Speciation of Metallothionein-like proteins of the Mussel Mytilus edulis at Basal Levels by Chromatographic Separations Coupled to Quadrupole and Double-Focusing Magnetic Sector ICPMS

摘要

Characterization and partial purification of metallothio-nein-like proteins (MLPs) of the mussel Mytilus edulis from natural populations of three coastal regions in Spain were pci-formed. Size exclusion chromatography (SEC) with quadrupole (Q-ICPMS) or double-focusing induc-tively coupled plasma mass spectrometiy (DF-ICPMS) detection was used first for specialion of cadmium in such natural samples and those of mussels exposed to 500 mg-L-’ Cd in an aquarium tank. SEC results showed always a single Cd—MLP peak (MLP fraction). The con-tents in Cd, Cu, and Zn of this MLP fraction, of the high molecular weight protein pool (HMW), and of the whole cytosol were then measured by DF-ICPMS. Then, a given aliquot (50 1tL) of MLPs with the highest values for IN molecular absorption at 254 nm (also the maximum sulfur and Cd, Cu, or Zn contents) was used to further fractionation. Fast protein liquid chromatography “on line” with Q-ICPMS was used for the purpose. Two Cd-Ml? isoforms (MLP-1, MLP-2), with retention times (t1) ci 15.7 and 16.0 mm, were then detected in cy~aoh of the mussel samples of aquarium tank and aim ci the industrial area and Galicia coast Conversely, wildmussels did not show any Cd-MLP signals at alL Analj~ ci essential elements copper and zinc in such cykuoh by FPLC-Q-ICPMS revealed that these two metak weu~ociated just to MLP-1. These results tend to indicatea different role for the two MLP isoforms detected inmmuseis (i.e., essential metals’ homeostasis role seemsb he tied to the MLP-1 isoform only). They illustrate the that trace metal speciation of unknown species in-materials is becoming a challenge and points ci several complementary analytical techniquesrequired speciation information.