Spring constant of a charged DNA molecule

[mpm]

I am having difficulty with this homework question. I am not even sure whether to start.

Question:

A molecule of DNA lies along a straight line. It is 1.061 micrometers long. The ends of the molecule become singly ionized; negative on one end, positive on the other. The helical molecule acts as a spring and compresses 0.6% upon becoming charged. The Coulomb constant is 8.99 x 10^9 N*m^2/C^2.

Determine the effective spring constant of the molecule. Take into account the compressed length when calculating the distance between the ends of the molecule. Answer in units of N/m.

Any help would be appreciateid.

 

[Gamma]

Coulomb force make the dna to shrink. Spring like force of the DNA acts opposite to the coulomb force. At the equilibrium point these forces are equal. Use this idea to find an equation and solve for k, the spring constant.