Carbonate natural fixation

Kelly DP, Syrett PJ. 1963. Effect of 2 4-dinitrophenol on carbon dioxide fixation by a Thiobacillus. Nature 197 1087-9. 

Carbon dioxide fixation is catalyzed by the enzyme ribulosebisphosphatecar-boxylase oxygenase (RuBisCO), which is the most abundant natural enzyme worldwide, and the least selective. In fact, RuBisCO does not follow the usual selectivity of enzymes, and at the same time promotes the carboxylation of ribulose (a C-5 sugar) to afford a C-6 sugar (with carbon fixation) and the oxidation of the same C-5 sugar, with a selectivity close to 50% [2]. 

Autotrophic microorganisms synthesize organic substances from carbon dioxide through a process known as carbon dioxide fixation. They are important in nature because carbon dioxide fixation works as a precursor for the organic substrates that form the basis of the food chain for other organisms. Autotrophic bacteria include those that obtain their energy from light (photoautotrophs) and those that obtain it from the oxidation of chemical bonds (chemoau-totrophs). 

Photosynthesis is the process in which light energy is used to convert carbon dioxide, one of the most stable molecules naturally occurring, into sugars and starches. This process is responsible for essentially all of the carbon atomic fixation on our planet - for essentially all of the biomass on earth. Quite literally, the earth s atmosphere has been converted from one of reducing power to one of oxidizing power by photosynthesis. Without the efficiency of this process life as we know it could not exist. The overall stochiometry of this process is given by... 

Catharanthus roseus, Digitata lanata, and Morinda citrifolia plant cells have been immobilized in calcium alginate gels and applied to the production and transformation of natural products.Chloroplasts of Brassica campestris L copolymerized with acrylamide have been used to investigate carbon dioxide fixation by the immobilized cells, whose fixation activity was 65% that of free cells but which were more stable than free cells to alkaline conditions and high temperature. 

Photochemical fixation of carbon dioxide is a function of green plants and some bacteria in nature in the form of photosynthesis. All living organisms on the Earth are indebted directly or indirectly to photosynthesis. Thus, many attempts have been made to simulate the photosynthetic system and make artificial systems, although to date very little success has been achieved. 

A detailed theoretical study of the properties of the redox system FeS/FeS2 was carried out in the Department of Geosciences of SUNY Stony Brook (Schoonen et al., 1999). The authors conclude that the hypothetical reduction of CO2 (by the FeS/FeS2 redox pair) formulated in Wachtershauser s early work, and the carbon fixation cycle on the primeval Earth associated with it, probably could not have occurred. This judgement is made on the basis of a theoretical analysis of thermodynamic data other conditions would naturally have been involved if CO had reacted rather than C02. It is not known whether free CO existed in the hydrosphere, or if so, at what concentrations. 

It has been suggested15 that apiose [3-(hydroxymethyl)-D-g cero-tetrose] (LVII), a branched-chain pentose,47 originates from the aldol reaction of dihydroxyacetone with glycolaldehyde. The origin of this and all other branched-chain sugars so far encountered in natural products is uncertain, but they may arise from intermediate branched-chain carboxylic acids which are believed to be formed in the fixation of carbon dioxide (see above). 

Transition-metal catalysed C02 fixation is among the most challenging subjects of research in organometallic and catalytic chemistry [1], C02 is a naturally abundant resource of carbon, but its reactivity is limited by a very high thermodynamical stability. In this regard, many attempts have been made to convert C02 into useful chemical species. 

Nitrate. Sodium nitrate, nitrate of soda, Chile saltpeter, caliche, [CAS 7631-99-4], NaN03, white solid, soluble, mp 308°C. source in nature is Chile, in the fixation of atmospheric nitrogen HN03 is frequently transformed by sodium carbonate into sodium nitrate, and the solution evaporated. Used tl) as an important nitrogenous fertilizer, (2) as a source of nitrate and HNO3, (3) in pyrotechnics, (4) in fluxes,... 

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