Titration microcalorimetry

Numerous attempts to determine the equilibrium constants using titration microcalorimetry failed, due to solubility problems encountered at the higher concentrations of catalyst and dienophile that are required for this technique. 

T. K. Dam and C. F. Brewer, Multivalent protein-carbohydrate interactions Isothermal titration microcalorimetry studies, Methods Enzymol., 379 (2004) 107-128. 

Fig. 16 Heat generated (Q) as a function of the amount of Ag03SCp3 added to solutions of 36 (filled circle), 38 (filled diamond), and 37 (filled square) in THF, as determined by isothermal titration microcalorimetry (T=28 °C, c=0.2 mm)...

Frazier, R.A., Papadopoulou, A., Mueller-Harvey, I., Kissoon, D., and Green, R.J., Probing protein-tannin interactions by isothermal titration microcalorimetry, J. Agric. Food Chem., 51, 5189, 2003. 

Portnaya, I., Cogan, U., Livney, Y.D., Ramon, O., Shimoni, K., Rosenberg, M., Danino, D. (2006). Micellization of bovine p-casein studied by isothermal titration microcalorimetry and cryogenic transmission electron microscopy. Journal of Agricultural and Food Chemistry, 54, 5555-5561. 

A significant part of medical and pharmacological research is conducted on the biochemical level. Calorimetric work on such systems usually has the character of thermodynamic measurements and can be considered as part of biophysical chemistry. Two types of experiments currently seem to be the most important studies of binding processes using titration microcalorimetry and investigations of thermal transitions involving high sensitivity DSCs. 

The development, manufacturing, and storage control of drugs has direct bearings on medicine, and some important uses of calorimetry in the pharmaceutical industry will therefore be pointed out. As a result of recent developments in microcalorimetry, techniques for thermodynamic characterization of binding reactions between drugs and biopolymers have become readily accessible. To an increasing extent, titration microcalorimetry is now used in the pharmaceutical industry. 

Quantitative investigation of recognition of this pair of liposomes was performed with isothermal titration microcalorimetry (ITC). It has been found that one-to-one binding between adenine and barbituric acid in the lipid/water/lipid interface occurs. However at T= 58°C, above the main lipid phase transition, the situation is different and no liposomal binding is detected. This is mainly due to the molecular disorder within the bilayer (liquid-disordered/liquid ordered phase coexistence) that limits the capacity of complementary moieties to bind, due to the weakening of the hydrogen bonds at these high temperatures. 

Interactions between water vapor and amorphous pharmaceutical solids were evaluated using isothermal microcalorimetry. " The desorption of water from theophylline monohydrate has been investigated using microcalorimetric approaches.The properties of surfactants and surface-active drugs in solution were studied by Attwood et al. " using calorimetry, while titration microcalorimetry has been utilized to elucidate the nature of specific interactions in several pharmaceutical polymer-surfactants systems. " Drug decomposition was evaluated as a function of different... 

Direct determination of adsorption enthalpies (or more precisely displacement enthalpies as indicated earfier) by titration microcalorimetry, which is the main form of calorimetry used in adsorption from solution. 

Whereas the binding of CBMs to insoluble carbohydrates can be monitored by the UV absorption of the protein, relatively large amounts are required, and in some of the early studies on CBDs they were made radioactive with to increase sensitivity. The general technical problem of monitoring the binding of soluble, non-chromophoric ligands to soluble CBMs, has, however, been solved only in the last decade, with the advent of isothermal titration microcalorimetry... 

Typical output from differential titration microcalorimetry experiments (binding of various polysaccharides to CBM 35 reproduced by kind permission of Prof. H. J. Gilbert). The top traces are the rates of heat change, the bottom their integrals. 

Co is the concentration defining the standard state by convention, Co = 1 mol. If Xd has been measured as a function of temperature, AH and A5d can be derived from its temperature dependence by applying the Vant Hoff law. In recent years, isothermal titration microcalorimetry (ITC) has also been used for that purpose. As reviewed by Fisher and Singh (1995) and Ladbury and Chowdhry (1996), microcalorimetry gives direct access to AH and, also, if the titration is performed at several temperatures, to the heat capacity change AGd at constant pressure. The first quantity is proportional to the heat evolved on mixing known amounts of the two components of a complex, and the latter is equal to... 

NB rrC = isothermal titration microcalorimetry. The enthalpy of ionization was plotted as a function of solution pH — DNA = titration performed in flie absence of DNA + DNA = titration performed in Oie presence of DNA complexed wiOi DOPE. 

UDA, the plant lectin from rhizomes of the stinging nettle, is comprised of two covalently linked hevein domains. The interaction of UDA with chit-ooligosaccharides has been studied by multiple methods, including X-ray, NMR titration data, laser photo-CIDNP methods, titration microcalorimetry, and also fluorescence measurements. 

J. L. Asensio, H.-C. Siebert, C.-W. von der Lieth, J. Laynez, M. Bruix, U. M. S. Soedjanaatmadja, J. J. Beintema, F. J. Canada, H. J. Gabius, and J. Jimenez-Barbero, NMR investigations of protein-carbohydrate interactions Studies on the relevance of Trp/Tyr variations in lectin binding sites as deduced from titration microcalorimetry and NMR studies on hevein domains. Determination of the NMR structure of the complex between pseudo-hevein and YA Y -triacetylchitotriose, Proteins, 40 (2000) 218-236. 

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