Misty Borja: Estimation of Cu Turnover in The Visceral Complex of Littorina littorea  By Isotopic Ratio Analysis Using ICP-MS. SE-IE HPLC/ICP-MS provides a powerful analytical technique to quantify the metal content of metalloproteins in cytosolic samples. Stable isotopic pulse chase studies can be used monitor the kinetics of exchange and turnover of metals in tissues and proteins. This technique currently offers the only method for studying the kinetics of metals such as Cu, which have radioisotopes with short physical half-lives.  SE-HPLC Elemental profiles shows the presence of two major pools of Cu binding proteins of <300K.Da and 17K.Da in the visceral complex of Littorina. The latter pool is induced by exposure to Cu. Isotopic ratio analysis shows that the metal associated with this pool is derived from both intrinsic and extrinsic sources and shows facile exchange relative to the high molecular weight pool.  The induction of the 17kDa protein pool causes a massive redistribution of metal in the animal, which results from its ability to competitively bind a variety of metals other than Cu including Zn, Pb, Co, Cd and Mn.  Further fractionation of this pool in a second dimension according to charge shows the presence of at least three major pools of metal binding protein in this weight range which elute at 3.0, 3.8 and 11.7 minutes which bind Cu + Co + Pb; Cu + Zn and Cd + Pb +Mn respectively. Although the identity of these proteins is unknown at this time, previous studies in our laboratory have shown the presence of three isoforms of metallothionein in this tissue. Amino-acid sequencing is currently being undertaken to confirm the identity of the metal binding proteins.  Quantitative analyses show that Cu exposure not only causes a redistribution in cytosolic metals but also causes a progressive and massive, 25 fold increase in Zn. Similar increases were also noted in Cd (x4-6), Co (x2), Mn (x24) and Pb (x16).  Comparisons between Tables 1 and 2 indicate the possibility of Mo contamination in the high ionic strength buffer used during ion exchange. The Mo resolves as a single major peak at 16 minutes implying ion chromatography that probably relates to chemical speciation and the presence of the molybdate ion (MoO4 2-).