Question

Tropomyosin is a 75 kDa muscle protein composed of two-stranded α-helical coiled coils. Estimate the length of the molecule. The answer is 50 nm.

Answer 1

Sol :-

Given, Tropomyosin is a 75 kDa muscle protein composed of two-stranded α-helical coiled coils.

Since, helix contain the approximately half of the weight of the protein, therefore

Weight of one helix is half = 75/2

= 37.5 KDa

= 37 KDa (approx.)

= 37000 KDa

Also,

Average weight of the amino acid = 110 Da

So,

Number of amino acids per chain = 37000 Da / 110 Da

= 336

Because, average length the helix per amino acid = 1.5 Å

So,

Estimate length of the molecule = 1.5 Å x 336 = 504 Å = 50 nm

Hence, Estimate length of the molecule = 50 nm