IC/92/331

INTERNAL REPORT

(Limited Distribution)

International Atomic Energy Agency

and

United Nations Educational Scientific and Cultural Organization

INTERNATIONAL CENTRE FOR THEORETICAL PHYSICS

CONFERENCE ON CHEMICAL EVOLUTION

AND THE ORIGIN OF LIFE

SUMMARIES

Trieste 26-30 October 1992

CONFERENCE ON CHEMICAL EVOLUTIONAND THE ORIGIN OF LIFE

Modern scientific thinking leads to the conclusion that the emergence of life is a necessaryconsequence of the evolutionary process in the universe. In this interdisciplinary conference, thefirst of its kind to be held at the International Centre for Theoretical Physics (ICTP), we will explorethe many aspects of cosmic evolution from the chemical history of the universe, the processes ofprebiological chemistry, self-organization, the earliest evidence of life, the origin of chirality to thesearch for extraterrestrial intelligence.

In this Internal Report we have gathered together the summaries of papers to be read atthe conference which were available at the time of going to press. The meeting was possible thanksto the generous support of the European Commission, ICTP, the International Centre for Scienceand UNESCO.

Cyril Ponnamperuma, Director

Julian Chela-Flores, Local Organizer

19 October 1992

Table of Contents

L.D. Barron

Luis J. Boya and Patricia Boya

Julian Chela-Rores

Ivan G. Draganic and Sofija I. Vujosevic

A. Figureau, E. Duval and A. Boukenter

A.S. Garay

G. Gilat

Bettina Heinz

Kaiser Jamil

L. Keszthelyi

R. Mohan

R. Navarro Gonzalez, Raj K. Khanna andC. Ponnamperuma

A. Negr6n-Mendoza and G. Albarran

VJ.A. Novik

C. Ponnamperuma

C. Ponnamperuma

C. Ponnamperuma

Abdus Salam

Wang Wenqing, Wu Jilan and Jian Jiang

True and false chirality

Viroids and the origin of life

Spontaneous regulating mechanismsthat may have led to the origin of life

Ionizing radiation and water in chemicalprocessing in the space and on the earlyearth

Search for phase transitions changingmolecular chirality

Experimental studies on the possibility ofchirality dependent time reversal

Chiral interaction and biomolecularevolution

Chromoproteinoids and their ability toform structures

The need to study the origin of life

Experiments in search of the origin ofbiomolecular asymmetry

Chiral forces and molecular dissymmetry

Could comets be carriers of intacthomochiral biomolecules from interstellarspace?

Chemical effects of ionizing radiation andsonic energy in the context of chemicalevolution

The role of neoteny and sociogenesis inthe evolution of cell structures

Lecture I - General overview

Lecture II - Prebiotic chemistry

Lecture in - Physicochemical basis for theorigin of the genetic code

The origin of chirality, the role of phasetransitions and their induction in aminoacids

Differences in radiolysis behaviour of D,Lamino acid in primary stage and thermo-dynamic equilibrium state

True and False Chirality

L. D. Barron

Chemistry Department, The University, Glasgow O12 8QQ, U.K.

The concept uf chirality is extended to cover systems that exhibitdistinguishable ejiantiomers under space inversion (or mirror reflection) onaccount of motion. This is achieved by applying the fundamental symmetryoperation of time reversal In addition to space inversion, and leads to a moreprecise definition of a chiral system than that usually employed. It followsthat, although spatial enantiomorphism Is sufficient to guarantee chirality Ina stationary system such as a finite helix or an asymmetric molecule,enantiomorphous systems are not necessarily chiral when motion is involvedwhich leads to the concept of true and false chiralitj' associated withtime-in variant and time non-invariant enantiomorphism, respectively. Parityviolation is shown to provide a cornerstone for the identification of truechirality. Examples of true chirality include a translating spinning particle,and a static magnetic field coJlincar with the propagation direction of anutipolarized light beam; while examples of false chirality Include a stationaryspinning cone, and collinear electric and magnetic fields. The concept of falsechirality, albeit in two dimensions, is also shown to arise In the anyon modelof high-temperature superconductivity.

It Is demonstrated that, although only a truly chiral influence such ascircularly polarized light or the weak neutral current, can induce ancnantlomeric excess in a reaction that has reached true thermodynamicequilibrium, false chirality can suffice in a reaction under kinetic control dueto a breakdown of conventional microscopic reversibility which must bereplaced by a new principle of enantiomeric microscopic reversibility. Theanalysis of the kinetic and thermodynamic aspects of the latter situationparallels that for the consequences of CP violation in particle-antiparticleprocesses Involving the neutral K-rneson,

Consideration of falsely chiral Influences greatly enlarges the range ofpossibilities for development of an enantiomeric excess in pre-biologicalchemical systems if the appropriate processes were far from equilibrium.

Viroids and the Origin of Life

Luis J. Boya and Patricia Boya

Universidad de Zaragoza, E-50009 Zaragoza, Spain

ABSTRACT

We shall argue for the necessity of an intermediate organized step in the biological worldat the origin, linking the longest random chains of about 100 nucleotides of RNA (Eigen)to the next level, this being perhaps RNA-plaut-viruses-like, but eventually DNAgenomes. We concur with the viroid hypothesis of Diener, as elaborated by Moya andothers. The main theoretical reasons arc (i) the length, 500-600 nn, (ii) "selfishcharacter," carrying no instructional information, (iii) restrictions to plants, (iv)concordance with the general "RNA world" idea (Gilbert), and (v) genetic linkage amongthem (Moya).

SPONTANEOUS REGULATING MECHANISMS THAT MAY HAVE LED TOTHE ORIGIN OF LIFE

Julian Chela-FloresInternational Centre for Theoretical Physics,Miramare P.O. Box 586; 34100 Trieste, Italy

andInstituto Internacional de Estudios Avanzados,

Apartado 17606 Parque Central, Caracas 10ISA,Venezuela.

ABSTRACT

According to Salam condensation may be relevant inbiochemistry, as a factor contributing to thehomochirality of amino acids. We attempt to show that DNApackaging may be modelled, by interpreting chromatin as aform of soft matter, in which a phase transition hasinduced chromatin into a condensed mode. In the contextof the origin of life we show the relevance ofsimultaneous discussion of DNA packaging, transcription,and DNA replication. Beyond a certain critical length ofthe protogenome (RNA), physical properties of inertcondensed matter may have given rise to a spontaneousregulating mechanism of certain significance for theevolution of life on Earth.

I01T1ZISG RADIATIOW AKD VATEB 15 CHEMICAL PROCBSSIIGIJff THE SPACE AJTD OS THE EARLY EAfiTH

Ivan G. Draganic and Sofijo I. VujewSevic

The Institute of Hurt"! ear- fJctonnes "Vinca."Belgrade, Yugoslavia

We review tae sources of ionizing radiation in Space and anearly Earth: cottmle rays, radioactive elements and naturalnuclaar reactors. Also the energies they d«posit (abctorb«ddoms) In water and water containing materials.

Sana general facts cm th« action of ionizlog radiation on waterand aqueous «jstens ( ice, liquid, vapor), are given. P««ultea£ «inulatlon «xperia»ents x-elev&nt to radiation processing*;of prveolar •at<=»i-i«l And Acmatary rnwlftl »r*t atnrveyed. Ther«eult€ of coftputar oiatulatiana of radiation-induced processesin wat«rc of early Earth are presented.

Ve consider th.e radiolyees of sane aqueous systenc of int«to the studies of ch«sical evolution. and their dependence antemperature, type, nnd energy of radiation.

Sane facts obtained by direct obtwrvatlrtn» of cosetar-y nuclei,and socw findings in geoche«l*try of early Haj-th, are examinedIn the light of results* an radiation cHe»istry relevant tocomets and priaitive oceans.

Future work is considered: evaluation of absorbed doae« due tocwBmlc-rav*. especially charged, particles at relativistic enar—g±9^i critical choice of a Model systea and working conditionsfor sluulatlon «xperinents; co«put#r slmulatloa of chanlcalprocesses. in particular the nonhenbOgf nescruSJ klnetl«« in icymatrix.

SEARCH FOR PHASE TRANSITIONS

CHANGING MOLECULAR CHIRAL1TY

A, Figureau", E. Duval" and A.. Boukenter"*

UniversiU Claude Bernard F-G9622 Villeurbannc Cedcx, Ranee

* Inetitut de Physique Nucleate de Lyou 1N2P3-CNRS** Laboratoirc dc Physicochiniie des Mnlcriaux Luminescents VKA 442 CNllS

Since Pasteur discovered in 1848 that biological molecules possess a rotatory power, tlicorigin of the chived purity in living organisme hoc been a constant preoccupation in biology,but the problem is not solved ycl (1). In particular, the appeal to weak interactions, afundamental physical process which is known to violate parity (2), lias not permitted so farto establish any firm relation between parity nonconservation and the complete dissymmetrybetween mirror image biological molecules. The main difficulty resides in the weakness of thephysical forces, and can be overcome only wJien tome amplification process can be proved tobe at work.

Recently such a mechanism was proposed (5), which does not seem to ask for any adhocnew concept : due to the attractive character of the parity violating force in electro-weakinteractions, a phase transition leading eventually to cnantiomotric purity is predicted. Phasetransitions at low temperatures have already been detected in biological materials (4), butno signature concerning the parity aspect was obtained.

We undertook this year in Lyon a scries of experiments to measure the rotatory powerof solutions containing organic dissymmetric molecules, in order to observe if it varies withtemperature. Our first measures involved cystine, which possesses a high rotatory power, Novariation of this quantity was observed down to ,6K. Lower temperatures will be attained ina next step.

(1) W,A. BONNER - Origins of Life, 21 (1991) 59

(2) T.D. LEE and C.N. YANG - Phys. Rev., 104 (1956) 254

(3) A. SALAM - J. Mol. Evol., S3 (1091) 105

(4) U. MIZUTANI, T.B., MASSALSKl, J.E. MCGINNES and P.M. CORRY -Nature 250 (1976) 505

EXPERIMENTAL STUDIES ON THE POSSIBILITY

OF CHIRALITY DEPENDENT TIME REVERSAL

A.S. Garay

Texas A&M University, College of Agriculture and Life Sciences,Department of Biochemistry and Biophysics,College Station, Texas 77843-2128, USA.

Biological evolution has a time direction which is seemingly opposite to the time

direction dictated by the second law of the thermodynamics. I share the scepticism

regarding the assumption of contemporary biology that the combination of open systems

with the chance mutation and selection of the fitest, can satisfactorily explain the origin

and the evolution of life. In the theoretical part of this presentation I will analyse the

modern concepts of time. e.g. the widely used expressions in physics: "time inversion",

"time reversal" etc, in connection with the origin and evolution of life. In the

experimental part I will present evidence that the beta decay of 32P and 22Na is different

in enantiomerie pairs. Since the decay constant is believed to be independent from the

chemical environment, in fact it enables age determination, living beings may represent

a time reversed "pocket" of matter in space. Some pitfalls of this idea will be discussed

in the final part.

CHIRAL INTERACTION AND BlOMOLECULAR EVOLUTION

G. GilatDepartment of Physics, Technion - Israel Institute of Technology,

Haifa 32000, Israel

ABSTRACT

Recent developments in the concept of chiral interaction open now newoptions and dynamical possibilities for biomolecules which have so far beenoverlooked. A few of these possibilities are mentioned, such as the control me-chanism of enzymatic activity and the role played by non-ergodicity in evolu-tionary processes. It is shown that chiral interaction, being a surface phenome-non, does not obey Barren's symmetry constraints, which are suitable for forcefields present in bulk interactions. In particular, the situation at the ocean-airsurface in the prebiotic era is described, as well as the possible role played bychiral interaction in conjunction with the terrestrial magnetic field normal tothe ocean surface, which could have lead to a process of dcraeenuizalion at theocean-air interface.

10

.SHROHOPHOTEINOIDS AMD THEIR ABILITY TO FOMI BOUNDARY

STRUCTURES

Bettina HeinzDepartment of ChenistryPalomar College, San Marcos, California, USA

Model systems for boundary structures and cellular systems,particularily when they are a result of natural simulationtxpvrinents, are always valuable tor the study of th« 'Origensof Life". Lyophilization ot chromoproteinoids - peptide likemolecules containing prosthetic groups - leads to the forma-tion of boundary structures.

The chromoproteinoide were produced by thermolysis of dry,racemio amino «oid mixtures, usually containing lysine as abasio amlno acid and two neutral amino acids. The fluores-cent pigments such as pteridines and flavins were formedvia cyellzation of lysine with different breakdown products ofthe amino acids. Freeze-drying of the golden colored,fiuores-oent oils, led to th» formation of ha*agonically ah aped ca-vities in the dried thermolysates - this being a consequenceof sublimating Ice orystals. Micrographs of this material inthin sections revealed a cellular matrix with similaritiesto epidermal cells. UV-activation showed that the boundariesDP 'cell walls' contained most of the fluorescent material.Since native peptides and proteins do not show thia phenomenonwhen subjected to lyophilization procedures, it seems essen-tial that the material contains a high concentration offluoreseent pigments. The ohromoproteinoid molecules of about3000 0 are usually 70% peptide and 30% chromophor.

The freeze-dried product, when viewed beneath an electronmlorosoope, shows a sponge-like material- When this material isau*pend«d In water and irradin*«d with UV light the otherwisestable structures completely dissolve. In saline solution,however, the structures remain intact.

Freeze-drying can be a natural phenomenon at low temperaturesand pressures. Thermolysis and Pyrolysis oecurrlng at elevatedtemperatures also have credibility as possible prebiotiereaction conditions on the primordial earth or elsewhere, Ashas been shown, both these reactions In succession can leadto the formation of a cellular network. The boundary structures,rich in chromophors and proteinatlous material, could play aninitial role in •stablishlnfl a primitive type of membranetransport system. During formation, the cellular structurescould encapsulate other biogenic substances like lipids,nuoleio acid bases, phosphates, and/or sugars. Some, like thelipids, oould migrate to special domains such as the cellularboundaries, thus aiding in the evolution of stable andfunctional membranes. The cellular collective offers protec-tion against dissipative forces and only after a successfulevolutionary development can the individual cell finallyarrive.

11

The Need to Srudy the Origin of Life

Kaiser Jamil

Indian Institute of Chemical TechnologyHyderabad-500007, A.p. India

Abstract

It is known that the components of our carbon-based organisms

are intercalated in many important ways and it is difficult to chan-

ge one part without producing effects which necessitate other changes,

So far suggestions about chemically alien types of organisms from

Meteorites etc. have not been testable. Hence we have to re-look

at our "chemical soup" theory - there seems to be a peculiar "Suit-

ability" in the particular chemical brew which constitutes living

things on our planet, but the very fact of familiarity with carbon

based life might increase our difficulty in appreciating the possi-

bility of other forms.

Formulating-alternative systems, in a general way is very com-

plicating and the results would be more complex than ever before.

However with the continuing development in chemical methods and

understanding various theoretical suggestions may in a century or

two become amenable to laboratory testing, but perhaps before then

we may have to recon with quite a lot of first-hand information

about the other planets of the solar system, and this may help in

12

Experiments in search of the origin of biomolecular asymmetry.

L. Keszthelyi

Institute of Biophysics, Biological Research Center, Szeged, Hungary, H-6701

The problem of the origin of the asymmetry of biomolecules attracted manytheoretical and experimental investigations. In spite of these studies the problem isstill open. In this paper recent experiments, experiments which need carefulrepetitions are reviewed and some experiments are suggested. The experimentsinvolve studies related to different types of physical effects possibly causingasymmetry: weak interaction, Earth rotation, magnetic and electric fields, circularlypolarized light, etc.

Chiral Forces and Molecular Dissymmetry

R.MohanM.P.I fur Biophysikalische Chemie

Gottingen,Germany

Introduction: Chiral molecules leading to helical macromoleculesseem to preserve information and extend it better. In the biological world RNA isthe very paradigm for self-replication, elongation and autocatalytic editing. Thenucleic acid itself is not chiral. It acquires its chirality by association with D-sugars. Although the chiral information or selectivity put in by the unit momoraeris no longer of much interest to the biologists - they tend to leave it to theDarwinian selection principle to toko ooro of it ac illuctratsd by Frank's model - itis vital to understand the origin of chirality .

There are three different approaches for the chiral origin of life: (1)Phenomenological, (2) Electromagnetic molecular and Coriolis forces and (3)atomic or or nuclear force, the neutral weak current(NWC).

The phenomenological approach involves spontaneous symmetrybreaking fluctuations in far from equilibrium systems(Prigogine,Goldanskii) ornucleation and crystallization(Kondepudi). Chance plays a major role in the chiralmolecule selected.

New Chemistry: Recently, within the past few years alone, there is aspurt of new activity in chemistry towards asymmetric synthesis, autocatalyticsynthesis of lipids(Leng) and oligomerization and autocatalytic (sclf-replicating)synthesis of nucleic acids (Rebccke, von Kidrowski.Ferris) without any enzyme ortemplate as it should be in the prebiotic stage. Also a variety of helical moleculeswith heavy metal atoms including knotted helice (Sauvage) are synthesisedbearing resemblance to a variety of DNA and RNA structures. The most excitingevent for us is the recent successful preparation of chiral molecules from achiralprecursors in good amount, purity and time. These are hit and run experimetsinvolving very selective metal ions(Mn2+,Pb2+ e t c ) . cocatalysts of diverse origins(one includes chinchona bark) in addition to proper temperature, pH and solvent.There is a single unifying theme in all these syntheses: Chiral molecule productionfrom racemic mixture, its polymerization and autocatalytic behaviour all involveorgano-metallic chemistry. It is different from the early solution-in-flaskexperiments with nothing more than external electromagnetic or gravitationalfields for induced chirality.

15

COULD COMETS BE CARRIERS OF INTACT HOMOCHIRAL

BlOMOLECULES FROM INTERSTELLAR SPACE?

R. Navarro Gonzalez*, Raj K. Khanna** and C. Ponnamperuma**

*Instituto de Ciencias Nucleares, U.N.A.H., A. Postal 70-543

H4x1co D.F. 04510 HEXI CO

"Department of Chemistry and Biochemistry, University of Maryland

College Park 20742, U.S.A.

It has been suggested that the synchrotron circularly polarized ultraviolet

light produced off-angle to the orbit of neutron star remanets of supernova

explosions interacted with Interstellar grains from the presolar nebula producing

chiral molecules. Furthermore, it has also been suggested that comets were the

carriers of such extraterrestrial sources of homochirality frum interstellar

space to the primitive Earth. We present here a computer model calculation of

the affect of ionizing radiation on cometary material, The external (cosmic

rays) and internal (embedded radionuclides) contributions were considered to

determine the degree of destruction of possible homochiral biomolecules present

such as amino acids and carboxylic acids. Our results suggest that an

insignificant degree of destruction (2-1296) of the homochiral biomolecules could

be expected. Thurufmi;, t u m v U tuuld be uaffieii of Intact homoehiral

biomolecules.

17

CHEMICAL EFFECTS OF IONIZING RADIATION AND SONIC ENSIVSY TN THECONTEXT OF CHEMICAL EVOLUTION.

Ai Negrdn-Mandoza and G. AlbarranInstituto de Ciencias Nucleates, UNAMA.P. 70-543 Mexico, D.F. 04510 Mexico.

Ionizing radiation and sonic energy are considered as sources forchemical evolution processes. These sources have still a modestplace in the interdificiplinary approach for the prebiologicalsynthesis of organic compounds.Studies in Radiation Chemistry and Sonochemistry can provide ai-i*ppar inciqht into the chemical processes that may have importancefor prebiotic chemistry( Tne pre»wut work aoncams with theavmlyoio of some rthftmical reactions induced by ionising radiationor cavitation in aqueous media that may be relevant to chemicalevolution studies.

18

0? BS05SST A5T> S0HIDAWWESTS TTT0? CELL STRtlCTTHS

7. J. A, HovakLaboratory of evolutionary Biology

Praha 2, Cs-128 00, C

In the research of questions concerning the origin oflife, the utilisation of regularities of biological evo-lution is very important next to the chemicsl and physi-cal CbiophysicalY notioas, since the prebiological period.Among them the lew of neoteny and principle- of sociogene-sis have not been elaborated sufTiciently from this pointof view till now. !The origin of the DHA double helix maybe viewd as the phylogeneticslly earliest case of the ne-oteny. - The charcter of neoteny is also shared by thebeginnings of sociogenesis on each of af the five gradesof individuals. Ihe neoteny consists here in thavt the se-cond step in the reproduction process, the separation ofdaughter, individuals, does not take place, so that they -remain together and create the beginning of s society Cco-iony). xhe colony integrities gradually v"thruuga ihv ui-u-ce3S of differentiation, the development of internal*envi-ronment, che correlations? into an individual of highergrade. In the coarse of subsequent phylogeny the sequenceof the events repeats * In this' way more and more complice^ted virion bodies evolved gradually from replicating pro-tein and DK& molecules integrating at the end into a pro-kryotfc cell, i.e.the grade I of sociogenesia. - An alter-native conception has been formulated to the generally ac-cepted aymbiogenesis theory, the theory of polyploid syn-bacteriogenesis. According to it the eukaryotic cell hasoriginated by gradual intern&x uivisions of the prokaryonffrhe ring DBA moleeula)" of the preceding prokaryotic cell.la the course of this very long pfaylogsne-tic process Cbe-twee-n 3,5 «id 1,5 thousands of millions years £ the firstsevers! generations of the DS!A molecules formed a nucleus, a number of the subsequent generations transformed intomitochondria and the third _series of generations gave o-rigin to plsstids Cthe chloroplasts ia_the gr l a plants?.— The chemical evolution in the direction towards the o-rigin of life is assumed to have takes place in the accu-mulations of organic matter ia the primary watexr basinsalong the estuaries of &ae original UJT? laad Bir-vams. Thisraaterial concentrated in the fora of coaoerrates ia whichthe synthesis took place of the first polypeptides Cprote-iaoids end spheroproteins later). Theiz* structure has de^srteTmlne& the bases sequence of the primary Dolvnacleotides'which grew to the beginnings of the" genetic"code gradually.Round the replicating D2TA molecules within the primary co-acervates the formation of the first coecervate-in-coscer-vate individuals started as the rising point towards the

19

LECTURE I - GENERAL OVERVIEW

Cyril Ponnamperuma

Department of Chemistry, University of Maryland,College Park, MD 20742, USA.

ABSTRACT

According to the Oparin-Haldane Hypothesis the origin of Lifa is a

necessary consequence of the evolutionary process in the Universe.

The idea of life arising from non life is inherent in the

philosophy and literature of the ancient thinkers and writers. The

concept of spontaneous generation is today presented with a more

scientific basis, under the heading of chemical evolution. The

modern thinking is based on the astronomical concept that the

conditions suitable for life are commonplace in the universe.

Modern biochemistry has highlighted the unity of all living matter.

Nucleic acids and proteins constitute the building blocks of life.

The Darwinian theory of evolution has outlined the sequence from

the first cell to the origin of intelligence. Since the laws of

physics and chemistry are universal laws the chemical evolution

that has taken place on earth must have happened elsewhere in the

universe, it is reasonable to believe that intelligent life must

also be present beyond the earth.

20

LECTURE II - PREBIOTIC CHEMISTRY

Cyril PonnamperumaDepartment of Chemistry, University of Maryland,

College Park, MD 20742, USA.

ABSTRACT

Prabiotic ehmnigtirv

The nucleic acids and proteins are at the basis of all life. The

energy sourea on the primitive earth acting on the earth's early

atmosphere are believed to have produced all the molecules

necessary for life. Laboratory experiments over the last four

decades have clearly established the prebiotic synthesis of these

components, amino acids, purines, pyrimidineB, carbohydrates. The

mechanisms of polymerization have also been outlined. We thus have

a sequence from atoms to small molecules to the large molecules

which are necessary for the emergence of life.

The analysis of meteorites has given us fresh evidence that these

reactions which we have presumed to have taken place on the

primitive earth may have also occurred in the early solar system.

The analysis of carbonaceous cohndrites has given us unmistakable

evidence for the presence of these mo1eculee in outer space.

Recent observational and theoretical studies have also pointed out

that comets may be the location for prebiotic reactions and may

also have contributed to organic matter on the primitive earth.

The radio astronomers studying interstellar media have also

provided us with ample evidence that there are a large number of

organic molecules in interstellar space. Organic chemistry appears

to be commonplace in the universe.

21

LECTURE III - PHYSICOCHEMICAL BASIS FOR THE ORIGIN

OF THE GENETIC CODE

Cyril PonnamperumaDepartment of Chemistry, University of Maryland,

College Park, MD 20742, USA.

ABSTRACT

A study of the association of homocodonic amino acids and selectedheterocodonic amino acids with selected nucleotid«s in aqueoussolution was undertaken to examine a possible physical basis forthe origin of codon assignments. These interactions were studiedusing 1H nuclear magnetic resonance spectroacopy (NMR).Association constants for the various interactions were determinedby fitting the changes in the chemical shifts of the anomeric andring protons of the nucleoside moieties as a function of amino acidconcentration to an isotherm which described the bindinginteraction.

The strongest association of all homocodonic amino acids were withtheir respective anticodonic nucleotide sequences. The strength ofassociation was seen to increase with increase in the chain lengthof the anticodonic nucleotide. The association of these aminoacids with different phosphate esters of nucleotides suggests thata definite isomeric structure is required for association with aspecified amino acid; the 5•-mononucleotides and (3'-S') - linkeddinucleotides are the favored geometries for strong associations.Use of heterocodonic amino acids and nonprotein amino acidssupports these findings. we conclude that there is at least aphysicochemical, anticodonic contribution to the origin of thegenetic code.

22

THE ORIGIN OF CHIRALITY, THE ROLE OF PHASE TRANSITIONSAND THEIR INDUCTION IN AMINO ACIDS

Abdus SalamDepartment of Theoretical Physics, Imperial College,

London, United Kingdomand

International Centre for Theoretical Physics, Trieste, Italy.

ABSTRACT

We present a brief review of the work in which it was suggested that chirality amongthe twenty amino acids which make up the proteins may be a consequence of a phasetransition which is analogous to that due to BCS superconductivity.

23

Differences in Radiolysis Behavior dt' D,L Amino Acidii Primary' Stage and Thermodynamic Equilihriura State

Wang Wenqing, Wu Jilan and Jian JiangPeking University

Beijing 100871 , P.R. of China

SUMMARY

If differential interaction of elementary paKiclefi with enantiomera

of utni.no ncide exists and what role it may play on the origin of life

cfciralit? are hitherto not concluded. The controversial experimental

requite, the poor reproducibi 1 ity of name, positive evidence and the

theoretical prediction of the effects which are well below the

threshold of experimental observation have Gpreaded the peHBimifitic

view. A series of experittente were designed to retest the problem, The

obtained data and the careful analysis or. the reference data, however,

favor the conclusion that there does exist differential Interaction of

elowntary particles witb D, L atr.ino acids. The differencee are truly

trivia) in magnitude, but it could be detected when the eveteci is far

from equilibrium (the primary stage), by instant meuHiirement as the

interaction is still proceeding. If the nyste^i is al the thermodynamic

equilibrium state, the difference would not be detectable. If an

effective amplification its involved In, the subtle difference would be

enlarged to the extent ;>f formation of macroscopically detectable

rhirnHty, So the poaaibilty that the aeyniitip.tricity of elementary

irradiation. More radicals were produced in D - U o m c r than in L-isamer,

but the chir»si]-val capillary column GC analysis showed no measurable

excess of any enantiomer. Selecting the tejiperattire at 77 K was

important to keep the 3 " particles from bcifig interfered by the

thermal movement and 'freeze' the formed radicals.

1. 3 ""Co Y-irradiation

Merwitz (1976) and Norden (1985) observed the Y-induced decafboxyla-

t i an rate of D-amino acids was 2.7, and 2,0 times respectively higher

than that of L-iaomerH, We doubt that the extremely small, energy

difference of enantiomers due to the presence nf parity violating weak

neutral current in electromagnetic interaction could cause B O

manifested cbir»l selectivity. The sublimed !>-, L- and DL-leucine in

solid state were irradiated by *°Co Y - r a y with the total dose: of 1OG~

1000 Gy. The GC analysis of D, L-isorcers, and CO 3, H a and N H 3 (G velues

up to 10*) showed no accumulation of any particular enantiomer. We

deduced that in Merwitz and Norden' * experiments some impurities

induce a cascade process. Norden 1 a observation that the large

difference of radiolysis rate between the isdfters of sublimed samples

did not appear between that of crystallized sa^plea confirms the

presence of the crystal effect.

The above discussion supports our view that fleraenlary particles do

differentially interact with enantionjerfi of amino acids.The difference,

though very small, could be detected by sensitive methods when the

system is far from e q u i l i b r i u m , but it could not cause macroscopic

excess of unc particular enantiomer without an additive to tiervfc as

the catalyst of an a m p l i a t i o n or ta quench some path of the reaction.

This additive was e x e m p l i f i e d in Akuboshi'a discovery that aaptrtic

acid is protected from radiation by the presence of alanine in the

solution.So the effort to highlighten ihe role of elementary particles

in the origin of lift chirality should not be given up, And rather

than the pure reaction system that we arc c u s t o m a r u e d in, the Bcarch

For the posflible additives which may present iu the primordial solp is

highly worthwhile.

26