A large RNA molecule M binds to a small ligand L to form ML. A student who excel

Question

A large RNA molecule M binds to a small ligand L to form ML.

A student who excels in "glorified cookery" has synthesized the ligrand molecule L, a drug, which if succeeds in binding to M with a binding constant larger than 10+6 Mol-1 at body temperature (37oC= 310K), will guarantee her a lifetime of wealth and ease.

The binding occurs by the following mass-action equilibrium: M+L <-----> ML, where the equilibrium binding constant is Keq= [ML]/([M][L]).

A gel retardation assay is used in which the presence of M and ML can be distinguished by separate spots on the gel. One can quantitate the amount M or Ml present by the intensity of the spot. One varies the concentration of L in various lanes of the gel to change the relative amounts of M and ML in each lane.

At 10oC (283K) the concentration of [L]= 10-7 molar when [ML]=[M]

At 20oC (293K) the concentration of [L]= 2x10-7 molar when [ML]=[M]

a) what is the value of the equilibrium constant at 10oC?

b)what is the value of the equilibrium constant at 20oC?

c) What is the enthalpy, H, for M binding to L, assuming that H and S are constant over the 0-50oC range. Give your answer in Joules of kJ.mol. R=8.31 J/K/mol

d) what is the value of the entropy S for M binding to L? Give your answer in J/mol/K

e) should the student celebrate? Why?

Explanation / Answer

A large RNA molecule M binds to a small ligand L to form ML. A student who excel

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