Cost-efficient, visible-light-driven hydrogen production from water is an attractive potential source of clean, sustainable fuel. Here, it is shown that thermal solid state reactions of traditional carbon nitride precursors (cyanamide, melamine) with NaCl, KCl, or CsCl are a cheap and straightforward way to prepare poly(heptazine imide) alkali metal salts, whose thermodynamic stability decreases upon the increase of the metal atom size. The chemical structure of the prepared salts is confirmed by the results of X-ray photoelectron and infrared spectroscopies, powder X-ray diffraction and electron microscopy studies, and, in the case of sodium poly(heptazine imide), additionally by atomic pair distribution function analysis and 2D powder X-ray diffraction pattern simulations. In contrast, reactions with LiCl yield thermodynamically stable poly(triazine imides). Owing to the metastability and high structural order, the obtained heptazine imide salts are found to be highly active photocatalysts in Rhodamine B and 4-chlorophenol degradation, and Pt-assisted sacrificial water reduction reactions under visible light irradiation. The measured hydrogen evolution rates are up to four times higher than those provided by a benchmark photocatalyst, mesoporous graphitic carbon nitride. Moreover, the products are able to photocatalytically reduce water with considerable reaction rates, even when glycerol is used as a sacrificial hole scavenger.

“The Easier the Better” Preparation of Efficient Photocatalysts—Metastable Poly(heptazine imide) Salts

Cardiolipin (CL) is a mitochondria-specific phospholipid and is critical for maintaining the integrity of mitochondrial membrane and mitochondrial function. CL also plays an active role in mitochondria-dependent apoptosis by interacting with cytochrome c (cyt c), tBid and other important Bcl-2 proteins. The unique structure of CL with four linoleic acid side chains in the same molecule and its cellular location make it extremely susceptible to free radical oxidation by reactive oxygen species including free radicals derived from peroxidase activity of cyt c/CL complex, singlet oxygen and hydroxyl radical. The free radical oxidation products of CL have been emerged as important mediators in apoptosis. In this review, we summarize the free radical chemical mechanisms that lead to CL oxidation, recent development in detection of oxidation products of CL by mass spectrometry and the implication of CL oxidation in mitochondria-mediated apoptosis, mitochondrial dysfunction and human diseases.

Free radical oxidation of cardiolipin: chemical mechanisms, detection and implication in apoptosis, mitochondrial dysfunction and human diseases

More than 80% of the rate acceleration for enzymatic catalysis of the aldose-ketose isomerization of (R)-glyceraldehyde 3-phosphate (GAP) by triosephosphate isomerase (TIM) can be attributed to the phosphodianion group of GAP [Amyes, T. L., O'Donoghue, A. C., and Richard, J. P. (2001) J. Am. Chem. Soc. 123, 11325-11326]. We examine here the necessity of the covalent connection between the phosphodianion and triose sugar portions of the substrate by "carving up" GAP into the minimal neutral two-carbon sugar glycolaldehyde and phosphite dianion pieces. This "two-part substrate" preserves both the alpha-hydroxycarbonyl and oxydianion portions of GAP. TIM catalyzes proton transfer from glycolaldehyde in D2O, resulting in deuterium incorporation that can be monitored by 1H NMR spectroscopy, with kcat/Km = 0.26 M-1 s-1. Exogenous phosphite dianion results in a very large increase in the observed second-order rate constant (kcat/Km)obsd for turnover of glycolaldehyde, and the dependence of (kcat/Km)obsd on [HPO32-] exhibits saturation. The data give kcat/Km = 185 M-1 s-1 for turnover of glycolaldehyde by TIM that is saturated with phosphite dianion so that the separate binding of phosphite dianion to TIM results in a 700-fold acceleration of proton transfer from carbon. The binding of phosphite dianion to the free enzyme (Kd = 38 mM) is 700-fold weaker than its binding to the fleeting complex of TIM with the altered substrate in the transition state (Kd = 53 muM); the total intrinsic binding energy of phosphite dianion in the transition state is 5.8 kcal/mol. We propose a physical model for catalysis by TIM in which the intrinsic binding energy of the substrate phosphodianion group is utilized to drive closing of the "mobile loop" and a protein conformational change that leads to formation of an active site environment that is optimally organized for stabilization of the transition state for proton transfer from alpha-carbonyl carbon.

/pdf/enzymatic-catalysis-of-proton-transfer-at-carbon-activation-1mak75wg9f.pdf

Enzymatic catalysis of proton transfer at carbon: activation of triosephosphate isomerase by phosphite dianion.

Ni(II) and Cu(II) metal complexes of simple unsymmetrical Schiff-base ligands derived from salicylaldehyde/5-methylsalicylaldehyde and ethylenediamine or diaminomaleonitrile (DMN) were synthesized. The ligands and their complexes were characterized by elemental analysis, 1H NMR, FT IR, and mass spectroscopy. The electronic spectra of the complexes show d–d transitions in the region at 450–600 nm. Electrochemical studies of the complexes reveal that all mononuclear complexes show a one-electron quasi-reversible reduction wave in the cathodic region. ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry, with nuclear hyperfine spin 3/2. The copper(II) complexes show a normal room temperature magnetic moment value μ eff = 1.70–1.74 BM which is close to the spin only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts were also carried out. The in vitro antimicrobial activity of the ...

Synthesis, characterization, and antimicrobial activities of nickel(II) and copper(II) Schiff-base complexes

Supramolecular medicinal chemistry field has been a quite rapidly developing, increasingly active and newly rising interdiscipline which is the new expansion of supramolecular chemistry in pharmaceutical sciences, and is gradually becoming a relatively independent scientific area. Supramolecular drugs could be defined as medicinal supermolecules formed by two or more molecules through non-covalent bonds. So far a lot of supermolecules as chemical drugs have been widely used in clinics. Supermolecules as chemical drugs, i.e. supramolecular chemical drugs or supramolecular drugs, which might have the excellences of lower cost, shorter period, higher potential as clinical drugs for their successful research and development, may possess higher bioavailability, better biocompatibility and drug-targeting, fewer multidrug-resistances, lower toxicity, less adverse effect, and better curative effects as well as safety, and therefore exhibit wide potential application. These overwhelming advantages have drawn enormous special attention. This paper gives the definition of supramolecular drugs, proposes the concept of supramolecular chemical drugs, and systematically reviews the recent advances in the research and development of supermolecules, including organic and inorganic complex ones as chemical drugs in the area of antitumor, anti-inflammatory, analgesic, antimalarial, antibacterial, antifungal, antivirus, anti-epileptic, cardiovascular agents and magnetic resonance imaging agents and so on. The perspectives of the foreseeable future and potential application of supramolecules as chemical drugs are also presented.

https://link.springer.com/content/pdf/10.1007%2Fs11426-009-0103-2.pdf

Review on supermolecules as chemical drugs

Effects of a number of quinones and diphenols of various structures on free-radical fragmentation processes taking place in &#102 -diols, glycerol, 2-aminoethanol, glycero-1-phosphate, ethylene glycol monobutyrate, maltose, and some lipids were investigated. Quinone additions have been found to change the direction of free-radical transformations of the compounds cited above by inhibiting formation of the respective fragmentation products owing to oxidation of radicals of the starting compounds. The results obtained and literature data available allow a suggestion to be made that the system quinone/diphenol is able to not only deactivate or generate such active species as O 2 &#148 &#109 but also control the realization probability of free-radical processes of peroxidation and fragmentation in biologically important molecules.

Quinones as Free-radical Fragmentation Inhibitors in Biologically Important Molecules

Investigation of effects produced by 26 various phenol and diphenol derivatives, including industrial and natural antioxidants (ionol, bis-phenol 2246, α-tocopherol), on final product yields of radiation-induced free-radical processes involving peroxyl, alkyl, α-hydroxyalkyl and α,β-dihydroxyalkyl radicals has been performed. Ionol and bis-phenol 2246 have been shown to be more effective than α-tocopherol or diphenol derivatives in suppressing hydrocarbon oxidation processes. At the same time, α-tocopherol and its water-soluble analogues, as well as diphenol-based substances, are more effective than phenol derivatives in regulating various homolytic processes involving carbon-centered radicals. This fact can be accounted for by taking into consideration the contribution to formation of the final product set and the respective yields made by semiquinone radicals and compounds with quinoid structure arising in the course of homolytic transformations in systems containing diphenol derivatives.

Effects of phenolic compounds on reactions involving various organic radicals.

Synthesis and biological evaluation of copper (II) complexes of sterically hindered o-aminophenol derivatives as antimicrobial agents.

The state of hydroxyacetone in neutral aqueous solutions was studied by 1H and 13C NMR and UV spectroscopy. In the concentration range 0.1-1.41 M, 96-98% of hydroxyacetone exists in the carbonyl form. The content of the hydrated form of hydroxyacetone is 2-4%. No dimeric and polymeric species were detected.

A 1H and 13C NMR and UV Study of the State of Hydroxyacetone in Aqueous Solutions

The kinetics of the isomerization and monomerization of the glycolaldehyde dimer in a D2O solution (pD = 4.3) at 25°C is studied by1H NMR spectroscopy (360 MHz). The dynamics of the concentrations of seven dimeric and two monomeric glycolaldehyde forms present in the solution is examined when the system attains equilibrium. A kinetic scheme of equilibrium attainment in an aqueous solution of glycolaldehyde is proposed. The apparent rate constants of the transformation of the molecular glycolaldehyde structures into each other are determined

G. K. Glushonok

Papers

Quinones as Free-radical Fragmentation Inhibitors in Biologically Important Molecules

Effects of phenolic compounds on reactions involving various organic radicals.

Synthesis and biological evaluation of copper (II) complexes of sterically hindered o-aminophenol derivatives as antimicrobial agents.

A 1H and 13C NMR and UV Study of the State of Hydroxyacetone in Aqueous Solutions

Kinetics of Equilibrium Attainment between Molecular Glycolaldehyde Structures in an Aqueous Solution