Question

Calculate the length in angstroms of a 100-residue segment of the α keratin coiled coil.

Short answer

The length of a 100-residue segment of the α keratin coiled coil is 145.7Å.

Step-by-step solution

α keratin coiled coil.

α keratin is a fibrous protein, made up of a repeating sequence of amino acids. It is the major component of vertebrate nails, hair, claw, epidermis of skin, etc.

The structure of α keratin resembles the structure of α helix. It contains 3.5 residues per turn and a length of 5.1 Å for each turn.

Calculation for the number of turns.

One turn in α keratin contains 3.5 residues. Thus,the number of turns that would contain 100 residues will be:

1 x 100/3.5

= 28.57 turns.

Calculation for the length of the α keratin.

In α keratin, one turn exhibits a length of 5.1Å. Thus, the total length exhibited by 28.57 turns will be:

28.57 x 5.1

= 145.707 Å.

Hence, the length of the α keratin will be 145.707 Å = ~145.7 Å.