Biochem 4000 - Lecture 3 PI

Home > Preview

The flashcards below were created by user Ant on FreezingBlue Flashcards.


  1. How often to α-helices repeat their structure (in Å)?
    Every 5.4Å
  2. Residues per α-helix turn?
    3.6
  3. What are the main torsion angles (φ & ψ) in α-helices?
    • -φ - -60°
    • -ψ - -50°
  4. Hydrogen bonding in alpha helices
    • All main chain atoms
    • Oi to Ni+4
  5. Three main types of helix
    • 413 - "Standard" α-helix
    • 510
    • 516
  6. What does 413 mean?
    • 4 - Four residues separating the H-bond
    • 13 - 13 atoms separating the H-bond
  7. Structure of a 310
    • Helix
    • Three residues per turn
    • Helix cap (C-terminus)
  8. Properties of a 516
    • 5 Residues per turn
    • Hole in the middle
    • Usually only one turn
    • Very rare
  9. Why is a hole in a helix problematic?
    Because unfilled space leads to instability
  10. What is a bidentate H-bond?
    A double hydrogen bond, found on helix caps (310)
  11. Why are many helices distorted?
    • Squashing against other secondary structures
    • Solvent induced distortions by rotating peptide group
    • Small proteins (-C-S-S-C-)
    • Metal ions
    • Proline
  12. How does proline affect long helices?
    • Produces a 20° bend
    • Disrupts 2 hydrogen bonds
  13. Why is proline only found in longer helices?
    Longer helices are more stable
  14. Explain solvent induced distortion?
    Two residues form hydrogen bonds form with an intermediary water molecule, disrupting the helical structure.
  15. Torsion angles of beta strands (φ & ψ)
    • φ - -140°
    • ψ - 130°
  16. β-strand structure
    • 3.5Å between residues
    • Pitch - 7.0Å
    • Side chains orthoganol to axis
  17. Why do R-groups all point away from eachother on sheets?
    To minimize steric conflict (esp larger groups)
  18. Broad structure of β-sheets
    Composed of two or more β-strands
  19. Parallel β-sheet
    • 4-6 Strands
    • Always in hydrophobic core
    • Bent (weaker) H-bonds
    • Smaller sheet twist
  20. Antiparallel β-sheet
    • 2-6 strands
    • Linear H-bonds
    • β-bulge distortion

Card Set Information

Author:
Ant
ID:
314917
Filename:
Biochem 4000 - Lecture 3 PI
Updated:
2016-02-11 21:03:07
Tags:
Biochemistry 4000
Folders:

Description:
Biochem
Show Answers:

Home > Flashcards > Print Preview