juliana

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Protobiont (Greek: prótos — first, primary and bios — life) means a
primary living structure. What is it that differentiates living organisms from
non-living matter? This is a basic issue of biology closely linked to the
problem of unity and differences between living and non-living nature.
The unity is exemplified by the fact that both forms of matter are built
up from chemical elements of an identical molecular, atomic and nuclearelectronic structure. They obey the same mechanical, physical and
chemical laws. This is an undisputed proof in favour of the materialistic
concept of life as a form of existence of matter and excludes whatever
interference of non-materialistic or spiritual forces in its origination. At
present 92 chemical elements are known in free state and with the ones
resulting from the nuclear reactions they amount to 111.
The differences between the two forms of matter are substantial but
sometimes hardly discernible because of their common material structure.
That is why only the most typical features of living nature differing from the
non-living one will be taken into consideration.
The chemical elements from which living nature is built are connected
between themselves in such a way as to form organic compounds of high
molecular weight, non-existing in non-living matter. These are mainly
proteins, nucleic acids, carbohydrates, lipids and enzymes (biocatalysts).
Enzymes take part in almost all life processes.
Metabolism in living systems is accompanied not only with the uptake
or releasing of energy, but also by synthesis of organic compounds
necessary for their growth and development. It is effectuated in a biological
way by specific mechanisms and reactions. Even its temporary cessation
leads to their death which is not found in non-living nature.
Reproduction of living organisms from their likes is carried out by
complex biological mechanisms, modes and forms non-existent in nonliving nature. They were formed as a result from a long chemical and
biological evolution.
Irritability in living organisms is a specific quality of theirs which is
designed to respond to outside and internal stimuli in a definite way —
contraction, shifting, hiding, etc. It is more strongly developed in the animal
kingdom but is also found in plants. It is sufficient only to touch the shy
plant Mimosa pudica, and it will immediately and graciously react by closing
its leaves.
Irritability in living organisms is closely linked to their adaptability in the
struggle for survival. Most often it is called “purposefulness” thus a certain
presence of the “supernatural” principle being imposed. In my opinion this
trait of life is a specific, more superior form of organization of matter just like
the feelings, emotions and mental activity that have become the
characteristics of man.
Other differences between living and non-living nature can also be
pointed out which for brevity will be omitted. Certain authors strive to prove
that the characteristics above are even valid for both forms of the existence

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Figure 1–3. Coacervate drops: (a, b) — general view under light microscope; (c) — a single coacervate drop; (d) — coacervate drops under a scanning electron microscope (After Evreinova, 1966; Evreinova et al., 1975).

It is necessary to note that no matter how attractive are the studies on
coacervate drops because of their opportunities for express results about
the origin and organization of the living systems, they bear in themselves a
serious defect — the initial components used are of biogenic origin, they
are synthesized by living organisms with naturally built-in secondary and
tertiary structures. For the purpose of eliminating this shortcoming, attempts
for the in vitro synthesis of biopolymers are made, i.e. without the
participation of any living systems.
According to Oparin (1966) coacervate drops are very comfortable
models for the reproduction of the possible paths in laboratory conditions
which the initial formation of both the structures and metabolic patterns
have followed under the action of the primitive systems underlying the
origination of life. This type of systems actively interacting with the
environment, displaying dynamic stability and the capacity not only to be
preserved but also to grow in the conditions of the “primary bouillon” were
called by him protobionts.

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image

Figure 1–2. Evolution tree of living organisms (After Alberts et al., 1986).

The interest towards the coacervate drops (Fig. 1–3) has grown
strongly. Intense studies were carried out resulting in the production of
various coacervates not only of gelatin and gummi arabica but also from
other organic polymers — albumins, histones, lipoids, nucleic acids,
chlorophyll, etc. According to data of Evreinova et al. (1975) more than 300
different coacervate systems are known in the literature.

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replied to himself — “because the D-rotating molecules are more easily
used of by the enzyme of the given type of fermentation than the L-ones”
(see Vallery-Radot, 1950).
Later on also the question arised, why only L-amino acids (see Fig. 2–
29) take part in protein construction and D-riboses (see Fig. 2–37 A) — in
the nucleic acids (D-ribose in RNA and D-2-deoxyribose in DNA). Because
of the lack of a categorical answer to this question and some exceptions to
the rule observed, the interest towards it is gradually receding.
And now let us consider the problem of the origin of life in another
aspect. Since the World Ocean is relatively boundless the whole of it could
not possibly has been engaged in the abiogenic chemical evolution of living
matter. “It is not very plausible — remarked Oparin — for the protobionts to
grow as a united whole mass. Under the influence of outer mechanical
forces (for example the wave beat) they could have been splintered just like
the splitting of emulsion drops upon shaking. At that, the greater size the
given protobiont reaches in the process of its growth, the greater are the
chances of its splitting into daughter formations. These formations to a
certain degree preserve the same organization of interaction with the
environment which was inherent in the initial protobiont since they were
simple splinters, parts of a relatively homogeneous formation in its whole
mass” (see Oparin, 1966).
It is hardly acceptable that only mechanical forces of that nature can
be the cause for the crushing of the formed mass of organic matter into
emulsion drops which would serve for the protobiont formation preceding
prokaryotes. No doubt that this is a complex physicochemical process
related to the energy potentials of chemical elements, their valency and
electron bonds which could be the subject of in-depth quantochemical
studies. No wonder the prokaryotes — bacteria and unicellular blue-green
algae which are thought to be the first representatives of living organisms
on Earth and stand at the beginning of the evolution tree (Fig. 1–2) have
formed and exist even now in the 1—10 μm order.
The coacervate drops idea belongs to the Dutch explorer Hugo
Bungenbreg de Jong (1932,1936). The term coacervation (from Latin —
gathering in piles, accumulation of colloidal solutions) was introduced by
him in the 1930s and he is considered the founder of the coacervate
hypothesis.
By mixing water solutions of gelatin and gummi arabica at certain
conditions of temperature and pH Bungerberg de Jong has obtained
strongly precipitous mixtures in which rows or groups of emulsion drops
freely drifting in the surrounding water, later fully devoid of the dissolved
polymers, have been formed of the molecules of the two components
(evenly distributed in the beginning). These formations visible under the
microscope he had called coacervate drops.

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image

Figure 1–1. Stereoisomers of the glyceraldehyde and alanine. In both
cases D- and L-isomers represent mirror images of one another.

It was L. Pasteur who first paid attention to this finding. Assuming
optical activity of living matter a criterion he defined it as “the sole
demarcation line (la seule ligne de demarcation) which can be drawn
between the chemistry of living and non-living matter”. Pasteur has made
considerable efforts for the clarification of this problem considering
molecular asymmetry a discovery of his showing the true path towards
revealing “the secrets of life”. His grandson Vallery-Radot remembers him
pondering over “why only D-tartaric acid is capable of fermentation” and he

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disposal much more numerous data from the well-developed by that time
physics, astronomy, geology, cosmology and other sciences having
relevance to the problem. He has taken into account the achievements of
biochemistry, cytology, molecular biology and genetics as well as the
results from the ever more precise light and electron microscopy, revealing
the structure of a variety of crystals, polypeptides and nucleic acids. All this
has helped him a lot to hold into the positions of the evolutionary
development of living organisms and to formulate clearly the putative
history of life beginning into three major stages: from the atom to the
molecule; from the molecule to the polymer; from the polymer to the
organism.

The model of J. Watson and F. Crick (1953) establishing the DNA
double helix structure and the role of nucleic acids in the reproduction of
living organisms have given Bernal the grounds to accept that life on Earth
is a function of the interaction of nucleic acids and proteins. This model will
be discussed in the following Chapter 2, Section 2.7. (Nucleicacids).
In contrast to Oparin, as a physicist and crystallographer Bernal
assumed that it is not the coacervates, but the adsorption of clay and soil
particles which was the cause for the condensation of organic substances
that has later on led to emergence of life. This hypothesis, however, did not
meet recognition as he himself admitted.
A hope that the main principle accounting for the differences between
living and non-living matter was raised by the discovery of molecular
asymmetry known as molecular chirality. The term “chirality” was
introduced by W. Thomson (Lord Kelvin) in 1884, which comes from the
Greek word for “hand”. According to Gutina and Kuzmin (1990) the most
correct term is molecular stereoisomery.
Stereoisomers are compounds which being of an identical chemical
composition and the same molecular weight display differing properties. As a
result of the spatial distribution of atoms their molecules are in two forms — D
and L, which turn the plane of polarized light to the right and left respectively;
the one being a mirror image of the other, just like two hands of the human
(Fig. 1–1).
Let us give some examples. Of the two forms of phenylalanine the Lisomer
causes grave diseases while its D-isomer is harmless; L-adrenalin
possesses a stronger hormonal action than its D-isomer.
It is thought that molecular asymmetry is attributable only to natural
organic compounds. All amino acids making up the proteins are L-forms
which upon hydrolysis in soft conditions preserve their optical activity. If
amino acids however are synthesized in laboratory conditions then optically
inactive forms are obtained. These are the so called racemic mixtures
consisting of equimolar quantities of D- and L-stereoisomers and are
denoted by the symbols DL.

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development provoked the greatest interest. Numerous studies have shown
that it is not just an organized drop of mucous matter and the elucidation of
its structure, organization, chemical composition, and emergence would
provide a clue to the understanding the origin of life. The cell nucleus and
division of the cells have been discovered and profound studies on proteins
and nucleic acids have been performed.
The first attempt to create a scientific view on the origin of life was
made by the well-known Russian biochemist A. I. Oparin in his book “The
Origin of Life” published in 1924. After that he elaborated his concept into a
trim and well-grounded biochemical theory in a number of other books and
articles (Oparin, 1936—74).
Making a good use of data and achievements of the different branches of
science of his time Oparin has directed the search for the solution of the
problem to World Ocean (hydrosphere), the “primeval bouillon” and
“coacervates” which in his opinion have served as a cradle for the abiogenic
evolution having led to the emergence of a qualitatively new form of matter —
the living matter. According to him hydrocarbon compounds formed in suitable
environment from the available gases in the primitive atmosphere — methane
(CH4), ammonia (NH3), hydrogen (H2) and water vapours were the initiators of
chemical evolution. Ultraviolet irradiation of the Sun (which in the absence of
the ozone layer has been reaching the earth surface unhindered and has
been quite abundant), radioactive emissions, the electrical discharges in the
atmosphere, the high temperature in the volcanic eruptions, etc. have supplied
the energy needed for that process.
Oparin’s theory has gained broad recognition. The outstanding
American scientist F. A. Lippmann has written: “This theory is the greatest
achievement in the field of science of the origin of life. It has shown me the
way personally. After I have read it a radical change in my work occurred”
(see Preface of Oparin, 1974).
A tribute to the problem is the article of J. Haldane (1929) also entitled
“The Origin of Life”, which was published only five years after Oparin’s
book. Haldane distanced himself from the spontaneous generation concept
of living organisms and has assumed that organic substances have been
formed prior to primeval organisms thus developing evolutionary views on
that issue. Besides, he has presumed that at the initial stages of life
formation the atmosphere has contained a very small quantity of oxygen
(O2) if any and the UV-rays were not retained in its upper layers as it was
happening later after the formation of the ozone ring round the Earth.
According to him the problem of life origins would be subjected to
speculations up to the moment when a living entity is synthesized or even a
kind of an independent organism, adding that speculations of that sort are
not futile since they could be experimentally proved.
In 1967 John Bernal published a book under the same title “The Origin
of Life” translated in Russian in two years time (Bernal, 1969). The author
was well acquainted with Oparin’s and Haldane’s works. He has had at

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Formation of Scientific Concepts on the origin of Life

Section 1.3. After a long historical period of the mankind’s development
characterized by mythical and religious ideas on how life has cropped up
and after proving the fallacy of the viewpoint of spontaneous generated life
in the conditions of the already existing organised living matter, the solution
of the problem of life origins and evolution has in itself gained scientific
grounds. A strong boost in that direction was produced by two great events
in science: 1) the success of the German chemist Friedrich Wöhler (1828)
who synthesized the first organic compound out of inorganic elements
identified as urea (H₂N—CO—NH₂), up to that point considered impossible;
2) the publication of Charles Darwin’s book “The Origin of Species” (1859)
which caused a revolution in science and dealt a crucial blow on the
metaphysical concepts of the invariability of species.
The problem has been set in right and the difficulties in its clarification
have become obvious. For a certain period of time (almost a century) the
opinion that this problem is frame insoluble has had prevalence. Darwin
himself has deliberately avoided the problem of the origins and organization
of living matter being very well aware of the great difficulties its eventual
clarification would be meeting. But as a man of genius he had given it a
thought. In a letter to his friend J. D. Hooker he had written:
“…A great deal of time will pass before we ourselves would be able to
observe how some mucus or protoplasm or something of this kind engenders
a living entity. I, however, have always regretted the fact that have walked in
the rut and have used the term “creation” taken from the Bible, as a result from
certain absolutely unclear processes “and everything emerged”. To dwell at
present upon the origin of life is simply incongruous. It would have been
equally successful to talk about the origin of matter” (29th March, 1863).
In another letter Darwin had shared his thoughts on the emergence of
living organisms in the presence of already existing ones:
“It is often said that all the conditions for the first production of a living
organism are now present which could ever have been present. But if (and
oh! what a big if!) we could conceive in some warm little pond, with all sorts
of ammonia and phosphoric acid salts, light, heat, electricity, etc. present,
that a protein compound was chemically formed ready to undergo still more
complex changes, at the present day such matter would be instantly
devoured or absorbed, which would not have been the case before living
creatures were formed” (1871). (see F. Darwin, 1887).
During this period of relative restraint towards finding a solution to the
problem, science went on developing. Mankind has entered the XX century.
Not only physics and chemistry but cytology, biochemistry and molecular
biology developed rapidly. The cell has become the object of interest for
many researchers. Its protoplasm with its inherent capacity for growth and

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Apart from the fact that the theory of spontaneous generation of living
organisms proved to be fallacious it also has produced some positive
effect. Its historic importance lies in the fact that it has rid the problem of the
origin of life of mystic and religious implications, thus attributing to it a
natural, down-to-earth approach.
The first successful stroke to the theory of spontaneous generation
(generatio spontanea) was dealt by the Italian physician and naturalist
Francesco Redi. In his remarkable work “Experiments on the Generation of
Insects” (Redi, 1668) he has proved that the white worms are not
spontaneously generated in meat but are developed from eggs laid by flies.
And if meat is protected from the access of flies which he had done, no worms
would appear.
Despite his successful experiments Redi could not fully free himself of
the self-generation concept.
He had admitted that in some cases self-generation could be obtained
(wood worms to engender from rotting
materials; the small worms in the oak to form from plant juices). Maybe,
owing to this fallacy of his, the theory of spontaneous generation of living
organisms could have been supported for one more century by authoritative
philosophers and naturalists. Save for R. Descartes this view was also
shared by G. Leibnitz (1646—1716), G. Buffon (1707—1788), C. Linnaeus
(1707—1778) for a some time, and others. The notorious Scottish naturalist
J. T. Needham (1749) has undertaken an experimental proof of the
“spontaneous generation of microbes”. His results have been subjected to
criticism by Lazzaro Spallanzani (1765, 1776) who proved his conclusions
wrong since he had not observed the conditions of total sterility.
The demise of the theory of spontaneous generation of the living
organisms has been achieved by Louis Pasteur (1860—63) who had
conducted brilliant in thought and precise in performance experiments in
his famous dispute with Felix Pouchet (1858—63). With the results from
these experiments Pasteur emerges as the final victor and is rewarded
the prize of the French Academy of Sciences especially established for
that purpose. He concluded his lecture held on April 7th 1864 in the
Sorbonne saying: “Never will the doctrine of spontaneous generation
recover from the mortal blow of this simple experiment” (cited by ValleryRadot, 1950).
He was acclaimed most uproaringly by the overcrowded
audience, thus his devotion and contribution to science met their due
recognition.

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The interest of man towards the origin of life proved to be much more
profound. It is pointless to survey the fantastic myths and religious ideas
created in the course of the millennia by man since they would not
contribute in the least to the objective treatment of this problem. According
to most of them life is engendered by a certain Creator, God or Spirit, who
by exercising an impact on the non-living matter has created living
creatures from earth and mud.
Along with these purely religious concepts there exist in the annals of the
ancient people of China, India, Babylon and Egypt also traditional beliefs in the
self-generation of aphids and insects by the action of heat and humidity, and
of lice, flies and beetles from the sweat of the cattle and the manure in the
stables, of worms from the sewer waters, and of frogs, mice and crocodiles
from the humus of the Nile River when heated by the Sun, etc.
The notion of the self-generation of living organisms has been further
developed by a variety of philosophers and schools in ancient Greece.
Phales of Millet (624—547 B. C.) as well as contemporaries of his have
believed that living organisms could be spontaneous engendered in the
alluvial soils and mud, i.e. the natural habitat where they have dwelt and
reproduced. This concept has received an especially broad presentation
in the works of Democritus (460—370 B. C.) and the above-mentioned
Aristotle.
The materialistic views of Democritus though episodic allowed him to
accept that matter lies in the basis of Universe which consists of a variety of
small particles (atoms) that are engaged in an unceasing movement and
are divided by hollow spaces. According to him the initial emergence of
living entities or their self-generation from water and mud is possible due to
the random but perfectly logical combinations of the atoms in their
mechanical movement when small particles of the wet earth collide and join
with the atoms of fire.
Aristotle taught that except by birth from their likes living organisms
can also be spontaneous self-generated from non-living matter, in the
support of which he has very skillfully and entertainingly supplied
examples. Moreover, this brilliant thinker of the ancient times has
produced a certain theoretical argumentation of the phenomenon and
developed it into his theory of spontaneous generation, which has played
a decisive role in the further course of development of the method by
which man has tried to tackle the problem of the origin of life. Due to his
great renown his views have occupied people’s minds for over two
millennia extending even to the time of the great French philosopher and
mathematician Rene Descartes (1596—1650) to whom humanity owes
the famous phrase: “I think consequently I exist” (Cogito ergo sum). The
Belgian chemist and physician van Helmont (1577—1644) has taken this
point of view so deep to his heart that he would even write prescriptions
for obtaining live mice from wheat grains.

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