Leslie Orgel
Leslie Eleazer Orgel | |
---|---|
Origin of life Orgel's rules | |
Awards | Fellow of the Royal Society |
Scientific career | |
Fields | Chemistry |
Institutions | University of Oxford University of Cambridge |
Leslie Eleazer Orgel
Biography
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Leslie Orgel was born in
Orgel started his career as a theoretical inorganic chemist and continued his studies in this field at Oxford, the California Institute of Technology, and the University of Chicago.
Together with
In 1955 he joined the chemistry department at Cambridge University. There he did work in transition metal chemistry and ligand field theory, published several peer-reviewed journal articles, and wrote a textbook entitled Transition Metal Chemistry: Ligand Field Theory (1960). He developed the Orgel diagram showing the energies of electronic terms in transition metal complexes.
Orgel formulated his
In 1964, Orgel was appointed senior fellow and research professor at the
Orgel's lab came across an economical way to make
Together with
His name is popularly known because of
In his book The Origins of Life, Orgel coined the concept of specified complexity, to describe the criterion by which living organisms are distinguished from non-living matter. He published over three hundred articles in his research areas.
In 1993, Orgel presented at the "What is Life?" Conference at
Orgel died of pancreatic cancer on 27 October 2007 at the San Diego Hospice & Palliative Care in
Research on the origin of life
Nucleobase synthesis
Orgel proposed a novel solution to a problem with Juan Oro's proposed mechanism of nucleobase synthesis on the early Earth, which relied on the reaction of five molecules of hydrogen cyanide (HCN) to form adenine. The problem with this was that it would require much more concentrated hydrogen cyanide than evidence suggested was present.
Orgel suggested that the hydrogen cyanide was frozen in solution.[8] This would concentrate HCN molecules in the spaces in between the crystal lattice of ice, and also solve the problem of HCN being too volatile in a liquid water solution.
Nucleoside formation
For nucleoside (nucleobase + ribose sugar) synthesis, Orgel suggested an almost opposite approach, heating a mixture of ribose and the purine nucleobases hypoxanthine, adenine, and guanine to dryness in the presence of magnesium ions.[9] This reaction puts the glycosidic bond in the correct position in two ways: the nucleobase attaches to the correct carbon on ribose, and in the correct orientation (the beta anomer).
However, the synthesis was later criticised because it only worked most with hypoxanthine, a nucleobase that is not relevant to current life on Earth, and because it was not specific for the ribose sugar and could instead be applied to other sugars.
RNA polymerization
Continuing his work studying the prebiotic synthesis of RNA, Orgel explored mechanisms by which inorganic phosphate[10] and nucleotide phosphoryl groups[11] could be chemically activated for condensation into nucleic acid polymers. Starting in the 1960s, Orgel explored a variety of cyanide-based activating agents which could have plausibly been present on a young earth. A carbodiimide reagent was found to be effective at activating nucleotide phosphoryl groups and promoting the formation of short Adenosine dimers and trimers.[12] In 2018, John D. Sutherland and co-workers proposed that methyl isocyanide and acetaldehyde could combine to form a pre-biotic phosphate activating agent which could plausibly have formed under early-earth conditions.[13]
Orgel also theorised that one single strand of RNA could have been the
The oligonucleotide products in early studies were typically characterized through a combination of 14C
Directed panspermia
Though he later downplayed the hypothesis, Orgel, along with Francis Crick, proposed a detailed panspermia scenario for the origin of life on Earth, going so far as to suggest that life on Earth was designed by an alien species and sent to Earth.[16] They proposed a design for the spaceship that aliens could have used to seed life on Earth.
RNA world
In the late 1960s, Orgel proposed that life was based on RNA before it was based on DNA or proteins. His theory included genes based on RNA and RNA enzymes.[17] This view would be developed and shaped into the now widely accepted RNA world hypothesis.
Almost thirty years later, Orgel wrote a lengthy review of the RNA World hypothesis.[18] This review highlighted many proposed syntheses for RNA and its parts in abiotic conditions, noted the significance of the discovery of ribozymes (RNA molecules that function as enzymes just as Orgel had once predicted) and at the same time, demonstrated nucleic acid polymers with alternatives to ribose such as threose nucleic acid (TNA) and peptide nucleic acid (PNA).
In conclusion, Orgel wrote, "One must recognize that, despite considerable progress, the problem of the origin of the RNA World is far from being solved."[18]
Awards
- Elected to the National Academy of Sciencesin 1990.
- Elected as a Royal Society of Londonin 1962.
- American Academy of Arts and Sciences
Books
- Leslie E. Orgel, An Introduction to Transition-Metal Chemistry. The Ligand Field Theory, 1961
- Leslie E. Orgel, The Origins of Life: Molecules and Natural Selection, 1973
- Leslie E. Orgel and Stanley L. Miller, The Origins of Life on the Earth, 1974
References
- ISSN 0080-4606.
- ISBN 978-0-879694-78-4.
- ISBN 978-0-87969-798-3
- PMID 13940312.
- ISBN 978-0-19-506133-8.
- ^ Dunitz, Jack D.; Joyce, Gerald F. (2013). "Leslie E. Orgel" (PDF). Biographical Memoirs of the National Academy of Sciences: 11.
- ^ Rice, Fredric L. "WHAT IS LIFE? The next fifty years Trinity College, Dublin, Ireland September 20th – 22nd". icr.provocation.net. Retrieved 18 November 2016.
- S2CID 31527498.
- PMID 4339529.
- S2CID 13005451.
- ^ S2CID 35649008.
- ^ PMID 5238657.
- PMID 29965757.
- ^ PMID 6247762.
- S2CID 4351826.
- .
- S2CID 5439488.
- ^ S2CID 4939632.
External links
- Register of the Leslie Orgel Papers at UCSD
- The Implausibility of Metabolic Cycles on the Prebiotic Earth
- Leslie Orgel's obituary on the Salk Institute website
- LA Times: "Leslie Orgel, 80; chemist was father of the RNA world theory of the origin of life", 31 October 2007
- "Leslie Orgel dies", The Scientist, 1 November 2007