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L-Cystine

L-Cystine

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 Name:L-Cystine
Synonyms:L(-)-3,3'-Dithiobis(2-aminopropanoic acid); 2-Amino-3-[(2-amino-2-carboxyethyl)dithio]propanoic acid
Molecular Formula:C6H12N2O4S2
Molecular Weight :240.29
CAS Registry Number:56-89-3
EINECS :200-296-3
 It is described by the formula (SCH2CH(NH2)CO2H)2. It is a colorless solid, and melts at 247-249°C. It was discovered in 1810 by William Hyde Wollaston but was not recognized as a component of proteins until it was isolated from the horn of a cow in 1899. Through formation of disulfide bonds within and between protein molecules, cystine is a significant determinant of the tertiary structure of most proteins. Disulfide bonding, along with hydrogen bonding and hydrophobic interactions is partially responsible for the formation of the gluten matrix in bread. Human hair contains approximately 5% cystine by mass.
Disulfide bonds can be broken at temperatures above about 150°C, especially at low moisture levels (below about 20%)
Specifications:
Test Items
 Standard
 
Specific rotation
Appearance of solution
Ammonium
Sulfate
Iron
Heavy metals
Arsenic
Other amino acids
Loss on drying
Sulphated ash
Assay
PH
 -215 to -225
Clarity clear, color not more intensely coloured than reference solution Y 7
Max 200ppm.
Max 200ppm.
Max 20ppm
Max 10ppm.
Max 1ppm
Not detectable.
Max 0.2%.
Max 0.1%
98.5% to 101.0%
5.0 to 6.5