Description
Compare two supplied dissociation constants as a binding free-energy difference.
Biophysical scalar models require explicit signal, concentration, temperature, energy and geometric conventions. Effective concentration differs from dimensionless activity, a single displacement differs from mean-square displacement, and a fluorescence yield ratio needs absorption and refractive-index corrections. Supplied model parameters do not establish that the model applies to an experiment.
Compare two supplied dissociation constants as a binding free-energy difference.
When to use this tool
Use Binding Free Energy Kd Ratio when you already have firstKd, secondKd, temperatureKelvin, gasConstantJoulesPerMoleKelvin and need to compare two supplied dissociation constants as a binding free-energy difference.
How to use the tool and how it works
- Enter firstKd, secondKd, temperatureKelvin, gasConstantJoulesPerMoleKelvin. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read firstMinusSecondFreeEnergyJoulesPerMole. Use the output convention below.
Require both Kd values, Kelvin temperature and gas constant positive; return R*T*(ln(firstKd)-ln(secondKd)) in J/mol for the stated R unit.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstKd | First Kd | Required. Finite number; strictly above 0. |
| secondKd | Second Kd | Required. Finite number; strictly above 0. |
| temperatureKelvin | Temperature Kelvin | Required. Finite number; strictly above 0. |
| gasConstantJoulesPerMoleKelvin | Gas Constant Joules Per Mole Kelvin | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| firstMinusSecondFreeEnergyJoulesPerMole | R*T*(ln(firstKd)-ln(secondKd)), for comparable dissociation constants on the same standard-state basis. | Required. Finite number. |
{
"input": {
"firstKd": 0.000002,
"secondKd": 0.000001,
"temperatureKelvin": 298.15,
"gasConstantJoulesPerMoleKelvin": 8.31446261815324
},
"output": {
"firstMinusSecondFreeEnergyJoulesPerMole": 1718.2820757981524
}
}Limitations and assumptions
- Kd units, standard states, temperature and binding convention must match. Lower first Kd gives negative first-minus-second free energy; this is not an absolute binding energy, fitted affinity, kinetics or actual molecular finding.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the complete physical model, calibrated measurements and uncertainty analysis. Check reference states, photon-signal bases, diffusion assumptions and binding-constant conventions before interpreting local contributions as physical measurements.
References
Similar or alternative tools
- Biophysical Temperature Energy Factor
Calculate supplied kBT thermal-energy scale.
- Osmosis Concentration Activity Term
Multiply supplied concentration by a supplied activity coefficient.