Joint Analysis of Proton-Coupled Binding Thermodynamics Using Multi-Buffer ITC and Dilution Blanks
The laboratory measured isothermal titration calorimetry data for the same ligand–receptor system in PIPES, MOPS, HEPES, and TRIS. Three independent titrations were performed in each buffer, and every binding experiment has a dilution blank from the same buffer and batch and using the same injection program. The per-injection integrated heats, heat uncertainties, measured cell/syringe concentrations, cell volume, buffer ionization enthalpies, and acceptance criteria are provided in /app/input.
Perform per-injection blank correction and uncertainty propagation, reconstruct the titration composition under finite-cell-volume conditions, and jointly fit the four buffers to determine the binding constant, number of active sites, intrinsic binding enthalpy, and number of protons taken up per binding event for each independent replicate. Then summarize the apparent binding enthalpies, fit residuals, and means/standard deviations of the three sets of global parameters at both the individual-titration and buffer levels; determine whether the data support a proton-coupled model; and provide the final acceptance conclusion.
Generate analysis.py, corrected_injection_heats.csv, run_fits.csv, buffer_summary.csv, replicate_global_fits.csv, global_thermodynamics.csv, itc_isotherms.png, buffer_enthalpy_linkage.png, itc_fit_residuals.png, and itc_linkage_report.md under /app/output. Retain explicit units in the results, and ensure that the figures, tables, and report are consistent with the CSV files. Do not read data from outside /app/input or hard-code reference results in the script.
Deliverables
This section defines only the submission format and content categories; it does not prescribe the analysis method or results. All files listed below are required and must be written directly to /app/output/.
/app/output/analysis.py
- Format and encoding:
.py text file, UTF-8.
General CSV Conventions
- Format and encoding: UTF-8, comma-separated CSV; use a period as the decimal separator; do not write an additional index column.
- The fields in the tables below are listed in the required column order. Fields separated by commas within the same table cell must appear consecutively in the file and retain the listed order.
/app/output/corrected_injection_heats.csv
- Row semantics: Each row corresponds to one injection in a binding titration, for a total of 216 rows.
- Stable keys:
buffer_id, replicate, and injection_index; run_id identifies the associated binding titration.
| Required field |
Type |
Unit |
Meaning |
run_id, buffer_id |
string |
— |
Binding titration identifier and buffer identifier |
replicate, injection_index |
integer |
— |
Independent replicate number and injection number |
injection_volume_uL |
number |
µL |
Volume of a single injection |
molar_ratio_total_ligand_to_receptor |
number |
dimensionless |
Molar ratio of total ligand to receptor |
binding_heat_uJ, blank_heat_uJ |
number |
µJ |
Binding-titration heat and paired blank heat |
binding_heat_sd_uJ, blank_heat_sd_uJ |
number |
µJ |
Uncertainties of the binding-titration heat and paired blank heat |
corrected_heat_uJ, corrected_heat_sd_uJ |
number |
µJ |
Corrected heat and its uncertainty |
predicted_corrected_heat_uJ, residual_uJ |
number |
µJ |
Predicted corrected heat and residual |
standardized_residual |
number |
dimensionless |
Standardized residual |
/app/output/run_fits.csv
- Row semantics: Each row corresponds to one binding titration, for a total of 12 rows.
- Stable key:
run_id; buffer_id and replicate specify its buffer and independent-replicate identities.
| Required field |
Type |
Unit |
Meaning |
run_id, buffer_id |
string |
— |
Binding titration identifier and buffer identifier |
replicate |
integer |
— |
Independent replicate number |
buffer_ionization_enthalpy_kJ_mol |
number |
kJ/mol |
Buffer ionization enthalpy |
Ka_M_inv_global_replicate |
number |
M⁻¹ |
Binding constant for the corresponding independent replicate |
n_sites_global_replicate |
number |
dimensionless |
Number of active sites for the corresponding independent replicate |
observed_binding_enthalpy_kJ_mol |
number |
kJ/mol |
Apparent binding enthalpy of the individual titration |
expected_from_linkage_kJ_mol |
number |
kJ/mol |
Apparent binding enthalpy corresponding to the proton-linkage relationship |
heat_rmse_uJ |
number |
µJ |
RMSE of the heat residuals |
maximum_abs_standardized_residual |
number |
dimensionless |
Maximum absolute standardized residual |
/app/output/buffer_summary.csv
- Row semantics: Each row corresponds to one buffer, for a total of 4 rows.
- Stable key:
buffer_id.
| Required field |
Type |
Unit |
Meaning |
buffer_id |
string |
— |
Buffer identifier |
buffer_ionization_enthalpy_kJ_mol |
number |
kJ/mol |
Buffer ionization enthalpy |
n_runs |
integer |
— |
Number of titrations included in the summary |
observed_binding_enthalpy_mean_kJ_mol, observed_binding_enthalpy_sd_kJ_mol |
number |
kJ/mol |
Mean and standard deviation of the apparent binding enthalpy |
heat_rmse_mean_uJ |
number |
µJ |
Mean RMSE of the heat residuals |
maximum_abs_standardized_residual |
number |
dimensionless |
Maximum absolute standardized residual |
/app/output/replicate_global_fits.csv
- Row semantics: Each row corresponds to the global result for one set of independent replicates, for a total of 3 rows.
- Stable key:
replicate.
| Required field |
Type |
Unit |
Meaning |
replicate |
integer |
— |
Independent replicate number |
Ka_M_inv |
number |
M⁻¹ |
Binding constant |
Kd_uM |
number |
µM |
Dissociation constant |
n_sites |
number |
dimensionless |
Number of active sites |
deltaH_intrinsic_kJ_mol |
number |
kJ/mol |
Intrinsic binding enthalpy |
protons_uptake_per_binding |
number |
protons/binding event |
Number of protons taken up per binding event |
deltaG_apparent_kJ_mol |
number |
kJ/mol |
Apparent binding free energy |
TdeltaS_linkage_intercept_kJ_mol |
number |
kJ/mol |
Entropic term corresponding to the proton-linkage intercept |
weighted_rmse |
number |
|
Weighted residual RMSE |
maximum_abs_standardized_residual |
number |
dimensionless |
Maximum absolute standardized residual |
/app/output/global_thermodynamics.csv
- Row semantics: A single-row summary of the three sets of independent replicates and the buffer proton-linkage results.
| Required field |
Type |
Unit |
Meaning |
n_replicate_global_fits |
integer |
— |
Number of independent global results included in the summary |
Ka_M_inv_mean, Ka_M_inv_sd |
number |
M⁻¹ |
Mean and standard deviation of the binding constant |
Kd_uM_mean, Kd_uM_sd |
number |
µM |
Mean and standard deviation of the dissociation constant |
n_sites_mean, n_sites_sd |
number |
dimensionless |
Mean and standard deviation of the number of active sites |
deltaH_intrinsic_kJ_mol_mean, deltaH_intrinsic_kJ_mol_sd |
number |
kJ/mol |
Mean and standard deviation of the intrinsic binding enthalpy |
protons_uptake_per_binding_mean, protons_uptake_per_binding_sd |
number |
protons/binding event |
Mean and standard deviation of the number of protons taken up per binding event |
deltaG_apparent_kJ_mol_mean, deltaG_apparent_kJ_mol_sd |
number |
kJ/mol |
Mean and standard deviation of the apparent binding free energy |
TdeltaS_linkage_intercept_kJ_mol_mean, TdeltaS_linkage_intercept_kJ_mol_sd |
number |
kJ/mol |
Mean and standard deviation of the entropic term corresponding to the proton-linkage intercept |
weighted_rmse_mean, weighted_rmse_sd |
number |
|
Mean and standard deviation of the weighted residual RMSE |
maximum_abs_standardized_residual_mean, maximum_abs_standardized_residual_sd |
number |
dimensionless |
Mean and standard deviation of the maximum absolute standardized residual |
buffer_linkage_intercept_kJ_mol |
number |
kJ/mol |
Intercept of the buffer enthalpy linkage |
buffer_linkage_slope_protons |
number |
protons/binding event |
Slope of the buffer enthalpy linkage |
buffer_linkage_R2 |
number |
dimensionless |
Coefficient of determination for the buffer enthalpy linkage |
assessment_status, failure_reasons |
string |
— |
Acceptance status and reasons for failure |
PNG Images
/app/output/itc_isotherms.png: Blank-corrected ITC isotherms./app/output/buffer_enthalpy_linkage.png: Plot of the relationship between buffer ionization enthalpy and apparent binding enthalpy./app/output/itc_fit_residuals.png: ITC fit residual plot.- All three figures must be valid, openable PNG files, clearly labeled, include units, and be consistent with the CSV contents.
/app/output/itc_linkage_report.md
- Format and encoding: Markdown, UTF-8.
- Content categories: paired blanks, finite cell volume, measured concentrations, binding constants and numbers of active sites, differences in apparent binding enthalpy among buffers, intrinsic binding enthalpy, proton linkage, independent-replicate results and their summary, residuals, and the acceptance conclusion.
