Hydrophobic Effect, Water Structure, and Heat Capacity Changes

1997 ◽  
Vol 101 (21) ◽  
pp. 4343-4348 ◽  
Author(s):  
Kim A. Sharp ◽  
Bhupinder Madan
Keyword(s):  
Heat Capacity ◽  
Hydrophobic Effect ◽  
Water Structure ◽  
Heat Capacity Changes

The thermodynamics of ionization of some fatty acids

1952 ◽  
Vol 215 (1122) ◽  
pp. 403-415 ◽  
Keyword(s):  
Fatty Acids ◽  
Heat Capacity ◽  
Acetic Acid ◽  
Dissociation Constants ◽  
Water Structure ◽  
Hydrocarbon Chain ◽  
Ionic Charge ◽  
Heat Capacity Changes ◽  
The Individual ◽  
Thermodynamics Of Ionization

The dissociation constants of the following fatty acids have been determined in water relative to acetic acid over the temperature range 0 to 60° C: propionic, n-valeric, n-hexoic, itfo-butyrie, iso-valeric, iso-hexoic, trimethylacetic, diethylacetic. Using Hamed’s data for acetic acid as standard, the individual dissociation constants have been evaluated. The available data for the fatty acids are analyzed to obtain the heats of ionization, and the entropy and heat capacity changes of ionization. These quantities are discussed in relation to the structure of the acid and the orientation of water molecules by the ions. It is conducted that the ions influence the water structure in a volume round the ionic charge of radius about 5 A, and that the effect of the ionic charge on the rigidity of the hydrocarbon chain and on the solvent structure both play an important part in determining the efatropy and heat capacity changes.

scholarly journals Analysis based on scaling relations of critical behaviour at PM–FM phase transition and universal curve of magnetocaloric effect in selected Ag-doped manganites

RSC Advances ◽  
2018 ◽  
Vol 8 (33) ◽  
pp. 18294-18307 ◽  
Author(s):  
S. Tarhouni ◽  
R. M'nassri ◽  
A. Mleiki ◽  
W. Cheikhrouhou-Koubaa ◽  
A. Cheikhrouhou ◽  
...  
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Magnetocaloric Effect ◽  
Critical Exponents ◽  
Critical Behaviour ◽  
Scaling Relations ◽  
Universal Curve ◽  
Magnetic Entropy ◽  
Heat Capacity Changes ◽  
Doped Manganites

The universal curves of magnetic entropy changes and heat capacity changes for Pr0.5Sr0.5−xAgxMnO3 (0 ≤ x ≤ 0.2) are obtained by using the critical exponents.

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.

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