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Heat Capacity Change (heat + capacity_change)

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Chemistry100%

Selected Abstracts

Heat capacity changes associated with nucleic acid folding

BIOPOLYMERS, Issue 1 2006
Peter J. Mikulecky
Abstract Whereas heat capacity changes (,CPs) associated with folding transitions are commonplace in the literature of protein folding, they have long been considered a minor energetic contributor in nucleic acid folding. Recent advances in the understanding of nucleic acid folding and improved technology for measuring the energetics of folding transitions have allowed a greater experimental window for measuring these effects. We present in this review a survey of current literature that confronts the issue of ,CPs associated with nucleic acid folding transitions. This work helps to gather the molecular insights that can be gleaned from analysis of ,CPs and points toward the challenges that will need to be overcome if the energetic contribution of ,CP terms are to be put to use in improving free energy calculations for nucleic acid structure prediction. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 38,58, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]

The conformational stability of the Streptomyces coelicolor histidine-phosphocarrier protein

FEBS JOURNAL, Issue 11 2004
Characterization of cold denaturation, protein interactions
Thermodynamic parameters describing the conformational stability of the histidine-containing phosphocarrier protein from Streptomyces coelicolor, scHPr, have been determined by steady-state fluorescence measurements of isothermal urea-denaturations, differential scanning calorimetry at different guanidinium hydrochloride concentrations and, independently, by far-UV circular dichroism measurements of isothermal urea-denaturations, and thermal denaturations at fixed urea concentrations. The equilibrium unfolding transitions are described adequately by the two-state model and they validate the linear free-energy extrapolation model, over the large temperature range explored, and the urea concentrations used. At moderate urea concentrations (from 2 to 3 m), scHPr undergoes both high- and low-temperature unfolding. The free-energy stability curves have been obtained for the whole temperature range and values of the thermodynamic parameters governing the heat- and cold-denaturation processes have been obtained. Cold-denaturation of the protein is the result of the combination of an unusually high heat capacity change (1.4 ± 0.3 kcal·mol,1·K,1, at 0 m urea, being the average of the fluorescence, circular dichroism and differential scanning calorimetry measurements) and a fairly low enthalpy change upon unfolding at the midpoint temperature of heat-denaturation (59 ± 4 kcal·mol,1, the average of the fluorescence, circular dichroism and differential scanning calorimetry measurements). The changes in enthalpy (m,Hi), entropy (m,Si) and heat capacity (m,Cpi), which occur upon preferential urea binding to the unfolded state vs. the folded state of the protein, have also been determined. The m,Hi and the m,Si are negative at low temperatures, but as the temperature is increased, m,Hi makes a less favourable contribution than m,Si to the change in free energy upon urea binding. The m,Cpi is larger than those observed for other proteins; however, its contribution to the global heat capacity change upon unfolding is small. [source]

Large-scale expression and thermodynamic characterization of a glutamate receptor agonist-binding domain

FEBS JOURNAL, Issue 13 2000
Dean R. Madden
The ionotropic glutamate receptors (GluR) are the primary mediators of excitatory synaptic transmission in the brain. GluR agonist binding has been localized to an extracellular domain whose core is homologous to the bacterial periplasmic binding proteins (PBP). We have established routine, baculovirus-mediated expression of a complete ligand-binding domain construct at the 10-L scale, yielding 10,40 milligrams of purified protein. This construct contains peptides that lie outside the PBP-homologous core and that connect the domain core to the transmembrane domains of the channel and to the N-terminal ,X'-domain. These linker peptides have been implicated in modulating channel physiology. Such extended constructs have proven difficult to express in bacteria, but the protein described here is stable and monomeric. Isothermal titration calorimetry reveals that glutamate binding to the domain involves a substantial heat capacity change and that at physiological temperatures, the reaction is both entropically and enthalpically favorable. [source]

Modeling of polycyclic aromatic hydrocarbon SLE in aromatic solvents

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010
Thenmozhi Muthukumarasamy
Abstract Equilibrium solubilities of polycyclic aromatic hydrocarbon (PAH) solutes naphthalene, fluorene, acenaphthalene, fluoranthene, anthracene, phenanthrene, pyrene, chrysene and triphenylene in benzene and substituted benzene solvents are predicted using the Dortmund-AU model. The Dortmund-AU method performs better than the UNIFAC and modified UNIFAC (Dortmund) models when applied to PAH in benzene systems, but the accuracy of predictions deteriorates in the case of PAHs that have melting points greater than 380 K. Accounting for the heat capacity change on melting term makes considerable difference to the ideal solubility calculation in the case of higher-melting PAHs. A new term is added to the residual part of activity coefficient in the UNIFAC model to derive a modified empirical version. Application of this model to PAH solid,liquid equilibria is verified and the results are compared with those of Dortmund-AU model. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Heat capacity changes associated with nucleic acid folding

BIOPOLYMERS, Issue 1 2006
Peter J. Mikulecky
Abstract Whereas heat capacity changes (,CPs) associated with folding transitions are commonplace in the literature of protein folding, they have long been considered a minor energetic contributor in nucleic acid folding. Recent advances in the understanding of nucleic acid folding and improved technology for measuring the energetics of folding transitions have allowed a greater experimental window for measuring these effects. We present in this review a survey of current literature that confronts the issue of ,CPs associated with nucleic acid folding transitions. This work helps to gather the molecular insights that can be gleaned from analysis of ,CPs and points toward the challenges that will need to be overcome if the energetic contribution of ,CP terms are to be put to use in improving free energy calculations for nucleic acid structure prediction. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 38,58, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]