polyoxometalate-based life
Polyoxometalate-based life is hypothetical life whose chemical building blocks are polyoxometalates – ions built up from a framework of several different transitional metal anions linked together by oxygen atoms and possibly also containing other atoms such as phosphorus or silicon. The possibility of polyoxometalate-based life has been explored experimentally by Lee Cronin at the University of Glasgow. Upon mixing polyoxometalates in solution Cronin has observed the chemicals self-assembling into miniature bubbles, which he has called inorganic chemical cells, or iCHELLs. By altering the metal oxide backbone of the bubbles, the bubbles can be given some of the characteristics of the membranes of natural cells. For example, an oxide with a hole as part of its structure becomes a porous membrane, selectively allowing chemicals in and out of the cell according to size, just like the walls of biological cells. Cronin's team has also made bubbles within bubbles, creating compartments that mimic the internal structure of living cells. The iCHELLs can also be given something akin photosynthetic apparatus by linking some oxide molecules to light-sensitive dyes.
Perhaps the biggest hurdle facing any would-be life based on polyoxometalates would be acquiring the ability to replicate using an information-storing molecules like DNA.