scholarly journals Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

2019 ◽  
Vol 15 ◽  
pp. 1321-1330 ◽  
Author(s):  
Valya K Nikolova ◽  
Cristina V Kirkova ◽  
Silvia E Angelova ◽  
Todor M Dudev
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Complex Formation ◽  
Gas Phase ◽  
Gibbs Free Energy ◽  
Metal Cations ◽  
Water Soluble ◽  
Model Systems ◽  
Solvent Treatment ◽  
Explicit Solvent

The molecular recognition in aqueous solution is extremely important because most biological processes occur in aqueous solution. Water-soluble members of the calix[n]arene family (e.g., p-sulfonato substituted) can serve as model systems for studying the nature and manner of interactions between biological receptors and small ions. The complex formation behavior of water-soluble p-sulfonatocalix[4]arene and thiacalix[4]arene and group IA, IIA and f-block metal cations has been investigated computationally by means of density functional theory computations in the gas phase and in aqueous environment. The calculated Gibbs free energy values of the complex formation reaction of these ligands with the bare metal cations suggest a spontaneous and energy-favorable process for all metal cations in the gas phase and only for Na+, Mg2+, Lu3+ cations in water environment. For one of the studied cations (La3+) a supramolecular approach with explicit solvent treatment has been applied in the study of the effect of metal hydration on the complexation process. The La3+ binding to the p-sulfonatocalix[4]arene host molecule (now in the metal’s second coordination shell) is still exergonic as evidenced by the negative Gibbs free energy values (ΔG 1 and ΔG 78). The combination of implicit/explicit solvent treatment seems useful in the modeling of the p-sulfonatocalix[4]arene (and thiacalix[4]arene) complexes with metal cations and in the prediction of the thermodynamic parameters of the complex formation reactions.

Evaluation of Gibbs free energy for the transfer of a highly hydrophilic ion from an acidic aqueous solution to an organic solution based on ion pair extraction

2002 ◽  
Vol 452 (1) ◽  
pp. 149-161 ◽  
Author(s):  
Yumi Yoshida ◽  
Zenko Yoshida ◽  
Hisao Aoyagi ◽  
Yoshihiro Kitatsuji ◽  
Akihiro Uehara ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Ion Pair ◽  
Organic Solution ◽  
Acidic Aqueous Solution

Raman spectroscopy and electrochemistry of water-soluble porphyrins at a silver electrode

1990 ◽  
Vol 68 (5) ◽  
pp. 787-790 ◽  
Author(s):  
Hideo Orita ◽  
Masao Shimizu ◽  
Chizuko Nishihara ◽  
Takashi Hayakawa ◽  
Katsuomi Takehira
Keyword(s):  
Aqueous Solution ◽  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Metal Cations ◽  
Silver Electrode ◽  
Water Soluble ◽  
Laser Raman Spectroscopy ◽  
Cyclic Voltammograms ◽  
Porphyrin Ring ◽  
Laser Raman

Cyclic voltammetry and laser Raman spectroscopy were applied to investigate insitu the properties and structures of metal meso-tetrakis (p-sulfonatophenyl)porphyrins (MeTPPS, Me = Co, Fe, Mn, Cu, Ni) adsorbed on a silver electrode in 0.05 M H2SO4 aqueous solution. The cyclic voltammograms for O2 reduction were investigated by changing the metal cations in the porphyrin ring. Among the porphyrins examined, only CoTPPS shows catalytic behavior for O2 electrochemical reduction. The Raman spectra of MeTPPS in aqueous solution are very similar to those of metal tetraphenylporphyrins (MeTPP), and the band assignments were carried out on the basis of the results for [FeTPP]2O. The Raman spectra of MeTPPS on a silver electrode were measured under a N2 or O2 atmosphere, changing the applied potentials and the metal cations in the porphyrin ring. Their spectra are very sensitive to metal cations, but not so to applied potential. Keywords: porphyrin, SERS, electrochemistry, dioxygen, silver electrode.

scholarly journals Insights into Solution Structures of Photosynthetic Protein Complexes from Small-Angle Scattering Methods

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 203
Author(s):  
Maksym Golub ◽  
Adrian Kölsch ◽  
Artem Feoktystov ◽  
Athina Zouni ◽  
Jörg Pieper
Keyword(s):  
Aqueous Solution ◽  
High Resolution ◽  
Photosystem I ◽  
Small Angle ◽  
Protein Complexes ◽  
Photosynthetic Pigment ◽  
Water Soluble ◽  
Model Systems ◽  
Radius Of Gyration ◽  
Pigment Protein Complexes

High-resolution structures of photosynthetic pigment–protein complexes are often determined using crystallography or cryo-electron microscopy (cryo-EM), which are restricted to the use of protein crystals or to low temperatures, respectively. However, functional studies and biotechnological applications of photosystems necessitate the use of proteins isolated in aqueous solution, so that the relevance of high-resolution structures has to be independently verified. In this regard, small-angle neutron and X-ray scattering (SANS and SAXS, respectively) can serve as the missing link because of their capability to provide structural information for proteins in aqueous solution at physiological temperatures. In the present review, we discuss the principles and prototypical applications of SANS and SAXS using the photosynthetic pigment–protein complexes phycocyanin (PC) and Photosystem I (PSI) as model systems for a water-soluble and for a membrane protein, respectively. For example, the solution structure of PSI was studied using SAXS and SANS with contrast matching. A Guinier analysis reveals that PSI in solution is virtually free of aggregation and characterized by a radius of gyration of about 75 Å. The latter value is about 10% larger than expected from the crystal structure. This is corroborated by an ab initio structure reconstitution, which also shows a slight expansion of Photosystem I in buffer solution at room temperature. In part, this may be due to conformational states accessible by thermally activated protein dynamics in solution at physiological temperatures. The size of the detergent belt is derived by comparison with SANS measurements without detergent match, revealing a monolayer of detergent molecules under proper solubilization conditions.

scholarly journals Molar Surface Gibbs Free Energy of the Aqueous Solution of the Ionic Liquid [C2mim][OAc]

2016 ◽  
Vol 32 (5) ◽  
pp. 1161-1167 ◽  
Author(s):  
Jing TONG ◽  
◽  
Teng-Fei CHEN ◽  
Duo ZHANG ◽  
Lin-Fu WANG ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Ionic Liquid ◽  
Gibbs Free Energy
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