Prebiotics

For prebiotics, there are problems if the gut flora does not contain their target microorganisms and there are a more limited range of available products than there are probiotics. Effects of prebiotics would be easier to define if their influence on the gut microflora could be standardized, that is, are any changes that ensue consistent across populations  

In the GI tract, prebiotics selectively stimulate indigenous beneficial bacteria such as bifidobacteria and lactobacilli (Reid etal. 2003b). However, recent studies show that other gut commensals, such as Faecalibacterium prausnitzii, also have the ability to degrade these compounds, producing butyrate as an end-product of fermentation (Ramirez-Farias et al. 2008). Products of prebiotic fermentation by lactobacilli and bifidobacteria, such as lactic and acetic acid, can also be subsequently degraded by other members of the gut (Duncan et al. 2004 Duncan, Louis, and Flint 2004 Falony etal. 2006). Although the 

Impact of Prebiotics on Short Chain Fatty Acid Production 

These dififerent mechanisms illustrate the complexity of regulation of the host metabolism by prebiotics. 

The addition of prebiotics in food may offer other benefits by improving host absorption of minerals (like calcium or magnesium). Recent advances in this field show that inulin-type fructans enhanced calcium absorption primarily via the colonic mucosa in humans (Abrams et al. 2007). This effect may be partially due to the interaction of inulin type fmctans with the Fok 1 gene, a genetic modifier of calcium absorption, as well as due to the acidic environment caused by the production of SCFA, which may increase the solubility of minerals and thus enhance their absorption (Abrams etal. 2005). Crude fractions of chicory (a source of inulin) have shown improved bone parameters relative to native or reformulated inulin in rats, suggesting possible synergies between inulin-t5 e fructans and other nutrients (Demigne et al. 2008). 

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Bachmann P A, Luisi P L and Lang J 1992 Autocataiytic seif-repiicating miceiies as modeis for prebiotic structures Nature 357 57-9... 

The predominance of L-amino acids in biological systems is one of life s most intriguing features. Prebiotic syntheses of amino acids would be expected to produce equal amounts of L- and D-enantiomers. Some kind of enantiomeric selection process must have intervened to select L-amino acids over their D-connterparts as the constituents of proteins. Was it random chance that chose L- over D-isomers ... 

A reversed, reductive TCA cycle would require energy input to drive it. What might have been the thermodynamic driving force for such a cycle Wachtershanser hypothesizes that the anaerobic reaction of FeS and H9S to form insoluble FeS9 (pyrite, also known as fool s gold) in the prebiotic milieu could have been the driving reaction ... 

Prebiotic chemistry of natural heterocycles, among them purines, pyrimidines, sugars, and riboflavin 97T11493. 

These tautomerization experiments have also been performed with uroporphyrinogens,25e 24 which are important intermediates in the biosynthesis of natural porphinoids and corrinoids. This has led to a deeper insight into biosynthetic pathways and a possible prebiotic origin of... 

The tautomerization of porphyrinogens to pyrrocorphins has been reported in detail in connection with the synthesis of chlorins (sec Section 1.2.1.3.), baeteriochlorins (see Section 1.3.1.) and isobacteriochlorins (see Section 1.4.1.3.). Therefore, only the porphyrinogen-pyrrocorphin tautomerization of uroporphyrinogen I octacarbonitrile 8- 96 will be described as it is of importance regarding the biosynthesis and a possible prebiotic formation of corrins.la,b-2 A major problem concerned with using this approach synthetically is the number of possible diastereomeric products (4 in a 1 1 1 1 ratio) obtained in the reaction and also the formation of isobacteriochlorin diastereomers 10. 

Iron, tris(hexafluoroacetylacetone)-structure, 1,65 Iron, tris(oxalato)-chemical actinometer, 1,409 photoreduction, 1,471 relief-image-forming systems, 6,125 Iron, tris(l,10-phenanthroline)-absorptiometry, 1,549 racemization, 1,466 solid state, 1,467 structure, 1, 64 lron(III) chloride amino acid formation prebiotic systems, 6,871 Iron complexes acetonitrile. 4,1210 acetylacetone, 2,371 amidines... 

Molybdenum hexafluoride. 3,1412 Molybdenum-iron-sulfur complexes, 4,241 Molybdenum oxide amino acid formation prebiotic systems, 6, 872 Molybdenum storage protein microorganisms, 6, 681 Molybdenum telluride, 3, 1431 Molybdenum tetraalkoxides physical properties, 2, 347 Molybdenum tribromide, 3,1330 Molybdenum trichloride, 3,1330 Molybdenum trifluoride, 3, 1330 Molybdenum trihalides, 3, 1330 bond lengths, 3, 1330 magnetic moments, 3,1330 preparation, 3,1330 properties, 3, 1330 structure, 3,1330 Molybdenum triiodide, 3,1330 Molybdenum trioxide complexes, 3, 1379 Molybdenum triselenide, 3, 143)... 

It is significant that the earliest records of life on Earth start shortly after the period of impact frustration. Apparently life formed as soon as the conditions permitted it. Life originated from compounds produced by prebiotic organic chemistry. The source of the molecules included those produced on Earth by energetic processes such as impacts and electrical discharges as well as those that fell in from space. Whatever processes occurred, they would have had to happen either in the deep ocean or in what might have been rare regions of land and shallow water. 

Chang, S., Desmarias, D., Mack, R., Miller, S. L., and Strathem, G. E. (1983). Prebiotic organic synthesis and the origin of life. In "Earth s Earliest Biosphere, Its Origin and Evolution" (J. W. Schopf, ed.), pp. 53-88. Princeton University Press, Princeton, New Jersey. 

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