Calculator Inputs
Example Data Table
This sample shows how concentration can change occupancy, specific binding, and total binding in a simple ligand-receptor system.
| Ligand (uM) | Specific Binding | Nonspecific Binding | Total Binding | Occupancy (%) |
|---|---|---|---|---|
| 0.10 | 5.71 | 4.12 | 9.83 | 4.76 |
| 0.50 | 24.00 | 4.60 | 28.60 | 20.00 |
| 1.00 | 40.00 | 5.20 | 45.20 | 33.33 |
| 2.00 | 60.00 | 6.40 | 66.40 | 50.00 |
| 5.00 | 85.71 | 10.00 | 95.71 | 71.43 |
Formula Used
The calculator combines direct binding, Hill-style cooperativity, receptor occupancy, and a linear nonspecific background term.
Fractional occupancy (θ) = [L]^h / (Kd^h + [L]^h)
Specific binding = Bmax × θ
Nonspecific binding = (slope × [L]) + intercept
Total binding = Specific binding + Nonspecific binding
Bound receptor = Rt × θ
Free receptor = Rt − Bound receptor
Occupied sites = Bound receptor × n
Association constant (Ka) = 1 / Kd(M)
Estimated ΔG = R × T × ln(Kd in molar units)
Here, [L] is ligand concentration, h is the Hill coefficient, Rt is total receptor concentration, and n is the number of sites per receptor.
How to Use This Calculator
- Enter the ligand concentration you want to evaluate.
- Add Kd, Bmax, receptor concentration, and sites per receptor.
- Adjust the Hill coefficient when binding is cooperative.
- Include nonspecific slope and intercept for background signal.
- Choose concentration units, set temperature, then submit.
- Review the result cards, graph, table, and export buttons.
Frequently Asked Questions
1. What does this calculator estimate?
It predicts occupancy, specific binding, nonspecific binding, total binding, receptor usage, site occupancy, association constant, and an estimated free-energy value from your entered parameters.
2. What is Kd in this model?
Kd is the dissociation constant. Lower Kd values indicate tighter ligand binding because half-maximal occupancy occurs at a lower concentration.
3. Why is the Hill coefficient included?
The Hill coefficient adjusts curve steepness. Values above one suggest positive cooperativity, while values below one suggest weaker cooperative behavior or heterogeneous binding.
4. What does Bmax represent?
Bmax is the maximum specific binding signal the system can reach when the available binding population is effectively saturated.
5. Why add nonspecific binding terms?
Real experiments often include background signal. The slope and intercept let you estimate that contribution and separate total signal from specific binding.
6. Can I use nM, uM, mM, or M?
Yes. Select the concentration unit that matches your data. The calculator also converts Kd to molar units for Ka and ΔG estimation.
7. Does this tool fit raw laboratory data?
No. It predicts results from entered parameters. Use nonlinear regression software when you need parameter fitting from experimental observations.
8. What should I export?
Export the predicted table and summary when you need clean reporting, quick sharing, or a convenient record for method notes and comparisons.