Evolution of Form by Selection for Fitnesss w Fig

8/14/2019 Evolution of Form by Selection for Fitnesss w Fig

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Evolution of Form by Selection for Fitness.

Darwinian evolution of silica sols may explain how

various fundamental aspects of silica sol chemistry are

identical to the fundamental requirements of biological systems.

It has been pointed out that while the unique ability of DNA to store and transmit information iscommonly held to be the basis of biology that this assumption might be incorrect has been pointed out

by the DNA expert Lima-de-Faria (1). A more useful working definition might be the ability of

particles, even inorganic particles including those which are not overtly crystalline and which possess

some kind of supramolecular structure, to self assemble in such a way as to reproduce themselves true

to form.

Different species of silica sols are known to produced by slight variation in the conditions of self

assembly of silicic acid obtained from depolymerisation of silicate minerals present in rocks (1)(2).

Each sol species might, as suggested by studies conducted industrial laboratories, be capable of

reproduction true to form (1) and also may be capable of evolution by slowly altering its form

eventually to generate a new species from the old. Therefore there are two ways of generating a new

species of silica sol, one the original primitive way caused by effect of random impurities on the selfassembly of silicic acid and the other the evolution of new species from an old species. This situation

(if its occurrence can be substantiated by further experimentation) is clearly highly relevant to biology.

Competition between species for nutrient (low molecular weight silicic acid) will tend to the favour

more efficient systems which will over long periods of time will eliminate the less efficient systems (a

sort of Ostwald ripening). The efficiency criteria are those that increase the efficiencies for growth and

reproduction processes.

Biological systems seem to have increased in complexity over long periods of time being able to

counteract the usual tendency of complexity as measured by entropy to diminish with time (at least for

closed systems but open systems such as biological cells are not obliged to increase in complexity with

time). This ability to spontaneously become more complex can be assumed to have also been present

in the pre-biological systems which evolved into biological ones. The self assembly process illustratedby silicic acid seems the most likely to be a natural example of this process (similar self assemblies of

other systems (1a) including inorganic colloids, are known, but a uniquely greater ability of the

tetrahedrally-linked polysilicate structures having similar bond strengths in all four directions seems to

optimise the possibility of generating random networks (3) (a possible and highly relevant exception is

the formation of aggregates of (hydrogen-bonded) water molecules which however would be expected

to be less stable but might be stabilised by interactions with silicate polymers (4); an argument can be

developed from this that those chemical polymer systems which interact in this way with water

molecule aggregates are also favoured by biology).

The silicic acid generated silica sol colloids also seem to demonstrate a less than crystalline order

rather than (or in combination with) a totally random (glass) type of non-order. The occurrence of such

(deterministic chaotic?) structures seems to be an important part of the required architecture of those

structures which are capable of both reproducing (like crystals) and of evolving in a biological manner.

Reproduction of crystal form is of course well known for the seeding of crystal structure, but such

higher order crystal structures (which easily diffract X-rays in conventional tests) seem to be strongly

inhibited from spontaneously evolving into other structures which can benefit cells engaged in

Darwinian evolution. The relative stability of crystal structures may simply be due to the restraints of

locked-in structure in any well defined 3D solid crystalline material. The structural retrains will be less

for a liquid crystal structure and these are more likely to have biological roles (cf. their occurrence in

membranes etc).

The absolute rejection of the physico-chemical properties of 3D crystalline order by biology seems a

fundamental principle governing the physical behaviour of all biological systems and those pre-

biological systems which were capable of evolving into full biological systems. In order to restrain the

formation of crystals (e.g. in commonly supersaturated solutions of calcium salts present in biological

cells) a sophisticated system of inhibition of crystallisation seems to be utilised by organism and any

failure of this system will tend to create an impetus for pathological conditions (5).


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The maintenance of non-crystalline order could also be encouraged by the use by biological systems of

other devices for preventing crystallisation. One of these might be the utilisation of range of random

polymer systems which are inclined to generate flexible rubbers by being endowed with the natural

steric hindrance (caused by a random distribution of monomer units in the polymer) for crystal

formation (which are exemplified by those polymer systems found in present day biology such as

proteins and nucleic acids; the utilisation by biology of specific sequences of amino acids and nucleic

acids to carry out specific tasks masks for biologists the background pure chemical preference of suchsystems (in a non-biological environment) for random sequence formation). Random sequences will

be formed when a growing polymer structure adds on new monomer units with equal probability (a

situation (isokinetic and isoequilibrium reactions) which clearly arises if the rates of the reactions of the

growing polymer with different monomers etc. are exactly the same) such a perhaps highly fanciful

situation could clearly lead to complete randomness. The generation of such equality of reaction rate

however can be seen to easily arise from the, poorly understood, but experimentally well founded

(presumably thermodynamically related) rule which apparently applies to a selected range of chemical

reactions where the usual requirements of the second law of thermodynamics seems to be replaced by

another law governing a strict requirement for entropy and enthalpy compensation (presumably in the

transition state complex) producing rate constants with compensated temperature dependent and

temperature independent terms in the usual formulation of the rate constant. This altered law may also

tend to favour the generation rather the degeneration of order over long periods of time. Such a

situation where sets of reaction rates become exactly the same is set up by the collapse of the usualrules of chemical kinetics which are replaced by the principles which apply to entropy-enthalpy

compensated systems. The compensated rate constant phenomenon is applicable to numerous types of

chemical reactions (reviewed by Leffler for such chemical reaction rate constants which were known in

1955 (6)) has been something an annoyance to theoretical physical chemists who find it difficult to

explain, and thereby have a tendency to dismiss its significance.

(A preliminary assessment seems to confirm that the preferred temperature for all biology- similar to

human body temperature could be a common one for those systems of related chemical reactions which

display the compensation effect (where any change in entropy is balanced by a proportional change in

enthalpy in the transition state complex model of chemical reaction rate theory). Compensated

entropy-enthalpy behaviour might also be applicable to the supramolecular structure behaviour of

liquid water which is by far the largest chemical structure type associated with biological activity).

Silica sols are able to arise in systems comprising almost all water to almost totally dehydratedsystems. Silica sols are useful for preparing catalysts . There is an enhancement of the catalytic

activity of dopants (e.g. transition metals and basic catalysts actions of e.g. Na+).

References).

(1) Lima-de Faria A Evolution without selection: form and function by autoevolution Elsevier 1988

(2) Grant D et al. Med Hypoth 1992 38 46-48; cf Brit Pats cited therein

(2a) e.g. Balazs AC and Epstein IR Science 2009 325 1632-1635

(3) Iler RK The chemistry of silica.. Wiley-Interscience 1979

(4) Grant D J Inorg Nucl Chem 19667 29 69-81

(5) Bernal JD Symp Soc Exptl Biol 1965 19 17-32

(6) Grant D et al.

(7) Med Hypoth 1992 38 49-55

(8) Leffler JE J Org Chem 20 1955 1202-1231

(9) Austen KRJ et al., Biopolymers 1988 27 139-155

(10) Norton IT 1983 JCS Faraday Trans 39 2501-2519

Footnote

The significance of the relationship (often strictly linear) between the temperature-dependent and

temperature-independent factors in compensated rate processes suggests that for these series of

reactions, entropy change (the temperature independent component) in the formation transition state

complex is not well defined or cannot be defined at all. In the latter case the second law of

thermodynamics can therefore not be directly applicable to such systems.

Compensated systems near their isokinetic temperature will tend to increase in complexity with time in

breach of the conditions of the second law of thermodynamics.

This reason for this is a mystery (and has often been dismissed as an artefact of experimentation).

But this is the ultimate basis of life.


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For rate constants in he usual format rate constant C= A.exp(-E/RT) (a specific chemical reation rate

constant in the usual format, A is the pre-exponential factor, E is the Arrhenius activation energy, R is

the gas constant T is the absolute temperature. When the Arrhenius rate expression logC=logA

E/2.303RT is compared for a series of reactions by plotting log A against E quite often a linear

relationship similar to that shown is revealed where the relationship is found to be valid

logA=E/2.303RTs) +log Co + (const); the value of the (const) is often = 0; the parameter Ts is theisokinetic temperature where all reactions of the class considered occur at the same rate (Co).

The rate constant expression may be rewritten, according to the transition state complex theory for

chemical reaction, in terms of entropic and enthalpic changes associated with a transition state complex

form in equilibrium amounts C = (kT/h)exp( S*/R)exp(- H*/RT). The existence of compensation

indicates linkage between allow entropy and enthalpy changes in the equilibria producing the activated

transition state complex. The juxtaposed particle and wave-like nature of matter may, however,

actually be how this arises.

Examples of Chemical Kinetic Parameter Entropy Enthalpy Compensation.

Is the occurence of allowable entropy and enthalpy change compensation related to how living things

self assemble? The kinetics of nucleation of supramolecular structure in anionic polysaccharides seems

to be a well-defined example of the numerous examples of compensated behaviour which have been

noted to occur with biopolymer solutions (i.e. aqueous solutions the unique chemical and physicalproperties of liquid water may assist here). A plot is shown below of the apparent enthalpy-entropy

compensataion effects which underlie the abilities of a range of salts to modifty the nucleation of phase

change of kappa and iota carrageenans are shown in the taking rate data from the literature (n.b. the

authors of the reports used (7,8) did not discuss the occurrence of compensation in their results).

During the authors industrial researches studies in 1968 rate constant data were collected from

Chemical Abstracts for chlorinated hydrocarbon dehydrochlorinations). Surprisingly even when

including both apparently homogeneous and heterogeneous reactions, all the data then available tended

to the same curve (shown below) {1 kcal = 4.186kJ}. It should be noted that analogous

dehydrobromination reactions seemed not to be compenstated. One possible explanation is that some

unknown effect of surfaces to which dehydrochlorinations ot dehydrobromination are especially

susceptible (but not currently evidenced for this however). Dehydrochlorinations might really be glass

surface base catalysed reactions or this might apply to the dhydrobrominations. Or a selective catalyticeffect of silicate glass surfaces, better for accomodating Cl-C bonds than for accomodating Br-C


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bonds? Perhaps glass surface catalysis is more common than thought (e.g. but applies only to those

relatively large number of reaction types for which compensation effects occur).

The compensation effect gives rise to an isokinetic temperature where all reaction rates for e.g. the

series of dehydrochlorinations become the same, i.e. the usual factors which affect the rate of chemical

reactions such as steric effects of the R groups (representing organic structures) in the

R1R2-CH-CCl-R1R2 (A) structure

are unable to influence the reaction rate. This situation, although it is only strictly true at the precise

isokinetic temperature but approximately true in the isokinetic temperture region, defies the usual logicof organic chemistry and hence suggests that what is actually being studied kinetically is not, e.g.,

structure (A) but something like structure (B)

R1R

2-CH-CCl-R

3R

4 -> R

1R2-CH==C-R3R4A || B ->R11R22C=CR33R4 +HCl

Cl Na+

-Si-O-Si-O (glass)+ (Si-OH)(+water)

The silicate structures at a glass or sol/gel surface are expected to be of a subcrystalline or entirely

amorphous order and exist in a range of structures of differing catalytic activities giving rise to a range

of individual reaction rates. Fitting of different A molecule sizes into appropriate slots in the catalytic

surface (different in size and shape for each case of different Rs) at or near the isokinetic temperature

could produce the observed lack of apparent dependence of the overall dehydrochlorination rate on thechemical nature of the R groups.

It might however have been expected that such overt surface effects would have been detected by the

skilled kineticists who reported these reaction rate constants. Therefore some indirect subtle surface

effect which escaped their detection be the origin of the effect (an effect of occluded surface water?)

Biological processes may have started off in the ancient earth at amorphous silica surfaces as

hypothesised by Grant et al (1) and this could point to a role for the unique surface activity and

associated water of silicates in promoting compensated reaction kinetics and in turn an apparent

tendency to ignore the second law of thermodynamics for long term alteration of biological structures.

Example of the control of chemical reaction rates by glass surfaces


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Ce(IV) sulphate/ sulphuric acid was a reagent in traditional oxidation reduction quantitative wet

solution analysis but auto-reduction of Ce(IV) (by oxidation of H2O to H+ and O2by a radical chain

process possibly initiated from .OH radicals generated at the glass surface of the flask) occurs for usual

analytical chemist consideration, above 40C. The existence of the auto-reduction reaction was

however, often obscured by a common process of deactivation of the catalytic surface by O2 as well as

a polymeric Ce(III) oxide product so the apparent occasional occurrence of the process had been a

puzzle.Adding additional glass surfaces or by chemical cleaning the deactivated glass surface promoted the

effect. The radical chain reaction nature of the auto-reduction process produced a sharp termination of

the process upon deactivation of the surface (Grant D 1964 J Inorg Nucl Chem 26 337-346)

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Evolution of Form by Selection for Fitnesss w Fig