Monday, January 15, 2007

 

Closing a loophole in the RNA World Hypothesis

New scientific research may close a major loophole in the RNA world hypothesis, the idea that ribonucleic acid - not the fabled DNA that makes up genes in people and other animals - was the key to life's emergence on Earth 4.6 billion years ago.

That hypothesis states that RNA catalyzed all the biochemical reactions necessary to produce living organisms. Only later were those self-replicating RNA units joined by organisms based on DNA, which evolved into more advanced forms of life.

But how did ribonucleic acid appear? Scientists have shown that other organic compounds can form spontaneously under conditions believed to exist on the primordial Earth.

The University of Manchester's John D. Sutherland and colleagues point out, however, that no plausible prebiotic synthesis of ribonucleotides, the components of RNA, has been reported. His group offers the large part of such a potential synthesis in an article scheduled for the Jan. 17 issue of the Journal of the American Chemical Society, a weekly publication.

The researchers describe a process in which each of the two components for a ribonucleotide form in different locations on the primordial Earth. They combine when one evaporates and is delivered to the location of the second component in rainfall.

Source: American Chemical Society/PhysOrg

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Based on the paper:

Two-Step Potentially Prebiotic Synthesis of alpha-D-Cytidine-5'-phosphate from D-Glyceraldehyde-3-phosphate

Carole Anastasi, Michael A. Crowe, and John D. Sutherland*

Abstract

5'-Ribonucleotide precursors of RNA have previously been difficult to synthesize under prebiotically plausible conditions because of the inaccessibility of ribose-5-phosphate. Here we demonstrate a process in which ribose-5-phosphate is bypassed, and a cytidine 5'-ribonucleotide is efficiently assembled under mild conditions in two steps from glyceraldehyde-3-phosphate, 2-aminooxazole, cyanoacetylene, and water.

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*John D. Sutherland's research interests at Manchester University's School of Chemistry:

Our research in biological chemistry is concerned with two aspects of evolution. We have an ongoing research programme in prebiotic chemistry focussing on the evolution of nucleic acids and genetically-coded proteins. This work involves synthetic and analytical chemistry.

The second research area is concerned with exploiting evolutionary methods for the discovery of new chemical and biological catalysts. We are developing new methods for the creation and screening of chemical and biological diversity. Our targets are hybrid, green fermentation/chemical routes to important pharmaceutical intermediates and products. This work is highly interdisciplinary and involves, molecular biology, synthesis, automated screen development and microbiology. Students and postdocs from both research areas acquire diverse skills in synthetic and biological chemistry.

Recent destinations for past members of the group include Cambridge University (4), Glaxo-Wellcome (2), Cambridge Antibody Technology, Maxygen, Phylos, Harvard Medical School, Sense Therapeutic, Loughborough University, St. Judes Childrens Hospital, Biotica, Oxford University, BP-Amoco and The Scripps Research Institute.

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See The RNA World by Sidney Altman (1989 Nobel Laureate in Chemistry):

The phrase "The RNA World" was coined by Walter Gilbert in 1986** in a commentary on the then recent observations of the catalytic properties of various RNAs. The RNA World referred to an hypothetical stage in the origin of life on Earth. During this stage, proteins were not yet engaged in biochemical reactions and RNA carried out both the information storage task of genetic information and the full range of catalytic roles necessary in a very primitive self-replicating system. Gilbert pointed out that neither DNA nor protein were required in such a primitive system if RNA could perform as a catalyst...

**"Origin of life: The RNA world"

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Also see "Exiting an RNA world" (full text):

"The RNA world hypothesis gains support from the in vitro evolution of a bifunctional ribozyme that can recognize an activated glutaminyl ester and subsequently aminoacylate a tRNA molecule."

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Comments:
Article sayd:...But how did ribonucleic acid appear? Scientists have shown that other organic compounds can form spontaneously under conditions believed to exist on the primordial Earth.

The University of Manchester's John D. Sutherland and colleagues point out, however, that no plausible prebiotic synthesis of ribonucleotides, the components of RNA, has been reported. His group offers the large part of such a potential synthesis in an article scheduled for the Jan. 17 issue of the Journal of the American Chemical Society, a weekly publication.

Jim says:
Since bio scientists now know all the components of the cell, lets have them assemble all the right component parts and 'manufacture' a living cell for all the world to see, doing this in their Laboratory. This would stop the arguments against evolution in an instant. It should be very simple for Intelligent humans to do it, since the common belief is that the first life form spontaneously came into being by the process of chance. In other words an accident of nature created the first living cell. Surely present day Intelligent bio-scientists can replicate the accidental creation of a cell.

All they need to do is get a cell wall and insert all the components they have manufactured. Of course we know that no human or even an army of Scientists can assemble the 'simple' cell. LONG before they might have stuffed the components into the cell wall, it will be way too late for the cell to be viable.

Come on now scientists make us a living cell from scratch. You have the knowledge, do it!

Jim
 
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