Formulas

Question 1

Molar Fraction of occupied Receptor

“f”

Answer 1

• KD = dissociation constant of receptor-antagonist complex (affinity)
• When [L] = KD, 50% protein is bound
• When [L] = 0.1 KD only 9% of the protein is bound
• When [L] = 10 KD, the protein is 91% saturated

Question 2

Cheng Prusoff Relation for Competitive Antagonism

KD

Answer 2

• KD = dissociation constant of receptor-antagonist complex (affinity)
• EC50 = [drug] that reduces response to 50% of the maximum value
• KL = dissociation constant of agonist used in the displacement assay (usually obtained from the literature or must determined beforehand)
• [L] = concentration of agonist in the displacement assay
• {1 + [L]/KL} the term called a dose ratio

Question 3

Lower KD or lower EC50 means?

Answer 3

GREATER AFFINITY / MORE POTENT DRUG

inversely related to potency