Abstract
Thiol and disulphide groups in proteins
react with neutral and alkaline cupric sulphite solutions and are thereby
converted into thiolsulphate (-SSO3H) groups. Solutions of
cuprammonium sulphite at pH 9-10.6 can dissolve large amounts of keratins ; under
other conditions the disulphide bonds can be broken without the proteins
entering solution. The reactions are highly specific, proceed to completion,
and large excesses of reagent are not required. The " S-sulphokerateines
" so obtained constitute a new class of water-soluble protein derivative.
The thiolsulphate group can be readily labelled with radioactive sulphur and
may be converted into a thiocyanate (" S-cyano-kerateine ") by
reaction with cyanide, and into a mixed disulphide by reaction with a thiol.
S-Cyanokerateines, containing the ?CH2SCN side chain, react with
cysteine to give thiocyanate ion and a protein containing lanthionine residues,
presumably by nucleophilic displacement of SCN- from the CH2
group.
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