Shares in Invitrogen tumbled 14.44 percent for the tracking period ended Tuesday, leading all decliners in the BCW Index this week. The firm missed Wall Street and internal targets for its third quarter at its BioReliance business continues to struggle (see article in this week's issue). Bruker also had a tough week, with its shares dropping 7.43 percent on the heels of its agreement to acquire an X-ray microanalysis business.