Calculations of the Gibbs Free Energy of Adsorption of Some Small Molecules and Amino Acid Decomposition Products on MCM-41 Mesoporous Silica

2013 ◽  
Vol 4 (14) ◽  
pp. 2298-2302 ◽  
Author(s):  
Vladimir Chashchikhin ◽  
Elena Rykova ◽  
Alexander Bagaturyants
Keyword(s):  
Free Energy ◽  
Amino Acid ◽  
Mesoporous Silica ◽  
Small Molecules ◽  
Gibbs Free Energy ◽  
Acid Decomposition ◽  
Free Energy Of Adsorption ◽  
Decomposition Products ◽  
Mcm 41

scholarly journals Entropy-Enthalpy Compensations Fold Proteins in Precise Ways

2021 ◽  
Vol 22 (17) ◽  
pp. 9653
Author(s):  
Jiacheng Li ◽  
Chengyu Hou ◽  
Xiaoliang Ma ◽  
Shuai Guo ◽  
Hongchi Zhang ◽  
...  
Keyword(s):  
Free Energy ◽  
Protein Folding ◽  
Amino Acid ◽  
Gibbs Free Energy ◽  
Energy Equation ◽  
Protein Structures ◽  
Water Molecules ◽  
Side Chains ◽  
Hydrophobic Collapse ◽  
Polypeptide Chains

Exploring the protein-folding problem has been a longstanding challenge in molecular biology and biophysics. Intramolecular hydrogen (H)-bonds play an extremely important role in stabilizing protein structures. To form these intramolecular H-bonds, nascent unfolded polypeptide chains need to escape from hydrogen bonding with surrounding polar water molecules under the solution conditions that require entropy-enthalpy compensations, according to the Gibbs free energy equation and the change in enthalpy. Here, by analyzing the spatial layout of the side-chains of amino acid residues in experimentally determined protein structures, we reveal a protein-folding mechanism based on the entropy-enthalpy compensations that initially driven by laterally hydrophobic collapse among the side-chains of adjacent residues in the sequences of unfolded protein chains. This hydrophobic collapse promotes the formation of the H-bonds within the polypeptide backbone structures through the entropy-enthalpy compensation mechanism, enabling secondary structures and tertiary structures to fold reproducibly following explicit physical folding codes and forces. The temperature dependence of protein folding is thus attributed to the environment dependence of the conformational Gibbs free energy equation. The folding codes and forces in the amino acid sequence that dictate the formation of β-strands and α-helices can be deciphered with great accuracy through evaluation of the hydrophobic interactions among neighboring side-chains of an unfolded polypeptide from a β-strand-like thermodynamic metastable state. The folding of protein quaternary structures is found to be guided by the entropy-enthalpy compensations in between the docking sites of protein subunits according to the Gibbs free energy equation that is verified by bioinformatics analyses of a dozen structures of dimers. Protein folding is therefore guided by multistage entropy-enthalpy compensations of the system of polypeptide chains and water molecules under the solution conditions.

Toward Accurate and Efficient Predictions of Entropy and Gibbs Free Energy of Adsorption of High Nitrogen Compounds on Carbonaceous Materials

2014 ◽  
Vol 118 (9) ◽  
pp. 4774-4783 ◽  
Author(s):  
Andrea Michalkova Scott ◽  
Leonid Gorb ◽  
Elizabeth A. Burns ◽  
Sergey N. Yashkin ◽  
Frances C. Hill ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Nitrogen Compounds ◽  
Carbonaceous Materials ◽  
High Nitrogen ◽  
Free Energy Of Adsorption

scholarly journals Hysteresis and thermodynamic properties of water sorption in ‘Malagueta’ pepper seeds

2018 ◽  
Vol 22 (9) ◽  
pp. 658-663
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Isneider L. Silva
Keyword(s):  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Water Sorption ◽  
Water Adsorption ◽  
Gravimetric Method ◽  
Free Energy Of Adsorption ◽  
Adsorption And Desorption ◽  
Moisture Contents ◽  
Compensation Theory

ABSTRACT The objective of this study was to determine hysteresis, enthalpy, entropy, enthalpy-entropy compensation theory and Gibbs free energy for water adsorption and desorption in ‘Malagueta’ pepper seeds. Hygroscopic equilibrium moisture contents were determined by the static gravimetric method, with water activity in the range from 0.29 to 0.90 and temperatures of 30, 40 and 50 °C. The hysteresis of the ‘Malagueta’ pepper seeds reduces with the increase of temperature. Enthalpy, entropy and Gibbs free energy of adsorption and desorption increase with the reduction of the moisture content of the seeds. The enthalpy-entropy compensation theory is valid for the sorption processes. The sorption of water between seeds and the surrounding air is a non-spontaneous process.

Enthalpy and interfacial free energy changes of water capillary condensed in mesoporous silica, MCM-41 and SBA-15

2006 ◽  
Vol 8 (27) ◽  
pp. 3223 ◽  
Author(s):  
Shigeharu Kittaka ◽  
Shinji Ishimaru ◽  
Miki Kuranishi ◽  
Tomoko Matsuda ◽  
Toshio Yamaguchi
Keyword(s):  
Free Energy ◽  
Mesoporous Silica ◽  
Interfacial Free Energy ◽  
Mcm 41

Can the Gibbs Free Energy of Adsorption Be Predicted Efficiently and Accurately: An M05-2X DFT Study

2011 ◽  
Vol 115 (11) ◽  
pp. 2423-2430 ◽  
Author(s):  
A. Michalkova ◽  
L. Gorb ◽  
F. Hill ◽  
J. Leszczynski
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Dft Study ◽  
Free Energy Of Adsorption

scholarly journals Porous and adsorption properties of hydrated cement paste

2004 ◽  
Vol 58 (1) ◽  
pp. 6-9 ◽  
Author(s):  
Biljana Marina ◽  
Snezana Brezovska ◽  
Donco Burevski ◽  
Biljana Panova
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Adsorption Isotherms ◽  
Favorable Effect ◽  
Hydrated Cement ◽  
Free Energy Of Adsorption ◽  
Characteristic Energy ◽  
Cement Pastes ◽  
Hydrated Cement Paste

Adsorption isotherms of benzene on hydrated cement pastes prepared by cement ground with and without the addition of grinding aids, triethanol amine (TEA) and ethylene glycol (EG) were investigated. The adsorption isotherms were interpreted by means of the Dubinin-Astakhov (DA) and Dubinin-Radushkevich-Stoeckli (DRS) equations. The microporous structure of cement gel (C-S-H) in the cement pastes, and changes in the Gibbs free energy of adsorption were determined. The mechanical properties of the cement pastes were also measured. It was evident that pastes with additives had different parameters of the DRS and DA equations: the volume and dimensions of the gel pores, the distribution of the dimensions, the characteristic energy of adsorption, and the change in the Gibbs free energy of adsorption. The mechanical properties were also different. The dispersity of the additive-containing ground cements had a favorable effect on the hydration processes. When applying TEA, it was also necessary to analyze its influence on the chemical behavior of hydration in the starting period.

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