So, according to the theory of absolute speeds the break of С-1H-bonds can occur faster, than С-2H-bonds (C-2H-bonds are more durable than C-1 , mobility of an ion 2H+ is less, than mobility of 1Н+, the constant of ionization 2Н2О is a little bit less than ionization constant of 2Н2О. Thus, in principle, the structures of [U -2H]labeled macromolecules may to be more friable that those are forming in ordinary H2O. But, nevertheless, the stability of [U -2H]labeled macromolecules probably depending on what particular bond is labeled with deuterium (covalent bonds -C2H that causing the instability or hydrogen bonds causing the stabilization of conformation of macromolecules via forming the three-dimentional netwok of hydrogen(deuterum) bonds in macromolecule) and what precise position of the macromolecule was labeled with deuterium. For example, the very valuable and sensitive for deuterium substitution position in macromolecule is the reactive center (primary isotopic effects). The non-essential positions in macromolecule are those ones that situated far away from the reactive center of macromolecule (secondary isotopic effects). It is also possible to make a conclusion, that the sensitivity of various macromolecules to substitution on 2Н bears the individual character and depending on the structure of macromolecule itself, and thus, can be varried. From the point of view of physical chemistry, the most sensitive to replacement of 1Н+ on 2H+ can appear the apparatus of macromolecular biosyntesis and respiration system, those ones, which use high mobility of protons (deuterons) and high speed of break of hydrogen (deuterium) bonds. From that it is posible to assume, that the macromolecules should realize a special mechanisms (both at a level of primary structure and a folding of macromolecules) which could promote the stabilizition of the macromolecular structure in 2H2O and somewhat the functional reorganization of their work in 2H2O.
A principal feature of the structure of such biologically important compounds as proteins and nucleic acids is the maintenance of their structure by virtue of the participation of many hydrogen bonds in macromolecule. One may expect that the hydrogen bonds formed by of many deuterium will be different in their energy from those formed by proton. The differences in the nuclear mass of hydrogen and deuterium may possibly cause disturbances in the DNA-synthesis, leading to permanent changes in its structure and consequently in the cells genotype. The multiplication which would occur in macromolecules of even a small difference between a proton and a deuteron bond would certainly have the effect upon its structure.
The sensitivity of enzyme function to structure and the presumed sensitivity of nucleic acids function (genetic and mitotic) to its structure would lead one to expect a noticeable effect on the metabolic pattern and reproductive behavior of the organism. And next, the changes in dissociation constants of DNA and protein ionizable groups when transfer the macromolecule from water to 2H2O may perturb the charge state of the DNA and protein. Substitution of 1H for deuterium also affects the stability and geometry of hydrogen bonds in apparently rather complex way and may, through the changes in the hydrogen bond zero-point vibrational energies, alter the conformational dynamics of hydrogen (deuterium)-bonded structures within the DNA and protein in 2H2O.
5. CONCLUSION
The successful adaptation of organisms to high concentration of 2H2O will open a new avenues of investigation with using [U- 2H]labeled macromolecules could be isolated from these organisms. For example, fully deuterated essential macromolecules as proteins and nucleic acids will give promise of important biological, medical and diagnostical uses. Modern physical methods of study the structure of [U- 2H]labeled macromolecules, particularly three-dimentional NMR in a combination with crystallography methods, X-ray diffraction, IR-, and CD- spectroscopy should cast new light on many obscure problems concerning with the biological introduction of deuterium into molecules of DNA and proteins as well as the structure and the function of macromolecules in the presence of 2H2O. The variety of these and other aspects of biophysical properties of fully deuterated macromolecules in the presence of 2H2O remain an interesting task for the future.
First,I hope that the structural and the functional studies of [U- 2H]labeled macromolecules can provide us to the useful information about a many aspects of the synthesis of fully deuterated macromolecules and their biophysical behaviour in 2H2O.
Second,the extensive body of available structural data about a cell protection system (at the level of the structure and the functioning of [U- 2H]labeled DNA and enzymes) will also form the basis for a particularly useful model for the study of biological adaptation to 2H2O in aspect of molecular evolution of macromolecules with difined isotopic structures.
Finally, we also believe, the research can make a favour the medicine and biotechnology, especially for creating a fully deuterated analogues of enzymes and DNA having something different properties then the protonated species and working in the presence of 2H2O.
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