David SheminDied 26 Nov 1991 at age 80 (born 18 Mar 1911).American biochemist who pioneered the use of radioactive and stable isotopes to trace chemical pathways by which the body creates its own materials, such as blood. He discovered the metabolic pathway by which the cell synthesizes heme (the red substance in haemoglobin), vitamin B-12 and related compounds. In 1946, with David Rittenberg, to investigate the path of glycine in the body, he ingested glycine labelled with atoms of the stable isotope nitrogen-15, and his blood was analyzed for products containing the tracer atoms. Hence they found glycine is used to synthesize the pyrrole rings of protoporphyrin. Further, he found that red blood cells had a lifespan of about 127 days, which led to understanding certain red blood cell diseases. He continued to study the mechanism of the intermediary metabolism of amino acids.« |
