Prof. Paul C. W. Davies Profile

Prof. Paul C. W. Davies

Regents Professor (FSC) at Arizona State Univ

SPIE Involvement:

Editor | Author

Proceedings Article | 9 October 2007 Open Access

Searching for an alternative form of life on Earth

P. C. W. Davies

Proceedings Volume 6694, 66940K (2007) https://doi.org/10.1117/12.742355

KEYWORDS: Organisms, Microorganisms, Planets, Biochemistry, Mars, Molecules, Arsenic, Bacteria, Carbon, Mirrors

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Proceedings Article | 14 September 2006 Open Access

Chirality, quantum mechanics, and biological determinism

P. Davies

Proceedings Volume 6309, 630908 (2006) https://doi.org/10.1117/12.690619

KEYWORDS: Quantum mechanics, Physics, Biology, Organisms, Microorganisms, Molecules, Proteins, Quantum information, Genetics, Astrobiology

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The holy grail of astrobiology is the discovery of a second sample of life that has emerged de novo, independently of life on Earth (as opposed to extraterrestrial life that shares a common origin with terrestrial life via a panspermia process). It would then be possible to separate aspects of biology that are lawlike and expected from those that are accidental and contingent, and thus to address the question of whether the laws of nature are intrinsically bio-friendly. The popular assumption that life is an almost inevitable product of physics and chemistry, and therefore widespread in the universe, is known as biological determinism. It remains an open question whether biological determinism is correct, as there is little direct evidence in its favour from fundamental physics. Homochirality is a deep property of known life, and provides an important test case for the competing ideas of contingency versus lawfulness - or chance versus necessity. Conceivably, a chiral signature is imprinted on life by fundamental physics via parity-violating mixing of the weak and electromagnetic interactions. If so, homochirality would be universal and lawlike. On the other hand, it may be the result of chance: a random molecular accident during the pre-biotic phase. If the latter explanation is correct, one could expect that a second sample of life may have opposite chiral signature even if it resembled known life in its basic biochemistry. There is thus a curious obverse relationship between chirality and biogenesis in relation to biological determinism. If the chiral signature of life is the product of chance, we may hope to discover "mirror life" (i.e. organisms with opposite chiral signature) as evidence of a second genesis, and the latter would establish that life's emergence from non-life is quasi-deterministic. On the other hand, if the chiral signature is determined by fundamental physics, then it may be much harder to establish an independent origin for extraterrestrial life with biochemical make-up resembling that of known life. Whilst the experimental search for a second sample of life - possibly by detecting a chiral "anomaly" - continues, some theoretical investigations may be pursued to narrow down the options. Chiral determinism would be an intrinsically quantum process. There are hints that quantum mechanics plays a key role in biology, but the claim remains contentious. Here I review some of the evidence for quantum aspects of biology. I also summarize some proposals for testing biological determinism by seeking evidence for a multiple genesis events on Earth, and for identifying extant "alien microbes" - micro-organisms descended from an independent origin from familiar life.

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Proceedings Article | 14 September 2006 Paper

Bacterial utilization of L-sugars and D-amino acids

Elena Pikuta, Richard Hoover, Brig Klyce, Paul Davies, Pauline Davies

Proceedings Volume 6309, 63090A (2006) https://doi.org/10.1117/12.690434

KEYWORDS: Molecules, Microorganisms, Proteins, Bacteria, Organisms, Comets, Tissues, Carbon, Crystals, Polymers

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The fact that organotrophic organisms on Earth use L-amino acids and D-sugars as an energy source is recognized as one of the universal features of life. The chirality of organic molecules with asymmetric location of group-radicals was described a relatively long time ago. Louis Pasteur observed that abiotic (chemical) processes produced mixtures with equal numbers (racemic) of the two forms but that living organisms possessed a molecular asymmetry that included only one of the enantiomers (homochirality). He speculated that the origin of the asymmetry of chiral biomolecules might hold the key to the nature of life. All of the amino acids in proteins (except for Glycine which is symmetrical) exhibit the same absolute steric configuration as L-glyceraldehyde. D-amino acids are never found in proteins, although they do exist in nature and are often found in polypeptide antibiotics. Constitutional sugars of cells, opposite to the amino acids, are the D-enantiomers, and the appearance of L-sugars in Nature is extremely rare. Notwithstanding this fact, the metabolism of some bacteria does have the capability to use amino acids and sugars with alternative chirality. This property may be caused by the function of specific enzymes belonging to the class of isomerases (racemases, epimerases, isomerases, tautomerases). In our laboratory, we have investigated several anaerobic bacterial strains, and have found that some of these bacteria are capable of using D-amino acids and L-sugars. Strain BK1 is capable of growth on D-arginine, but its growth characteristics on L-arginine are approximately twice as high. Another alkaliphilic strain SCA^T (= ATCC BAA-1084^T = JCM 12857^T = DSM 17722^T = CIP 107910^T) was found to be capable of growth on L-ribose and L-arabinose. It is interesting that this strain was incapable of growth on D-arabinose, which suggests the involvement of some alternative mechanism of enzyme activity. In this paper, we describe the preliminary results of these microbiological studies and discuss some possible implications.

Proceedings Article | 22 September 2005 Open Access

The search for life in the universe

P. Davies

Proceedings Volume 5906, 59060I (2005) https://doi.org/10.1117/12.624239

KEYWORDS: Planets, Physics, Microorganisms, Mars, Organisms, Stars, Genetics, Molecules, Chemistry, Carbon

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Proceedings Article | 25 May 2004 Paper

Quantum fluctuations and life

Paul Davies

Proceedings Volume 5472, (2004) https://doi.org/10.1117/12.561309

KEYWORDS: Quantum mechanics, Molecules, Quantum information, Quantum computing, Proteins, Data processing, Molecular biology, Quantum information processing, Superposition, Quantum efficiency

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Proceedings Article | 25 May 2004 Open Access

Quantum clocks and the foundations of relativity

Paul Davies

Proceedings Volume 5472, (2004) https://doi.org/10.1117/12.547361

KEYWORDS: Particles, Quantum mechanics, Quantum clocks, Clocks, Theory of relativity, Relativity, Quantum physics, Time metrology, Physics, Superposition

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