What can be implied for Kd, the dissociation constant for drug-receptor complex at equilibrium?
Because Kd is a dissociation constant, the smaller the Kd, the larger the concentration of the drug-receptor complex, the more stable is that complex, and the greater is the affinity of the drug for the receptor
Identify two reasons why drug-receptor complex are unfavorable?
– It causes a loss in conformational degrees of freedom for both the ligand and protein – It also causes the loss of three rotational and three translational degrees of freedom
– Predicts that the response is directly related to the number of receptors bound by an agonist. – The more drugs bound to the receptor the greater the response (receptors can The more drugs bound to the receptor, the greater the response (receptors can become saturated).
– Suggests that the number of drug-receptor interactions per unit time determines the intensity of the response. – Drugs that associate with then rapidly dissociate from the receptor, allow hd l l b li ihh hihi another drug molecule to subsequently interact with the receptor, which is expected to produce a greater response.
– Suggests that as the drug approaches the receptor a conformational change occurs in the receptor to allow for effective binding. –This theory suggests that the receptor does not normally exist in the proper conformation for drug binding, and dissociation of the drug from the receptor allows the receptor to revert to its original form.
Macromolecular Perturbation Theory
– Suggests that two types of conformational change exist, and that the rate of their existence determines the observed biological response. – Agonists produce the specific perturbation required for a biological response, while antagonists produce a non-specific perturbation which fails to produce a biological response.
Indicates that receptors are always in a dynamic equilibrium between active and inactive states. Agonists function by shifting the equilibriu toward the active state, while antagonists prevent the active state.
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