Flashcards in Receptors I Deck (51)
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1
What drug type creates a response in the cell
agonist
2
What is occupation of a drug-receptor governed by?
Affinity
3
What is activation of a drug-receptor governed by?
efficacy
4
What part of a drug receptor reaction is reversible
occupation forming a complex
5
What is the ratio of reversibility of a drug receptor reaction governed by?
affinity of the drug
6
Describe the reversibility of drugs with high affinities
slow reversibility
7
Describe occupancy
proportion of receptors occupied will vary with the drug concentration
8
What does occupancy vary between
0 and 1
9
How much drug is present at 0 occupancy
none
10
How can we measure occupancy
by measuring response
11
Describe the relationship between occupancy and response
high occupancy means there is a large response
12
Can you measure antagonists activity using occupancy
NO
13
Examples of ligands
neurotransmitters, hormones, growth factors, cytokines, drugs, toxins
14
Examples of protein targets
receptors, ion channels, enzymes, transporters
15
Describe a ligand binding practical
tissue prep with radio-ligand, incubation, filtration, rinse, count, data analysis
16
True or False - most ligands bind non-specifically to tissue, filter paper, glass
TRUE
17
How can non-specific ligand binding be reduced
reduced by anti-absorbants
18
What are some examples of anti-absorbants
albumin, collagen, o-catechol
19
What is the function of rinsing in a ligand binding practical
remove unbound radioligand from incubation medium
20
What is a key measurement in receptor ligand assays
specific and non specific binding
21
What are the disadvantages of using a radio ligand
degradation
22
How can you prevent degradation of radio ligands
free radical scavenger, store at low temp, avoid light, incorporation of antioxidant
23
What are radio ligands labelled with
radio active labels
24
Name two radio labels
tritum, iodine
25
What are the disadvantages of tritum
specialised labs required, expensive
26
What are the advantages of tritum as a label
high specific activities, good stability, long half life
27
What are the advantages of iodine as a label
easy and cheap, if aromatic hydroxyl group can be incorporated at high specific activities
28
What are the disadvantages of iodine
more readily degraded, short half life, activity of ligand can be reduced
29
What tissue would you select for your ligand binding practical
tissue that contains the receptors of interest
30
What can the tissue be in the ligand binding practical
isolated membranes, slices, synaptosomes, purified receptors
31
What must incubation preserve
integrity of ligands and binding sites
32
What happens during the tissue incubation period of the ligand binding practical
enzymes are liberated
33
What is the effect of enzymes being liberated during the tissue incubation period
enzymes break down receptors of interest
34
What are the enzymes liberated during the tissue incubation period
proteases
35
How can the effect of enzymes be minimised during the tissue incubation period
protease inhibitors added for peptides, anti-oxidants if ligand is oxidisable
36
What is the temperature during the incubation period
low room temperature to 0 degrees
37
How is the tissue and bound ligand separated from free ligand
filtration or centrifugation
38
What is a problem when separating bound ligand from free ligand during the practical
rate of dissociation of ligand-receptor complex
39
What must speed of separation of bound ligand from free ligand be compatible with
affinity of ligand for receptor
40
What type of separation does lower affinity of ligand receptor require
faster/more efficient separation
41
How do you work out specific binding
subtract non specific binding from total bound
42
How is ligand receptor binding data plotted
semi-logarithmic scale
43
What is saturable binding
specific binding
44
Why is radio-ligand binding saturable
total number of receptors is limited
45
What does the Langmuir equation describe
relationship between receptor occupancy, affinity and drug concentration
46
What is Bmax in the Scatchard equation
maximum amount of drug which can bind specifically to receptors
47
What is F in the Scatchard equation
free ligand concentration
48
What is KD in the scatchard equation
dissociation constant for radio ligand
49
What determines the dissociation constant for the radio ligand
saturation analysis
50
What is KD a measure of
affinity
51
