Europium(III) complexation with salicylic acid at elevated temperatures

Curium(III) and europium(III) as luminescence probes for plant cell (Brassica napus) interactions with potentially toxic metals

We have investigated the interaction of the actinide Cm(III) and its lanthanide homologue Eu(III) with cells of Brassica napus in suspension. This study combines biochemical techniques (plant cell response) with spectroscopic experiments to determine the chemical speciation of hazardous metals in contact with the plant cells. Experiments conducted over a period of 7 d showed that B. napus cells were able to bioassociate both potentially toxic metals in significant amounts up to 0.58 µmol Eu/g_{fresh cells} and 1.82 µmol Cm/g_{fresh cells} at 30 µM Eu(III) and 0.68 µM Cm(III), respectively. For Cm(III), a biosorption process could be identified as soon as 5 h post-exposure with 73 ± 4% of the Cm(III) bioassociated. Luminescence spectroscopy results based on UV and site-selective excitation confirmed the existence of three Cm(III)/Eu(III) [M(III)] species in both the supernatants and cells. The findings detailed herein support that M(III) coordinates to two kinds of carboxyl groups and phosphate groups.

Plant cell (Brassica napus) response to europium(III) and uranium(VI) exposure

Experiments conducted over a period of 6 weeks using Brassica napus callus cells grown in vitro under Eu(III) or U(VI) stress showed that B. napus cells were able to bioassociate both potentially toxic metals (PTM), 628 nmol Eu/gfresh cells and 995 nmol U/gfresh cells. Most of the Eu(III) and U(VI) was found to be enriched in the cell wall fraction. Under high metal stress (200 μM), cells responded with reduced cell viability and growth. Subsequent speciation analyses using both metals as luminescence probes confirmed that B. napus callus cells provided multiple-binding environments for Eu(III) and U(VI). Moreover, two different inner-sphere Eu3+ species could be distinguished. For U(VI), a dominant binding by organic and/or inorganic phosphate groups of the plant biomass can be concluded.

The interaction of Eu(iii) with organoborates – a further approach to understand the complexation in the An/Ln(iii)–borate system

A combination of different spectroscopy techniques, DFT calculations and advanced data analysis explained the Eu(iii)–organoborate complexation.

Paramagnetic decoration of DNA origami nanostructures by Eu³⁺ coordination

The folding of DNA into arbitrary two- and three-dimensional shapes, called DNA origami, represents a powerful tool for the synthesis of functional nanostructures. Here, we present the first approach toward the paramagnetic functionalization of DNA origami nanostructures by utilizing postassembly coordination with Eu(3+) ions. In contrast to the usual formation of toroidal dsDNA condensates in the presence of trivalent cations, planar as well as rod-like DNA origami maintain their shape and monomeric state even under high loading with the trivalent lanthanide. Europium coordination was demonstrated by the change in Eu(3+) luminescence upon binding to the two DNA origami. Their natural circular dichroism in the Mg(2+)- and Eu(3+)-bound state was found to be very similar to that of genomic DNA, evidencing little influence of the DNA origami superstructure on the local chirality of the stacked base pairs. In contrast, the magnetic circular dichroism of the Mg(2+)-bound DNA origami deviates from that of genomic DNA. Furthermore, the lanthanide affects the magnetic properties of DNA in a superstructure-dependent fashion, indicative of the existence of superstructure-specific geometry of Eu(3+) binding sites in the DNA origami that are not formed in genomic DNA. This simple approach lays the foundation for the generation of magneto-responsive DNA origami nanostructures. Such systems do not require covalent modifications and can be used for the magnetic manipulation of DNA nanostructures or for the paramagnetic alignment of molecules in NMR spectroscopy.

Americium(iii) and europium(iii) complex formation with lactate at elevated temperatures studied by spectroscopy and quantum chemical calculations

Spectroscopic techniques (NMR and ATR FT-IR) in combination with calculations (DFT) show that the hydroxyl group of the lactate is deprotonated under complex formation with Eu(iii).

Electrospray ionization mass spectrometric studies on uranyl complex with α-hydroxyisobutyric acid in water-methanol medium

RATIONALE

Hydroxycarboxylic acids are extensively used as chelating agents in the liquid chromatographic separation of actinides and lanthanides. They are also used as model compounds to understand the binding characteristics of humic substances. A systematic study of the speciation of uranyl-α-hyydroxyisobutyric acid (HIBA) in water-methanol is essential, as it is important to understand the various mechanisms responsible for the separation of these species in liquid chromatography.

METHODS

ESI-MS studies were carried out using a tandem quadrupole-time-of-flight mass spectrometer in positive and negative ion mode. The effects of solution composition, solute concentration and supporting electrolyte concentration on the ESI-MS behavior of the uranyl species were studied. Transmission parameters such as the quadrupole ion energy and collision cell energy were optimized for acquiring the spectra of uranyl-HIBA species, ensuring that the spectra reflect the solution equilibrium conditions.

RESULTS

The solution composition and concentration of the uranyl salt were found to influence the major uncomplexed uranyl species. Although the ESI parameters did not influence the species distribution of uranyl-HIBA, the transmission parameters did have a significant effect. The overall trend in the complexation reaction between uranyl and HIBA was studied as a function of ligand-to-metal ratio. The species distribution obtained in positive ion mode was similar to that obtained in negative ion mode.

CONCLUSIONS

The study presents the optimization of the mobile phase conditions and the ESI-MS parameters for the speciation of the uranyl-HIBA system. The methodology was applied to obtaining the distribution of complexed and uncomplexed uranyl species for monitoring the trend in the complexation reaction.