Thermodynamic study

The two-stage model is conceptually very useful because it separates the thermodynamics of insertion from helix assembly. When examining the stability of membrane proteins in the bilayer, the second stage is presumably the most relevant since the extrusion of the protein back into the aqueous environment should be extremely unfavorable. This idea is supported by the experiments discussed below. The two-stage model may not contain sufficient detail to describe the folding process in all cases, however. For example, the F and G helices of bacteriorhodopsin do not spontaneously form helices in vesicles, indicating that these peptides require assistance from the remainder of the protein to fold properly (Hunt et al., 1997). 

Thermodynamic measurements will, in the end, provide the quantitative descriptions of the atomic interactions needed for computational predictions of membrane proteins. With membrane proteins, of course, these interactions must include all the interactions among the water, 

The nature of the unfolded state in denaturant and how it relates to the denatured state under native conditions in the bilayer is a major issue in all denaturation experiments. Thermodynamic arguments from the two-stage model suggest that the relevant denatured state has lost its tertiary structure and maintained the transmembrane helix secondary structure. As noted above, CD spectra on thermally denatured bacteriorhodopsin suggest that the denatured protein maintains most of its helical secondary structure. The extent to which tertiary structure is disrupted is unclear, however. It is possible that some stable interhelical interactions are maintained even at high temperature. The helical secondary structure content is also maintained in SDS micelles, and near-UV circular dichroism (CD) spectra suggest substantial loss or 

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A general prerequisite for the existence of a stable interface between two phases is that the free energy of formation of the interface be positive were it negative or zero, fluctuations would lead to complete dispersion of one phase in another. As implied, thermodynamics constitutes an important discipline within the general subject. It is one in which surface area joins the usual extensive quantities of mass and volume and in which surface tension and surface composition join the usual intensive quantities of pressure, temperature, and bulk composition. The thermodynamic functions of free energy, enthalpy and entropy can be defined for an interface as well as for a bulk portion of matter. Chapters II and ni are based on a rich history of thermodynamic studies of the liquid interface. The phase behavior of liquid films enters in Chapter IV, and the electrical potential and charge are added as thermodynamic variables in Chapter V. 

The thermodynamic study of thiazole and of some of its binary mixtures with various solvents has led to the determination of important practical data, but also to the discovery of association phenomena between thiazole and some solvents and of thiazole self-association. 

A parallel thermodynamic study of 2-methylthia2ole was performed by Goursot and Westnim (299). The stable form was characterized by a temperature of melting of 248.42°K, an enthalpy of melting of 2907 cal mole and an entropy of melting of 11.70 cal mole ... 

A large number of thermodynamic studies of binary systems were undertaken to find and determine eventual intermolecular associations for thiazole Meyer et al. (303, 304) discovered eutectic mixtures for the following systems -thiazole/cyclohexane at -38.4°C, Wt = 0.815 -thiazole/carbon tetrachloride at -60.8°C, Mt = 0.46 -thiazole/benzene at -48.5°C, nr = 0.70. 

The conclusion of all these thermodynamic studies is the existence of thiazole-solvent and thiazole-thiazole associations. The most probable mode of association is of the n-rr type from the lone pair of the nitrogen of one molecule to the various other atoms of the other. These associations are confirmed by the results of viscosimetnc studies on thiazole and binary mixtures of thiazole and CCU or QHij. In the case of CCU, there is association of two thiazole molecules with one solvent molecule, whereas cyclohexane seems to destroy some thiazole self-associations (aggregates) existing in the pure liquid (312-314). The same conclusions are drawn from the study of the self-diffusion of thiazole (labeled with C) in thiazole-cyclohexane solutions (114). 

Examples of the hydroquinone inclusion compounds (91,93) are those formed with HCl, H2S, SO2, CH OH, HCOOH, CH CN (but not with C2H 0H, CH COOH or any other nitrile), benzene, thiophene, CH, noble gases, and other substances that can fit and remain inside the 0.4 nm cavities of the host crystals. That is, clathration of hydroquinone is essentially physical in nature, not chemical. A less than stoichiometric ratio of the guest may result, indicating that not all void spaces are occupied during formation of the framework. Hydroquinone clathrates are very stable at atmospheric pressure and room temperature. Thermodynamic studies suggest them to be entropic in nature (88). 

Reproduced and rounded from unpublished Center for Apphed Thermodynamic Studies, Moscow ID report, 1981. For a thermodynamic diagram to 350 bar, 370 C, see Rombusch, U. K., Allgem. Waime., 11,3 (1962). 

THERMODYNAMIC STUDIES ON THE PROTONATION EQUILIBRIA OF SOME HYDROXAMIC ACIDS IN NaNOj SOLUTIONS IN WATER AND IN MIXTURES OF WATER AND DIOXANE... 

By measuring the retention volume of a solute, the distribution coefficient can be obtained. The distribution coefficient, determined over a range of temperatures, is often used to determine the thermodynamic properties of the system this will be discussed later. From a chromatography point of view, thermodynamic studies are also employed as a diagnostic tool to examine the actual nature of the distribution. The use of thermodynamics for this purpose will be a subject of discussion in the next chapter. It follows that the accurate measurement of (VV) can be extremely... 

We carried out thermodynamic studies on the crystallization from melts of flexible-chain polymers uniaxially stretched at various degrees of molecular orientation in the melt and studied the effect of the stretching stress on thermodynamic parameters such as degree of... 

A system is the region in space that is the subject of the thermodynamic study. It can be as large or small, or as simple or complex, as we want it to be, but it must be carefully and consistently defined. Sometimes the system has definite and precise physical boundaries, such as a gas enclosed in a cylinder so that it can be compressed or expanded by a piston. However, it may be also something as diffuse as the gaseous atmosphere surrounding the earth. 

The intended audience of the second volume entitled Chemical Thermodynamics Advanced Applications is the advanced student or research scientist. We have used it, independently of the first volume, as the text for an advanced topics graduate level course in chemical thermodynamics. It can also serve as an introduction to thermodynamic studies involving more specialized disciplines, including geology, chemical separations, and biochemistry, for the research scientist in or outside of those disciplines. We hope it will be especially helpful for non-thermodynamicists who might be unfamiliar with the power and utility of thermodynamics in diverse applications. Given the more advanced nature of the material covered here, problems are only provided at the end of the chapters in this volume. Taken together, the two volumes make an excellent reference source for chemical thermodynamics. 

The water elimination reactions of Co3(P04)2 8 H20 [838], zirconium phosphate [839] and both acid and basic gallium phosphates [840] are too complicated to make kinetic studies of more than empirical value. The decomposition of the double salt, Na3NiP3O10 12 H20 has been shown [593] to obey a composite rate equation comprised of two processes, one purely chemical and the other involving diffusion control, for which E = 38 and 49 kJ mole-1, respectively. There has been a thermodynamic study of CeP04 vaporization [841]. Decomposition of metal phosphites [842] involves oxidation and anion reorganization. 

Vapor pressures of phases in these systems were measured by the Knudsen effusion technique. Use of mass spectrometer-target collection apparatus to perform thermodynamic studies is discussed. The prominent sublimation reactions for these phases below 2000 K was shown to involve formation of elemental plutonium vapor. Thermodynamic properties determined in this study were correlated with corresponding values obtained from theoretical predictions and from previous measurements on analogous intermetallics. 

Relatively few thermodynamic studies have been performed on compounds involving Th, U and Pu with noble metals. Most of the previous work has involved electrochemical cell determinations of free energies of formation, hence little has been published concerning the sublimation behavior of actinide intermetallics. 

This order corresponds to numerous results of kinetic and thermodynamic studies 113) u4) and seems to be based on energetic effects in the present case. 

Lackey, W., Hanigofsky, J., and Freeman, G., Experimental Whisker Growth and Thermodynamic Study of the Hafnium-Carbon System for Chemical Vapor Deposition Applications, 7] Amer. Ceram. Soc., 73(6) 1593-98 (1990)... 

Up to now, the intermolecular potential models are only fair in reproducing the wavenumbers of the external modes. Although various refinements have been made, none of the models seems to be superior to the others. More recently developed intermolecular potentials have been applied to structural and thermodynamical studies but not to the analysis of the vibrational spectra [122-125]. 

During this period of intensive development of unit operations, other classical tools of chemical engineering analysis were introduced or were extensively developed. These included studies of the material and energy balance of processes and fundamental thermodynamic studies of multicomponent systems. 

Brouillard, R. and Delaporte, B., Chemistry of anthocyanin pigments. 2. Kinetic and thermodynamic study of proton-transfer, hydration, and tautomeric reactions of mal-vidin-3-glucoside, J. Am. Chem. Soc., 99, 8461, 1977. 

I. Gybbs, Thermodynamic Studies, Foreign Literature Publ., Moscow, 1950... 

Avdeef, A. Zelazowski, A. J. Garvey, J. S., Cadmium binding by biological ligands. 3. Five- and seven-cadmium binding in metallothionein A detailed thermodynamic study, Inorg. Chem. 24, 1928-1933 (1985). 

Rakhshaee, R., Khosravi, M., and Ganji, M.T., Kinetic modeling and thermodynamic study to remove Pb(II), Cd(II), Ni(II) and Zn(II) from aqueous solution using dead and living Azollafiliculoides, Journal of Hazardous Materials, B134, 120-129, 2006. 

Unsually short NMR T, relaxation values were observed for the metal-bonded H-ligands in HCo(dppe)2, [Co(H2)(dppe)]+ (dppe = l,2-bis(diphenylphosphino)ethane), and CoH(CO) (PPh3)3.176 A theoretical analysis incorporating proton-meta) dipole-dipole interactions was able to reproduce these 7) values if an rCo H distance of 1.5 A was present, a value consistent with X-ray crystallographic experiments. A detailed structural and thermodynamic study of the complexes [H2Co(dppe)2]+, HCo(dppe)2, [HCo(dppe)2(MeCN)]+, and [Co(dppe)2(MeCN)]2+ has been reported.177 Equilibrium and electrochemical measurements enabled a thorough thermodynamic description of the system. Disproportionation of divalent [HCo(dppe)2]+ to [Co(dppe)2]+ and [H2Co(dppe)2]+ was examined as well as the reaction of [Co(dppe)2]+ with H2. 

Thermodynamic studies are also limited in that they provide information only about the bulk process they cannot provide information about the behavior of individual molecules. For that level of detail, we rely on quantum mechanics and statistical thermodynamics. 

T. K. Dam and C. F. Brewer, Thermodynamic studies of lectin-carbohydrate interactions by isothermal titration calorimetry, Chem. Rev., 102 (2002) 387 -29. 

Biver, T., De Biasi, A., Secco, E, Venturing M., and Yarmoluk, S. (2005) Cyanine dyes as intercalating agents Kinetic and thermodynamic studies on the DNA/Cyan40 and DNA/CCyan2 systems. Biophys. J. 89, 374-383. 

Ethanol can be derived from biomass by means of acidic/enzymatic hydrolysis or also by thermochemical conversion and subsequent enzymatic ethanol formation. Likewise for methanol, hydrogen can be produced from ethanol with the ease of storage/transportation and an additional advantage of its nontoxicity. Apart from thermodynamic studies on hydrogen from ethanol steam reforming,117-119 catalytic reaction studies were also performed on this reaction using Ni-Cu-Cr catalysts,120 Ni-Cu-K alumina-supported catalysts,121 Cu-Zn alumina-supported catalysts,122,123 Ca-Zn alumina-supported catalysts,122 and Ni-Cu silica-supported catalysts.123... 

There have been a very large number of other thermodynamic studies involving the interaction of crowns with a wide range of metal-ions (Izatt et al., 1985). In general, as for the examples already discussed, the complexes are found to be enthalpy-stabilized with the entropy term also contributing to the stability in a number of cases. 

A major way of supplying work to a process is by setting the temperature of the heat that is added to the process. It is known from the thermodynamic study of Carnot engines that heat at high temperature has the ability to do work, and the quality or the work potential depends on its temperature. Thus, when we add heat to a process we are equivalently adding a certain amount of work to the process that we could access if the process is designed for reversibility. 

Berti, P., Cabani, S. Conti, G., Mollica, V. (1986) The thermodynamic study of organic compounds in octan-l-ol. J. Chem. Soc., Faraday, Trans. 1, 82, 2547. 

Burris, D.R., MacIntyre, W.G. (1986) A thermodynamic study of solutions of liquid hydrocarbon mixtures in water. Geochim. Cosmochim. Acta 50, 1545-1549. 

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