MACS Matchmaker

Langmuir 1:1 Binding

The simplest reversible binding model: one analyte binds one ligand to form one complex. Use this simulator to build intuition for how the association rate, dissociation rate, and analyte concentration shape the response curve.

Reaction
AanalyteLligandkₒₙkₒffA·Lcomplex
dR(t)dt=kon C (Rmax−R(t))−koff R(t)\frac{dR(t)}{dt} = k_{on}\, C\, (R_{max} - R(t)) - k_{off}\, R(t)

R(t): response over time · C: analyte concentration · Rmax: maximum binding capacity · kon: association rate constant · koff: dissociation rate constant.

Assumptions
  • Pseudo-first order: analyte concentration in solution is constant.
  • Mass transport from bulk to surface is fast and not limiting.
  • One-to-one stoichiometry; no cooperativity.
  • Fully reversible.
Parameters

kon (M⁻¹ s⁻¹)

koff (s⁻¹)

Concentration series (nM)
Kinetic mode
Single-cycle: concentrations are injected sequentially on the same surface, no regeneration.

Noise σ (pg/mm²)

Derived quantities

KD = koff / kon = 10 nM

Req at C = 800 nM: 99 pg/mm²

Time to 95% of Req (highest C): 37 s

Diagnostic cues

Curves bend more sharply than kon × C predicts → suspect mass transport.

Dissociation does not return to baseline → suspect drift, low koff, or non-specific binding.

Replicates of the same concentration disagree → check immobilization homogeneity.

Export traces as CSV
Current parameters: k_on = 1.0e5 M⁻¹ s⁻¹, k_off = 1.0e-3 s⁻¹, R_max = 100 pg/mm².