1. What is KD in Biochemistry?

KD (Dissociation Constant) is a fundamental parameter in biochemistry that quantifies the affinity between a ligand and its receptor. It represents the concentration of ligand at which half of the receptors are occupied at equilibrium.

2. How Does the Calculator Work?

The calculator uses the KD equation:

Where:

• \( k_{off} \) — Dissociation rate constant (s⁻¹)
• \( k_{on} \) — Association rate constant (M⁻¹ s⁻¹)

Explanation: KD is calculated as the ratio of the dissociation rate to the association rate, providing a measure of binding affinity.

3. Importance of KD Calculation

Details: Accurate KD determination is crucial for understanding molecular interactions, drug development, and characterizing binding kinetics in biochemical systems.

4. Using the Calculator

Tips: Enter koff in s⁻¹ and kon in M⁻¹ s⁻¹. Both values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What does a lower KD value indicate?
A: A lower KD value indicates higher binding affinity between the ligand and receptor.

Q2: How is KD related to binding affinity?
A: KD is inversely proportional to binding affinity - lower KD values correspond to stronger binding.

Q3: What are typical units for KD?
A: KD is typically expressed in molar units (M), with common values ranging from nM to mM depending on the binding interaction.

Q4: How is KD measured experimentally?
A: KD can be measured through various techniques including surface plasmon resonance (SPR), isothermal titration calorimetry (ITC), and fluorescence polarization.

Q5: What's the relationship between KD and IC50?
A: While related, KD is an equilibrium constant for binding, while IC50 is the concentration that inhibits 50% of biological activity under specific assay conditions.