Membranes primitive

Davis F, Collyer SD, Higson SPJ (2005) The Construction and Operation of Anion Sensors Current Status and Future Perspectives. 255 97-124 Deamer DW, Dworkin JP (2005) Chemistry and Physics of Primitive Membranes. 259 1-27 Debaene F, see Winssinger N (2007) 278 311-342... 

For several years, Pier Luigi Luisi and co-workers from the Polymer Institute of the ETH in Zurich have been working on the problem of the emergence of primitive membranes. The oldest fossils (see Sect. 10.1) indicate that the first life forms already had cell-like structures, i.e., life has been based on the following three important principles for 3.5 billion years (or maybe less ) (Luisi, 1996) ... 

D. W. Deamer and J. P. Dworkin have reported in detail on the contribution of chemistry and physics to the formation of the first primitive membranes during the emergence of precursors to life the authors discussion ranges from sources of amphiphilic compounds, growth processes in protocells, self-organisation mechanisms in mixtures of prebiotic organic compounds (e.g., from extracts of the Murchison meteorite) all the way to model systems for primitive cells (Deamer and Dworkin, 2005). 

A different approach is proposed by Ourisson and his group. They start from the consideration that the amphiphilic molecules in primitive membranes must have been very different from the modem eucaryotic ones (Ourisson and Nakatani, 1994), and they argue that simple polyprenyl or dipolyprenyl phosphates satisfy... 

Deamer, D. W., Harang-Mahon, E., and Bosco, G. (1994). Self-assembly and function of primitive membrane structures. In Early Life on Earth. Nobel Symposium No. 84, ed. S. Bengston. Columbia University Press, pp. 107-123. 

Pozzi, G., Birault, V., Werner, B. (1996). Single-chain polyprenyl phosphates form primitive membranes. Angew. Chem. Int. Ed. Engl, 35, 177-9. 

Because the lipid components of membranes must be in a fluid state to function as membranes in living cells, it is reasonable to assume that primitive membranes in the first forms of cellular life must also have had this property. Straight-chain hydrocarbons have relatively high melting points due to the ease with which van der Waals interactions can occur along the chains. Any discontinuity in the chains interrupts these interactions and markedly decreases the melting point. As an example, stearic acid contains 18 carbons in its alkane chain and melts at 68 °C, while oleic acid, with a cis-double bond between carbons 9 and 10, has a melting point near 14 °C. If cellular life today requires fluid membranes, it is reasonable to assume that the earliest cell membranes were also composed of amphiphilic molecules in a fluid state. 

Although the establishment of the availability of the fundamental units of DNA, RNA and proteins was a critical component to the investigation of the origin of biological molecules and life on Earth, the simple presence of these molecules is a long step from functioning cells. Scientists and evolutionary biologists propose a number of methods by which these molecules could concentrate into a crude ceU surrounded by a primitive membrane. 

Pozzi G, BiraultV, Werner B, Dannenmuller O, Nakatani Y, Ourisson G, Terakawa S (1996) Single-chain polyterpenyl phosphates form primitive membranes. Angew Chem Int Ed Engl 35 177-180... 

It looks reasonable to hypothesize that globally ubiquitous iron oxides were incorporated into life development from the early evolutionary stage, but subsequent to the synthesis of simple amines and organic acids. The diffusion of sulfide across primitive membranes is also meaningful for the maintenance of the thioester world . An intracellular iron redox cycle, driven possibly by light and sulfide, could have supported chemosynthesis. Iron respiration and photometabolism could have processed on the external surface of vesicles. This would have contributed to a vectorial transport of thioesters and protons into vesicles and accordingly to the development of the early protonmotive transport system. 

Are the n-acyl phospholipids of classical membranes, or the more recently discovered archaeal lipids, plausible constituents of primitive membranes ... 

At present, polyprenyl phosphates, with ( -15 25 chains, are the simplest vesicle-fomiing phospholipids known, and they may have been the most primitive membrane constituents. We have been pleased to discover that the properties of vesicles... 

Furthermore, the head-groups of archaeal phospholipids are much too complex to be archaic, and I have postulated that polyprenyl phosphates might have been the most primitive membrane constituents. These phosphates can be biosynthesized by quite simple reactions, which, as we have shown, can be simulated in vitro from their C5 precursors (Desaubry et al., 2003). 

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