5. Consider three proteins in equilibrium between their unbound and ligand-bound

Question

5. Consider three proteins in equilibrium between their unbound and ligand-bound states. G) For the first protein, addition of the ligand leads to the emergence of a second set of resonances in the NMR spectrum. The intensity of the second set of peaks increases as ligand is added, while the intensity of the first set of resonances decreases. (ii) For the second protein, there is only one set of resonances for the free state, all partly bound states, and the fully saturated state. The chemical shift of the resonances changes as a function of ligand concentration. (i) For the third protein, the NMR spectra show very sharp resonances in the free state and in the saturated state, but extremely broadened resonances for partly bound states. The chemical shifts of resonances in the free and bound states are different. (a) Which regime of chemical exchange is reflected in the protein-ligand complexes described in (), (ii), and(iii). What determines the exchange regime?

Explanation / Answer

a. In Protein-ligand complexes described in above three situations, the regime of chemical exchange is conformational equilibrium, protonation or deprotonation, and binding of the protein to the ligand. The exchange regime is detected by the change in frequency in the NMR spectra due to chemical shift.

b. we can say that exchange rate is very high. The average weight of ligand and protein is more or less similar.

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