Law of Mass Action Flashcards
The law of mass action was postulated by who and in what year?
CM Guldberg and P Waage in 1864
State the law of mass action
The rate of reaction is directly proportional to the product of the active mass (concentration) of the reactants.
At equlibrium, all receptors are equally accessible to ligands. T or F?
True
At equilibrium, the receptor ligand binding is reversible. T or F?
True
At equilibrium, all receptors are either free or bound to ligand; there is no more than one affinity state or states of partial binding. T or F?
True
At equilibrium, binding does not alter the ligand or receptor. T or F?
True
Following LMA, drugs combine with their receptors at a rate dependent on the conc. of the drugs and conc. of the receptors. T or F?
True
Types of Labeled LBA?
- Flourescent
- Radioligand BA
- Bioluminescent BA using nanoluciferase
- Selenium labeling of peptide ligands
What is the importance of ligand binding assays
To quantify drug-receptor interactions
What is a ligand binding assay?
It is an analytical procedure that measures binding of ligands to receptors and other molecules.
What is the purpose of radioactivity in LBA?
As a detection method to measure amount of ligand
What are the types of LBA?
- Labeled LBA
- Label-free LBA
- Structure-based LBA
- Thermodynamic BA
- Whole cell LBA
Types of label-free LBA?
- Surface plasmon resonance
- Plasmon waveguide resonance
- Whispering gallery micro resonator
- Resonant waveguide grating
- Mass spectrometry
Types of structure based LBA?
- NMR
- X-ray crystallography
Types of thermodynamic binding assays?
- Thermal denaturation assays
- Isothermal titration calorimetry
Types of whole cell LBA
Surface acoustic wave biosensor
What is a radioligand?
A radioactively labeled ligand that can bind with any target of interest e.g receptors
What is the importance of RLBA?
- Allows for the determination of the rate and extent of binding interactions.
- Gives information on no of binding sites, affinity and accessibility of various drugs
The equilibrium dissociation constant(Kd) is a measure of?
The stability of the L-R complex
Kd is the inverse measure of?
Affinity
A high-affinity drug has a ___ Kd
Low.
A high-affinity drug will bind to a greater no of its receptor at a lower conc. T or F?
True
When 50% of the receptors are occupied, the conc. of free receptors will equal that of bound receptors. T or F?
True
At 50% occupation, [Ligand] = Kd. True or False?
True
What is Kd?
The concentration of ligand at equilibrium that is required to occupy half the receptors
T or F
For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is that [ligand] at which max binding is observed.
False
T or F
For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is the equilibrium constant for R.L formation
False. It is the equilibrium dissociation constant
T or F
For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding has units of per M
F. Unit is M
T or F
For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is a second order rate constant
False
T or F
For an isolated, simple receptor system of the type R + l = R.L, Kd for ligand binding is that [ligand] at which 1/2 of the receptor exists R.L
True
What is the formula for fractional occupancy?
[Ligand]/[Ligand + Kd]
Receptor fractional occupancy is?
The proportion of the receptors that are bound to or occupied by the drug.
Who postulated the receptor occupancy theory?
Clark
State the receptor occupancy theory?
The fraction of the receptor bound is directly proportional to tissue response
What are the limitations of the receptor occupancy theory?
- The slope of the conc.-response curves for certain drugs were steeper than predicatable by FO equation.
- Extremely high conc. of certain other drugs failed to produce maximum response.
