Isobiology: A Variational Principle for Exploring Synthetic Life.

Most developments in synthetic biology try to depart from life as we know it, attempting to create orthogonal constructions. Here, following a variational principle, I try to explore how slight changes in the buildup of cells reveal critical features of life's physics. In a first section, I suggest that we use stable isotopes of the atoms of life to see how living cells fare, beginning with life in heavy water. Subsequently, isotopes of the other main biogenic atoms are suggested as an extension of the variational principle, despite their likely very small influence on the course of biological activity. Finally, two atoms of the second row of Mendeleev's table, boron and fluorine are explored as a further extension of the principle. The use of the former is still in its infancy, whereas the latter, based on existing fluorinases, could open the door to a more general use of halogens in synthetic biology.
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