1. Information needed for calculations
Specific activity = 19.5 Ci mmolˉ1
1 Ci = 2.22 x 10ˉ12 dpm (Disintegrations per minute)
1 mmol = 19.5 x (2.22 x 10ˉ12) dpm

2. Information needed for calculations II
Calculate the total number moles bound in each tube = tube dpm
19.5 x (2.22 x 10ˉ12 dpm)
e.g. if tubes dpm = 788
No. mmol = 788
= 1.82 x 10ˉ11 mmol / 1.82 x 10ˉ14 mol

3. Quantify receptor affinity for a drug and so classify receptor types
Use 1:
Quantify receptor affinity for a drug and so classify receptor types
14 receptors identified for
5-hydroxytryptamine (5-HT)
all with a radioactive ligand for
ligand binding analysis
5-HT1A,B 5-HT2A,B 5-HT3 5-HT4
2 cannabinoid receptors, each
with a radioactive ligand
CB1 CB2

4. Use 2:
Find molecular shape of drug binding pocket : drugs by computer design? 7 6 5 1
antagonist
agonist 2 3 4

5. Selective drug target for analgesia??
Use 3:
Receptor localisation and expression levels in normal/diseased organs and cells
P2X3 receptor
(an extracellular ATP receptor)
found only in sensory neurone C-fibres
Selective drug target for analgesia??