KERATIN

Keratin is insoluble in water, dilute acid, and dilute base. Keratins such as hair, epithelium, wool, contain up to 20% of non keratins, are only slightly cross linked and easily degraded. Cystine is present in considerable amounts and forms disulfide bonds.

H-C-SH              H₂C-S-S-CH₂
 I                                I           I
H-C-NH₂  ->  NH2CH    HCNH₂
 I                                I           I
COOH       HOOC         COOH

Transition of disulfide groups into thiol groups is equivalent to transition of stable compound into unstable one. Under action of alkali substances Na2CO3, NaOH, Na2S cyanides and borates the disulfide group is transformed. Hydrolitic splitting of disulfide bond when sulfur is bound to peptides occur at pH 10.6.

R-CH₂-S-S- CH₂-R + OH- -> R-CH₂-S-OH  +  -S-CH₂-R

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