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

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.