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PRIMORDIAL SOUP
By Sean Henahan, Access Excellence
LA JOLLA- In a simulation of the days when the Earth was covered in primordial ooze, researchers at the University of California, San Diego have synthesized pantetheine, an ingredient considered essential for the development of life on the planet. The nature of the origin of life remains one of the most intriguing questions in biology. Researchers at the University of California, San Diego's Specialized Center of Research and Training in Exobiology are approaching the question by simulating environmental conditions as they are thought to have existed in "prebiotic" times. The researchers are studying the abiotic synthesis of biomolecules to determine which ones could have been present on Earth before life arose and, thus, may have been important to the first living organisms. The UCSD research team is led by Dr. Stanley Miller. Dr. Miller is well known for his 'primordial soup' experiment conducted in 1953. At that time he demonstrated that amino acids could be formed by passing an electric current through a flask of methane. This suggested that life could have arisen from materials and conditions present in early Earth history. Dr. Miller believes many other chemicals in addition to amino acids would have to have been present to facilitate the transition to living organisms. In particular, the presence of pantetheine could have enhanced the transition process. Pantetheine is related to coenzyme A, an essential component for protein formation. Coenzyme A is used by every known organism to assist in a wide variety of chemical reactions and it is possible that in the very earliest organisms this role was played by pantetheine alone, notes Miller. In their recent experiment, the UCSD scientists heated a mixture of pantoyl lactone, beta- alanine and cysteamine at 40 degrees C (105 degrees F). All three chemicals are believed to have been present on the early Earth. Among the other chemicals formed was pantetheine. This suggests pantetheine could have been created at the margins of evaporating pools of water in prebiotic times. "These components are extremely soluble and so would have been preferentially concentrated in evaporating bodies of water, for example on beaches and at lagoon margins. Our results show that amide bonds can be formed at temperatures as low as 40 degrees C, and provide circumstantial support for the suggestion that pantetheine and coenzyme A were important in the earliest metabolic systems," noted Miller. There are two main hypotheses regarding the prebiotic synthesis of coenzymes. One, the "RNA world" hypothesis, holds that coenzymes were part of the covalent structure of RNA, and assisted in the RNA-based metabolism. Another hypothesis suggests that the RNA world was preceded by a thioester world. According to that hypothesis, coenzyme A played an essential role in the activation of amino acids and hydroxy acids in peptide synthesis. The research provides evidence for the presence of an important ingredient in the original soup of life. It has been demonstrated that amino acids can form abiotically in a number of ways and are used by modern organisms for the manufacture of proteins. Sugars, however, which are components of modern genetic materials such as DNA or RNA are thought to be too unstable to have been widespread on Earth before life arose. Another of the remaining "big questions" is how and when did non-living molecules turn into life forms and begin to make copies of themselves. The current research appeared in the Feb. 23 issue of the journal Nature (v.373, Miller et al.). Transmitted: 95-03-20 19:34:24 EST
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