Radiation Mechanism of Biosphere Homochirality Origin
Experimental Testing of Radiation Mechanism of Chiral Biosphere Dissymmetry Origin
Tech Area / Field
3 Approved without Funding
VNIITF, Russia, Chelyabinsk reg., Snezhinsk
- Moscow Institute of Physics and Technology, Russia, Moscow reg., Dolgoprudny\nNPO Mayak, Russia, Chelyabinsk reg., Oziorsk\nFIAN Lebedev, Russia, Moscow
- University of Houston, USA, TX, Houston\nInstitute for Advanced Studies, Japan, Tokyo\nYokohama National University, Japan, Yokohama
Project summaryThe biological homochirality phenomenon was discovered about 150 years ago by L. Pasteur who observed that there is a fundamental difference between organic and inorganic in Nature associated with "mirror dissymmetry" of organisms. There is an equal amount of "left" and "right" chiral molecules in inorganic nature, whereas living organisms use only one of the mirror isomers such molecules as amino acids and sugars and do not use another (nucleinic acids contain only D (right) sugar isomers: ferments contain only L (left) isomers of amino acids). Homochirality or "chiral purity" (CP), along with genetic code, which is universal for all living on the Earth organisms, is a distinctive and key property of living. It is impossible to find a solution to the fundamental problem of life origin without solving the problem of the CP origin. Furthermore, CP of biopolymers is a necessary condition for their normal functioning. Therefore, the problem of the CP origin is one of the key problems for understanding processes, which lead to creation of self-reproducing biological systems. It is also speculated that CP may be related to such extremely important problems of mankind as the organism aging problem and oncology illness initiation.
Despite a number of CP-origin hypothesis, the issue remains open. There are two main approaches to its solution: biogenic or abiogenic. In the biogenic scenario, it is assumed that one type of isomers was selected in the course of vital activity and struggle for existence of primary organisms. However, such approach faces a number of fundamental problems.
Two lines of investigations are under development in the context of abiogenic approach. One of them assumes that spontaneous mirror symmetry violation is possible owing to racemic-state instability under nonequilibrium conditions. In this case, the chirality choice is a random one and depends on fluctuation character. In the other variant, it is assumed that there was an influence of some asymmetrical physical factor, which provided an advantage for one of the isomer type. A mixed variant seems to be the most appealing. It accounts for both possible spontaneous violation and influence of an asymmetrical factor, which determined the chirality choice. In this case, (fast) fluctuations are averaged, and small (but constantly acting) factor turned out to be essential. It is expected that autocatalysis may increase the asymmetric-factor effect. The "radiation" mechanism due to interaction of molecules with spiral particles seems to be the most effective. Such particles (i.e., b-particles emitted by radioactive nuclei) are polarized: their spins are parallel (b+-decay) or antiparallel (b--decay) to the direction of their motion. The polarization degree is proportional to the ratio of particle velocity to the velocity of light v/c. Achiral reactants irradiated by such particles are subjected to the chiral influence which may cause preferable dissociation or production of molecules with definite chirality. Leptons can be spiral (helical) particles: neutrinos, electrons (positrons) and muons produced in weak decays of elementary particles and nuclei. Decays of radioactive nuclei 14C, 40K, 235U, 26Al, which are abundant in the Earth' crust, ocean and biosphere, can be a source of helical electrons. By now a number of studies were carried out to investigate the effectiveness of helical electrons for inducing asymmetric synthesis or radiolysis of racemic mixtures. However, up to now, there is no clear answer to these questions.
Besides a "warm" (on the Earth or other planets) scenario of life origin, "cold" (cosmic) scenarios are also under consideration, where the main stages of life origination, including formation of self-reproducing structures, are transferred in open space, more precisely, to gas-dust clouds. These scenarios are based on modem ideas of deep-cold chemistry (V. I. Goldanskii was the first who pointed out the possibility of "cold life prehistory" on the basis of nonzero rate of chemical reactions al low temperatures discovered by him), as well as on recent geological and astrophysical discoveries. In cosmic scenarios, it is assumed that organic compounds produced in a gas-dust cloud can be transported to a planet during its accretion and as a result of adsorption on its surface. The possibility of the organic matter mirror symmetry violation is a key condition in these scenarios.
The main conjectured space factors of chiral influence, in one way or another, are connected with supernova explosions. In the paper by T. Saito and V. Tsarev (to he published), some efficient mechanisms of chiral influence were pointed out. They are associated with fluxes of helical electrons from decays of neutrons (which are ejected at the supernova explosions), as well as with direct interactions of neutrinos ejected by supernovas. Nuclear matter inside a supernova is heavily enriched by neutrons. Subsequent to a supernova explosion, its core can become a neutron star or a black hole, or it could be completely disrupted. Simultaneously, the supernova outer layers (including radioactive nuclei and about 1055 neutrons) with a mass of about 10 solar masses are ejected by the explosion into surrounding space. Decays of these neutrons (as well as unstable nuclei) produce left-polarized electrons with energy of about 0.4 MeV, which are the main source of chiral influence.
The purpose of the project is an experimental check of the radiation mechanism of the chiral influence, which may be a fundamental mechanism providing the chiral dissymmetry both for terrestrial and cosmic scenarios of life origin. For this aim, irradiation of various targets containing both (1) liquid racemic mixtures of chiral organic materials, and (2) achiral gas mixtures, which simulate the primitive Earth's atmosphere content.
In the first case, the efficiency of the chiral dissymmetry production in radiolysis under the action of helical particles (electrons) will be verified.
In the second case, the problem is more complex and interesting. First of all, the results of previous study [K. Kobayash el al.. Adv. Space Res. 15, 127 (1995); 16, 21 (1995)] of the ammo acid synthesis under irradiation of gas mixtures by elementary particle fluxes (from accelerators) will be verified, A radically new step in comparison with the indicated previous study will consist in using (natural) chiral agent, i.e., polarized electrons, and studying not only synthesis of the simplest organic material, but also its (possible) chiral dissymmetry. The new aspect in comparison with other studies will consist in direct analysis of products of asymmetrical radiolysis and synthesis.
Competence of the project participants casts no doubts and is confirmed by numerous evidences. In particular, RFNC-VNIITF has a great experience in conducting radiation studies of various materials (license GAN RF #UO-03-206-0600, August 5, 2001) and producing radiation devices (patents RU 2032236C1, RU 2059418C1, RU 2093911C1).
The participation of leading scientists from Cosmic Ray Department of the Lebedev Institute of Physics in the project is assumed, which have high authority among Russian and foreign scientists.
They have an experience in conducting exobiological studies, in particular within the INTAS project #97-1247.
The MFTI is a respected and prestigious institute of the Russian Federation, The participants from this Institute has reach experience in using the circular dichroism technique for analysis of the optical activity of coordinational compounds with organic and inorganic ligands. PO «Mayak» is the major Russian designer and manufacturer of various radioisotope sources.
The potential collaborators are the groups from the Institute of Advanced Studies (Tokyo, Japan) and Yokohama University (Yokohama, Japan). They are the leading Japanese specialists in the exobiology.
The investigation under consideration is of the "basic research" category. The main results of the accomplishment of the proposed work will be experimental verification of the possibility of the chiral dissymmetry production in radiolysis and synthesis of organic compounds under the action of electrons from a radioactive source 90Sr + 90Y.
We shall measure both the yield of amino acid synthesis products and degree of chiral dissymmetry in radiolysis and synthesis. The observation of the indicated effects will be of great importance for solving such fundamental problems as life origin and searching for extraterrestrial life, as well as, possibly, for practical studies related to the problems of the organism aging and cancer origination.
As part of the project, one of the main aims of the ISTC will he realized: efforts of weapon specialists will be reoriented to a peaceful activity related to obtaining more complete knowledge of fundamental aspects оf life origin: the experimental verification of the hypothesis on a key role оf helical particle influence (here, electrons) in origination of chiral dissymmetry of bioorganic world.
The realization of the project is possible in the event when three following basic tasks are performed:
Task 1. The following preliminary procedures are performed:
- Elaboration of the experimental methodology, determination of the necessary irradiation level;
- Preparation of gaseous and liquid targets, whose construction ensures required mechanical robustness and tightness and provides "transparency" of the vessels to the electron irradiation;
- Elaboration, manufacturing and certification of the electron sources on the basis of 90Sr + 90Y;
- Preparation of measuring equipment;
- Elaboration and manufacturing of a test bed and radiation chamber.
Task 2. The irradiation performance of the gas and liquid targets.
Task 3. The optical activity investigation of the irradiated targets to find the chiral dissymmetry level and chemical analysis to find the radiolysis and synthesis products. The order оf accomplishing the indicated problems is determined by the project aim and the logic of the experiment.
The work on the project will be done in a constant contact with the project collaborators, i.e., the Institute of Advanced Studies (Tokyo, Japan) and Yokohama University (Yokohama, Japan).
In accord with the activity scope, the role of the foreign collaborators will consist in scientific and technical collaboration, in particular in the preparation of the gas and liquid targets for the irradiation, and in parallel investigations in the field of chemical analysis of the synthesis products.
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