Isothermal Titration Calorimetry Can Provide Critical Thinking Opportunities

Abstract

College chemistry faculties might not have considered including isothermal titration calorimetry (ITC) in their majors' curriculum because experimental data from this instrumental method are often analyzed via automation (software). However, the software-based data analysis can be replaced with a spreadsheet-based analysis that is readily accessible to undergraduate students. This article describes a three-phase study (three lab periods) of cation−hexametaphosphate complexation via ITC, including the asymptote method by which students perform their own ITC data analysis, to demonstrate how ITC experiments can provide students with critical thinking opportunities comparable to other data-analysis-intensive physical-analytical experiments.

A molecular understanding of magnesium aluminium silicate – drug, drug – polymer, magnesium aluminium silicate – polymer nanocomposite complex interactions in modulating drug release: Towards zero order release

“…Callies and Hernández Daranas, 2016 have reported the use of ITC to provide accurate and important information about the mechanisms of binding of molecules (Callies and Hernández Daranas, 2016). From the resulting data, binding site size, affinity (Ka), changes in enthalpy (ΔH), entropy (ΔS), Gibbs free energy (ΔG) and stoichiometry (N) of the binding events can be determined through the fitting of independent binding sites, sequential binding sites, competitive binding and dissociation models (Moore et al, 2016). For a simple single binding site model, the non-linear least squares fit of the data can be used to determine Ka and ΔH, followed by the calculation of ΔG and ΔS using the known relationship between the van't Hoff equation and change in Gibbs free energy:…”

Probing the bilayer-monolayer switching of capping agents on Au nanorods and its interaction with guest molecules $$^{\S }$$ §

“…ITC is based on the principle of dynamic power compensation, wherein the amount of power required for maintaining a constant temperature difference between the sample and the reference cell is measured. [18][19][20] A small power is continuously applied to the sample cell by the feedback system, to determine the baseline level. Each injection of the syringe solution triggers the binding reaction; depending on the binding affinity and the concentration of reactants in the cell, a certain amount of complex is formed.…”

“…16 Rao and coworkers utilized the technique to study the mechanism of cysteine and 3-mercaptopropionic acid induced linear assembly of Au nanorods (AuNRs). 17 Herein, we use a combination of ITC [18][19][20] and surface-enhanced Raman scattering (SERS) [21][22][23] to study the interaction of molecules with the surface of AuNRs. While ITC helps in analyzing the nanorod (NR) molecule interactions, SERS can function as a molecular sensing platform.…”

Real time calorimetric characterisation of clay – drug complex dispersions and particles

“…2) (Duff et al, 2011). The heat absorbed or released as chemical bonds form or break is then measured as the power that must be supplied to maintain both sample and reference cells at a constant temperature (Moore et al, 2016, Di Trani et al, 2017). Experiments can be performed under different conditions, such as variable temperatures or buffer giving detailed information about the studied systems (Duff et al, 2011).…”

“…Experiments can be performed under different conditions, such as variable temperatures or buffer giving detailed information about the studied systems (Duff et al, 2011). Independent binding sites, sequential binding sites, competitive binding and dissociation models can be fitted to the resulting data to yield binding site size, affinity (K a ), changes in enthalpy (ΔH), entropy (ΔS) or Gibbs free energy (ΔG) and stoichiometry (N) of the binding events (Moore et al, 2016). For a simple single binding site model, the non-linear least squares fit of the data can be used to determine K a and ΔH, followed by the calculation of ΔG and ΔS using the known relationship between the van’t Hoff equation and change in Gibbs free energy:ΔG=ΔH-TΔS(1a)=-RTlnKa(1b)

Fig.

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