Difficulty: Easy
Correct Answer: Hill plot
Explanation:
Introduction:Cooperativity describes how binding of one ligand molecule affects affinity for additional molecules, typical in multimeric proteins. This question asks for the plot used to quantify cooperativity.
Given Data / Assumptions:
Concept / Approach:
The Hill plot linearizes cooperative binding data by plotting log[θ/(1−θ)] versus log[S] (or log[L]), where θ is fractional saturation. The slope gives the Hill coefficient nH, indicating positive cooperativity (nH > 1), non-cooperative behavior (nH ≈ 1), or negative cooperativity (nH < 1).
Step-by-Step Solution:
1) Collect saturation or velocity data over substrate concentrations spanning sub- and supra-K0.5 ranges.2) Convert to fractional saturation or use v/Vmax to approximate θ for enzymes.3) Plot log[θ/(1−θ)] versus log[S] to obtain a straight line over the cooperative range.4) Determine slope = nH, intercept provides apparent affinity parameter.Verification / Alternative check:
Non-linear regression with the Hill equation v = Vmax * S^nH / (K0.5^nH + S^nH) provides nH directly and serves as a numerical cross-check.
Why Other Options Are Wrong:
B: Koshland’s model explains mechanism but the suggested curve alone does not yield a simple numeric nH. C: Michaelis–Menten hyperbola applies to non-cooperative enzymes. D: Graphical determination is possible. E: Eadie–Hofstee is for MM kinetics, not specifically for cooperativity degree.
Common Pitfalls:
Over-interpreting nH as the exact number of binding sites; it is an empirical index of cooperativity strength.
Final Answer:
Hill plot
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