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The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the 1950s. But to date still little is understood. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring and a ferrihydric core at the center. This work sheds light on the interactions of early actinides (Th, Pu) at oxidation state +IV with ferritin and its ability to store those elements at physiological pH compared to Fe. The ferritin–thorium load curve suggests that ThIV saturates the protein (2840 Th atoms per ferritin) in a similar way that Fe does on the protein ring. Complementary spectroscopic techniques (spectrophotometry, infrared spectroscopy, and X‐ray absorption spectroscopy) were combined with molecular dynamics to provide a structural model of the interaction of ThIV and PuIV with ferritin. Comparison of spectroscopic data together with MD calculations suggests that ThIV and PuIV are complexed mainly on the protein ring and not on the ferrihydric core. Indeed from XAS data, there is no evidence of Fe neighbors in the Th and Pu environments. On the other hand, carboxylates from amino acids of the protein ring and a possible additional carbonate anion are shaping the cation coordination spheres. This thorough description from a molecular view point of ThIV and PuIV interaction with ferritin, an essential iron storage protein, is a cornerstone in comprehensive nuclear toxicology. [ABSTRACT FROM AUTHOR]

Separation processes based on room temperature ionic liquids (RTIL) and electrochemical refining are promising strategies for the recovery of lanthanides from primary ores and electronic waste. However, they require the speciation of dissolved elements to be known with accuracy. In the present study, Eu coordination and EuIII/EuII electrochemical behavior as a function of water content in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][NTf2]) was investigated using UV–visible spectrophotometry, time‐resolved laser fluorescence spectroscopy, electrochemistry, and X‐ray absorption spectroscopy. In situ measurements were performed in spectroelectrochemical cells. Under anhydrous conditions, EuIII and EuII were complexed by NTf2, forming Eu−O and Eu−(N,O) bonds with the anion sulfoxide function and N atoms, respectively. This complexation resulted in a greater stability of EuII, and in quasi‐reversible oxidation–reduction with an E0' potential of 0.18 V versus the ferrocenium/ferrocene (Fc+/Fc) couple. Upon increasing water content, progressive incorporation of water in the EuIII coordination sphere occurred. This led to reversible oxidation–reduction reactions, but also to a decrease in stability of the +II oxidation state (E0'=−0.45 V vs. Fc+/Fc in RTIL containing 1300 mm water). [ABSTRACT FROM AUTHOR]