Drug Affinity Flashcards
What affects drug affinity?
The ability of a drug to fit in the molecular target
What bonds form between drug and the molecular target?
Rarely covalent
van der Waals
ionic/
hydrogen bonding
How is affinity measured?
It is given as the concentration of a drug needed to bing 50% of all receptors
Describe radioligand binding assays
Radiolabel the drug
Add the drug and receptor to well
Allow to reach equilibrate
Wash the plate and any unbound ligand will wash away, leaving bound ligand
Add excess of unlabelled drug to outcompete the radioligand that has non-specifically bound to determine how much binds to the receptors
Describe saturation binding
A direct measure between Kd and Bmax and describes a linear relationship between ligand and non specific clinging sites
Describe a Scatchard plot
A plot of bound ligand against the bound ligand/free lighand
Describe a competition binding assay
A small proportion of radiolabelled ligand is bound to the receptor and the experimental drug is added and the amount needed to outcompete 50% of the radioligand is measured
What is Kd?
The concentration of ligand needed to bind 50% of receptors
What is Ki?
Kd derived from IC50
What is Km?
The concentration of substrate that give 50% maximal rate in an enzyme substrate complex
What is Bmax?
Maximal binding
What is IC50?
The concentration of competitor needed to remove 50% radio ligand
What is Vmax?
The maximum rate
