Sulfur and the origins of life
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Both organic and inorganic sulfur play an important role in fundamental contemporary biochemistry, suggesting that life's common ancestor used sulfur in its metabolism. In support of this idea is the widely held belief that present-day sulfurmetabolising thermophilic bacteria are the most primitive organisms within the biosphere. This thesis postulates that sulfur may have been important in the origins of life, and reports investigates several interesting and potentially prebiotic reactions involving sulfur. Three different types of chemistry were investigated. The formation of pyrophosphate from phosphate with thioesters over metal phosphate precipitates has been reported; this can be considered a biomimic of the important succinyl-CoA synthetase-catalysed reaction in the citric acid cycle of present-day organisms. The ability of ferrous sulfide and/or ferrous phosphate precipitates to catalyse pyrophosphate production with thioesters or metal ion-bound thioacids as condensing agents was investigated. No pyrophosphate production was detected, but interesting results regarding the effect of ferrous ions in solution and ferrous sulfide precipitates and ferrous phosphate precipitates on the rate of hydrolysis of thioacetic acid are reported. Ferrous ion- and sulfide ion-mediated redox chemistry of thioesters and metal-ion bound thioacids was investigated. The motivation for these experiments came from the involvement of thioesters in contemporary biochemical redox reactions. No ferrous ion- or sulfide ion-dependent redox chemistry was demonstrated. Finally amide bond formation between amines and metal ion-bound thioacids was investigated. It was discovered that nickel sulfide precipitates are efficient catalysts in this process. Nickel sulfide would have been present in the oceans of primordial earth, and may therefore have been an important prebiotic catalyst in the origin of amide bonds in metabolism.