Solvent clustering, polar network density, and thermodynamic interactions in coordination polymers: an inverse gas chromatography study of metal-ion-containing polyesters of poly(diethylene glycol-co-succinic acid)

1995 ◽  
Vol 73 (11) ◽  
pp. 1855-1861 ◽  
Author(s):  
G. Julius Vancso ◽  
Zhanjie Tan
Keyword(s):  
Gas Chromatography ◽  
Metal Ions ◽  
Succinic Acid ◽  
Diethylene Glycol ◽  
Metal Ion ◽  
Inverse Gas Chromatography ◽  
Volume Fraction ◽  
Central Metal ◽  
Cluster Integrals ◽  
Finite Concentration

The spatial distribution of toluene and THF in the polyester poly(diethylene glycol-co-succinic acid) and its Mg2+-containing "telechelic" derivative was described by Kirkwood–Buff–Zimm (KBZ) cluster integrals. The values of KBZ integrals as a function of the volume fraction of solvent in the polymer–solvent systems were obtained from finite concentration inverse gas chromatography measurements utilizing the elution-on-a-plateau technique. The results show that toluene has a higher self-affinity to form clusters in the pure polyester than THF, which is more homogeneously distributed in the polymer. Data for preferential solvation indicate that a segregation of parts of the polymer chains is present in the toluene–polyester system. When metal ions are introduced, the self-affinity of the solvent molecules to gather increases, whereas solvent clusters of toluene form in the free volume, and the gathering of the THF is likely to take place close to the metal ions. Based on the electron donacity values of the various donor groups present in the metal-ion-containing polymer it was assumed that THF in the Mg2+-containing polyester will be bound to the central metal ion while the apolar toluene will participate in the solvation of the apolar parts of the polymer and will be "repelled" from the ion-containing regions. The concentration of these ionic centres, which act as effective cross-links in the coordination polymer, was determined from measurements of thermodynamic activity. A comparison of the experimental and estimated effective cross-link density values indicates a nearly atomic dispersion of Mg2+ in the metal-ion-containing polyesters. Keywords: inverse gas chromatography, cluster integrals, solvent partition in polymers, metal-ion-containing polyesters, Flory–Huggins interaction parameter.

MetLigDB: a web-based database for the identification of chemical groups to design metalloprotein inhibitors

2011 ◽  
Vol 44 (4) ◽  
pp. 878-881 ◽  
Author(s):  
Hwanho Choi ◽  
Hongsuk Kang ◽  
Hwangseo Park
Keyword(s):  
Drug Discovery ◽  
Metal Ions ◽  
Metal Ion ◽  
Central Metal ◽  
Amino Acid Residues ◽  
Web Based ◽  
Additional Information ◽  
Chemical Groups ◽  
Insight Into ◽  
Chelating Groups

MetLigDB (http://silver.sejong.ac.kr/MetLigDB) is a publicly accessible web-based database through which the interactions between a variety of chelating groups and various central metal ions in the active site of metalloproteins can be explored in detail. Additional information can also be retrieved, including protein and inhibitor names, the amino acid residues coordinated to the central metal ion, and the binding affinity of the inhibitor for the target metalloprotein. Although many metalloproteins have been considered promising targets for drug discovery, it is difficult to discover new inhibitors because of the difficulty in designing a suitable chelating moiety to impair the catalytic activity of the central metal ion. Because both common and specific chelating groups can be identified for varying metal ions and the associated coordination environments, MetLigDB is expected to give users insight into designing new inhibitors of metalloproteins for drug discovery.

Determination of surface heterogeneity of d-mannitol by sessile drop contact angle and finite concentration inverse gas chromatography

2010 ◽  
Vol 387 (1-2) ◽  
pp. 79-86 ◽  
Author(s):  
Raimundo Ho ◽  
Steven J. Hinder ◽  
John F. Watts ◽  
Sarah E. Dilworth ◽  
Daryl R. Williams ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Contact Angle ◽  
Inverse Gas Chromatography ◽  
Sessile Drop ◽  
Surface Heterogeneity ◽  
Finite Concentration

Filler-Elastomer Interactions. Part VI. Characterization of Carbon Blacks by Inverse Gas Chromatography at Finite Concentration

1992 ◽  
Vol 65 (5) ◽  
pp. 890-907 ◽  
Author(s):  
Meng-Jiao Wang ◽  
Siegfried Wolff
Keyword(s):  
Gas Chromatography ◽  
Energy Distribution ◽  
Inverse Gas Chromatography ◽  
General Trend ◽  
High Energy ◽  
Carbon Blacks ◽  
Finite Concentration ◽  
Good Agreement

Abstract Carbon blacks ranging from N110 to N990 were characterized by means of inverse gas chromatography at finite concentration. The isotherms, net heat, and spreading pressures for benzene and cyclohexane adsorption suggest a general trend of increasing surface activity with increases in specific surface area. This is in good agreement with surface-energy measurements reported previously. The energy-distribution function of adsorption shows that while the concentrations of low-energy sites are comparable for most of the carbon blacks, differences exist with regard to high-energy sites. These suggest that small-particle-size blacks possess a greater number of high-energy centers. The graphitization of carbon blacks results in a considerable reduction in their adsorption capacity and narrows the energy distribution of their surfaces. One can therefore conclude that high-energy sites play an important role in the determination of the surface energies and reinforcing ability of carbon blacks.

scholarly journals Synthesis and photovoltaic properties of octacarboxy-metallophthalocyanine dyes applied in dye-sensitized solar cells

2012 ◽  
Vol 77 (9) ◽  
pp. 1223-1237 ◽  
Author(s):  
Ling Jin ◽  
Wei Chen ◽  
Dajun Chen
Keyword(s):  
Solar Cells ◽  
Metal Ions ◽  
Metal Ion ◽  
Dye Sensitized Solar Cells ◽  
Closed Shell ◽  
Open Shell ◽  
Central Metal ◽  
Photovoltaic Properties ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

A series of octacarboxy-metallophthalocyanine dyes, i.e., MgOCPc, MnOCPc, FeOCPc and ZnOCPc with different central metal ions were designed and synthesized by microwave irradiation. The effects of the introduction of different metal ions with variant 3d orbitals (3d0, 3d5, 3d6, and 3d10, respectively) in the centre of the phthalocyanine rings on the thermal, photophysical, and electrochemical properties of octacarboxy-metallophthalocyanines were characterized and evaluated in details. The results showed that ZnOCPc and MgOCPc with closed-shell metal ions and FeOCPc with an open-shell metal ion had excellent thermal property. However, MnOCPc with a half-full-shell metal ion had a lowest decomposition temperature and largest Q band red shifts. By theoretical calculation, the energy gaps of MgOCPc, MnOCPc, FeOCPc and ZnOCPc were 0.11, 0.10, 0.20 and 0.22V, respectively. Applied in TiO2 nanocrystalline dye-sensitized solar cells (DSSC), the photovoltaic properties of the four dyes were obtained under AM1.5 irradiation (100 mW cm-2).

scholarly journals Enzymes of heme metabolism is the kidney. Regulation by trace metals which do not form heme complexes

1977 ◽  
Vol 146 (5) ◽  
pp. 1286-1293 ◽  
Author(s):  
MD Maines ◽  
A Kappas
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Early Period ◽  
Reciprocal Relationship ◽  
Central Metal ◽  
Ion Regulation ◽  
Heme Metabolism ◽  
Rate Limiting

The in vivo regulation by metal ions of the enzymes of heme metabolism in kidney-particularly of ALAS, the rate-limiting enzyme in heine formation- was investigated. Ni(2+) and Pt(4+), metals which do not enzymatically form metalloporphyrins, were found to regulate ALAS in kidney as they do in liver. The pattern of this regulation was generally similar to that observed with heme and metal ions in liver, i.e., a late increase in enzyme activity after an early period in which ALAS activity was unaltered or inhibited. The metals did not interact with the enzyme in vitro to alter its activity. In this study no direct reciprocal relationship between ALAS activity and total cellular heine content was demonstrated. The metal ions, particularly Pt(4+), also altered the activity of other enzymes of heme biosynthesis in kidney. Pt(4+) severely inhibited the activity of ALAD and UROS. Ni(2+) and Pt(4+) were potent inducers of heme oxygenase, the initial and rate-limiting enzyme in heine degradation. It is proposed that the physiological regulation of ALAS is mediated through the action of metal ions, rather than by the cellular content of heine, and that the regulation of ALAS by heine reflects the action of the central metal ion of heme rather than that of the entire metalloporphyrin complex. In this proposed mechanism for metal ion regulation of ALAS, the tetrapyrrole moiety of heine is considered to function principally as an efficient carrier of metal to the regulatory site for ALAS production, inasmuch as the tetrapyrrole ring itself has been shown in earlier studies not to have any effect on ALAS activity. The production of heine oxygenase is believed to be similarly regulated.

Electronic structures, spectroscopic properties, and reaction activities of porphyrins with alkali metal ions: density functional theory approach to the central metal effects

2012 ◽  
Vol 16 (07n08) ◽  
pp. 927-934 ◽  
Author(s):  
Luyang Zhao ◽  
Dongdong Qi ◽  
Lijuan Zhang ◽  
Ming Bai ◽  
Xue Cai
Keyword(s):  
Density Functional Theory ◽  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Density Functional ◽  
State Transitions ◽  
Theory Approach ◽  
Central Metal ◽  
Functional Theory ◽  
Molecular Stability

Density functional theory (DFT) calculation method was employed to investigate a series of nine alkali metal porphyrins (alk-Pors), namely HLiPor , HNaPor , HKPor , Li2Por , LiNaPor , LiKPor , Na2Por , NaKPor , and K2Por . These molecules show different configurations depending on different metal ions which locate over the central hole of the porphyrin ligand. Alk-Pors with larger-radius metal ion have smaller binding energy and thus is more difficult to keep stable. Further detailed molecular stability analysis was carried out by noncovalent interaction and electrostatic interaction via RDG and NBO charge distribution. UV-vis spectra of these nine compounds also show different spectral shapes depending on the central metals, and the dominant state transitions with high degeneracy are revealed to be influenced by high molecular symmetric order. Finally their difference in reactivity due to the electronegativity of central metals and the nature of porphyrin rings are predicted by electrostatic potential and Fukui functions.

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