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# The electrostatic energy of interaction, Uelectrostatic, between two atoms i and j, is described by Coulomb's

law

Consider the electrostatic interaction between a negatively charged amino acid (e.g.

glutamate) and a positively charged amino acid (e.g. arginine) separated by r Å.

Part A:

What is the force required to increase the separation of the two charges by 0.1 Å?

Assume the charges are exposed to water (dielectric constant = 78.4). Give your

Hint: calculate the electric force between the two charges in the initial state (when they are separated by r Å) and in the final state (when they are separated by (r + 0.1) Å). What is the force required to separate the charges?

Part B:

Now suppose the glutamate and arginine residues are buried in the core of the protein (ε = 2). What is true regarding

the force required to increase the separation of the two charges by 0.1 Å?

Multiple Choice:

A. The forces are the same in both cases

B. The force is about 40 times greater when the residues are exposed to water

C. The force is about 40 times greater when the residues are buried in the core of the protein.

D. The force is about 1600 times greater when the residues are exposed to water

E. The force is about 1600 times greater when the residues are buried in the core of the protein. Part A
Let the change of glutamine be Ploi low
= - 4 centopub
arginine be - +
&quot;. Electric force betwen these changes
=
471 ( 78 . 4 * 8 . 35 4 * 10-12 ) * 78 x 10 -10
newto
B
9 ( D)
= 8 (- 4... ### Why Join Course Hero?

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