vimal
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Disulphide linkages. R - S - S - R
they are mostly found in proteins right? esp. Insulin. Now, the question says:
In the analysis of insulin, attempting to reduce the chain length, the disulphide linkages are first broken down.
write the products obtained when the disulphide linkage is treated with:
HS-CH2-CH2-OH
HCOOOH performic acid
Vimal
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runlabrun
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found this in a few secs on google dont know if its what you want or not....
http://www.med.unibs.it/~marchesi/pps97/course/insulin/sange...
-rlr
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JohnWW
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The only natural amino-acid, of the 23 natural ones, containing a disulfide linkage R-CH2-S-S-CH2-R is cystine, HOOC-CH(NH2)-CH2-S-S-CH2-CH(NH2)-COOH.
It is reversibly reducible to 2 molecules of cysteine, HOOC-CH(NH2)-CH2-SH, containing -SH groups.
The disulfide linkages in cystine units are important in determining the overall shapes of protein molecules, because their cross-linking of chains of
amino-acid units results in 3-dimensonal rigidity. This is why cystine is most common in "hard" proteins such as keratin, as in hair, nails,
horns, and skin.
There is also a natural S-S containing carboxylic acid, lipoic acid, cyclo-(-S-S-CH2-CH2-CH-)-(CH2)4-COOH, which is an important cofactor in
biological oxidations. It is reversibly reducible to dihydrolipoic acid, HS-CH2-CH2-CH-(CH2)4-COOH.
In nature, the disulfide linkage in the above compounds is not oxidized, but is reduced to two -HS groups. Treatment with an oxidant like performic
acid would not be similar to any natural biochemical reaction. The reaction products would probably be initially two molecules of a sulfoxide
containing tetravalent sulfur, -CH2-SH=O, and further oxidation would probably result in a substituted sulfurous acid, -CH2-S(OH)=O, and then a
sulfonic acid, -CH2-SO2-OH. Treatment with a mixed thiol and alcohol like HS-CH2-CH2-OH would most likely result in an ester and/or thioester.
[Edited on 2-2-2005 by JohnWW]
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