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The Chemical Constitution and Physical Properties of Bisulphited Wool *
Author(s) -
CARTER E. G. H.,
MIDDLEROOK W. R.,
PHILLIPS H.
Publication year - 1946
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1946.tb02415.x
Subject(s) - chemistry , cystine , lanthionine , wool , cysteine , reactivity (psychology) , stereochemistry , thiol , organic chemistry , medicinal chemistry , amino acid , biochemistry , enzyme , pathology , medicine , alternative medicine , archaeology , history
Summary1 Evidence is surveyed for the existence of four subfractions of the cystine‐ S of wool (A, B, C and D). which differ in their reactivity towards sodium bisulphite and alkalis. These four subfractions fall into two approximately equal main fractions (A + B) and (C + D): (A + B) gives thiol and S ‐cysteine‐sulphonate groups with bisulphite; (C + D) does not react with cold bisulphite, but under the action of hot bisulphite decomposes and yields combined a ‐aminoacrylic acid. With alkalis, fraction (A + B) gives combined lanthionine, whereas fraction (C + D) again gives combined a ‐aminoacrylic acid. 2 Subfraction A of the combined eystine is probably influenced by neighbouring free carboxyl groups, whereas subfraction B is under the influence of less polar groupings. 3 Under the experimental conditions examined, no difference has been detected between the reactivities of the cystine subfractions of extended and unextended wool fibres. 4 Breaking subfraction A of the cystine cross‐linkages increases the ease of extension more than breaking subfraction B, but the ease of extension of fibres with fraction (A + B) broken can be increased greatly by monochloroacetic acid.Fibres of which (A + B) has been broken do not supercontract until they have been boiled: they then supercontract even when boiling causes the disulphide cross‐linkages to reform. Even when boiled, the fibres of which only subfraction B has been broken will not supercontract. After fibres have been boiled in sodium bisulphite solution, supercontraction cannot be prevented by rebuilding fraction (A + B).5 Under the experimental conditions we have used the S ‐cysteinesulphonate groups of bisulphited wool do not react with methylamine, indicating that the setting of bisulphited wool may not be due to interaction between S ‐cysteinesulphonate groups and free amino‐groups to produce ‐SNH ‐ cross‐linkages. 6 Experiments on the setting of extended bisulphited hairs suggest that breaking fraction (A + B) alone will not bring about conditions conducive to set. A rise in temperature is also necessary and is effective even when fraction (A + B) remains broken. 7 Suggestions are advanced to account for the difference in reactivity between subfractions A and B and fractions (A + B) and (C + D), and the evidence is discussed in favour of the view that the chief factor in the stability of keratin and other fibrous proteins is main‐chain adhesion. Polar side‐chains are potential sources of weakness since they can give rise to swelling and hydration. In the keratins their activity is suppressed by the close proximity of disulphide cross‐linkages.