Outer space synthesis

The synthesis and characterisation of a further compound which had been detected in outer space, cyanobutadiyne (2,4-pentadiynenitrile), has been carried out at the University of Rennes in France. This molecule belongs to a class in which one or more C-C triple bonds and only one carbonitrile substituent are present (H-(C= C%-C=N). These are often found in ISM the simplest, cyanoacetylene (H-C=C-C=N), has been detected several times in experiments intended to simulate the Titanian atmosphere. The largest molecule ever found in outer space, HCnN, is also a member of this family (Trolez and Guillemin, 2005). 

The molecules may not have been formed on Earth but brought there from outer space (from within or from outside the solar system) by meteorites or comets (exogenous synthesis). 

The source of organic materials. Possible sources cited have included mineral-catalyzed hydrothermal synthesis, atmospheric syntheses driven by radiation or electrical discharges (see Section 5.1), and delivery from outer space (see Section 5.2). Cleaves and Chalmers have summarized the alternatives.61... 

The typical production technologies for combustion synthesis were described in Section II. It is evident that apparatus needed for synthesis is relatively simple, especially since no additional equipment is needed for bulk heating of the material (e.g., furnaces, plasma generators, etc.). In addition, it has been reported that replacing conventional furnaces with a CS apparatus leads to significant reduction in workspace requirements (Merzhanov, 1992). Finally, owing to low power requirements, combustion synthesis technology is one of the few methods of materials synthesis that is feasible in outer space (Hunter and Moore, 1994). 

Thus, in little more than three decades after Wohler s accidental synthesis of urea, it was learned that living organisms exhibited a unique capacity to distinguish a molecule from its mirror image. So profoundly indicative of Life is the handedness of carbon-containing molecules that a search for the existence of Life in outer space once centered on finding such optically active molecules in matter-... 

The suggested accumulation of complex but photostable it-systems in the UV-il-luminated environments is in agreement with the presence of polycyclic aromatic hydrocarbons in meteorites [194,286], as well as with the reported synthesis of nucleotides from simpler precursors at the outer surfaces of Russian spacecraft [287]. Generally, one would expect that complex organic compounds would break into pieces in outer space. This is not the case instead, the pieces join together at surfaces to build complex aromatic 7t-systems that apparently are more stable than simpler compounds against diverse types of cosmic radiation. 

Earth s life forms. Careful analytical work proved that this optical activity was not the result of some Earth-based contaminant. In the past decade experiments have shown that with only the small amount of enantiomeric excess that these amino acids possess, some of them, such as the two shown below which have a fully substituted chirality center and cannot racemize, can effect a resolution of racemic amino acids through relatively simple processes such as crystallization. These events leave behind aqueous solutions of L-amino acids in high enantiomeric excess. Moreover, once these chiral L-amino acid solutions are generated, they can catalyze the enantiocontrolled synthesis of D-carbohydrates, which is what we all possess as well. As such, it is conceivable that the origin of chirality may well have come from outer space. 

The er is a three-dimensional membrane system (57-62). As visualized in a transmission electron microscope, there are two parallel membranes with an intervening electron transparent space, the lumen. The form and abundance of the er vary. The rer are flattened sacs with numerous attached ribosomes (15-20 nm). In contrast, the smooth er (ser) lacks ribosomes. The er seems to function as a communication system within cells and can be continuous with the outer nuclear envelope. Although the rer is involved in protein synthesis, the ser functions in glycosylation. 

Most of the mitochondrial proteins are nuclear encoded and thus must be targeted into mitochondria and sorted into some of their components after their synthesis at the cytosol. Because mitochondria have two membranes, there are four localization sites the matrix, the inner membrane, the intermembrane space, and the outer membrane (Fig. 6). Although there has been considerable progress in our understanding of these processes, some questions still remain. Moreover, the total picture is rather complicated and contains many exceptions. A simplified view is presented here based mainly on the view of Pfanner and Mihara (Mihara and Omura, 1996 Pfanner et al., 1997 Pfanner, 1998). There are also a number of other excellent reviews on this subject (Schatz, 1996 Stuart and Neupert, 1996 Neupert, 1997 Roise, 1997). 

The endoplasmic reticulum (ER) is composed of flattened sacs and tubes of membranous bilayers that extend throughout the cytoplasm enclosing a large intracellular space. The luminal space (Fig. 1-5) is continuous with the outer membrane of the nuclear envelope (Fig. 1-10). It is involved in the synthesis of proteins and their transport to the cytoplasmic membrane (via vesicles, small spherical particles with an outer bilayer membrane). The rough ER (RER) has flattened stacks of membrane that are studded on the outer (cytoplasmic) face with ribosomes (discussed later in this section) that... 

Reactants and products must diffuse through high-molecular-weight liquid hydrocarbons during FT synthesis. The liquid phase may be confined to the mesoporous structure within catalyst pellets or extend to the outer surface and the interstitial spaces between pellets, depending on the reactor design and hydrodynamic properties. In packed-bed reactors, the characteristic diffusion distance equals the radius of the pellets plus the thickness of any liquid boundary layer surrounding them. Intrapellet diffusion usually becomes... 

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