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Martin Kamen

(27 Aug 1913 - 31 Aug 2002)

Canadian-American biochemist who co-discovered (27 Feb 1940) the synthesis of the isotope carbon-14 by bombarding a target of graphite with sub-atomic particles. He worked with Sam Ruben at Berkeley, California.

Short biography of Martin Kamen >>

Unlocking the Enigma of Photosynthesis with Radioactive Carbon

The early research of Martin Kamen and Samuel Ruben (1941)

Research published in 1941 cast doubt on longstanding theories about photosynthesis, by employing radioactive carbon-14, in breakthrough experiments at the University of California. The work was conducted by Dr. Samuel Ruben of the Department of Chemistry and Dr. Martin D. Kamen from the Radiation Laboratory.

Carbon-14 atoms were produced using an atom-smashing cyclotron, by bombarding a target of graphite with deuterons (the nuclei of heavy hydrogen, containing a proton and an additional neutron). These radioactive atoms provided a pivotal new technique to explore plant chemistry, powerful enough to challenge existing notions about photosynthesis.

As a result of their studies, a previously unknown compound was identified that carries out what had earlier been thought to be the role of formaldehyde as an intermediary in the process of photosynthesis.

Scientists formerly had hypothesized that during photosynthesis, plants take in carbon dioxide, light, and water, to initially produce formaldehyde. This formaldehyde was then thought to undergo further reactions, driven by chlorophyll, to produce carbohydrates and other essential organic molecules.

However, the new research traced the path of radioactive carbon through the chemical changes during stages of photosynthesis. These experiments showed that formaldehyde did not contain the radioactive carbon—and thus was not the intermediary as once thought. Instead another, as yet unidentified, compound absorbed most of the radioactive carbon, suggesting that this compound might play the role that formaldehyde was initially believed to perform in photosynthesis.

Understanding photosynthesis is at the heart of the broader biological context of animals in the intricate web of life.

All animals, ranging from humans to microscopic organisms, rely on plants’ remarkable capability to transform basic inorganic elements into organic forms digestible for animals. Without the intervention of plants, animals would be unable to derive sustenance directly from nature’s primary sources like soil, water, and air. Through a complex chemical process involving chlorophyll, the green pigment in plants, they can transform these essential elements into a range of organic foods, from sugars to vitamins. This transformative process is what we know as photosynthesis.

Scientists have long been perplexed by the intricacies of photosynthesis. Numerous theories have been proposed, but definitive proof remained elusive due to the limitations of chemical investigative methods.

The prevailing belief was that plants, using light, carbon dioxide, and water, first produced formaldehyde, which acted as a preliminary step before chlorophyll initiated the creation of nutrients such as carbohydrates. To test this, Ruben and Kamen introduced algae to an environment rich in radioactive carbon dioxide. As these plants absorbed the radioactive carbon from the air, scientists could trace its path. Contrary to expectations, formaldehyde produced by the plants lacked the radioactive carbon.

Surprisingly, they identified an unforeseen compound that had absorbed most of the radioactive carbon—positioning itself as the real initial phase in photosynthesis. The exact chemical structure of this pivotal compound is still under investigation.

Furthermore, Drs. Ruben and Kamen, with their team debunked the notion that photosynthesis exclusively occurs in the presence of light. Their findings suggested that certain stages of photosynthesis might not be dependent on light, as plants continued to absorb radioactive carbon dioxide even in complete darkness.

Thus, the work by Dr. Ruben and Dr. Kamen has reshaped our understanding of photosynthesis, challenging long-held beliefs and unveiling new avenues for exploration. As we delve deeper into this critical biological process, the broader implications for fields like agriculture and bioenergy become ever more significant. Such discoveries underscore the evolving nature of scientific knowledge and the exciting horizons yet to be explored.

Ref: 'Radioactive Carbon Reveals Secrets of Photosynthesis', The Science News-Letter (25 Oct 1941), 40, No. 17, 268.

See also:

27 Aug - short biography, births, deaths and events on date of Kamen's birth.
Hot Carbon: Carbon-14 and a Revolution in Science, by John Marra. - book suggestion.
Booklist for Carbon.

Nature bears long with those who wrong her. She is patient under abuse. But when abuse has gone too far, when the time of reckoning finally comes, she is equally slow to be appeased and to turn away her wrath. (1882) -- Nathaniel Egleston, who was writing then about deforestation, but speaks equally well about the danger of climate change today.

Carl Sagan: In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) ...(more by Sagan)

Albert Einstein: I used to wonder how it comes about that the electron is negative. Negative-positive—these are perfectly symmetric in physics. There is no reason whatever to prefer one to the other. Then why is the electron negative? I thought about this for a long time and at last all I could think was “It won the fight!” ...(more by Einstein)

Richard Feynman: It is the facts that matter, not the proofs. Physics can progress without the proofs, but we can't go on without the facts ... if the facts are right, then the proofs are a matter of playing around with the algebra correctly. ...(more by Feynman)