Recorded: 08 Jun 2006
The approach that was being used in the early fifties in the Huntington laboratories was primarily taking an organ from a living animal. We focused entirely on animals. It was a hospital environment. We all had a background in medicine. So we used rat liver as a key experimental model, experimental material. We put the chopped up liver from a rat into a test tube and homogenized it. That is with a pencil going down into the test-tube actually breaking it up into broken cell preparations. We then turned to the ultracentrifuge which was a key way of separating the components of cells and were able to show for instance we were the first to show, the first of two laboratories actually to show that the material that sediment down most rapidly in the centrifuge, the heaviest materials were ribosomes, the next material was soluble material and so we could separate. It was a way of separating the components of the cell to see which parts of the cell were carrying out a particular job you were interested in. We were interested in how proteins were made, so we would add radioactive amino acids. These were carbon 14 labeled amino acids. These were added to a tube containing the pieces of the rat’s cells that we were interested in and these would be incubated for a very short period then the whole reaction was stopped chemically. We would then analyze where the radioactivity was in these living cells in these parts of living cells and that would tell us where the amino acids were going when they were incubated at say at 37 degrees centigrade for a short period of time.
So it was that kind of approach. The molecular biologists on the other hand were not at all interested in this—in the contents of the black box that we were sort of in. We were interested in the mechanical processes conveying amino acids to proteins. They were interested in more theoretical questions about how information and genetic material mainly DNA got finally into proteins in the right order. So there were two totally different fields for a while.
Mahlon Hoagland, a molecular biologist who was one of the discoverer of the transfer ribonucleic acid - tRNA. He received a medical degree from Harvard Medical School in 1948. He served as a doctor during the Second World War. When the War ended he returned to Harvard and became researcher in the Huntington Laboratories at the Massachusetts General Hospital in Boston. He worked in the bacteriology and immunology department of Harvard Medical School from 1952 till 1967.
Working together with Paul Zamecnik and Elizabeth Keller he discovered the initial steps of protein synthesis. Two years later in 1958 Hoagland and Zemecnik discovered tRNA. His main input to the laboratory was in his work with amino acid activating enzymes. He noticed that certain enzymes were required to activate amino acids so they could combine with tRNA molecules and eventually be incorporated into new protein molecules. These enzymes were named aminoacyl tRNA synthetases.
In 1957 Hoagland moved to Cambridge where he worked for a year with Crick at Cambridge University. Working together they tried to explain the genetic code.
He was Associate Professor of Microbiology at Harvard Medical School and in 1967 was appointed professor in the biochemistry department at the Dartmouth Medical School. After 3 years he left Dartmouth and became Director and President of the Worcester Foundation for Experimental Biology in Massachusetts. He retired in 1985.
Mahlon Hoagland was awarded the Franklin Medal for life science. He was a member of the American Academy of Arts and Sciences and the US National Academy of Sciences. He died on September 19, 2009.
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