Prebiotic chemical evolution

From the viewpoint of a model of prebiotic chemical evolution and of the primitive atmosphere of the Earth,174175 photosynthetic reactions of C02 were also examined, and formaldehyde with various nitrogen-containing products was obtained. 

The term chemical evolution" was introduced by the Nobel Prize winner Melvin Calvin and refers to the process of the synthesis of biochemically important molecules from small molecules and certain chemical elements under the (hypothetical) conditions present on prebiotic Earth. It is assumed that the smaller building block molecules such as amino acids, fatty acids or nucleobases were formed initially, and that these underwent polycondensation to give macromolecules in later stages of development. 

It is intriguing that Mo is an important element in biology despite its scarcity at the Earth s surface—indeed, no element of similar scarcity is so biochemically ubiquitous. The reason for this paradoxical combination is unknown. Possible explanations include the unique chemical character of this element, evolutionary adaptation to the abrmdance of Mo in oxygenated oceans relative to other transition metals, a legacy of prebiotic chemical evolution in Mo-rich environments (e.g., in association with sulfide minerals), or some combination of these factors. Regardless, this paradox has inspired creative hypotheses about the importance of Mo in evolution (Crick and Orgel 1973 Anbar and Knoll 2002). 

The conclusion is that membranous vesicles readily form a variety of amphiphilic molecules that would have been available in the early Earth environment, along with hundreds of other organic species. It is likely that during the chemical evolution leading to the first catalytic and replicating molecules, the ancestors of today s proteins and nucleic acids, membranous vesicles were available in the prebiotic environment, and ready to provide a home for the first forms of cellular life. 

Ferris and Antonucci73 have reported a photochemical synthesis of imidazo[4,5-d]imidazole (80) from 4-aminoimidazole-5-carbonitrile (78), which has attracted interest since 78, and its photochemical precursor diaminomaleonitrile (77) have been proposed74 as key intermediates in the prebiotic chemical evolution of purines. Mechanistic studies7311 suggest that the fused pyrazole 79 may be an intermediate. 

M. T. Beck, Prebiotic Coordination Chemistry The Possible Role of Transition Metal Complexes in the Chemical Evolution , in Metal Ions in Biological Systems , ed. H. Sigel, Dekker, New York, 1978, vol. 7. 

Ferris, J. P, and Hagan, W. J. (1984) HCN and Chemical Evolution The Possible Role of Cyano Compounds in Prebiotic Synthesis, Tetrahedron, 40, 1093-1120. It should be kept in mind that the compounds described in this paper do not have the foundation attached. 

Dondi D, Merli D, Pretali L, Fagnoni M, Albini A, Serpone N. Prebiotic chemistry chemical evolution of organics on the primitive Earth under simulated prebiotic conditions. Photochem Photobiol Sci 2007 6 1210-17. 

On the other hand, in the formation of guanine quartet-based hydrogels, it was shown that the system selected those components that generated the most stable gel [50] (see Fig. 5 in [50]). Such a self-optimization behavior may be of much deeper general significance, namely for prebiotic chemical evolution, whereby selection is driven by phase cohesion, the entity selected being that giving the most stable... 

Generally speaking, the chance to establish autocata-lytic cycles during chemical evolution (Orgel 2003) with or without external selecting influences is rather small. On the other hand, some (not all of the) similarities between product patterns of prebiotic simulation experiments and contemporary biochemistry suggest that the principal biochemical structures kept constant throughout the existence of life on Earth. Hence auto-catalytic feedback loops came into existence only later. 

Roy D, Najafian K, Schleyer PV. Chemical evolution The mechanism of the formation of adenine under prebiotic conditions. 48. Proc. Natl. Acad. Sci. U. S. A. 2007 104 17272-17277. 

Ferris IP, Goldstein G, Beaulieu DJ. Chemical evolution IV. An evaluation of cyanovinyl phosphate as a prebiotic phosphorylating agent. J. Am. Chem. Soc. 1970 92 6598-6603. 

Since the terrestrial rock record has hitherto failed to furnish unequivocal evidence of prebiotic organic chemistry, early chemical evolution was almost certainly confined to the Hadean era bracketed by the time of Earth s formation ( 4.5 billion years ago) and the onset of the sedimentary record about 3.8 billion years ago (Figure 29). 

Chemical evolution concerns the chemical processes that occurred on the ancient Earth about 4.5-3.5 million years ago. It is important to note that it preceded biological evolution that resulted in the formation of protocells. These forerunners of today s living cells were capable of self-reproduction at the expense of some protometabolism. After Oparin s ideas of the origin of life became widely known and especially after Stanley Miller reported his prebiotic soup experiments in 1953, the concept of chemical evolution became accepted. 

Ferris JP, Hagan J (1984) HCN and chemical evolution the possible role of cyano compounds in prebiotic synthesis. Tetrahedron 40 1093-1125... 

Dondi, D., Merli, D., Pretali, L., Fagnoni, M., Albini, A., Serpone, N., Prebiotic Chemistry Chemical Evolution of Organics on the Primitive Earth under Simulated Prebiotic Conditions, Photochem. Photobiol. Sci. 2007, 6, 1210 1217. 

The influence of plant sterols on the phase properties of phospholipid bilayers has been studied by differential scanning calorimetry and X-ray diffraction [206]. It is interesting that the phase transition of dipalmitoylglycerophosphocholine was eliminated by plant sterols at a concentration of about 33 mole%, as found for cholesterol in animal cell membranes. However, less effective modulation of lipid bilayer permeability by plant sterols as compared with cholesterol has been reported. The molecular evolution of biomembranes has received some consideration [207-209]. In his speculation on the evolution of sterols, Bloch [207] has suggested that in the prebiotic atmosphere chemical evolution of the sterol pathway if it did indeed occur, must have stopped at the stage of squalene because of lack of molecular oxygen, an obligatory electron acceptor in the biosynthetic pathway of sterols . Thus, cholesterol is absent from anaerobic bacteria (procaryotes). 

In this volume the emergence of chemical complexity has been divided into three evolutionary episodes stellar evolution and the emergence of elemental diversity, planetary evolution and the emergence of mineralogical diversity, and prebiotic chemical evolution. All of these episodes depend on evolutionary processes that produce change over time under selective pressure (Zaikowski, this volume), and all of them continue to this day. 

Chessari, S. Thomas, R. Polticelli, F. Luisi, P. L., The production of de novo folded proteins by a stepwise chain elongation A model for prebiotic chemical evolution of macromolecular sequences. Chemistry Biodiversity 2006, 5, 1202-1210. 

Chemical evolution across space time from the Big Bang to prebiotic chemistiy / Lori Zaikowski, Jon M. Friedrich, editors. 

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