Silicon [ isotope ? ] Life ????
berezin at MCMAIL.CIS.MCMASTER.CA
Tue Apr 15 10:58:07 EST 1997
On 15 Apr 1997, William Bains wrote:
< ... snip ... >
> One speculative idea (I think attributable to Larry Niven, following
> Cairns' ideas on the mineral origins oflife) is that life *was* originally
> silicon based, but was eradicated by the oxygen-producing carbon biosphere
> we have today. Under this scenario, oxygen was originally produced as a
> toxic secondary metanolite, and its central role in energy metabolism is a
> relatively recent adaptation. This, of course, does not address any of the
> problems with using silicon in the first place.
> William Bains
Interesting idea. Reposting earlier article
(1988) were a somewhat similar suggestion
(speculation) was based on isotopic permutations
of C-12 and C-13 ('isotopic biology')
ISOTOPIC RANDOMNESS AS A BIOLOGICAL FACTOR
Alexander A. BEREZIN
Department of Engineering Physics,
McMaster University, Hamilton,
Ontario, Canada, L8S 4L7
We discuss an alternative source of randomness
originating at the atomic level due to the
diversity of stable isotopes. This randomness
could contribute to mutation mechanisms through
atomic scale variations of bond lengths and
strengths, differences in the reaction rates, etc.
In terms of purposeful experimentation, isotopic
replacements in living organisms give an
independent parametrization which allows to
correlate the global biological variables with
the level of individual atoms. We review the work
done so far, and suggest some further experimental
possibilites by analogy with some isotopic
effects and isotopic structuring in solid state
Key words: Stable isotopes, isotopic randomness,
isotopic replacements, carbon-14,
Earlier I discussed the model of alternative genetic
code based on combinations of stable isotopes
(Berezin, 1984 a). The concept was later developed
further (Berezin, 1986). Here I would like to
discuss a yet another line of research in fundamental
and applied biology which somehow seems to be
underestimated. The subject is the purposeful
shift of isotopic abundancies of stable isotopes
in living organisms in order to establish some
physiological and behaviorial correlations with
In the present paper we suggest some types of
experiments on isotopic replacements in living
organisms. To some extent, the possibilities to
be discussed here arose by analogy with some less
known manifestations of isotopic randomness and
isotopic structuring in solid state physics. We
should stress that the subject of isotopic
replacements in biology should not be confused
with studies on radioactive and stable trace
isotopes which constitute one of the pillars of
nuclear medicine and will not be discussed in
the present paper.
Some isotope-related effects in biology
It is known, that physical characteristics of
isotopically pure substancies are generally quite
close, but not exactly the same. For example,
there are some differences (about 1 part per
several thousand) in equilibrium lattice constants
of natural (i.e. isotopically blended) and
isotopically purified crystals; the thermodynamical
characteristics of heavy water are not the same as
light water (e.g. critical temperature is 643.9
and 647.1 K respectively), etc. We live in the
environmenrt of fixed isotopic ratios. For example,
carbon is 98.9 % carbon 12-C and 1.1 % 13-C,
nitrogen is mostly 14-N, oxigen is 16-O, etc.
At the same time, minority stable isotopes
(13-C, 15-N, 17-O, 18-O, etc.) are also have
their share, they are relatively easily obtainable
as pure isotopes, and nonradioactive. One may ask
what will happen with a living organism if we
intentionally shift naturally occuring isotopic
ratios ? Will such change affect the rate of
metabolism, aging processes, adaptability, etc.?
Previously several authors discussed various
unexpected roles which isotopes can play in life
matters. Mann and Primakoff (1981) have indicated
the possible origin of biological chirality
(asymmetry between left and right) from beta-decay
of isotopes 14-C and 40-K. The present author have
mentioned 14-C decays as a possible contributing
factor of carcinogenesis and genetic mutations
(Berezin, 1984 b) while Keswani (1986) pointed
on random disintegrations of 14-C as a likely
source of spontaneous and unpredictable
triggerings of brain processes (e.g. sudden
It is known that microorganisms could shift
isotopic abundancies of heavier elements, e.g.
32-S and 34-S (Thode, 1980). These shifts,
however, are due to some tiny differences in
reaction rates leading to some preference in
isotope incorporation, gravitational (weight)
fractionation, etc. The observed shifts usually
do not exceed 1 % in relative change of isotopic
proportions in comparison with standard
abundancies. At the same time, some reactions
sensitive to nuclear magnetic moment (NMM) could
lead to a much greater segregation efficiency.
While the mass difference between stable isotopes
is at best a few per cent (except, of course,
hydrogen & deuterium pair) the difference of NMM
could be much more drastic. For instance, 12-C has
zero NMM while 13-C has a non-zero NMM and,
consequently, responds very differently to a
magnetic interaction. Using reactions involving
magnetic (hyperfine) interactions the single-stage
segregation efficiency of about 50 % for 13-C
and 12-C has been obtained (Epling and Florio,
Numerous studies on heavy water enrichment in
living organisms have been undertaken since
1930-s starting almost immediately after the
discovery of deuterium in 1932. In his review
Katz (1960) gives interesting examples of
deuteration effects on mice and rats showing
that both animals cannot survive replacement of
more than about one-third of the body water by
D2O. Most of the changes induced by deuteration
(e.g. loss of reproductive capacity) are
reversible upon the replacement of deuterium
back by ordinary hydrogen. Katz (1960) have
also mentioned the possibility of isotopic
replacements for stable isotopes of C, O, N
and S. The actual experiments on isotopic
replacements in animals for elements heavier
than hydrogen have been reported for 13-C
(Gregg et al., 1973) and 18-O (Wolf et al. 1979).
Both experiments succeeded in replacing of
about 60 % of all body carbon or oxygen in mice
by 13-C or 18-O (their normal isotopic abundance
is 1.1 % and 0.2 %, respectively). No
pathalogical changes have been found in any
organs. However, I did not find any specific
studies of how such metamorphosis affects
various physiological responses. Several
experimental suggestions are mentioned in
the next Section.
Some possibe experiments on isotope effects
The presence of the majority of elements in
two or more stable isotopes is one of the prime
facts of Nature. Therefore, even from the general
point of view it seems unlikely that the diversity
of stable isotopes could remain totally irrelevant
to Earth's biology. Here I will list several
lines of possible studies, complimentary to
those which have been mentioned in the preceeding
paragraph. It should, of course, be kept in mind
that the following list inevitably has some degree
of subjectiveness and speculativeness.
1) Combinations of isotopes.
An obvious extension of studies on 13-C and 18-O
mice (or for that matter on simplier organisms,
e.g. drosophila) would be a combination of two
or more stable isotopes in variable ratios. For
instance, the cummulative effect of triple
replacement 12C -> 13C, 16O -> 18O and 14N -> 15N
could lead to much stronger effects than either
of them separately.
2) Thermal regulation.
Isotopic replacement of C, O and N changes
densities of all structures by several per cents.
Diffusivities and other kinetic characteristics,
especially those related with tunneling, could
change even more strongly. Thus, isotopic
replacements may lead to a "fine tuning" of
thermal regulation mechanisms in mammalia.
Similarly, isotopic shift can change a speed
of propagation of nerve impulses and other
3) Magnetic effects.
Magnetic effects in biology are generally
considered to be subtle, but could be of
importance for some specific cases (e.g.
orientation of birds, responce of some
microorganisms, etc). In view of the differences
in NMM between 12-C and 13-C (see above),
magnetic experiments on 13C-organisms may
lead to non-trivial insights.
4) Isotopic fluctuations.
Any carbon chain contains 1 % of 13-C atoms.
This, in fact, is a very large concentration.
If similar concentration relates to an impurity
in crystal this will change its properties in a
noticable way (i.e. Rayleigh scattering of light
on isotopic fluctuations, modification of thermal
conductivity, etc.). Same applies to minority
isotopes of oxygen and nitrogen. Performance
of DNA, for example, can be affected by positional
fluctuations of minority isotopes. This, in turn,
could contribute to mutability and, consequently,
one may suggest that isotopic randomness may act
as an additional genetic factor. Fluctuations
are proportional to the square root of number
of particles. Therefore, the effective (average)
size of isotopic fluctuations will be appreciably
different if, say, the concentration of 13-C is
changed from 1 % to 0.1 % (in this example the
size of fluctuation will increase by 10^(1/3) =
2.15, if the distribution is uniform in 3 dimensions;
for low dimensional systems, e.g. carbon chains,
the size scales differently). One may think,
therefore, of some kind of "inverse" experiments
to those done with 13-C and 18-O mice (Gregg et al.,
1973; Wolf et al., 1979). Namely, the use of
major isotopes (12-C, 16-O, 14-N) but purified
from the admixture of minor isotopes could
suppress fluctuations and this may result in
"improving" of genetic stability
5) "Isotopic indeterminism".
We can also note that isotopic randomness by
itself creates an additional dimension in the
genetic domain because the nominally identical
molecules (e.g. symmetrical spirals of DNA) are,
in fact, never the same. Natural isotopes
of H, C, N, O, etc. are randomly distributed
among the correspondingly equivalent positions.
The number of differnt combinations of isotopes
in the structurally same molecule is practically
uncountable and leaves far behind the number of
electrons in the whole Universe. It is possible
to speculate that this "isotopic uniqueness" of
each multi-atomic structure could serve as an
immanent (and virtually unexhaustable) resource
of unpredictability and individuality in actual
living beings. In this respect isotopic
randomness could act as a counterpart (or
competitor) of the "standard" quantum mechanical
6) Positional correlations.
As a supplement to item #5, it is also conceivable
to think of possible positional correlations of 12-C
and 13-C during DNA reduplication. Namely, does
a secondary spiral has any trace of the individual
12C-13C pattern of the prime spiral ? The
establishing of even a weak positional correlation
would certainly be of interest, and experiments
with organisms enriched by 13C to a variable
degree (i.e. 10 %, 20 %, etc) could provide a
key for such studies.
To summarize, we discussed the question of the
effects of isotopic replacements in biology.
Isotopic diversity is known to affect various
physical and chemical properties of solids
(e.g. Berezin, 1984c). Similarly, it likely can
lead to some non-trivial manifestations
in biological domain. It is quite possible that
substantial differnces may occur for only some
selected properties (e.g. radiation resistance)
while other characteristics may not change
drastically. We have stressed here the potential
of studies of changes of isotopic ratios in
biological systems. This gives a new parameter (in
fact, a whole range of continuosly changing
parameters) to be correlated with global biological
There is, of course, a massive amount of
biological and medical studies on radioactive and
trace isotopes or on tiny variations of isotopic
ratios in living tissues. What we are discussing
here, however, is related to the _stable_ isotopes
for which isotopic ratios are purposefully shifted
in significant proportions and in the entire
organism. The possibility of using isotopic ratios
to control various processes could even have long
range practical implications in the developing
of "isotopic drugs", etc. In view of the above, it
seems likely that the isotopic option is worth of
emphasizing, further thinking and experimentation.
BEREZIN, A.A., 1984 a. Isotopic Biology.
Il Nuovo Cimento, 3D, 914-916.
BEREZIN, A.A., 1984 b. Inherent genetic
instability due to the presence of 14C-atoms
in information bearing structures. Bulletin
of the American Physical Society, 29, 635.
BEREZIN, A.A., 1984 c. Isotopic disorder as
a limiting factor for the mobility of charge
carriers. Chemical Physics Letters,
BEREZIN, A.A., 1986. On the mechanisms of
information transfer inisotopic biology.
Kybernetes (U.K.), 15 , 15-18.
EPLING, G.A. & FLORIO, E., 1981. Isotopoe
enrichment by photolysis on ordered surfaces.
Journal of the American Chemical Society,
GREGG, C.T., HUTSON, J.Y., PRINE, J.R.,
OTT, D.G. & FURCHNER, J.E., 1973.
Substantial replacements of mammalian body
carbon with carbon-13.
Life Sciences, 13, 775-782.
KATZ, J.J., 1960. Chemical and biological
studies with deuterium.
American Scientist, 48, 544-580.
KESWANI, G.H., 1986. Carbon-14 in the brain
and other organs: chance within. Speculations
in Science and Technology, 9, 243-244.
MANN, A.K. & PRIMAKOFF, H., 1981. Chirality
of electrons from beta-decay and the
left-handed asymmetry of proteins.
Origins of Life, 11, 255-265.
THODE, H.G., 1980. Sulphur isotope ratios
in late and early precambrian sediments and
their implications regarding early environments
and early life. Origins of Life, 10, 127-136.
WOLF, D., COHEN, H., MESHORER, A., WASSERMAN,
I. & SAMUEL, D., 1979. The effect of 18-C on the
growth and reproduction of mice. In "Stable
Isotopes", E.R. Klein and P.D. Klein (eds), Acad.
Press, NY, S.Francisco, London, pp. 353-360.
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