receptors revisited

Question 1

occupancy meaning

Answer 1

proportion of receptors occupied - will vary with conc

number occupied / number total receptors

Question 2

affinity meaning

Answer 2

Affinity is how avidly a drug binds its receptor or how the chemical forces that cause a substance to bind its receptor

Question 3

Radioligand binding assay key points and steps

Answer 3

preparation formed of receptor of interest and suitable radioligand incubated.

wash solution to remove non bound ligand

measure radioactivity

measures - receptor density and the affinity of the radioligand to receptors
the higher the receptor conc in general - the better the binding

Question 4

how to test using radioligands the non specific binding?

Answer 4

add excess non radioligand and it will outcompete

Question 5

two types of radioactive atoms you can add, advantages and disadvantages fro both

Answer 5

3H - long half life of 12 years, stable, no effect structure or nature

125I - shorter half life -67 days, its bigger so more effect likey and degrades easily

Question 6

what happens when you break open cells into a smoothie and how to limit problem

Answer 6

release proteases from lysosomes so need to add protease inhibitors and keep cold 0-4 degrees

Question 7

what is seen on a scatchard plot

Answer 7

specific vs non specific binding

Question 8

how to calculate Kd from a scatchard and what is Kd

Answer 8

a dissociation content that tells you affinity of drug. 50% of the max and read down

Question 9

type of curve on scatchard graph for non and specific binding

Answer 9

non specific - linear curve
specific - reaches saturation so it a rectangular hyperbola

if put on a log scale more of a sigmoidal curve