Ionizing Radiation: Friend or Foe of the Origins of Life?

Article (PDF Available)inOrigins of Life 42(5) · October 2012with32 Reads
Impact Factor: 1.11 · DOI: 10.1007/s11084-012-9314-1 · Source: PubMed

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CONFERENCE REPORT
Ionizing Radiation: Friend or Foe of the Origins of Life?
Z. P. Zagórski & E. M. Kornacka
Received: 22 August 2012 / Accepted: 28 August 2012 /
Published online: 19 October 2012
#
The Author(s) 2012. This article is published with open access at Springerlink.com
Keywords Origins of life
.
Ionizing radiation
.
Prebiotic reactions
.
Radiation induced
reactions
.
Evolution
Ionizing radiation is defined as electromagnetic or corpuscular radiation, of energy of quanta
resp. particles, which are able to detach an electron from any atom or molecule, as an object
of inte raction. The act of ionization creates rea ctive species like ion-radicals and free
radicals, which start sequences of chemical reactions even of high activation energies.
Similar effects can be started by another energetic interactions of existing energy, close to
ionizing radiation, e.g. by electrical discharges in gases like an atmosphere of a planet.
Lightning, not strictly speaki ng ionizing radiations but rather a source of high energy
chemistry was very early responsible for more concentrated deposition of energy than by
ionizing radiation, calculating the amount of energy per unit of volume. Therefore it was
easier to notice the connection to the beginnings of life, as Miller (1953) has done in his
classic experiment consisting in the demonstration of the formation of amino acids by
electric discharges in a gaseous mixture of hydrogen, carbon dioxide, ammonia and water.
His next paper (Miller 1955) presented the possibility of formation of more complicated
compounds, including polymers. One can conclude that all sources of energy able to start
formation of reactive species are potentially friendly to the origins of life, also, possibly in
other places of the Universe.
The Early Earth was from the beginnings penetrated by ionizing radiation, of intensity
much higher than now. The origins of radiations were very different, from sources present on
the Earth, like radiations of radioactive elements, to radiations coming from outer space like
cosmic radiation. Therefore all kinds of ionizing radiations were represented, of different
particles and quanta and of very different quality expressed by their LET value (linear
energy transfer) (Zagórski 2010a, b, c). The chemical action of ionizing radiation is more
diluted (calculating it to the unit of volume) in comparison to Millers experiment using
Orig Life Evol Biosph (2012) 42:503505
DOI 10.1007/s11084-012-9314-1
Z. P. Zagórski (*)
:
E. M. Kornacka
Centre for Radiation Research, Institute of Nuclear Chemistry and Technology,
PL-03-195 Warsaw, Poland
e-mail: z.zagorski@ichtj.waw.pl
Page 1
electric discharges in gaseous mixtures of compounds of carbon, hydrogen, oxygen, nitrogen
and sulphur and therefore was not more closely investigated. Future investigation cannot be
limited to the gas phase but should be extended to aqueous systems (including the Darwinian
small pond), containing radioactive potassium and multiphase systems, e.g. uranium ore
immersed in aqueous solutions of proper starting compounds. Anyway, sources of energy as
software can work creatively only in suitable locations, in analogy to hardware in
computer calculations (Zagórski 2010a).
One can expect similar products of ionizing radiation interaction as with electric dis-
charges and the same main trouble, i.e. production of racemic amino acids, without any
enantiomorphic excess. Chemical changes induced in the media by radiation are of prebiotic
character but could not alone be responsible for the decisive (as far we know) character for
the formation of life. For instance they could not contribute to the separation of racemic
mixtures into separate enantiomorphic species. In spite of no optical activity segregation,
one can call ionizing radiation and its cousins in the high energy chemistry family friends to
the origins of life chemistry. That field of research is not exhausted yet and many prebiotic or
probiotic reactions hopefully will be found with active involvement of ionizing radiation in
the formation of different organics.
Coming to the second face of ionizing radiation connections to life, are chemical effects
connected with modification of the molecules of life. They can be of destructive character
but sometimes play a supporting role by positive action in biological evolution. Omnipresent
ionizing radiation was acting on every sort of chemical compounds in the chain of origin of
life and evolution of the biosphere, from prebiotic compounds, sometimes created with the
participation of ionizing radiation to more or less developed organisms classified as living
creatures. The action of radiation can be a direct one on molecules absorbing it, or an indirect
one, by products of radiolysis of the medium on dispersed compounds in it and on
organisms. Even high LET value radiations of low penetration, like alphas from radon,
abundant on early Earth, were of enormous influence, because they were able to penetrate
everything exposed to the air, including the first living creatures inhaling the air (Zagórski
2010b). Whatever the detailed chemical effects, investigated and generalized by principles
of radiation chemistry, absorption of ionizing radiation means a supply of energy to the
system, participating in the so called chemical evolution (no direct analogy to the
Darwinian biological evolution). Chemical changes induced in the media by radiation were
of prebiotic character but could not alone be responsible for decisive (as far we know)
character for the formation of life. For instance, as mentioned before, they could not
contribute to the separation of racemic mixtures into separate enantiomorphic species.
Organics in meteorites, whatever the mechanisms of the formation from carbon, are
exposed to different ionizing radiations during travel in space and in effect, are modified. For
instance, the Cataldo group is devoted in a series of publications (Cataldo et al. 2011a, b, c)
to investigation of the radiolysis of amino acids, known from their presence in meteorites.
Radiation induced changes of organic compounds start from dehydrogenation (Zagórski
2006a, b)energetically the easiest way; later comes deamination and decarboxylation.
These phenomena exclude a possibility of transfer of life from far corners of the Universe,
the concept still alive as the panspermia hypothesis (Zagórski 2007).
Answering the question in the title of the summary, one can say that the ionizing radiation
could be a friend as being involved in creation of organics (e.g of methane from carbon
dioxide, Zagórski et al. unpublished), or polymerization of acetylene, probably present in
aqueous systems near volcanos).
As concerns radiation being a foe, one can consider the depolymerization action on
compounds already formed before. On the other hand, the chemical bonds disruptive action
504 Z.P. Zagórski, E.M. Kornacka
Page 2
on information transmitting compounds (RNA and later DNA) was contributing to muta-
tions, decisive elements in the Darwinian evolution of Life. In conclusion, the role of
ionizing radiation in origins of life and early evolution cannot be neglected and demands
further research in both categories of friend and foe.
Acknowledgments The membership in the Management Committee (20082012) of the European COST
action CM0703 (Systems Chemistry) is acknowledged. The project is supported by the grant from the Polish
Ministry of Science and Higher Education no. 365/N-COST/2008/0 (20082012).
Open Access This article is distributed under the terms of the Creative Commons Attribution License which
permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source
are credited.
References
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Cataldo F et al (2011c) A detailed analysis of the properties of radiolyzed proteinaceous amino acids. J
Radioanal Nucl Chem 287:903911
Miller SL (1953) A production of amino acids under possible primitive Earth conditions. Science 117:528
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Miller SL (1955) Production of some organic compounds under possible primitive Earth conditions. J Am
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Zagórski ZP (2006a) Abstraction of hydrogen from organic matters caused by ionizing radiation in outer
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Zagórski ZP (2006b) Radiation induced dehydrogenation of organics: from amino acids to synthetic polymers
to bacterial spores. Indian J Radiat Res 3:8993
Zagórski ZP (2007) Relation of panspermia hypothesis to astrobiology. Orig Life Evol Biosph 37:351355
Zagórski ZP (2010a) Role of radiation chemistry in the origin of life, early evolution and in transportation
through cosmic space. Chapter 5 in Astrobiology: Emergence, Search and Detection of Life (V.A.
Basiuk Ed.), American Scientific Publishers, pp 97154
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Ionizing Radiation 505
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