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Selenocysteine in pH=7

  1. Nov 26, 2009 #1
    Hi, this problem is puzzling me since all options seem false for my understanding:

    The uncommon amino acid selenocysteine has an R group with the structure —CH2—SeH (pKa ≈ 5).
    In an aqueous solution, pH = 7.0, selenocysteine would:

    A) be a fully ionized zwitterion with no net charge.
    B) be found in proteins as d-selenocysteine.
    C) never be found in a protein.
    D) be nonionic.
    E) not be optically active​

    I think it has a negative net charge since pKa<pH and its ionic (no a,d). It has a optically active alfa carbon (no e). All proteins have l-form amino acids (no b). Selenocysteine is found in some proteins though its not common (no c).

    Where am I wrong? :confused:

    ps. this is not a homework
  2. jcsd
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