Aqueous Solutions of Nonpolar Compounds. Heat-Capacity Effects

1972 ◽  
Vol 50 (2) ◽  
pp. 133-138 ◽  
Author(s):  
R. D. Wauchope ◽  
R. Haque
Keyword(s):  
Heat Capacity ◽  
Temperature Coefficient ◽  
Solution Process ◽  
Positive Temperature Coefficient ◽  
Heat Capacity Change ◽  
Positive Temperature ◽  
Capacity Change ◽  
Heat Capacity Changes ◽  
Nonpolar Compounds ◽  
Better Than

The method of Clarke and Glew has been used to obtain estimates of the precision of measurement of the thermodynamic functions for the solution of hydrocarbons, the noble gases, and inert diatomic gases in water. In some cases, the precision of the data is such that a statistically significant value for the temperature coefficient of the heat-capacity change for the solution process is obtained. Comparison with the theory of Nemethy and Scheraga shows that their calculations of heat-capacity changes at 25 °C are better than previously believed, but that their prediction of a positive temperature coefficient for this quantity is in contradiction with most data.

scholarly journals Thermodynamics of DNA: heat capacity changes on duplex unfolding

2019 ◽  
Vol 48 (8) ◽  
pp. 773-779 ◽  
Author(s):  
Anatoliy Dragan ◽  
Peter Privalov ◽  
Colyn Crane-Robinson
Keyword(s):  
Heat Capacity ◽  
Accessible Surface Area ◽  
Solvent Accessible Surface Area ◽  
Polar Component ◽  
Heat Capacity Change ◽  
Dna Duplex ◽  
Capacity Change ◽  
Heat Capacity Changes ◽  
Accessible Surface ◽  
Lower Magnitude

Abstract The heat capacity change, ΔCp, accompanying the folding/unfolding of macromolecules reflects their changing state of hydration. Thermal denaturation of the DNA duplex is characterized by an increase in ΔCp but of much lower magnitude than observed for proteins. To understand this difference, the changes in solvent accessible surface area (ΔASA) have been determined for unfolding the B-form DNA duplex into disordered single strands. These showed that the polar component represents ~ 55% of the total increase in ASA, in contrast to globular proteins of similar molecular weight for which the polar component is only about 1/3rd of the total. As the exposure of polar surface results in a decrease of ΔCp, this explains the much reduced heat capacity increase observed for DNA and emphasizes the enhanced role of polar interactions in maintaining duplex structure. Appreciation of a non-zero ΔCp for DNA has important consequences for the calculation of duplex melting temperatures (Tm). A modified approach to Tm prediction is required and comparison is made of current methods with an alternative protocol.

Heat capacity changes in carbohydrates and protein–carbohydrate complexes

2009 ◽  
Vol 420 (2) ◽  
pp. 239-247 ◽  
Author(s):  
Eneas A. Chavelas ◽  
Enrique García-Hernández
Keyword(s):  
Heat Capacity ◽  
Heat Capacity Change ◽  
Energy Storage Devices ◽  
Covalent Interaction ◽  
Storage Devices ◽  
Functional Roles ◽  
Capacity Change ◽  
Carbohydrate Complex ◽  
Heat Capacity Changes ◽  
Formation Heat

Carbohydrates are crucial for living cells, playing myriads of functional roles that range from being structural or energy-storage devices to molecular labels that, through non-covalent interaction with proteins, impart exquisite selectivity in processes such as molecular trafficking and cellular recognition. The molecular bases that govern the recognition between carbohydrates and proteins have not been fully understood yet. In the present study, we have obtained a surface-area-based model for the formation heat capacity of protein–carbohydrate complexes, which includes separate terms for the contributions of the two molecular types. The carbohydrate model, which was calibrated using carbohydrate dissolution data, indicates that the heat capacity contribution of a given group surface depends on its position in the saccharide molecule, a picture that is consistent with previous experimental and theoretical studies showing that the high abundance of hydroxy groups in carbohydrates yields particular solvation properties. This model was used to estimate the carbohydrate's contribution in the formation of a protein–carbohydrate complex, which in turn was used to obtain the heat capacity change associated with the protein's binding site. The model is able to account for protein–carbohydrate complexes that cannot be explained using a previous model that only considered the overall contribution of polar and apolar groups, while allowing a more detailed dissection of the elementary contributions that give rise to the formation heat capacity effects of these adducts.

scholarly journals Dynamical origins of heat capacity changes in enzyme catalysed reactions

2017 ◽  
Author(s):  
Marc W van der Kamp ◽  
Erica J. Prentice ◽  
Kirsty L. Kraakmann ◽  
Michael Connolly ◽  
Adrian J. Mulholland ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Active Site ◽  
Reaction Rates ◽  
Heat Capacity Change ◽  
Catalysed Reaction ◽  
Capacity Change ◽  
Heat Capacity Changes ◽  
Dynamics Simulations ◽  
Alpha Glucosidase ◽  
Activation Heat

AbstractHeat capacity changes are emerging as essential for explaining the temperature dependence of enzyme-catalysed reaction rates. This has important implications for enzyme kinetics, thermoadaptation and evolution, but the physical basis of these heat capacity changes is unknown. Here we show by a combination of experiment and simulation, for two quite distinct enzymes (dimeric ketosteroid isomerase and monomeric alpha-glucosidase), that the activation heat capacity change for the catalysed reaction can be predicted through atomistic molecular dynamics simulations. The simulations reveal subtle and surprising underlying dynamical changes: tightening of loops around the active site is observed as expected, but crucially, changes in energetic fluctuations are evident across the whole enzyme including important contributions from oligomeric neighbours and domains distal to the active site. This has general implications for understanding enzyme catalysis and demonstrating a direct connection between functionally important microscopic dynamics and macroscopically measurable quantities.

Positive temperature coefficient of resistance of tetragonal Ti4+ doped nano SrFeO3−δ

2013 ◽  
Vol 561 ◽  
pp. 174-179 ◽  
Author(s):  
A. Sendilkumar ◽  
K.C. James Raju ◽  
P.D. Babu ◽  
S. Srinath
Keyword(s):  
Temperature Coefficient ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Temperature Coefficient Of Resistance
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