Fig. 1. Gel-permeation chromatography of acute Cd-exposed (20 mg l^–1, 2 days) N. diversicolor gut supernatant. Column: Hi- Load Superdex 75 Prep grade (Pharmacia); sample volume: 2 ml; flow rate: 1 ml min^–1; elution buffer: 10 mmol l^–1 Tris-HCl, pH 8.6. (A) The absorbance profile at 280 nm shows three main protein peaks, I, II and III. (B) Analysis of the Cd content (µg ml^–1) of the chromatographic fractions shows that this metal is associated with components eluted in the void volume of the column (>70 kDa) likely to represent the hemoglobin (peak I in A) and components of the second main peak (peak II in A). (C) Enzyme-linked immunosorbent assay (ELISA) using the mAb anti-MPII revealed that peak II fractions contain the Cd-binding protein MPII.