Question

A 25,000 Da protein contains a single binding site for a molecule (ligand), whose molecular weight is 2,500 Da. Assuming high affinity and physiologically irreversible binding, the amount of the ligand required to occupy all the binding sites in 10 mg protein will be

(a) 0.1 mg

(b) 1 mg

(c) 10 mg

(d) 100 mg

Answer 1

Answer is : (b) 1 mg

Assuming x as the amount of ligand to occupy all the binding sites in 10 mg protein.

x mg/Protein in grams = Ligand molecular weight/Protein molecular weight

x = 2500/25000 x 10 = 1 mg