Effect On Biological Systems
Different isotopes of chemical elements have slightly different chemical behaviors, but for most elements the differences are far too small to use, or even detect. For hydrogen, however, this is not true. The larger chemical isotope-effects seen between protium (light hydrogen) versus deuterium and tritium manifest because bond energies in chemistry are determined in quantum mechanics by equations in which the quantity of reduced mass of the nucleus and electrons appears. This quantity is altered in heavy-hydrogen compounds (of which deuterium oxide is the most common and familiar) more than for heavy-isotope substitution in other chemical elements. This isotope effect of heavy hydrogen is magnified further in biological systems, which are very sensitive to small changes in the solvent properties of water.
Heavy water is the only known chemical substance that affects the period of circadian oscillations, consistently increasing the length of each cycle. The effect is seen in unicellular organisms, green plants, isopods, insects, birds, mice, and hamsters. The mechanism is unknown.
To perform their tasks, enzymes rely on their finely tuned networks of hydrogen bonds, both in the active center with their substrates, and outside the active center, to stabilize their tertiary structures. As a hydrogen bond with deuterium is slightly stronger than one involving ordinary hydrogen, in a highly deuterated environment, some normal reactions in cells are disrupted.
Particularly hard-hit by heavy water are the delicate assemblies of mitotic spindle formation necessary for cell division in eukaryotes. Plants stop growing and seeds do not germinate when given only heavy water, because heavy water stops eukaryotic cell division. The deuterium cell is larger and a modification of the direction of division. The cell membrane also changes, and it reacts first to the impact of heavy water. In 1972, Henry Crespi and Joseph Katz from USA demonstrated that the increase of the percentage content of deuterium in water reduces plant growth. Vitaliy Shevtz, Oleg Mosin, Dmitriy Skladnev (Russia) and Ignat Ignatov (Bulgaria) conduct research and analyses on the growth of microorganisms in artificial conditions of a heavy hydrogen environment. In this environment, all the hydrogen atoms of water are replaced with deuterium ones. This is one of the interesting biological phenomena. With over 50% of deuterium in the water molecules, plants die. Experiments conducted by Skladnev, Mosin et al. show that microorganisms can live in 98% heavy water.
It has been proposed that low doses of heavy water can slow the aging process by helping the body resist oxidative damage via the isotope effect. A team at the Institute for the Biology of Ageing, located in Moscow, conducted an experiment to determine the effect of heavy water on longevity using fruit flies and found that while large amounts were deadly, smaller quantities increased lifespans by up to 30%.
Read more about this topic: Heavy Water
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