AL - Quantitative Studies II Flashcards
(15 cards)
Q: What are some advantages of a Direct Plot? (3)
- No data transformation required
- No need for modelling
- No distortion of data points
Q: What is required to interpret a Direct Plot? (1)
- Must know Bmax (maximum binding)
Q: What are the relationships between Bmax and Kd? (3)
- 90% Bmax at 9 × Kd
- 95% Bmax at 19 × Kd
- 99% Bmax at 99 × Kd
Q: What is the purpose of a Scatchard Plot? (1)
- To linearise binding data for determining receptor-ligand affinity and capacity
Q: How do you interpret a Scatchard Plot? (2)
- Slope = −1/Kd → steeper slope = higher affinity
- X-intercept = Bmax → total number of binding sites
Q: What does a curved Scatchard plot suggest? (1)
- Indicates more than one type of binding site (site heterogeneity)
Q: What does a “bent” Scatchard plot indicate? (2)
- Site heterogeneity
- Negative cooperativity
Q: What happens in a Hill Plot when n > 1, n = 1, and n < 1? (3)
- n > 1 → positive cooperativity
- n = 1 → non-cooperative binding
- n < 1 → negative cooperativity
Q: What does the Hill coefficient (n) represent? (1)
- The degree of cooperativity in ligand binding
Q: What is the purpose of a Displacement Curve? (1)
- To study competitive binding between labeled and unlabeled ligands
Q: What does IC50 mean? (2)
- Concentration of unlabeled ligand needed to displace 50% of labeled ligand
- Lower IC50 = higher potency
Q: What is the formula for Ki (inhibition constant)? (1)
- Ki = IC50 / (1 + [L]/Kd)
Q: What does the Ki value represent? (1)
- The binding affinity of an inhibitor — lower Ki = more potent
Q: How do cooperative interactions affect displacement curves? (2)
- Steeper slope with positive cooperativity
- Quantified by the Hill coefficient in a Hill plot
Q: What can influence displacement curves in cloned receptors? (1)
- G-protein coupling can alter receptor affinity and binding behaviour, even with only one receptor type
