The reactivity of the disulphide bonds of wool

Abstract

1. Fully reduced and S-carboxymethylated wool samples were prepared in which either the readily reducible cystine bonds or those that could only be reduced with difficulty were specifically labelled with iodo[2-(14)C]acetate; these two cystine fractions correspond to the (A+B) and (C+D) cystine fractions respectively, of Middlebrook & Phillips (1942). 2. Radioactively labelled peptides were isolated from partial acid hydrolysates of these wool samples. 3. It appears that the (A+B) cystine residues probably owe their increased reactivity to being in a more polar environment. 4. The implication of these results for the problem of characterizing the disulphide bonds of wool is briefly discussed.

Selective biodegradation of keratin matrix in feather rachis reveals classic bioengineering

“…The present study raises as many questions as are answered. Incumbent on selective biodegradation was anticipation of a high sulphur content of the matrix, as shown in mammalian a keratins (Alexander & Earland 1950;Gillespie et al 1968;Lindley & Cranston 1974). Selective biodegradation has certainly occurred and raises the question of the possible similarity of the b-keratin matrix of the feather with that of the a keratins of mammals, supporting recent proposals (reviewed in Bragulla & Homberger 2009) that the b keratins of sauropsid hard-cornified tissues resemble the nonfilamentous KFAPs of mammals (i.e.…”

“…We anticipated the possibility of selective biodegradation occurring on the basis of the two general classes of proteins present in keratin, a high-sulphur fraction of the amorphous matrix (derived from the sulphur -sulphur cross-links that keep the fibres intact) and a low sulphur fraction of the microfibrillar component. Although these fractions were determined on a keratins (Alexander & Earland 1950;Gillespie et al 1968;Lindley & Cranston 1974), we believed, as implied by some workers (Wainwright et al 1976), that the fractions might be similar in b keratins. We mention in parentheses subsequent research (Eckhart et al 2008) that shows that cysteine-rich a keratins are not restricted to mammals and that the evolution of mammalian hair may have involved the cooption of pre-existing structural proteins (lizards and birds) and, interestingly, that in the keratins in lizard claws there were sulphur -sulphur bonds unrelated to mammalian counterparts.…”

Mass Spectrometry-Based Protein Footprinting for Higher-Order Structure Analysis: Fundamentals and Applications

“…The oxidized form of cysteine, cystine, exists with a disulfide bond. Cystine footprinting, interestingly, originates from the analysis of wool and its oxidation. , To label disulfide bonds, cystine residues need to be reduced to cysteine. Many reducing reagents are available, including cyanide, phosphorothioate, (2 S )-2-amino-1,4-dimercaptobutane, bis-(2-mercaptoethyl)­sulfone and N , N ′-dimethyl- N , N ′-bis­(mercaptoacetyl)­hydrazine, sodium borohydride, and 2,3-dimercaptopropanol, that can deliver effective disulfide reduction.…”

Wool research in the Division of Protein Chemistry, C.S.I.R.O

“…As yet little is known about the distribution of disulphide bonds in wool. Lindley and Cranston (1974) have shown that the reactivity of these bonds with thioglycollate, and hence the ease with which they can be ruptured is greatly affected by the nature of the adjacent amino acid residues. Disulphide groups in proximity to polar residues appeared to be more reactive than those associated with non-polar residues.…”