Glossary and equations

Terminology, keyboard conventions, calculation symbols, equations, and references.

Last verified: 2026-09-23

Use the tables to look up terms and symbols, and the equation index to reach each calculation beside its workflow and assumptions. Start with Quick start for instructions.

Workspace terms

Term	Meaning in FT-ITC Analysis
Experiment Data	One imported or application-created ITC dataset, including its details and analysis state.
Data / Results	The workspace list containing experiments and stored Analysis Results.
Selected	The item currently shown or targeted by a selection-specific command.
Active experiments	Experiments included in a multi-experiment operation.
Solution	A fitted model state for one experiment.
Analysis Result	A stored fit result with one or more member solutions and the fit state used to create it.
Attribute	Experiment metadata used for organization or analysis context.
Valid result	An Analysis Result whose recorded fit inputs still match the current project state.
Correlation view	Pearson correlations between fitted parameter coordinates across residual-bootstrap refits that have finite values for every displayed parameter, with diagnostics for simulation precision.
Pearson correlation	A value from −1 to +1 describing linear co-variation between two fitted coordinates.
Monte Carlo precision interval	Approximate Fisher-transformation interval describing how precisely the correlation coefficient $r$ is estimated from the finite retained-refit ensemble; it is not uncertainty for either fitted parameter or a model-validity assessment.
AIC / AICc	Fit-comparison scores that account for parameter count; smaller is preferred only for comparable observations and likelihood conventions. They do not establish model adequacy. See Information criteria for weighting, variance estimation, member scope, and AICc's small-sample approximation.

Uncertainty terms

Term	Meaning in FT-ITC Analysis
Best-fit value	Parameter value from the primary optimization. Resampling estimates uncertainty around this value but does not replace it with a resampling mean or median.
Standard deviation (SD)	For residual-bootstrap parameters, the root-mean-square deviation of retained refit values from the primary best-fit value, transformed or propagated for display. Profile-likelihood results use the equivalent display scale defined below.
95% confidence interval (CI)	For a residual-bootstrap parameter, the 2.5th and 97.5th percentiles of the retained refit distribution, transformed for display. Profile-likelihood intervals use likelihood-threshold endpoints. Derived quantities use the application's uncertainty-propagation rules. Intervals can be asymmetric around the best-fit value.
Automatic uncertainty display	Shows CI for a materially asymmetric stored interval and SD otherwise. It selects a presentation separately for each reported quantity.
Displayed parameter uncertainty	Fitted-parameter uncertainty after conversion or propagation into the quantity shown to the user. The Automatic display decision is applied to this displayed quantity.
Profile likelihood	A 95% interval search that holds one parameter at trial values while refitting the others. A bound reached before the threshold is censoring, not a confidence endpoint. See Profile-likelihood uncertainty for calibration and relative-weight assumptions.
Profile equivalent SD	Symmetric `value ± SD` display scale computed from a complete asymmetric profile interval; it is a display equivalent, not a Gaussian sampling SD.

Keyboard conventions

The application command modifier is Command on macOS and Ctrl on Windows or Linux.

Shortcut	Function
Command/Ctrl + O	Open data or a project.
Command/Ctrl + S	Save the current project.
Command/Ctrl + Shift + S	Save the project under another name.
Command/Ctrl + E	Open data export.
Command/Ctrl + P	Print the active graph or figure.
Command/Ctrl + Z	Restore the most recently removed item.
Command/Ctrl + I	Invert the Active Experiment Data set.
Command/Ctrl + comma	Open Preferences.
Command/Ctrl + Q	Quit FT-ITC Analysis.
F1	Open Help and Guide on Windows and Linux. On native macOS, choose Help > FT-ITC Analysis Help.
Enter	Open Details for the selected Data/Results item on Windows and Linux.
Left / Right	Change the selected injection in Process Data.
Space	Copy the selected integration end-point offset to the next injection in Process Data; the start is also copied when that processing option is enabled.

Thermodynamic symbols

Symbol	Meaning
$N$	Stoichiometry or site-number term under the selected model.
$\alpha$	Syringe-side active-concentration correction when syringe correction is enabled.
$K_{\mathrm{a}}$	Association constant.
$K_{\mathrm{d}}$	Dissociation constant.
$K_{i}$	Macroscopic association constant for sequential transition $i$ .
$\beta_{i}$	Cumulative sequential association product $\prod_{j=1}^{i} K_j$ .
$F_{i}$	Fraction of macromolecule in sequential state $MX_{i}$ .
$\bar{\nu}$	Mean ligand occupancy in the sequential model.
$\Delta H$	Binding enthalpy change.
$\Delta G$	Gibbs free-energy change.
$-T\Delta S$	Entropic contribution reported by the application at the evaluation temperature.
$\Delta C_{\mathrm{p}}$	Heat-capacity change in a supported temperature-dependent analysis.
$q$	Integrated injection heat.
$\sigma$	Standard uncertainty or spread, according to context.
Offset	Energy-per-mole-of-injectant correction included in the modeled injection heat.

Calculation symbols

Symbol	Meaning
$P(t)$	Differential power at time $t$ in a thermogram.
$b(t)$	Estimated baseline at time $t$ .
$n_{i}$	Amount injected in injection $i$ .
$r_{i}$	Residual for injection $i$ : observed heat minus model heat.
$r_{jk}$	Pearson correlation between fitted parameter coordinates $j$ and $k$ .
$\theta_{bj}$	Value of fitted coordinate $j$ in complete bootstrap refit $b$ .
$\sigma_{i}$	Processing-derived uncertainty for injection $i$ .
$R$	Gas constant.
$T$	Absolute temperature, in kelvin, for thermodynamic relationships.
$I$	Ionic strength used in salt analysis.
$c_{\mathrm{salt}}$	Recorded concentration of the single salt used for Salt Dependence.
$\Delta n_{\mathrm{H}^{+}}$	Fitted slope of observed binding enthalpy against buffer ionization enthalpy: net proton uptake (positive) or release (negative) per binding event.
$\Delta H_{0}$	Buffer-independent binding enthalpy at the experimental pH: the Protonation intercept, retaining binding-partner protonation heat.
$s$	Salt-dependence slope: change in ln(Kd / M) per change in ln(Salt concentration / M).
$\mathrm{RSS}$	Raw residual sum of squares, $\sum r_i^2$ , over included injections.
$Q$	Standardized residual sum of squares, $\sum (r_i/\sigma_i)^2$ . Weighted AIC/AICc estimates a common variance multiplier as $Q/n$ .
$L$	Gaussian likelihood used for AIC/AICc.
$n$	Number of included observations in the information-criterion calculation.
$p$	Number of free fitted parameters in the saved global model; shared coordinates count once and member coordinates count per member.
$K$	AIC/AICc likelihood parameter count: $p + 1$ in both weighting modes, including one estimated common residual variance or one estimated multiplier of the injection-error variances.

Equation index

Relationship	Local explanation
Integration and molar normalization	Integration calculation
Processing-derived injection heat SD	Noise calculation and limits
Dilution-driven dissociation of an associated pair	Dissociation
Sequential binding polynomial and ligand balance	Sequential Binding Sites
Thermodynamic conversion and −TΔS	Thermodynamic relationships
Fit residuals, RMSD, and weighting	Weight by injection error
AIC, AICc, Gaussian likelihood, and parameter counting	Information criteria
Temperature-dependent constraints	Linked temperature calculation
Parameter correlation (Pearson residual bootstrap)	Parameter correlation
Bootstrap SD and percentile confidence interval	Residual-bootstrap calculation
Automatic uncertainty display	Automatic display calculation
Salt dependence	Salt
Protonation dependence	Protonation
Buffer correction	Buffer Subtraction
Tandem reload mixing	What happens at a reload

Units are those shown by the application or export.

References

FT-ITC Analysis repository
FT-ITC Analysis website
FT-ITC Project Viewer
Software DOI: 10.5281/zenodo.14832177
Malvern Instruments, MicroCal ITC Analysis Software Using Origin User Manual, MAN0577-02-EN-00 (20 May 2015), section 12.3.1, equations 2 and 4; section 12.3.6, equation 30 (dimer dissociation).
Help > Citation for the current paper citation, versioned software citation, and BibTeX
Philippe Dumas, Isothermal titration calorimetry in the single-injection mode with imperfect mixing, European Biophysics Journal 51, 77–84 (2022). The application's Ideal continuous mixing option is inspired by the paper but uses ideal mixing with a finite-injection numerical approximation; it does not implement the paper's imperfect-mixing model.
Ernesto Freire, Arne Schön and Adrián Velazquez-Campoy, Isothermal titration calorimetry: general formalism using binding polynomials, Methods in Enzymology 455, 127–155 (2009). The application's Discrete displacement option uses this convention for concentrations and displaced-volume heat compensation, retaining FT-ITC's equilibrium solvers and offset convention.

Scientific claims and model-specific methods require the primary literature appropriate to the experiment and analysis.