Scientists Closer to Solving the Origin of Life on Primitive Earth
Posted by schafersman at 5/14/2009 3:27 AM CDT
http://www.chron.com/commons/reader...&plckScript=blogScript&plckElementId=blogDest
With masterful scientific work, Dr. John D. Sutherland, a chemist at the University of Manchester, has solved a major problem concerning the origin of life: how the building blocks of RNA, called nucleotides, could have spontaneously assembled themselves in the conditions of primitive Earth. This discovery will quickly lead to further discoveries about life's origin and scientists may ultimately have a plausible explanation for how information-carrying biological molecule could have emerged through natural processes from chemicals on early Earth.
Scientists have long suspected that the first forms of life carried their biological information not in DNA but in RNA. The RNA before DNA theory has been accepted by origin of life theorists for many years. Two Nobel Prize winners, Thomas Cech and Sidney Altman, have written brief essays about this probability. Before DNA, all life existed in an RNA World. RNA has many chemical abilities, such as catalyzing reactions, transporting biological information within a cell, and preserving biological information between generations. DNA is a more stable molecule and it appears that RNA gave up the task of preserving and transporting biological information between individuals and generations to DNA.
RNA is composed of four nucleotides, so the question was how these chemical building blocks could spontaneously and naturally synthesize and join together on primitive Earth. The nucleotides--each formed of a chemical base, a ribose sugar molecule, and a phosphate group--can form spontaneously from natural chemicals that could be present in early Earth environments, but until now there was no known way the separate and different nucleotides would chemically join together. This is the problem that Dr. Sutherland and his colleagues solved.
Dr. Sutherland searched for ten years, methodically working through every possible combination of starting chemicals to try and make them react in different orders and different combinations. He and his colleagues ultimately discovered their non-intuitive recipe which will be published in this week's Nature. As explained in the article in the New York Times by science writer Nicholas Wade, the only source available to me right now,
[FONT=trebuchet ms,geneva]Charles Darwin would have been proud of [/FONT][FONT=trebuchet ms,geneva]John Sutherland.[/FONT]
Posted by schafersman at 5/14/2009 3:27 AM CDT
http://www.chron.com/commons/reader...&plckScript=blogScript&plckElementId=blogDest
With masterful scientific work, Dr. John D. Sutherland, a chemist at the University of Manchester, has solved a major problem concerning the origin of life: how the building blocks of RNA, called nucleotides, could have spontaneously assembled themselves in the conditions of primitive Earth. This discovery will quickly lead to further discoveries about life's origin and scientists may ultimately have a plausible explanation for how information-carrying biological molecule could have emerged through natural processes from chemicals on early Earth.
Scientists have long suspected that the first forms of life carried their biological information not in DNA but in RNA. The RNA before DNA theory has been accepted by origin of life theorists for many years. Two Nobel Prize winners, Thomas Cech and Sidney Altman, have written brief essays about this probability. Before DNA, all life existed in an RNA World. RNA has many chemical abilities, such as catalyzing reactions, transporting biological information within a cell, and preserving biological information between generations. DNA is a more stable molecule and it appears that RNA gave up the task of preserving and transporting biological information between individuals and generations to DNA.
RNA is composed of four nucleotides, so the question was how these chemical building blocks could spontaneously and naturally synthesize and join together on primitive Earth. The nucleotides--each formed of a chemical base, a ribose sugar molecule, and a phosphate group--can form spontaneously from natural chemicals that could be present in early Earth environments, but until now there was no known way the separate and different nucleotides would chemically join together. This is the problem that Dr. Sutherland and his colleagues solved.
Dr. Sutherland searched for ten years, methodically working through every possible combination of starting chemicals to try and make them react in different orders and different combinations. He and his colleagues ultimately discovered their non-intuitive recipe which will be published in this week's Nature. As explained in the article in the New York Times by science writer Nicholas Wade, the only source available to me right now,
[FONT=trebuchet ms,geneva]Instead of making the starting chemicals form a sugar and a base, they mixed them in a different order, in which the chemicals naturally formed a compound that is half-sugar and half-base. When another half-sugar and half-base are added, the RNA nucleotide called ribocytidine phosphate emerges. A second nucleotide is created if ultraviolet light is shined on the mixture. The reactions he has described look convincing to most other chemists. “The chemistry is very robust — all the yields are good and the chemistry is simple,” said Dr. Joyce, an expert on the chemical origin of life at the Scripps Research Institute in La Jolla, Calif. In Dr. Sutherland’s reconstruction, phosphate plays a critical role not only as an ingredient but also as a catalyst and in regulating acidity. Dr. Joyce said he was so impressed by the role of phosphate that “this makes me think of myself not as a carbon-based life form but as a phosphate-based life form.”[/FONT]
Both reactions start off with simple chemicals believed to have been present on the primitive earth. They are glyceraldehyde, cyanimide, cyanoacetaldehyde and cyanoacetylene. These chemicals will naturally form the base cytosine and ribose. But the cytosine cannot be made to join to the ribose under natural conditions. Working through all possible chemical combinations for 10 years, Dr. Sutherland's team discovered a different and quite unintuitive route. Their reaction system combines the carbon-nitrogen chemistry that leads to the bases with the carbon-oxygen chemistry that makes the sugars. They make a half-sugar/half-base, add another half-sugar and then a half-base to make an intermediate that easily becomes ribo-cytidine phosphate. Ultraviolet light converts ribocytidine to the uracil-containing nucleotide.
[FONT=trebuchet ms,geneva]Once the four nucleotides have been formed, they can join together to make an RNA molecule. If Dr. Sutherland's work is correct, it provides for the first time a plausible explanation of how an information-carrying biological molecule like RNA could have arisen on early Earth. Now that the origin of the information-bearing molecule can be explained, the natural origin of the information itself will be the next object of investigation by biochemists. Much work has already been conducted in this area, but scientists were always unsure of how the molecules that carried the information were constructed. Now that this is probably known, efforts to discover how biological information originated will be accelerated, and this will directly lead to a deeper explanation of both the origin of life and the origin of species.[/FONT][FONT=trebuchet ms,geneva]Charles Darwin would have been proud of [/FONT][FONT=trebuchet ms,geneva]John Sutherland.[/FONT]
