Structures of proteins - Alpha helix

Two researchers who contributed theories to protein shaping

1. G.N. Ramachandran

2. Linus Pauling and Robert Cory

G.N. Ramachandran

• Can calculate the distance and charge of proteins

• Coexist with rules and laws/ used mathematics

  • Calculated lowest energy possible because proteins need to be stable (neutral charges)

Linus Pauling and Robert Cory

Used images

Theories of secondary protein structures

1. Circular Structure

2. Left Handed Helix

3. Right Handed Helix

4. Sheet Like Structures

5. Triple Helix (gly)

6. Turns or Bends

Circular structures

G.N. Ramachandran

• Proteins can coexist as a circle

• Theoretically possible but never seen

Left and Right Handed Helix

• Form alpha helix

• If a protein has a helix, it can have two versions: Left and right

  • A left-handed Helix is not possible because when aa are synthesized, they are in L orientation (counterclockwise), which does not allow a left-handed helix to be created

Sheet like structures

Beta-sheets are a type of secondary structure in proteins characterized by strands of amino acids connected laterally by hydrogen bonds, forming a sheet-like structure. They are one of the two main types of secondary structures in proteins, the other being alpha-helices.

Triple Helix (gly)

where three polypeptide chains are intertwined into a single, stable helical structure.

Turns or bends

Linus Pauling and Robert Cory

• Discovered by imaging

• Turns and bends are types of secondary structural elements in proteins that facilitate changes in direction within the polypeptide chain, enabling the protein to fold into its three-dimensional shape.

4 points when examining helixes in proteins

1. 3.6 aa per turn of helix

2. Hydrogen bond between aa where aa 1 is bonded to aa 5, aa 2 is bonded to aa 6, etc.

3. The orientation of carbonyl and amino groups is in line with the major axis of the helix.

4. The side chain is perpendicular to the axis of the helix

How are amino acids 1 and 5, 2 and 6, etc. linked?

Between oxygen of carboxyl and hydrogen of the amine group.

• EX: Oxygen of 1 and Hydrogen of 5

What direction does oxygen face in an alpha helix? Hydrogen?

• O faces C terminus where H faces the N terminus