Thermosynthesis is a theoretical mechanism proposed by Anthonie Muller for biological use of the free energy in a temperature gradient to drive energetically uphill anabolic reactions. It makes use of this thermal gradient, or the dissipative structure of convection in this gradient, to drive a microscopic heat engine that performs condensation reactions. Thus negative entropy is generated. The components of the biological thermosynthesis machinery concern progenitors of today's ATP synthase, which functions according to the binding change mechanism, driven by chemiosmosis. Resembling primitive free energy generating physico-chemical processes based on temperature-dependent adsorption to inorganic materials such as clay, this simple type of energy conversion is proposed to have sustained the origin of life, including the emergence of the RNA World. For this RNA World it gives a model that describes the stepwise acquisition of the set of transfer RNAs that sustains the Genetic code. The phylogenetic tree of extant transfer RNAs is consistent with the idea.
Thermosynthesis may still occur in some terrestrial and extraterrestrial environments. However, no organisms are known at present that use thermosynthesis as a source of energy, although it is possible that it might occur in extraterrestrial environments where no light is available, such as on the subsurface ocean that may exist on the moon Europa. Thermosynthesis also permits a simple model for the origin of photosynthesis. It has moreover been used to explain the origin of animals by symbiogenesis of benthic sessile thermosynthesizers at hydrothermal vents during the Snowball Earths of the Precambrian. Preliminary experiments have started to attempt to isolate thermosynthetic organisms.
A Dutch biochemist and physicist Anthonie Muller wrote many papers on thermosynthesis since 1983. He defined thermosynthesis as: "Biological heat engines working on thermal cycling." also as: "Theoretical biological mechanism for free energy gain from thermal cycling, tentatively stated as the energy source for origin of life."
The thermosynthesis concept, biological free energy gain from thermal cycling, is combined with the concept of the RNA World. The resulting overall origin of life model suggests new explanations for the emergence of the genetic code and the ribosome. It is proposed that the first protein named pF(1) obtained the energy to support the RNA World by a thermal variation of F(1) ATP synthase's binding change mechanism. It is further proposed that this pF(1) was the single translation product during the emergence of the genetic machinery. During thermal cycling pF(1) condensed many substrates with broad specificity, yielding NTPs and randomly constituted protein and RNA libraries that contained self-replicating RNA. The smallness of pF(1) permitted the emergence of the genetic machinery by selection of RNA that increased the fraction of pF(1)s in the protein library: (1) an amino acids concatenating progenitor of rRNA bound to (2) a chain of 'positional tRNAs' linked by mutual recognition, and yielded a pF(1) (or its main motif); this positional tRNA set gradually evolved to a set of regular tRNAs functioning according to the genetic code, with concomitant emergence of (3) an mRNA coding for pF(1).
- Anthonie W.J. Muller (1983). "Thermoelectric energy conversion could be an energy source of living organisms". Physics Letters A 96 (6): 319–321. Bibcode:1983PhLA...96..319M. doi:10.1016/0375-9601(83)90189-5.
- Anthonie W.J. Muller (1993). "A mechanism for thermosynthesis based on a thermotropic phase transition in an asymmetric biomembrane". Physiological Chemistry and Physics and Medical NMR 115: 95–111.
- Anthonie W.J. Muller and Dirk Schulze-Makuch (2006). "Sorption heat engines: simple inanimate negative entropy generators". Physica A 362 (2): 369–381. arXiv:physics/0507173. Bibcode:2006PhyA..362..369M. doi:10.1016/j.physa.2005.12.003.
- Anthonie W.J. Muller (1995). "Were the first organisms heat engines? A new model for biogenesis and the early evolution of biological energy conversion". Progress in Biophysics and Molecular Biology 63 (2): 193–231. doi:10.1016/0079-6107(95)00004-7. PMID 7542789.
- Anthonie W.J. Muller (1996). "The thermosynthesis model for the origin of life and the emergence of regulation by Ca2+". Essays in Biochemistry 31: 103–119. PMID 9078461.
- Anthonie W.J. Muller and Dirk Schulze-Makuch (2006). "Thermal energy and the origin of life". Origins of Life and Evolution of Biospheres 36 (2): 77–189. Bibcode:2006OLEB...36..177M. doi:10.1007/s11084-005-9003-4. PMID 16642267.
- M. Kaufmann (2009). "On the free energy that drove primordial anabolism". International Journal of Molecular Sciences 10 (4): 1853–1871. doi:10.3390/ijms10041853. PMC 2680651. PMID 19468343.
- Anthonie W.J. Muller (2005). "Thermosynthesis as energy source for the RNA World: a model for the bioenergetics of the origin of life". Biosystems 82 (1): 93–102. doi:10.1016/j.biosystems.2005.06.003. PMID 16024164.
- F.J. Sun and G. Caetano-Anolles (2008). "The origin and evolution of tRNA inferred from phylogenetic analysis of structure". Journal of Molecular Evolution 66 (1): 21–35. doi:10.1007/s00239-007-9050-8. PMID 18058157.
- Anthonie W.J. Muller (1985). "Thermosynthesis by biomembranes: energy gain from cyclic temperature changes". Journal of Theoretical Biology 115: 319–321. doi:10.1016/S0022-5193(85)80202-2. PMID 3162066.
- Anthonie W.J. Muller (1996). "Life on Mars?". Nature 380 (6570): 100. Bibcode:1996Natur.380..100M. doi:10.1038/380100b0. PMID 8600375.
- Anthonie W.J. Muller (2001). "The thermosynthesis model for the origin of life: implications for Solar System exploration" (PDF). Marsbugs 8 (15): 3–6. Archived from the original (PDF) on September 4, 2006.
- Anthonie W.J. Muller (2003). "Finding extraterrestrial organisms living on thermosynthesis". Astrobiology 3 (3): 555–564. Bibcode:2003AsBio...3..555M. doi:10.1089/153110703322610645. PMID 14678664.
- Louis N. Irwin; Dirk Schulze-Makuch (2008). Life in the Universe: Expectations and Constraints (Advances in Astrobiology and Biogeophysics). Berlin: Springer. p. 73. ISBN 3-540-76816-5.
- Anthonie W.J. Muller (2005). "Photosystem 0, a proposed ancestral photosystem without reducing power that uses metastable light-induced dipoles for ATP synthesis". arXiv:physics/0501050 [physics.bio-ph].
- Anthonie W.J. Muller (2009). "Emergence of animals during Snowball Earths from biological heat engines in the thermal gradient above submarine hydrothermal vents". Origins of Life and Evolution of Biospheres 39 (3-4): 321–322. Bibcode:2009OLEB...39..179.. doi:10.1007/s11084-009-9164-7. PMC 2691805. PMID 19468860.
- Anthonie W.J. Muller (2008). "Emergence of animals from heat engines. Part 1. Before the Snowball Earths". arXiv:0811.1375 [physics.bio-ph].
- Anthonie W.J. Muller (2009). "Animal emergence during Snowball Earths by thermosynthesis in submarine hydrothermal vents". Nature Precedings. doi:10.1038/npre.2009.3333.2. Retrieved 2009-06-20.
- Anthonie W.J. Muller (2006). "A search for thermosynthesis: starvation survival in thermally cycled bacteria". arXiv:physics/0604084.