Biochem 4000 - Lecture 3 PI
Home > Preview
The flashcards below were created by user
on FreezingBlue Flashcards.
How often to α-helices repeat their structure (in Å)?
Residues per α-helix turn?
What are the main torsion angles (φ & ψ) in α-helices?
Hydrogen bonding in alpha helices
- All main chain atoms
- Oi to Ni+4
Three main types of helix
- 413 - "Standard" α-helix
What does 413 mean?
- 4 - Four residues separating the H-bond
- 13 - 13 atoms separating the H-bond
Structure of a 310
- Three residues per turn
- Helix cap (C-terminus)
Properties of a 516
- 5 Residues per turn
- Hole in the middle
- Usually only one turn
- Very rare
Why is a hole in a helix problematic?
Because unfilled space leads to instability
What is a bidentate H-bond?
A double hydrogen bond, found on helix caps (310)
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
How does proline affect long helices?
- Produces a 20° bend
- Disrupts 2 hydrogen bonds
Why is proline only found in longer helices?
Longer helices are more stable
Explain solvent induced distortion?
Two residues form hydrogen bonds form with an intermediary water molecule, disrupting the helical structure.
Torsion angles of beta strands (φ & ψ)
- 3.5Å between residues
- Pitch - 7.0Å
- Side chains orthoganol to axis
Why do R-groups all point away from eachother on sheets?
To minimize steric conflict (esp larger groups)
Broad structure of β-sheets
Composed of two or more β-strands
- 4-6 Strands
- Always in hydrophobic core
- Bent (weaker) H-bonds
- Smaller sheet twist
- 2-6 strands
- Linear H-bonds
- β-bulge distortion
Home > Flashcards > Print Preview