A quantum-chemical study of the binding ability of βXaaHisGlyHis towards copper(II) ion

The present study analyzed binding of Cu2+ to tetrapeptides in water solution at several levels of theoretical approximation. The methods used to study the energetic and structural properties of the complexes in question include semiempirical hamiltonians, density functional theory as well as ab initio approaches including electron correlation effects. In order to shed light on the character of interactions between Cu2+ and peptides, which are expected to be mainly electrostatic in nature, decomposition of interaction energy into physically meaningful components was applied

Systematic Review of Potential Health Risks Posed by Pharmaceutical, Occupational and Consumer Exposures to Metallic and Nanoscale Aluminum, Aluminum Oxides, Aluminum Hydroxide and Its Soluble Salts

Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007). Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of “total Al”assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al+ 3 to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)+ 2 and Al(H2O)6 + 3] that after complexation with O2•−, generate Al superoxides [Al(O2•)](H2O5)]+ 2. Semireduced AlO2• radicals deplete mitochondrial Fe and promote generation of H2O2, O2 • − and OH•. Thus, it is the Al+ 3-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer\u27s disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances

The trans Effect in Palladium Phosphine Sulfonate Complexes

Palladium phosphine sulfonate complexes constitute an efficient family of catalysts for both homopolymerization of ethylene and copolymerization of ethylene with a number of polar monomers. Their catalytic mechanisms have been extensively studied but not fully understood at the electronic structure level. The energy decomposition analysis, complemented with the inspection of the natural orbitals for chemical valence, reveals that their catalytic activity can be rationalized in terms of the so-called <i>trans effect</i>. Furthermore, our analysis shows that the competition for the σ donation of the two ligands PMe₃ and L, of the palladium phosphine sulfonate complexes, to the same orbital of Pd in the trans isomer and to different orbitals in the cis isomer is the origin of the trans effect. Although the dominance of the phosphine group prevents an efficient interaction of the ligand L with the Pd atom, the large stabilization gained by the phosphine group renders a very stable trans complex

The long-term environmental behaviour of strontium and barium released from former mine workings in the granites of the sunart region of Scotland, UK

The concentrations of strontium and barium have been measured in water, sediment and the shells of mussels (Mytilus edulis) from a river system in the Sunart region of Scotland. UK. The aim was to establish the fate and mobility of these elements. which are slowly being released from old mine workings on the Strontian granites. Enhanced strontium (1500-2000 mug l(-1) and 250-290 mugl(-1)) and barium concentrations (316 mug l(-1) and 83 mug l(-1) ) were found in the waters originating from the two mine drains studied. Both element were also found at significant levels in the river sediment, taken from the vicinity of each drainage site (Sr: 225 mugg(-1) and 120-125 mugg(-1): Ba: 1380 mugg(-1) and 126-170 mugg (-1)). The data suggests that the sediments are acting as a reservoir for these group II cations from where the,, become distributed throughout the river system. Strontium is found to be incorporated into the shells (3.16 3.46 mugg(-1)) and pearl, (3.57 mugg(-1)) of the blue mussel. located at the estuarine margin some 10 km downstream. at values close to the maximum expected (3.3% by weight of the calcium content). The study presents a view of the fate of barium and itronijuni in a river system over a prolonged period of time. As such it provides valuable information for studies that seek to model the impact of the accidental release of barium and strontium (including the important radionuclide Sr-90) into the environment

Flavin bioorthogonal photocatalysis toward platinum substrates

Catalytic reactions that use metal complexes as substrates, rather than catalysts, are nearly unknown. We recently demonstrated that certain flavins (FLs) are potent redox photocatalysts capable of converting PtIV anticancer prodrug complexes into PtII drugs in the biological environment. Herein, we investigate the mechanism of these artificial photocatalytic reactions employing four different free flavins, namely, riboflavin (Rf), flavin mononucleotide (FMN), tetra-O-acetyl riboflavin (TARF) and lumiflavin (Lf), and the flavoprotein miniSOG (mini Singlet Oxygen Generator), together with a panel of PtIV substrates conveniently selected. NMR, steady-state, and time-resolved optical spectroscopy studies highlight that light activation of FLs in the presence of NADH as electron donor (pH 7-7.5) eventually leads to the generation of the reduced FLH- species which catalyzes the PtIV-to-PtII conversion with turnover frequency (TOF) values ranging between 1.3 and 30 min-1 and turnover number (TON) values reaching 500. Comparable catalytic efficiency is also found for reactions performed in cell culture medium. Density functional theory suggests that activation via reduction of the PtIV complexes may be influenced by H-bonding interactions between the FL catalyst and the metal substrate and confirms that both the isoalloxazine and ribityl moieties of the FLs determine the catalytic efficiency of the process. The FMN-containing miniSOG is a less effective catalyst (TOFs < 5.6 min-1) because the formation of the doubly reduced FMNH- competes with an electron transfer reaction involving the protein matrix which quenches the FMN excited state to give a singly reduced FMN N.