4.2 2ndProtein Flashcards
Secondary Structure
The spatial arrangement of aa residues that are NEAR one another in the linear seq
What are elements of secondary structure?
alpha helix and beta strand
What structure is an alpha helix?
A rodlike structure with a tightly coiled backbone
What stabilizes the alpha helix?
Intrachain Hbonds
What type of bond is between the main chain CO and NH groups?
Hbonds
How many aa residues are there per turn of a heliz?
3.6
Which aa are close to eachother due to the turn of the helix?
aa spaced 3 or 4 apart in a seq
Where are the aa spaced 2 apart in a seq?
They are on opposite sides of the helix and are unlikely to make contact
Pitch
The length of one complete turn alinf the helix and is equal to the product of translation and the number of residues per turn 1.5A x 3.6 = 5.4
Which way is energetically more favourable?
Right handed twist
Why is right handed more energetically favourable?
bc there are fewer steric clashes bw the side chain and backbone
How are beta sheets stabilized?
by Hbonds b/w polypeptide strands
What is a B sheet composed of?
Two or more polypeptide chains called B strands
What is the distance b/w adjacent aa in a B strand?
3.5 A
What is the distance b/w adjacent aa in a alpha helix?
1.5A
