F. Hoffmann-La Roche Ltd. of Basel, Switzerland, has purchased 454 Life Sciences of Branford, Conn., a majority-owned subsidiary of CuraGen Corp., also of Branford. Under terms of the agreement, Roche will pay holders of the acquired company’s shares a total of $140 million in cash. The shareholders may receive up to $14.9 million in additional cash from holders of currently outstanding stock options and warrants. The employees of 454 Life Sciences, which develops and commercializes instrumentation for high-throughput DNA sequencing, will remain at their current location and become part of the Roche Diagnostics Div.