Isothermal titration calorimetric

Table 8 Binding parameters of t-RNA complexation with berberine and palmatine obtained from spectrophotometric, spectrofluorimetric and isothermal titration calorimetric study [214]... 

Markova, N., Haelen, D., The development of a continuous isothermal titration calorimetric method for equilibrium studies Anal. Biochem. 2004, 331, 77-88. 

Hibbits, K. A., Gill, D. S., and Willson, R. C. (1994). Isothermal titration calorimetric study of the association of hen egg lysozyme and the anti-lysozyme antibody HyHEL-5. Biochemistry 33(12), 3584-3590. 

The four-wall water-soluble cavitand IV-5 (Scheme 12.16) forms a stable deep cavity that has a high affinity towards choline B-1 and acetylcholine B-2 (association con-stants>10 M ) in DjO. Interestingly, the trimethylammonium head of B-1 is pointed inward into the cavity of the host. In contrast, the long chain trialkylanunonium ions, such as dodecyltrimethylanunonium ion, are bound with the (helical folded) alkyl chain in the cavity, but with an association constant of >1(1 M . In addition to the favourable electrostatic interaction between the tetracarboxylate wider rim and the tetraalkylam-monium core, hydrophobic interactions dominate the binding in this case and reveal the bitopic character of both the host and the guest. Isothermal titration calorimetric data have shown that the complex formation is both enthalpically and entropically driven. 

Zheng PJ, Wang C, Hu X, Tam KC, Li L. 2005. Supramolecular complexes of azocellulose and alpha cyclodextrin isothermal titration calorimetric and spectroscopic studies. Macromolecules 38(7) 2859 2864. 

Isothermal titration calorimetric studies of the transfer of molecules between these phases have been conducted using various experimental protocols. Three such protocols are indicated in Fig. 5. 

WAN Wang, C. and Tam, K.C., Interactions between polyfacrylic acid) and sodium dodecyl sulfate isothermal titration calorimetric and surfactant ion-selective electrode studies, J. Phys. Chem. B, 109, 5156, 2005. 

Walter SM, Kniep F, Rout L, Schmidtchen FP, Herdtweck E, Huber SM (2012) Isothermal titration calorimetric titrations on charge-assisted halogen bonds role of entropy, counterions, solvent, and temperature. J Am Chem Soc 134 8507... 

The enthalpy change associated with formation of a thermodynamically ideal solution is equal to zero. Therefore any heat change measured in a mixing calorimetry experiment is a direct indicator of the interactions in the system (Prigogine and Defay, 1954). For a simple biopolymer solution, calorimetric measurements can be conveniently made using titra-tion/flow calorimeter equipment. For example, from isothermal titration calorimetry of solutions of bovine P-casein, Portnaya et al. (2006) have determined the association behaviour, the critical micelle concentration (CMC), and the enthalpy of (de)micellization. 

Horn, J. R., Russel, D., Lewis, E. A., Murphy, K. P. van t Hoff and calorimetric enthalpies from isothermal titration calorimetry are there significant discrepancies Biochemistry 2001, 40, 1774-1778. 

Several applications of isothermal titration calorimetry to biochemical systems have been published recently. Franghanel et al. [240] proposed a new calorimetric method to investigate slow conformational changes in proteins and peptides, Tsamaloukas et al. [241] studied the interactions of cholesterol with unsaturated phospholipids and D Amico et al. [242] determined the binding enthalpies of a-amylases to different substrates. 

Horn, J. R. Russell, D.M. Lewis, RA. Murphy, KP. (2001) Van t hoff and calorimetric enthalpies from isothermal titration calorimetry Are there significant discrepancies . Biochemistry 40,1774 - 1778. 

The enthalpies of micellization, AH, , can be calculated indirectly by use of the van t Hoff treatment or directly by isothermal titration calorimetry (ITC). Except for few cases (e.g., some nonionic surfactants), the results of these methods do not agree [38]. The main reason is that there is no provision in van t Hoff equation for factors that are important for micelle formation of ionic surfactants, in particular, the dependence of micellar geometry, surface-charge density, and extent of hydration on temperature T) [38]. On the other hand, the effects of (T) on the aforementioned micellar parameters are included in the direct (i.e., calorimetric) determination of AH, . From Gibbs free energy relationship, any uncertainty introduced in the calculation of Ai7, j will be carried over to so that A5 rK > AS, Where available, therefore, we compare the thermodynamic quantities of micellization, based on experimental data of the same technique. 

Here Kassoc is the association constant. To utilize this method, one must do either an isothermal titration or measure a series of changes in IR-spectra to determine the association constant [63]. It is worth noting that the degree of ion doping and water incorporation correlates with the Hofmeister series [63]. Since PE-PE bonds are broken by incorporation of counter ions, the association constant can also be used indirectly to estimate the PE-PE interaction strength. Calorimetric measurements done by SchlenoflF to directly determine the enthalpy of PE complex formation for strong PEs, resulted in values close to 0 [63]. 

A 5 ml volume of the 0.5 mol 1 solution of BF3 etherate in nitrobenzene is placed in the calorimetric cell under dry nitrogen or argon. The syringe pusher is filled with a sufficient volume of 2.5 mol 1 pyridine solution. Using these values, 0.100-0.200 ml injection steps allow for 5-10 additions. For an isothermal titration calorimeter, the time interval between each injection should be sufficient for the signal to return to the baseline (for a Dewar calorimeter, allowance is made for temperature stabilization after each injection). When the temperature of the system is equilibrated, the data acquisition and the injection programme are started. A preliminary experiment should be carried out to measure the blank value, corresponding to the heat of dilution of pyridine solution in the pure solvent. 

The different mixing vessels that are described in the previous paragraph are designed for the interaction between two components and are not well adapted for titration studies. In the Isothermal Titration Calorimetry, aliquots of sample B is added in a volume of sample A, located in the calorimetric vessel and maintained under a constant stirring (Fig. 2.26). 

As discussed in chapters 7 and 8, the initial step of the data analysis of a isoperibol calorimetry experiment is the determination of the enthalpy of the isothermal calorimetric process, A//ICp, usually at the reference temperature of 298.15 K. The value of A/Ticp corresponding to any point p along the titration period is given by (recall the discussion of equation 8.1)... 

As mentioned above, titration methods have also been adapted to calorimeters whose working principle relies on the detection of a heat flow to or from the calorimetric vessel, as a result of the phenomenon under study [195-196,206], Heat flow calorimetry was discussed in chapter 9, where two general modes of operation were presented. In some instruments, the heat flow rate between the calorimetric vessel and a heat sink is measured by use of thermopiles. Others, such as the calorimeter in figure 11.1, are based on a power compensation mechanism that enables operation under isothermal conditions. 

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