"We used to think if we could understand what carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur were doing, we would immediately be able to understand biology," Morowitz says, listing elements that constitute a large proportion of Earth's biomass. "But now we're finding that these other fairly rare elements, transition metals, are necessary in biology, so we ask, 'What was their role in the origin of life?'"
The proposal suggests that the rise of life forms is a natural consequence of the unique properties of transition metals and ligand field theory, which describes the characteristics of ligand complexes.
"The idea has emerged from a study of the periodic table. We strongly feel that unless you're able to see how life comes about in some formal chemical way, you're never really going to solve the problem," Morowitz says.
Morowitz and his colleagues are preparing experiments to test the catalytic properties of transition metal-ligand complexes built with different types of ligands. Ligands known to bind tightly to transition metals include molecules produced during the course of the reductive citric acid cycle, a series of biochemical reactions essential for many microorganisms.
"We think life probably began with the reductive citric acid cycle, and there is evidence that under hydrothermal vent conditions some of the cycle's intermediates form," Morowitz says. "We are going to start with these molecules and mix them with various transition metals, cook them at different temperatures for a while, and see what kinds of catalysts we've made."
Such experiments could reveal what kinds of catalytic reactions took place to lay the foundations for life. The hypothesis also allows for the possibility that life could have arisen more than once.
"Life could have originated multiples times, and, if we find life elsewhere in the universe, it could
|Contact: Carol Schachinger|
Marine Biological Laboratory