For this exercise, assume that a protein of 100 amino acid residues is subjected

Question

For this exercise, assume that a protein of 100 amino acid residues is subjected to this procedure at 25C and that the unfolding free energy change for this protein is 30 kJ/mol.

(a) What is the minimum amount of mechanical work that would be required to unfold the protein? Assuming that the unfolding process occurs a distance of 2 nm, calculate the average force applied by the AFM

(b) Calculate the minimum amount of work required to stretch the unfolded polypeptide chain into a single conformation.

(c) Explain, in structural and thermodynamic terms why the work required for the two steps is so different. (The work that you calculate for one of the steps should be about 20-times larger than for the other.)

(d) Calculate the distance between the ends of the fully extended polypeptide chain. (This corresponds to the structure in a single strand.)

(e) Calculate the average force for the step of stretching the unfolded polypeptide into a single conformation.

Explanation / Answer

Minimum amount of mechanical work and the average force applied by the AFM

Under an ideal thermodynamic reversible reaction, mechanical work is equal to free energy change

So work done is = 30 kJ/mol.

Now to calculate the average force applied by AFM for 100 amino acid polypeptide unfolding process, we use the formula:

Work = force x distance

30= F x (2 nm) = f = (30 x 103 Joule)/(2nm) = 15000 nNewton = 15µNewton. [1 µNewton= 103 nNewton]

Related Questions

Navigate

• Browse (All)
• Browse F
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.