home
projects
events
publications
 
members
subdivisions
awards
press-centre
 
contacts
news
photoalbum
links
Mail address
38, B.Fakelny per.,
Moscow 109147,
Russia
Phone
+7(495) 939-7165
Ph./Fax
+7(495) 685-5395
   
 
| SITE MAP | F.A.Q. |
REGISTRATION FORGOT PASSWORD WHY TO REGISTER?

Thermodynamic nature of the biological evolution. The model and the reality


HomepageINSTITUTE of Physico-Chemical Problems of EvolutionBiological Evolution and AgingThermodynamic nature of the biological evolution

This paper is dedicated to the memory of professor Cyril Ponnamperuma

G.P.GLADYSHEV

Institute of Ecological Biophysical Chemistry, Academy of Creative Endeavors, 36 Novy Arbat, Moscow 121205, Russia

Macrothermodynamic model describing the evolution of supramolecular structures and chemical composition of living objects in the course of ontogenesis, and also at long periods of biological evolution in general, is presented. The study of quasi-closed (thermodynamically and kinetically) systems, namely, the phases of supramolecular structures of biomass enables one to make the conclusion about the thermodynamic nature of biological evolution. According to the Second Principle of thermodynamics, this nature leads to the variation of chemical composition and structure of living systems in the process of their development. By means of direct and indirect proofs, it is shown that the specific Gibbs function of supramolecular structure formation for the tissue of animals in the course of ontogenesis tends to a minimum. The conclusion that thermodynamics is the motive force of the biological evolution, is verified.

Key words: Biological evolution, macrothermodynamics, hierarchical system, quasi-closed system, ontogenesis, phylogenesis, chemical composition of living bodies.

The origin and evolution of life is the origin and evolution of the thermodynamic self-organized (self-assembled), self-reproduced polyhierarchic systems.

1. Introduction

The understanding of the evolution and behaviour of natural systems is mostly based on classical natural science. Two approaches play prevailing role here: the thermodynamic one and the kinetic one. Thermodynamic description of systems and phenomena is based on the concept of the equilibrium state. Thermodynamics answers the question about the direction of a process before the equilibrium is achieved. It does not use time as a parameter and does not consider the mechanisms of phenomena. In contrast, kinetics deals directly with the rates of processes and studies their mechanisms.

During the recent decades, foundations of non-equilibrium thermodynamics for near-equilibrium systems ( irreversible processes) have been developed. This allowed the combination of both approaches mentioned above. However, the results obtained so far can be applied only to a few simple phenomena. A similar situation takes place for the thermodynamics of systems that are far from equilibrium and for synergetics. Both of them are based on purely kinetic methods.

Restricted scopes of the approaches mentioned above lead a number of researchers to the opinion that the evolution of living systems hardly agrees with the Second Principle of thermodynamics.

Recently a new scientific area appeared - hierarchic thermodynamics (structural thermodynamics), or macrothermodynamics [1-6] - which points out the way to study living objects on the basis of equilibrium thermodynamics [7,8] and some branches of the physical chemistry of natural systems [1,9-11]. Besides, macrothermodynamics is also based on the principles of macrokinetics. In a certain sense, it is an alternative to the thermodynamics of near-equilibrium systems. Macrothermodynamic models are advantageous when used for the study of slightly non-equilibrium processes of structure formation, which are analogues of slightly non-equilibrium phase transitions.

In a few recent works approaches to the development of the macrothermodynamic theory of biological evolution have been pointed out [1,2]. A model has been created whose main elements have been verified in various studies. At the same time, the model has never been presented in relation to physical and chemical phenomena in a clear compact form, understandable for biologists. Certainly, this complicates the understanding of the approach suggested by the author, and - which is more significant - does not allow one to estimate the scope of the theorys predictions. One of the reasons for such a situation was the authors desire to find the motive force of the evolution (for all biological hierarchies) based on the general deductive principles (first of all, on the principle of reductionism). Besides, the absence of strict experimental proofs of the model apparently did not promote its wide use.

After the first works of the author have been published [2] an essential advance has been achieved. With the help of quantitative data, it became possible to apply the model to the evolution of the chemical composition of living objects and to prove that the model agreed with reality [1,3-6].

In the present paper, the physico-chemical model of biological evolution is briefly described for the case of the evolution of biotissue`s supramolecular structures (their chemical composition and structure). Besides, a few experimental results confirming the model, are presented.

2. The model of a living system evolution

Consider a certain volume of biotissue (biomass) as a heterogeneous thermodynamic system consisting of a liquid phase (water solution of physiological substances), and a phase of supramolecular structures (a supramolecular frame of biological structures), which appeared due to the aggregation (self-assembly) of molecules and supramolecular structures of different hierarchies [5,6]. Besides, the phase of supramolecular structures results from slightly non-equilibrium phase transitions.

We suppose that there is local supramolecular equilibrium in all points (microvolumes) of the phase of supramolecular structures (which also includes small molecules). According to this, let us call the self-assembly phenomenon, which leads to the supramolecular phase formation, the thermodynamic self-organization. This notion must be distinguished from Prigogines dynamic (kinetic) self-organization, or simply self-organization, in Prigogines terms, which can be observed in systems far from equilibrium. The existence of local equilibrium means that at times comparable with the characteristic periods of relaxation to equilibrium we deal with a set of microvolumes constituting the phase under consideration, - which are thermodynamically quasi-closed. It is obvious hence that the integral value of the specific (averaged over the volume) Gibbs (or Helmholz) function of supramolecular structure averaged local conformation approaches a minimum:

min; min , (1)
For the phase of supramolecular structures of constant composition
(at times of relaxation to local equilibrium)

where V is the volume of the system, m is the mass of the selected microvolumes, x, y and z are the coordinates; the sign "-"means that the specific value is considered; the sign "~" points out the heterogeneous nature of the system. We should mention that nobody seems to doubt the validity of Eqn (1) at present.

At times much longer than those needed for relaxation to the local intermolecular equilibria, the biosystem is naturally open - there is a flow of matter passing through it. It seems as the biosystem is blown up, its volume and mass increasing. The model assumes that the average chemical composition of the flow of matter is constant (although it fluctuates near the average value).

Thus the nature of the substance coming into the system (into the phase of supramolecular structures) practically does not vary. In other words, the supramolecular phase (structure) of an organism undergoes an evolution against the background of the flow of chemical substances of almost constant composition, which come into the system. If the flow is slow enough then we can assume that the liquid phase of the biosystem is always in equilibrium with the flux. This provides constant average concentrations of substances coming into the liquid phase. This phase together with the environment can therefore be considered as a thermostat (in the broad sense of this term - T, p, concentrations of the chemical components and other parameters are constant) for the phase of supramolecular structures.

Chemical composition of a biosystems phase of supramolecular structures varies slowly at times comparable with the duration of adaptive processes and ontogenesis (it also varies in the course of phylogenesis and at long periods of biological evolution in general). As the biotissue gets older, the supramolecular structures become more stable thermodynamically (here we mean the stability of supramolecular structures but not of the chemical substance they contain).

Selection of supramolecular structures with higher thermodynamic stability (structural stabilization of phase [1,2]) is determined by the thermodynamic factor. Indeed, it is admitted that the retention (holding) time (this term is taken from chromatography) of molecules (macromolecules) in supramolecular phase, , is related to the value of the Gibbs function of supramolecular structure formation:

~ , (2)

where R is the gas constant.

The most long-holded molecules of the supramolecular phase (coming into the biosystem from the environment or produced in the course of the biosynthesis) initiate the selection of similar molecules. This also changes the composition and chemical nature of the phase of supramolecular structures. As we have already pointed out, these changes result from the thermodynamic factor, though in its kinetic form (Eqn 2). Thus, above all, those molecules are accumulated in the microvolumes of the phase of supramolecular structures whose absorption (self-assembly) is most beneficial thermodynamically (these molecules have higher affinity for the phase of supramolecular structures). If there are mechanisms of matrix synthesis, such molecules have advantages for reduplication (reproduction). Due to all this, the absolute value of the specific Gibbs function of supramolecular structure formation, , (or the absolute value of the specific Helmholtz function, which, for the condensed phase, practicaly, coincides with it) grows as the biotissue gets older, becoming more negative. It follows that

min; min (3)
For the phase of supramolecular structures of varying composition
(for the times of ontogenesis, phylogenesis, etc.)

Eqn (3) means that the value of (Eqn 1), whose minimum corresponds to a local equilibrium (), in the course of ontogenesis (and also phylogenesis and long stages of evolution) varies slowly, tending to a still lower value ().

Let us note for clarity that Eqn (3) follows from the fact that the phase of supramolecular structures (or biotissue as a whole) is partly quasi-closed in relation to the outcoming flows of matter. This kinetical (dynamical) quasi-closeness leads to the accumulation of aggregates of molecules with higher thermodynamic stability in the unit volume of the phase of supramolecular structures [1, p.90-92]. Eqs (2) and (3) actually determine the time axis (kinetic parameter) for the variations of and , and, consequently, also for their sum, whose value is negative:

(4)

The last conclusion, however, as we have already stressed, relates to the case where the flow of the matter coming into the biosystem has constant composition. If the composition of the incoming matter varies in time (for instance, at some physiological anomalies or variable parameters of the thermostat), then the system can become not quasi-closed kinetically, and the variation of can become uncertain.

The model described here has a simple analogue an adsorption (absorption) system, which is open and which slowly receives a flow of substance with constant composition. Inside the system, this substance undergoes phase or chemical changes [1, p.90-92]. Indeed, suppose that a homogeneous flow at the input contains a fatty acid and water as basic components, and there is microemulsion formed inside a column (reactor), so that the fatty acid concentration in the microemulsion is high. Then the column will be soon overfilled with the fatty acid and will stop operating. (Here the fact is demonstrated that the system is partly quasi-closed kinetically.) Apparently, there is no doubt that the tendency presented in Eqn (3) is valid in this case ([2], pp.71-75; 90-92; 163-165).

Eqn (3) means that as the biotissue gets older, it must normally get enriched by chemical compounds with the most negative values of the Gibbs function of supramolecular structure formation (). Substances with high energetic capacity, having less negative values of the Gibbs function of chemical compounds formation (from simple substances or elements), , - are namely of this kind, and this follows from the theory and has been found out experimentally [1, 13-15]. These are lipids, proteins, polysaccharides, nucleic acids and so on, substances that force water out of the biotissue volume as it ages. Such tendencies must also be observed in phylogenesis and at long periods of the biological evolution when the average chemical composition of the environment can be considered as constant (in this case, one can assume that the biosystems are partially quasi-closed kinetically).

The model considers the processes of self-assembly independently of the regime in which chemical reactions in the liquid phase take place. The processes of supramolecular structure formation move the substance synthesis and transport mechanisms to the background: they only use these substances for the building of supramolecular structure of biotissue. The model has also serious grounds to admit that the thermodynamic system under consideration is a simple one - by definition, only expansion work is produced in it (this kind of work is rather small in condensed phases). To be sure, this approximation becomes unjustified while studying, for instance, the evolution of a population (when it is considered by itself), which is a structure of high hierarchy performing mechanical or any other work. (Here the role of interacting particles is played by organisms, and the study is focused on irreversible processes that are not accompanied by the entropy variation [1,16,17]).

Functioning of biological systems (for instance, of biotissue) is possible if these systems are penetrable enough for the matter, which is the building material for supramolecular structure. Besides, as it has been first pointed out in paper [5], there should exist not only internal, but also external forces leading to the mixing inside the substance - to the metabolism. This role is played by periodic fluctuations of the environment (thermostat) parameters around their mean values. Let us stress that these necessary periodic variations of external parameters are the essential thermodynamic effect of the environment on the evolution of biosystems. We obtain that the joint action of internal thermodynamic factors (observed inside the system) and of external thermodynamic effects (variations and oscillations of the environmental physical parameters) determine the direction and rate of the evolution.

In the model presented here special attention is paid to the physical chemistry of supramolecular structures, which should be considered as one of the keys to the understanding of biological evolution. It can be easily proved that this model does not contradict the kinetic theory of Darwin and Wallace and pacifies the disputes around it.

3. On the experimental proofs of the model

According to the model presented above, a biosystem under normal physiological conditions expands in the course of ontogenesis. According to Eqs (3), (4), the system is enriched by energy-intensive substances, which oust water from the biotissue. The experimental proofs of this have been published in [1-6]. In Fig.1 the theoretical scheme is shown demonstrating how the supramolecular (im) and chemical (ch) parts of the specific Gibbs function of the biotissue vary in the course of ontogenesis (ont) and phylogenesis (ph). (In the first papers by the author the chemical part of the Gibbs function was denoted by index m - molecular.)

Indeed, there has been obtained various material concerning the changes in the gross chemical composition of organisms (of their organs and tissues) in the course of ontogenesis, phylogenesis and biological evolution in general. A typical example of the variation of chemical compound water - organic substances in the brains of different animals, depending on relative levels of their evolutionary development, published in paper [2].

Fig.1. Schematic variation of the specific values that are parts of the Gibbs function of a biosystem j, in the course of ontogenesis and phylogenesis. This scheme can be also applied to the long periods of biological evolution. For instance, biosystem j is a biotissue of an animal. and are the specific values of chemical (ch) and supramolecular (im) parts for j-th system; and denote the time for ontogenesis and phylogenesis, respectively; and are measured in relative units ( > ); are arbitrary functions; values of with indices characterize the specific values constituting the Gibbs function of structure formation (the specific Gibbs free energy of the corresponding structure formation) of the system at a certain time moment; values vary in the course of evolution due to the variation in the chemical composition of organisms or species.
Now our aim is to show that the discussed variation of chemical composition results from the tendency of a biosystem to get (to aspire) to supramolecular equilibrium in the course of the evolution. In other words, the validity of Eqs (3), (4) is to be proved on the experimental basis.

Several results relating to the chemical composition variation of proteins and nucleic acids in the course of the evolution of organisms are discussed in papers [1,5,6,18]. However, there is still a lack of reliable information unambiguously confirming the thermodynamic nature of changes in the composition of these natural polymers. This is well illustrated by the growth of the melting temperature of chromatin in the course of ontogenesis. This growth is believed to indicate definitely that the evolutionary aging of chromatin in the ontogenesis has thermodynamic nature [1, p. 161-163]. New results [18] make it possible to conclude that the evolutionary optimization of the RNA structure is determined not only by the thermodynamic stability of its secondary structure, but also by that of its tertiary structure. This explains why not only the sequences containing GC pairs are selected in the course of evolution (which is most beneficial thermodynamically for the secondary structure formation). In the course of the evolution, sequences including AU pairs are also selected. We obtain (according to the theoretical predictions) that the thermodynamics of tertiary and higher supramolecular structures influences the chemical composition and structure of the RNA. Therefore, from our view point, selection of natural (AUGC) sequences is most advantageous macrothermodynamically. P.Shuster considers these sequences as the most stable ones with respect to mutations.

Recently new data appeared in literature that unambiguously prove, after some calculations, the thermodynamic direction of the biotissue development in the course of ontogenesis. For instance, by means of differential scanning calorimetry the relation was studied between the age of the collagen tissue of a rat's tail tendon and the temperature and heat of its denaturation [19]. Based on the study of about a hundred samples, it was found out that as the age of the tissue varies from 2 weeks to 2 years, its denaturation (melting) temperature increases by 6C - approximately from 58C to 64.5C. According to our estimation, the denaturation enthalpy variation, increases in this process from 6.0Cal/g to 7.6Cal/g . The thermal capacity variation corresponding to the transition of the biotissue from the native state to the denaturated one is = 0.096Cal/deg g ( ).

Using the data presented, one can easily, with the help of the Gibbs-Helmholz equation, which takes into account the heat capacity variation at a phase transition, calculate with a considerable accuracy (not accounting for the heat capacity variation with the increase of temperature) the Gibbs function variation corresponding to the supramolecular structure formation at a standard (reference) temperature, ( :

, (5)

Assuming, for example, T=298.2 K (25C) for the tissue of, say, a 2-year-old rat, we obtain:

For the tissue of a two-week-old animal .

Calculations carried out for different stages of the ontogenesis show that indeed, in accordance with the theory, the value of for the intact collagen of a rat's tail tendon tends to a minimum as the rat gets older. In the case under consideration it varies by value Note that a rough estimate, according to the approximate equation , yields the value (for standard temperature, T0=40C ). Variations of (and also of at the aging of the collagen tissue correlate with the changes in the amount of water, whose concentration in the tissue varies within the range of 78-58% weight units [20].

The absolute values of calculated here for the collagen tissue are smaller than the analogous values for the processes of some pure chemical substances condensation [5,21,22]. This contradicts neither the physical picture of the life phenomenon, nor other well-known facts [8,10,20,23,24].

There are grounds to suppose that the presented experimental results can be of greatest importance. They will stimulate new studies aimed at further verification of the fact that the Second Principle can be applied to the evolution of biological and other natural systems.

4. Conclusion

The existing experimental data allow to state that the macrothermodynamic (hierarchic thermodynamic) model of the living systems evolution can be applied to the real world: thermodynamics is the motive force of the evolution.

References

  1. Gladyshev G.P. (1988) Termodinamika i makrokinetika prirodnykh ierarkhicheskih processov (Thermodynamics and Macrokinetics of Natural Hierarchic Processes), Moscow, Nauka, 287.
  2. Gladyshev G.P. (1978) On the Thermodynamics of Biological Evolution, J.Theoret.Biol., 75, 425-441. (Preprint, Chernogolovka, Inst. Chem. Phys., 1977, May, 46).
  3. Gladyshev G.P. (1987) On the Macrokinetics and Thermodynamics of Natural Hierarchic Processes, Zhurn. Fizicheskoi Khimii, 61, No 9, 2289.
  4. Gladyshev G.P. (1993) Macrothermodynamics of Biological Evolution, J.Biol. Systems, 1, No 2, 115-129.
  5. Gladyshev G.P. (1994) The Motive Force of Biological Evolution, Vestnik RAN, 64, No 3, 221-228.
  6. Gladyshev G.P. (1995) On the Thermodynamic Nature of Biological Evolution, Izvestia RAN. Seria biol., , No 1, 5 -14. (a misprint in the paper title is due to the correctors mistake).
  7. Gibbs J.Willard, The Collected Works of J.Willard Gibbs, Ph.D.L.L.D., 1, Thermodynamics, 55-349. New York, London, Toronto: Longmans, Green & Co.
  8. Denbigh K.G. (1968) Theory of Chemical Reactors. M., Nauka, 22-23.
  9. Fox S.W. and Dose K. (1972) Molecular Evolution and the Origin of Life. Freeman.
  10. Tanford Ch. (1994) The Hydrophobic Effect and The Organization of Living Matter. In: Origins of Life. The Central Concepts. Ed. Deamer D.W., Fleischaker G.R. Jones and Bartlett Publishers, Inc. Boston-London, 233-239.
  11. Calvin M. (1969) Chemical Evolution. Oxford: At Clarendon Press.
  12. 12. Ponnamperuma C. (1972) The Origins of Life. N.Y.Dutton,.
  13. Stull D.R., Westrum E.F.Jr., Sinke G.C. (1969) The Chemical Thermodynamics of Organic Compounds. New York, London, Sydney, Toronto: John Wiley & Sons, Inc., (Russian Transl. 808)
  14. Gladyshev G.P. (1995) Thermodynamics and Biological Evolution, J.Biolog.Phys., 20, 213-222.
  15. Gladyshev G.P., Kitaeva D.Kh.(1995) On the thermodynamic Nature of Evolutionary Processes, Izvestia RAN. Seria biol., No 4.
  16. Denbigh K.G. (1989) Note on Entropy, Disorder and Disorganization, Brit. Jour. Phil. Sci., 40, 323-332.
  17. Denbigh K.G. (1989) The Many Faces of Irreversibility, Brit. Jour. Phil. Sci., 40, 501 -518.
  18. Shuster P. (1993) RNA Based Evolutionary Optimization, Origins of Life and Evolution of the Biosphere, 23, 373-391.
  19. Zereteli G.I., Belopolskaya T.V. (1994) Biofizika, 39, No 5, 793-794.
  20. Nikitin V.N., Perskii E.E., and Utevskaya L.A. (1977) Vozrastnaya I Evolutsionnaya Biokhimiya Kollagenovykh Struktur (Age and Evolutionary Biochemistry of Collagen Structures), Kiev: Naukova Dumka.
  21. Vakulichev L.V., Gladyshev G.P. (1989) On the Grounds of the Macrothermodynamic Model of Biological Evolution, Zhurn. Fizicheskoi Khimii, 63, No10,.2751-2756.
  22. Gladyshev G.P., Gladyshev D.P. (1994) On the Model of the Biological Systems Evolution, Izvestia RAN. Ser.biol., No 1, 14-19.
  23. Aleksandrov V.Ja. (1975) Kletki, makromolekuly I temperatura (Cells, Macro-molecules, and Temperature). Leningrad: Nauka,. 330 p.
  24. Cantor S.R., Shimmel P.R. (1980) Biophysical chemistry, part 3, San Francisco: W.H.Freemen.

Academy
Order of Glory


Institute of Physico-Chemical Problems of Evolution


Commmerce and Law
Institute

© . .
© AVE- ( ):, .


Rambler's Top100