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Merrifield Solid-Phase Peptide Synthesis quiz

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  • What type of bead is used as the solid support in Merrifield solid-phase peptide synthesis?
    Chloromethylated polystyrene beads are used as the solid support.
  • What is the purpose of protecting the amino group of an amino acid in this synthesis?
    The amino group is protected to prevent unwanted reactions during peptide chain assembly.
  • Which reaction mechanism is used to attach the first protected amino acid to the polystyrene bead?
    An SN2 nucleophilic substitution mechanism is used for attachment.
  • What is the role of DCC in the Merrifield peptide synthesis?
    DCC facilitates peptide bond formation by absorbing the water produced during the condensation reaction.
  • How is the protecting group removed from the amino acid during the synthesis cycle?
    The protecting group is removed by hydrolysis, exposing the free amino group.
  • What chemical is used to cleave the completed peptide chain from the polystyrene bead?
    Hydrofluoric acid (HF) is used to release the peptide chain from the bead.
  • What type of reaction forms the peptide bond between amino acids in this method?
    A condensation reaction forms the peptide bond, with the loss of water.
  • Why is the process called 'solid-phase' peptide synthesis?
    Because the peptide chain is assembled on a solid polystyrene bead, not in solution.
  • What is the function of the chloromethyl group on the polystyrene bead?
    It acts as a reactive site for the SN2 attachment of the first protected amino acid.
  • What happens to the polystyrene bead after the peptide chain is cleaved?
    The bead remains as waste, while the peptide is isolated.
  • What is the repeating cycle in Merrifield synthesis for elongating the peptide chain?
    The cycle involves deprotection, coupling with a protected amino acid, and repetition as needed.
  • What is the initial preparation step (step 0) before the main synthesis steps?
    Amino acid protection, where the amino group is protected by an acyl group.
  • What is the main advantage of using the Merrifield solid-phase method?
    It allows efficient and automated synthesis of peptides by iterative cycles on a solid support.
  • What is lost during the peptide bond formation step?
    A molecule of water is lost during the condensation reaction.
  • How can the length of the peptide chain be controlled in this synthesis?
    By repeating the cycles of deprotection and coupling with additional protected amino acids.