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Homochirality in chains

It was mentioned earlier that homochirality gives the question why this and not that a particular meaning in the case of macromolecules. Why homochiral macromolecules Assume for a moment that both l and d forms of the natural a-amino acids are present. Then, a protein with 50 residues would in principle exist in all its 2 diastereoisomeric forms. By utilizing only one enantiomer, nature reduces this number 2 to onel What a trick  [Pg.76]

These arguments suggest that homochirality was most probably already implemented in the early stages of the origin of life, as it would have been very difficult to reach the high order and selectivity of the first self-reproducing cells if all possible diastereomeric macromolecules had been around. [Pg.76]

As already mentioned, this high stereochemical order is a case of kinehc control, as all these polymers are the product of highly speciahzed enzymes. Shll, chain stereoregularity in polypeptides and/or polynucleohdes has some addihonal features of interest for the held of the origin of life. This is covered in the next sechons. [Pg.78]

Such a capability of an oligonucleotide system deserves special attention in the context of the problem of the origin of biomolecular homochirality breaking molecular mirror symmetry by de-racemization is an intrinsic property of such a system whenever the constitutional complexity of the products of co-oligomerization exceeds a critical level. [Pg.80]

The natural tendency of polypeptide chains to grow homochirally may suggest an alternative mechanism for the breaking of symmetry, based on macromolecules instead of monomers. The argument is that it should be easier to separate enantiomeric homochiral chains, rather than racemic low-molecular-weight monomers, from each other. It has been shown for example that when the NCA-polycondensation is performed on mineral support, the oligomeric product remained absorbed on the surface. The lower oligomers are, however, easily [Pg.81]


See other pages where Homochirality in chains is mentioned: [Pg.76]    [Pg.77]   


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