Miller and Bada

Miller and Bada (1988) and Miller et al. (1989) attempted to answer the question as to whether biogenesis processes can occur at hydrothermal vents in regions of the deep sea. Miller states clearly that biomolecules could not have been formed under such conditions. Holm (1992) sums up Miller s arguments in the following four points ... 

We also know that a considerable enrichment of prebiotic moieties may have come from submarine vents and other hydrothermal sources (see, for example, Miller and Bada, 1988 Holm and Andersson, 1998 Stetter, 1998). Let s start with the 1979 discovery of deep-sea vents with black smokers, which are associated with an extraordinary abundance of the most phylogenetically primitive organisms on Earth. This ecosystem is sulphur based, and is distinct from the more familiar, photosynthetically-based ecosystem that dominates Earth s surface. Corliss et al. (1981) were struck by the richness of the vent biota, based on chemosynthesis, and proposed that these were the origin of life. 

Recently, Miller and Bada have questioned this hypothesis, as they showed that these conditions induce decomposition of small organic compounds rather than synthesis [25]. 

The importance of this sensational discovery for biogenesis research only became apparent in the next few years (Lahav, 1999). It is clear that prebiotic chemistry is much more complex and versatile than was thought about 50 years ago, when Stanley Miller carried out his first successful amino acid syntheses. Experiments similar to the ones described above, as well as new ones which must first be devised, could help to slowly close the wide gap which still exists between the prebiotic and the living worlds (Wills and Bada, 2000). 

Shock s postulates led Bada et al. (1995) and others to react critically. Thus Bada, Miller and Zhav are of the opinion that quasi-equilibrium calculations provide flawed descriptions of the experimental observations. They believe that thermodynamic calculations cannot be used for organic compounds in high temperature vents. 

Lazcano, A. and Bada, J. L. (2003). The 1953 Stanley L. Miller experiment fifty years of prebiotic organic chemistry. Orig. Life Evol. Biosph., 33, 235 2. 

Figure 8.3 A photograph of (a) original set-up for the Miller-Urey experiment and (b) a reproduction of this experiment at NASA laboratories. (Partially reproduced from Lazcano and Bada [22] with kind permission from Springer Science + Business Media. Kluwer Academic Publishers 2003. Picture (b) by courtesy of NASA)...

Mesmer RE, Patterson CS, Busey RH, Holmes HF (1989) Ionization of acetic acid in NaCl (aq) media a potentiometric study to 573 K.J Phys Chem 93 7483-7490 Miller SL, Bada JL (1988) Submarine hot springs and the origin of life. Nature 334 609-611... 

E. L. Shock (1990) provides a different interpretation of these results he criticizes that the redox state of the reaction mixture was not checked in the Miller/Bada experiments. Shock also states that simple thermodynamic calculations show that the Miller/Bada theory does not stand up. To use terms like instability and decomposition is not correct when chemical compounds (here amino acids) are present in aqueous solution under extreme conditions and are aiming at a metastable equilibrium. Shock considers that oxidized and metastable carbon and nitrogen compounds are of greater importance in hydrothermal systems than are reduced compounds. In the interior of the Earth, CO2 and N2 are in stable redox equilibrium with substances such as amino acids and carboxylic acids, while reduced compounds such as CH4 and NH3 are not. The explanation lies in the oxidation state of the lithosphere. Shock considers the two mineral systems FMQ and PPM discussed above as particularly important for the system seawater/basalt rock. The FMQ system acts as a buffer in the oceanic crust. At depths of around 1.3 km, the PPM system probably becomes active, i.e., N2 and CO2 are the dominant species in stable equilibrium conditions at temperatures above 548 K. When the temperature of hydrothermal solutions falls (below about 548 K), they probably pass through a stability field in which CH4 and NII3 predominate. If kinetic factors block the achievement of equilibrium, metastable compounds such as alkanes, carboxylic acids, alkyl benzenes and amino acids are formed between 423 and 293 K. 

Peltzer E. T., Bada J. L., Schlesinger G., and Miller S. L. (1984) The chemical conditions on the parent body of the Murchison meteorite some conclusions based on amino, hydroxy and dicarboxylic acids. Aulv. Space Res. 4, 69-74. 

Bada, J. L., Bigham, C. and Miller, S. L. (1994). Impact melting of frozen oceans on the early Earth implications for the origin of life. Proceedings ofthe National Academy of Sciences, USA, 91, 1248-50. 

The rate of racemization of aspartic acid as a function of pH at 117.2°C is shown in Figure 1. The rates were calculated from Equation 12. The rates of deamination of aspartic acid at each pH value were calculated from the data given by Bada and Miller (38). The results in Figure 1 are the average values for samples heated for at least two... 

Bada, J.L. and Miller, S.L., 1968a. Ammonium ion concentration in the primitive ocean. Science, 159 423—425. 

Parker ET, Cleaves FU, Dworkin JP, Glavin DP, Callahan MP, Aubrey A, Lazcano A, Bada R. Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. Proc Natl Acad Sci USA. 2011 108 5526-31. 

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