Peptides self-replication

Lee, D. H., Severin, K., Yokobayashi, Y, and Ghadiri, M. R. (1997). Emergence of symbiosis in peptide self-replication through a hypercyclic network. Nature, 390, 591. ... 

Peptide self-replication via template-directed ligation. Chem. Eur. J. 1997, 3, 1017-1023. 

Another intriguing example of peptide interaction inspired by phenomena fonnd in natnre was condncted by combining the original peptide self-replicator T with a set of single residue mutant electrophile and nucleophile (Figure 11). The subunits were altered by replacing valine and leucine with an alanine residue in positions 9 and 26 of the electrophile (E9a) and nucleophile (N26a). respectively. These conservative replacements were already shown to have a dramatic effect on the antocatalytic and... 

New developments in chemistry can arise from the planning and testing of new synthetic methods. In contemporary chemistry, we can see developments whose roots can be found in biological processes, as the terms signal recognition , replication , autocatalysis or self-replication indicate. Modern ideas in these areas can be found in laboratories where work on peptide chemistry is being carried out. 

The scientific world was amazed to hear that David Lee, from the laboratory of Reza Ghadiri (Scripps Research Institute, La Jolla, California), had found a self-replicating peptide (Lee et al., 1996) there are analogies to the experiments with oligonucleotides (see Sect. 6.4). Lee was able to show that a certain peptide, containing 32 amino acids, can both function as a matrix and also support its own synthesis autocatalytically. The information transfer is clearly more complex than that involved in nucleic acid replication. In the case of this particular peptide, both the... 

In accordance with the autocatalytic process, matrices are again formed. It is surprising that the autocatalysis decreases when only 1 of the 15 building blocks of the peptide has the opposite handedness, e.g., when the N-peptide fragment contains one D-amino acid as well as the 14 L-amino acids. These experimental results show that such a system is able to form homochiral products via self-replication. It can be assumed that similar mechanisms influenced the origin of homochirality on Earth (Saghatelian et al., 2001 Siegel, 2001). 

The minimal cell, as the simplest system which has all the required properties of life (metabolism, self-reproduction and the ability to evolve), is presently studied as part of a new research discipline synthetic biology. This includes subjects such as synthesis in branches of biological systems, for example, of new RNA species, new peptides and new nucleic acid analogues, as well as the synthesis of peptide nucleic acids. One example is the work of M. R. Ghadiri and G. von Kiedrowski on self-replication of oligonucleotides and oligopeptides (Luisi, 2006b). 

Figure 2 Examples of coiled-coils used as engineering materials—transplantable oligomerization module (a) [24,25,27], epitope-displaying scaffold (b) [26], biorecognition element (c) [28], allosteric switch (d) [29], and self-replicating peptide (e) [30]. 

The machinery of the amphiphilic polypeptide templates has been successfully used to engineer self-replicating peptides. The principles described above are... 

Two independent screens have been developed to investigate the effects of fluorinated building blocks on the interactions of the dimeric peptide assembly. The impact of fluorine side chain substitutions on the stability of coiled coil folding has been studied using temperature-dependant CD spectroscopy. The second screen is based on the ability of a-helical peptides to self-replicate. Thus, peptide... 

The original system is based on peptides that contain heptad repeats, where the first and fourth positions of the repeat are hydrophobic amino acids. Such sequences form a-helices, which assemble into coiled-coil structures, as represented in Figure 7.10. The principle is then the same as that used for von Kiedrowski s self-replicating nucleotides (von Kiedrowski 1986), in the sense that a full-length peptide template (having in this case 32-35 residues) directs the condensation of the two half-length peptide substrates. 

We have also learned that self-replication is not a prerogative only of nucleic acids, but it can be shared by different kinds of chemical families see the formose reaction, the self-replicating peptides, and the self-reproducing micelles and vesicles. The list should include the cellular automata and the corresponding devices of artificial life. Self-reproduction of vesicles and liposomes is important because it represents a model for cell reproduction. 

Issac, R. and Chmielewski, J. (2002). Approaching exponential growth with a self-replicating peptide. J. Am. Chem. Soc., 124, 6808-9. 

The division of function between DNA (genetic information storage) and protein (catalysis) was, according to the RNA world hypothesis, a later development. New variants of self-replicating RNA molecules developed, with the additional ability to catalyze the condensation of amino acids into peptides. Occasionally, the peptide (s) thus formed would reinforce the self-replicating ability of the RNA, and the pair—RNA... 

Difunctional binding and catalysis has been observed in functionalized cyclo-dextrins [5.66] and in a hydrogen bonding cleft [5.67], Functionalized crown ethers have been used as reagent for peptide synthesis [5.68]. Self-replication processes also involve bond formation reactions they will be discussed in Section 9.6. 

Among the hot debate between theories concerning either a gradual change from RNA self-replication to RNA coded protein synthesis as in the RNA-world, or a merger of systems involving co-evolved RNA and catalytic peptides, another type of molecule - lipids - have until recently been overlooked. 

Chiral surfaces Enantiomorphous crystals Homochiral peptides Mirror symmetry breaking Non-linear kinetics Self-replication of peptides... 

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