The Twenty

Atlas/Cys

C

Cysteine

Cys

PolarNon-essentialHydrophilicSide-chain pKa 8.4103 Da

Thiol (–CH₂SH)

  • Two cysteines can oxidize to a cystine disulfide bridge.
  • The thiol (pKa ≈ 8.4) is a common nucleophile in active sites.

Mastery: unseen

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Structure of Cysteine
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