Scientist. A pioneer of molecular biology, he was the co-discoverer of transfer RNA (tRNA), which improved our understanding of protein synthesis. His invention of antisense therapy paved the way for a new class of anti-viral drugs. Raised in Cleveland, Zamecnik studied medicine at Dartmouth and received his M.D. from Harvard (while working as a ski instructor) in 1936. When he returned to Cleveland for training, Dr. Zamecnik accepted an oncology internship because the surgery program was full; his interest in research was triggered when the autopsy of an obese woman showed too much fat and too little protein, but no specific cause of death. Desiring to learn just how the body makes proteins (an unstudied area at the time), he took a fellowship in Denmark, though his study there was to be halted by World War II. During the war he took a research job at the Rockefeller Institute and then accepted a faculty position at Harvard. In the early 1950s, his lab at Massachusetts General Hospital invented a cell-free system for protein synthesis using rat livers; this lead to his discovery of (along with Drs. Mary Stephenson and Mahlon Hoagland) of tRNA, which controls protein structure by determining which amino acid is incorporated into the molecule at a given site. Further curosity resulted in his study of the DNA molecule, which is made up of two intertwined strands: a sense strand provides the protein pattern, while an antisense strand gives stability. Dr. Zamecnik's work with the Rous Sarcoma virus demonstrated that introduction of "defective" antisense segments into a gene could block messinger RNA (mRNA), and thus prevent viral replication. (The 1978 paper detailing the work has been cited about 900 times). At the time of the doctor's death, only one antisense drug was on the market (Vitravene for CMV retinitis), though more were anticipated. He never stopped working; faced with age-mandated retirement at Harvard in 1979, he joined the Worcester Foundation, then moved back to Massachusetts General in 1997. Nominated for the Nobel Prize several times, he never won. Still, his honors were many; six honorary degrees, the American Cancer Society National Award in 1968, election to the National Academy of Sciences, also in 1968, the 1991 National Medal of Science, and the Lasker Prize in 1996. At his death, he had published roughly 240 papers and held a dozen patents. When asked why he didn't retire, he said simply: "I'm better at this than I am at gardening or carpentry".