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Biological Chemistry

The Origin Of Life

by Rudy Baum, Editor-in-chief
June 26, 2006 | A version of this story appeared in Volume 84, Issue 26

Editor's Page

"One of the greatest challenges of the next century will be for chemists to make life. A system that is self—replicating, self-organizing, and even has the possibility of evolving into other things—I think this is possible."-Richard N. Zare, chemistry professor, Stanford University

Zare made that prediction in 1997 in an interview for an article that looked at the future of chemistry on the occasion of C&EN's 75th anniversary. Creating artificial life from a mixture of relatively simple lipids, nucleic acids, and amino acids that might have existed on a primitive, abiotic Earth has been a dream of chemists for at least the past several decades. The motivation is not so much to create life as to demonstrate the feasibility of life arising spontaneously from nonliving molecules.

The origin of life on Earth is one of the fundamental questions of science. We know that, once a living cell exists—one with the molecular machinery of replication in place—evolution will give rise to the spectacular diversity of forms life on Earth takes. What we don't know is how that primitive cell that gave rise to all of life-the last common ancestor—came into being.

Earlier this month, I attended a workshop in Stockholm on the origin of life sponsored by the Nobel Foundation and organized by Bengt Nordén, a biophysical chemistry professor at Chalmers University of Technology. The workshop brought together about 75 scientists, most of them chemists, who are probing various aspects of this complex problem.

"Life is incredibly complex, but all of biology is the same biology," Gerald F. Joyce, a chemistry professor at Scripps Research Institute, said during his talk at the opening session of the workshop. That biology has double-stranded DNA as the carrier of the genetic code being transcribed to produce RNA, which is translated into functional proteins. "The problem is, it is a complex biology that one wouldn't expect to have arisen from an abiotic world," Joyce said.

In 1968, Francis H. Crick suggested that the first enzyme might have been an RNA replicase made up of RNA rather than protein, Joyce noted. In 1986, Walter Gilbert coined the term "RNA world" to describe an early stage of life in which RNA was the primary biological molecule, carrying the primitive genetic code and catalyzing the reactions necessary for life. In the 1980s, Thomas R. Cech and Sidney Altman demonstrated that RNA could, in fact, function as an enzyme.

Much of the research discussed at the workshop takes off from this notion of an RNA world. Joyce and coworkers, for example, have developed methods for carrying out evolution in the test tube to produce molecules with novel functional properties. Starting with a mixture of primitive RNAs of varying composition, they show that molecules with enzymatic activity can evolve over time.

To take another example, Jack W. Szostak, a Howard Hughes Medical Institute investigator and professor at Harvard Medical School, and coworkers are working to create a "protocell" with the ability to grow, replicate genetic material, and divide. In his talk, Szostak rattled off the numerous challenges this effort faces: It must be a spontaneous process (no preexisting biochemical machinery); it must provide for membrane growth and vesicle division; the membrane must be permeable to ions and nucleotides; there must be a nucleic acid template with directed copying; there must be nucleic acid strand separation and complete replication cycles. Szostak's group has made real progress in its quest but still seems dauntingly far from its goal.

Yet another example is the work of Donna G. Blackmond, a chemical engineering professor at Imperial College, London, who has provided a kinetic model that explains how the homochirality exhibited by living molecules came to be.

Many other topics were discussed at the workshop. The environment of early Earth and how it might have given rise to the organic molecules that were the precursors of life. The possibility that organic molecules, including selectively chiral ones, were transported to Earth on comets and asteroids. The minimum number of genes required for an independent cell.

For some of the scientists at the workshop, probing the origin of life is their primary research interest. For many others, it is a fascinating secondary question that their unique chemical perspective can shed useful light on. In either case, the energy and intellect focused on the question in Stockholm was bracing.


Thanks for reading.


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