more stable toward alkali than wool that had been reduced and alkylated in the same way, since the alkali-solubility [24] of the scale material was found to be only 42 percent and that of the treated wool 85 percent.…”

Section: Discussionmentioning

confidence: 98%