Fig. 2. Analysis of proteins in giant basal spicules from M. chuni. (A) Protein extracts were prepared from the outer lamellar region of the spicules (la; lane a) or from total spicule (to; lane b) and size separated by 10% SDS-PAGE. The gels were stained with Coomassie Brilliant Blue. Size markers are given (M). (B) Corresponding western blot from the separation of a protein extract obtained from lamellae; the blot was reacted with polyclonal antibodies raised against silicatein (PoAb-aSILIC) and then with labelled secondary antibodies (lane a). In a separate series, the blot was first incubated with PoAb-aSILIC that had been adsorbed with recombinant silicatein (ads), and then incubated with the labelled secondary antibodies (lane b). (C) Analysis of a total spicule extract by two-dimensional gel electrophoresis (first isoelectric focusing and then size separation). The arrows mark the positions of the two sets of proteins in the total spicule extract, the 27/30 kDa molecules and the 70 kDa polypeptides. The gel was stained with Coomassie Brilliant Blue. Further details are given under Materials and methods.