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Characterization Techniques for Bio-Nanocomposites
Published in Shrikaant Kulkarni, Neha Kanwar Rawat, A. K. Haghi, Green Chemistry and Green Engineering, 2020
Any chemical or physical change is associated with a change in heat or enthalpy; the calorimeter can be used as a universal detector. It helps in studying specifically the interactions of biomacromolecules with other molecules, or metal ions and the assembly of macromolecular complexes, and finally with nano-objects. ITC quantifies the heat liberated or the change in enthalpy (H) during a reaction. The stoichiometry and association constant (Ka) can be determined by titration mode. The system works by comparing thermocoupled sample and reference cells. Upon titration of a chelating agent or ligand in the sample cell, heat is either liberated (exothermic) or absorbed (endothermic), and the heat is measured based on the quantum of power required to maintain the temperature balance between sample and reference cells.
Biophysical and Biochemical Characterization of Peptide, Protein, and Bioconjugate Products
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Tapan K. Das, James A. Carroll
ITC is a sensitive technique measuring heat changes from weak or strong binding interactions, such as antibody–antigen binding or receptor–ligand binding. It is quite versatile and can be applied to a wide variety of molecules in solution without any pretreatment (such as fixation of matrix) [189–193]. ITC can also detect weak interactions with dissociation constants of sub-mM. Appropriate control experiments must be conducted as several sources of heat change (e.g., heat of dilution) can introduce artifacts.
Macrocyclic Anion Receptors
Published in Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney, Macrocyclic Receptors for Environmental and Biosensing Applications, 2022
Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney
Isothermal Titration Calorimetry (ITC) measures the heat released or absorbed on interaction of the host with a guest by titrating one reactant into a second reactant under isothermal conditions. ITC can determine all the thermodynamic parameters (stoichiometry, ΔH, ΔS, ΔCp, ΔG) in one experiment. The limitation of the technique lies in the fact that it is sensitive to equilibria, which are not involved with the host-guest interaction, but are associated with the absorption or release of heat.
Exploring the binding mechanism of Ginsenoside Rd to Bovine Serum Albumin: Experimental studies and computational simulations
Published in Journal of Dispersion Science and Technology, 2022
Jialiang Lin, Min Tang, Manjunath D. Meti, Yong Liu, Qingguo Han, Xu Xu, Yuan Zheng, Zhendan He, Zhangli Hu, Hong Xu
ITC is a straightforward and reliable technique to thermodynamically characterize the binding processes of small molecules to biological macromolecules.[53,56] The ITC profile for the titration of BSA by GSRd at 310 K in 0.02 M phosphate buffer (pH 7.4) are shown in Figure 8. It is displayed from Figure 8a that the binding process of GSRd to BSA is endothermic, resulting in positive peaks in the plot of power versus time. The calorimetric data were fitted to a single set of identical sites model and the model employed was the only one yielding a reasonable fitting of the experimental data, as shown in Figure 8b. The enthalpy change (△H0) and entropy change (△S0) for the binding reaction were obtained directly, to be 5.00 kJ mol−1 and 102.1 J mol−1 K−1, respectively. And the Gibbs free energy change (△G0) was calculated from equation (5) to be −26.65 kJ mol−1. The negative △G0 indicated that the binding process of GSRd to BSA was a spontaneous process.[57,58] The positive △H0 illustrated that the binding process was endothermic and driven by a large favorable entropy increase.
Calorimetry for studying the adsorption of proteins in hydrophobic interaction chromatography
Published in Preparative Biochemistry and Biotechnology, 2019
Agnes Rodler, Rene Ueberbacher, Beate Beyer, Alois Jungbauer
ITC, on the other hand, allows the direct measurement of the enthalpy change resulting from the interaction between two molecules. In a typical ITC experiment, defined amounts of protein Pr are consecutively added to a defined amount ν of ligand L such as suspended chromatography beads in a calorimeter cell (Figure 6B). Each injection and the resulting adsorption reaction are characterized by a shift in the Gibbs energy of the system toward a new equilibrium state (Figure 7). Upon adsorption, heat is released or absorbed. The heat difference over time between the sample cell and a reference cell is measured by precision thermoelements. The heat of adsorption Q is calculated by integrating the power P over the time t:
Exploration of ligand-induced protein conformational alteration, aggregate formation, and its inhibition: A biophysical insight
Published in Preparative Biochemistry and Biotechnology, 2018
Saima Nusrat, Rizwan Hasan Khan
Isothermal titration calorimetry quantifies the global heat change taking place in protein during complex formation with ligands (at a constant temperature). ITC is performed when ligand is titrated into a solution containing protein, thereby generating or absorbing heat and gives the result in terms of thermodynamic parameters. Almost all chemical and biochemical processes involve heat change virtually, thus ITC could be recommended for several applications like protein–peptide, protein–protein, protein–ligand, enzyme–inhibitor or enzyme–substrate, binding studies of antibody–antigen, DNA–protein interactions as well as enzyme kinetics. Many different techniques are used to study protein–ligand interaction, which are listed in Table 2.