Elastin-like polypeptide serves as a vector for thermally-targeted delivery of therapeutics, including cytotoxic chemotherapeutic drugs such as doxorubicin. The invention consists of using a second selector to mask out all or at least a large fraction of the parent ions as well as those metastable daughter ions, which are produced by the decomposition of parent ions after post-acceleration. The driving assembly is mounted on the mounting plate and includes a driver, and a transfer rod coupled to the driver.