Peptides and Proteins Flashcards
Where is the peptide bond formed?
Between the amino terminus of one amino acid and the carboxyl terminus of another.
What terminus do you start at when writing the sequence of a peptide?
The N-terminus
What is the R-group?
The side chain
Why is the peptide bond shorter than would be expected for a single bond?
Due to its partial double bond character.
What configuration does the peptide bond nearly always take?
The trans configuration as it is more energetically favourable.
Which amino acid is often found in cis configuration?
Proline due to the presence of the gamma methylene group.
Can phi and psi bonds rotate?
Yes
How do you determine whether a bond is phi or psi from a Newman projection?
If the turn is anti-clockwise from the group in front to the group behind is anticlockwise the bond is Phi.
If the turn from the group in front to the group behind is clockwise the bond is Psi.
What determines higher order structure of a peptide?
Rotations around the Phi and Psi bonds.
What is a dihedral angle?
The angle between two planes.
What is the observed dihedral angle for Phi?
Around -60 to -120.
What are the observed dihedral angles for Psi?
-60 and +120
What is the energy of a hydrogen bond?
Around 5Kcal
What is the ideal length for an Hydrogen bond?
1.8 angstroms
When is an hydrogen bond strongest?
When the two bonds, 1 and 2, are in line.
