ELM 3.2

Question 1

What is the relationship between Kd and affinity for drugs?

Answer 1

High Kd = low affinity
Low Kd = high affinity (binds tightly)

Question 2

If you want to find out how much times something’s affinity is of another, how do you calculate this?

Answer 2

Divide the low affinity value by the high affinity value

Question 3

Is Kd normally distributed?

Answer 3

No, but log Kd is

Question 4

Selectivity is what?

Answer 4

Affinity or potency of one drug at receptor A vs its affinity or potency at receptor B

Question 5

What is the equation for specific binding?

Answer 5

Specific binding = total binding - NSB (non-specific binding)

Question 6

How do you measure non-specific binding?

Answer 6

Duck and owls on ship analogy - choose a ligand that is chemically dissimilar (so that it is less likely to form same nsb) - you can’t stop radioligand from binding to nsb sites bc they’re so numerous

Question 7

What is the Kd?

Answer 7

Concentration that gives 50% Bmax

Question 8

How do we define ‘high’ and ‘low’ affinity for Kd?

Answer 8

E-10 to 1E-9 M: very high affinity
1E-9 to 1E-8 M: high affinity
1E-8 to 1E-7 M: moderate affinity
1E-7 or lower: low affinity

Question 9

Hill equation simplified

Answer 9

Make Bmax 100:

concentration = 100*[concentration]/(Kd+[concentration])