3: Amino Acids and Peptides
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- 3.3: Cysteine Chemistry
- Two cysteine side chains can covalently interact in a protein to produce a disulfide. Just as HOOH (hydrogen peroxide) is more oxidized than HOH (O in H2O2 has oxidation number of 1- while the O in H2O has an oxidation number of 2-) , RSSR is the oxidized form (S oxidation number 1-) and RSH is the reduced form (S oxidation number 2-) of thiols. There oxidation number are analogous since O and S are both in Group 6 of the periodic table and both are more electronegative than C.