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The electron affinity of astatine.

ABSTRACT: One of the most important properties influencing the chemical behavior of an element is the electron affinity (EA). Among the remaining elements with unknown EA is astatine, where one of its isotopes, ²¹¹At, is remarkably well suited for targeted radionuclide therapy of cancer. With the At^- anion being involved in many aspects of current astatine labeling protocols, the knowledge of the electron affinity of this element is of prime importance. Here we report the measured value of the EA of astatine to be 2.41578(7)?eV. This result is compared to state-of-the-art relativistic quantum mechanical calculations that incorporate both the Breit and the quantum electrodynamics (QED) corrections and the electron-electron correlation effects on the highest level that can be currently achieved for many-electron systems. The developed technique of laser-photodetachment spectroscopy of radioisotopes opens the path for future EA measurements of other radioelements such as polonium, and eventually super-heavy elements.

SUBMITTER: Leimbach D

PROVIDER: S-EPMC7393155 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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The electron affinity of astatine.

Leimbach David D Karls Julia J Guo Yangyang Y Ahmed Rizwan R Ballof Jochen J Bengtsson Lars L Boix Pamies Ferran F Borschevsky Anastasia A Chrysalidis Katerina K Eliav Ephraim E Fedorov Dmitry D Fedosseev Valentin V Forstner Oliver O Galland Nicolas N Garcia Ruiz Ronald Fernando RF Granados Camilo C Heinke Reinhard R Johnston Karl K Koszorus Agota A Köster Ulli U Kristiansson Moa K MK Liu Yuan Y Marsh Bruce B Molkanov Pavel P Pašteka Lukáš F LF Ramos João Pedro JP Renault Eric E Reponen Mikael M Ringvall-Moberg Annie A Rossel Ralf Erik RE Studer Dominik D Vernon Adam A Warbinek Jessica J Welander Jakob J Wendt Klaus K Wilkins Shane S Hanstorp Dag D Rothe Sebastian S

Nature communications 20200730 1

One of the most important properties influencing the chemical behavior of an element is the electron affinity (EA). Among the remaining elements with unknown EA is astatine, where one of its isotopes, <sup>211</sup>At, is remarkably well suited for targeted radionuclide therapy of cancer. With the At<sup>-</sup> anion being involved in many aspects of current astatine labeling protocols, the knowledge of the electron affinity of this element is of prime importance. Here we report the measured va ...[more]

PMID: 32733029

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Project description:Electron capture dissociation (ECD) and electron transfer dissociation (ETD) of doubly protonated electron affinity (EA)-tuned peptides were studied to further illuminate the mechanism of these processes. The model peptide FQpSEEQQQTEDELQDK, containing a phosphoserine residue, was converted to EA-tuned peptides via beta-elimination and Michael addition of various thiol compounds. These include propanyl, benzyl, 4-cyanobenzyl, perfluorobenzyl, 3,5-dicyanobenzyl, 3-nitrobenzyl, and 3,5-dinitrobenzyl structural moieties, having a range of EA from -1.15 to +1.65 eV, excluding the propanyl group. Typical ECD or ETD backbone fragmentations are completely inhibited in peptides with substituent tags having EA over 1.00 eV, which are referred to as electron predators in this work. Nearly identical rates of electron capture by the dications substituted by the benzyl (EA = -1.15 eV) and 3-nitrobenzyl (EA = 1.00 eV) moieties are observed, which indicates the similarity of electron capture cross sections for the two derivatized peptides. This observation leads to the inference that electron capture kinetics are governed by the long-range electron-dication interaction and are not affected by side chain derivatives with positive EA. Once an electron is captured to high-n Rydberg states, however, through-space or through-bond electron transfer to the EA-tuning tags or low-n Rydberg states via potential curve crossing occurs in competition with transfer to the amide pi* orbital. The energetics of these processes are evaluated using time-dependent density functional theory with a series of reduced model systems. The intramolecular electron transfer process is modulated by structure-dependent hydrogen bonds and is heavily affected by the presence and type of electron-withdrawing groups in the EA-tuning tag. The anion radicals formed by electron predators have high proton affinities (approximately 1400 kJ/mol for the 3-nitrobenzyl anion radical) in comparison to other basic sites in the model peptide dication, facilitating exothermic proton transfer from one of the two sites of protonation. This interrupts the normal sequence of events in ECD or ETD, leading to backbone fragmentation by forming a stable radical intermediate. The implications which these results have for previously proposed ECD and ETD mechanisms are discussed.

Dataset Information

The electron affinity of astatine.

Publications

The electron affinity of astatine.

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