Characterizing the general chelating affinity of serum protein fetuin for lanthanides
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ORIGINAL PAPER
Characterizing the general chelating affinity of serum protein fetuin for lanthanides Roger M. Pallares1 · Nagender R. Panyala1 · Manuel Sturzbecher‑Hoehne1 · Marie‑Claire Illy1 · Rebecca J. Abergel1,2 Received: 24 March 2020 / Accepted: 31 August 2020 © Society for Biological Inorganic Chemistry (SBIC) 2020
Abstract Fetuin is an abundant blood protein that participates in multiple biological processes, including the transport and regulation of calcium. Fetuin is also known to have a high affinity for uranium (as the uranyl dioxo cation) and plutonium, thus it has been suggested as one of the main endogenous chelating biomolecules involved in the transport of actinides following an internal uptake event. Nevertheless, no direct measurements of its affinity for f-elements beside these two actinides have been reported. Here, we investigate the interaction between fetuin and trivalent lanthanides, such as samarium, europium, terbium, and dysprosium, by mass spectrometry and fluorescence spectroscopy. Mass spectrometry results indicated that fetuin has four metal binding sites for the metal ions studied. Upon formation, the metal–protein complexes showed luminescence emission as a result of antenna sensitization of the metal ions, whose photophysics were characterized and exploited to perform direct spectrofluorimetric titrations. Furthermore, the thermodynamic constants were calculated for all complexes, confirming the ′ formation of stable complexes with log 𝛽4 values between 26 and 27. In characterizing the affinity of the serum protein fetuin for several f-elements, this study expands upon the initial findings focused on uranyl and plutonium, and contributes to a better understanding of the internal distribution and deposition of lanthanides, potentially representative of trivalent actinides. Keywords Fetuin · Lanthanides · Luminescence · Mass spectrometry
Introduction The potential release of toxic radionuclides to the environment as a consequence of industrial activities, such as the processing of nuclear fuel and waste, and accidents in nuclear plants, is considered an important public health and environmental issue [1]. The radionuclides generated during such nuclear-centric activities stem largely from the f-block, including lanthanide (Ln) fission products and actinides (An) [2–4]. Although exposure to these radionuclides has been Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00775-020-01815-x) contains supplementary material, which is available to authorized users. * Rebecca J. Abergel [email protected] 1
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
Department of Nuclear Engineering, University of California, Berkeley, CA 94720, USA
2
associated with the development of several pathologies, the biological pathways and biochemical mechanisms involved after internal contamination with most f-elements is still not well understood [5, 6]. Although Ln ions are not known to participa
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