Determining the Dehydroalanine and Amide Contents of Wool as a Means of Estimating Damage Caused by Alkaline Treatments

Abstract

Two analytical methods for determining the extent of alkaline damage to wool are described. In the first method, the dehydroalanine residues formed by alkali were first converted to pyruvic acid by acid hydrolysis. The enzyme-catalyzed reduction of pyruvic acid to lactic acid by reduced nicotinamide-adenine dinucleotide (NADH) was then used to determine quantitatively the pyruvic acid content of the hydrolysate. Reproducible results were obtained provided they were extrapolated to zero time of hydrolysis and the conditions of reduction with NADH were closely controlled. In the second method, amide contents were determined by estimating the ammonia produced when the wool samples were hydrolyzed with 6 N sulfuric acid at 110°C for 8 hours. Quantitative results were obtained without the need to extrapolate to zero time of hydrolysis. The methods were used to analyze wool samples that had been treated with sodium carbonate and sodium hydroxide solutions at temperatures up to 40°C. A linear correlation was found between the decreases in cystine and amide contents and the increase in dehydroalanine content.

Get full access to this article

View all access options for this article.

References

Bergmeyer, H.U. , "Methods of Enzymatic Analysis" (in German), 1st ed., Verlag Chemie, Gmbh Weinheim / Bergstrasse, Germany, 1962, p.p. 36-40, 253-259, 736.

Bohak, Z. , N-(DL-2-Amino-2-Carboxyethyl)-L-Lysine, a New Amino Acid Formed on Alkaline Treatment of Proteins, J. Biol. Chem. 239, 2878-2887 (1964).

Charwat, H.E. , Views on the Dyeing of Mixtures of Wool and Cotton with Reactive Dyestuffs (in German), Schriftenr. Dtsch. Wollforschungsinst. RWTH Aachen 83, 244-265 (1981).

Clarke, H.T. , and Inouye, J.M. , Some Observations on the Action of Alkali upon Cystine and Cysteine, J. Biol. Chem. 89, 399-419 (1930).

Corfield, M.C. , and Robson, A. , The Amino Acid Composition of Wool, in " Proc. Int. Wool Text. Res. Conf. Australia," C, 1955, pp. 79-86.

Corfield, M.C. , Wood, C. , Robson , A. , Williams, M.J. , and Woodhouse , J.M. , The Formation of Lysinoalanine During the Treatment of Wool with Alkali, Biochem. J. 103, 15-16c (1967).

Crewther, W.G. , Fraser, R.D.B. , Lennox, F.G. , and Lindley, H. , Chemical Reactivity of Keratins, Adv. Protein Chem. 20, 252-256 (1965).

Cuthbertson, W.S. , and Phillips , H. , The Action of Alkalis on Wool: The Subdivision of the Combined Cystine into Two Fractions Differing in Their Rate and Mode of Reaction with Alkalis, Biochem. J. 39, 7-17 (1945).

Czok, R. , and Lamprecht, W. , in "Methods of Enzymatic Analysis" (in German), 2nd ed., Verlag Chemie, Gmbh Weinheim /Bergstrasse, Germany, 1974, p. 1491.

10.

Harris, M. , Effect of Alkalis on Wool, Am. Dyes. Rep. 24, 562-567 (1935).

11.

Inglis, A.S. , Roxburgh, C.M. , and Takayanagy , H. , Analysis for Amide Nitrogen in Proteins, Anal. Biochem. 61, 25-31 (1974).

12.

International Wool Textile Organization, Specifications of Test Methods, code IWTO-15-66(D), Method for Colorimetric Determination of Cystine and Cysteine in Hydrolysates of Wool (in German), 1966.

13.

Leach, S.J. , and Parkhill, E.M.J. , Amide Nitrogen in Proteins, in "Proc. Int. Wool Text. Res. Conf. Australia," C 1955, pp. 92-101.

14.

Mellet, P. , The Influence of Alkali Treatment on Native and Denatured Proteins, Textile Res. J. 38, 977-983 ( 1968).

15.

Mellet, P. , and Louw, D.F. , The Modification of Silk Fibroin by Alkali, Chem. Commun. 17,396-397 (1965).

16.

Otterbum, M.S. , in "Chemistry of Natural Protein Fibers," R. S. Asquith , Ed., Plenum Press, New York. London, 1977 , pp. 69-71.

17.

Patchomik, A. , and Sokolovsky , M. , Nonenzymatic Cleavages of Peptide Chains at the Cysteine and Serine Residues Through Their Conversion into Dehydroalanine, I: Hydrolytic and Oxidative Cleavage of Dehydroalanine Residues, J. Am. Chem. Soc. 86, 1206-1212 (1964).

18.

Rambacher, P. , On the Reactivity of Sulfur in Cystine Derivatives and Proteins with Special Consideration of Wool Keratin (in German), thesis . Würzburg University. 1939.

19.

Schöberl, A. , and Hornung, T. , On the Effect of Alkalis on Cystine and Cystine Derivatives (in German), Liebigs Ann. Chem. 534, 210-225 (1938).

20.

Wieland, T. , and Wirth, L. , Paper Chromatographic Analysis of the Composition Products of Serin, Threonine, and Cysteine Formed During the Heating with Alkali (in German), Chem. Ber. 82, 468-473 (1949).

21.

Zahn, H. , Kunitz, F.-W. , and Hildebrand, D. , The Rôle of SH-Groups in Wool, J. Textile Inst. 51, T740-T749 ( 1960).

22.

Ziegler, K. , The Influence of Aikali Treatment on Wool, in " Proc. Int. Wool Text. Res. Conf. Paris," II, 1965, pp. 403-413.