Distribution of thirteen (non)essential elements in the soluble fraction of the digestive gland of freshwater mussel Unio crassus from a reference and a polluted site: An SEC-ICP-MS analysis.

SEC-ICP-MS was applied to investigate for the first time the distributions of thirteen (non)essential elements (Ag, As, Bi, Cd, Co, Cu, Fe, Mn, Mo, Pb, Se, Tl and Zn) in the soluble fraction of the digestive gland of the freshwater mussel Unio crassus to assess how different environmental metal exposure levels influence metal-binding patterns. The majority of essential elements were predominantly associated with high and medium molecular mass ligands (HMM, MMM). Iron mainly eluted within two HMM-peaks which coeluted with apoferritin protein standard (∼400 kDa). Furthermore, essential elements also associated with low and very low MM ligands (LMM, VLMM), suggesting a possible binding to proteins/peptides with transport and/or detoxification functions (e.g., iron transit pool; selenoneine), or specifically to, for example, metallothioneins (MT; Cu and Zn) and vitamin B12 (Co). Studied non-essential elements generally eluted within LMM and VLMM regions, indicating certain degrees of their detoxification via different ligands (GSH, distinct MT-isoforms), with the exception of Bi and Tl, which were notably bound to MMM/HMM-ligands in all samples, pointing to potential toxic interactions.