Atomistic origin of selective Cs accumulation in mushrooms; DFT analysis for alkali metal cation complexation selectivity of scissors-like pigments

Suno, Hiroya  ; Machida, Masahiko  

Generally, fungi accumulate radioactive Cs much more than higher plants. Particularly, some species of fungi have been well-known to selectively accumulate high amounts of radioactive Cs (Cs, Cs) released by nuclear accidents in their fruiting bodies compared with other species. This is a highly concerned issue in the contaminated forest areas, because consumption of mushrooms is one of the main routes of internal radiation for the residents in addition to consumption of other contaminated forest foods. So far, several investigations have focused on only one pigment molecule, norbadione A, observed mainly inside the mushroom caps, selectively complexing Cs cations, though there exist a huge variety of pigment molecules inside mushrooms. Here, we examine systematically which type of pigment molecules can selectively complex Cs cations, by using a state-of-the-art computational technique. We consequently find that a symmetric scissors-like structure, formed with two equivalent pulvinic acid moieties, is crucial for the Cs complexation selectivity, from comparative analysis among four scissors-like pigments. We thus predict that mushroom species including such symmetric scissors-like pigments can keep high Cs radioactivity.