Self-organization and breaking of symmetry

Self-assembly of chiral molecules may result in organized aggregates displaying a remarkable enhancement of ophcal achvity. The best known examples are amino-acid residues that assume a periodic conformation - an a-helix or a p-sheet chain. In this case, the enhancement of optical activity is due to the onset of a parhcular rigid conformation. 

Ribo also suggests that this might be relevant in a prebiotic scenario, at the early stages of the origin of life, since there may well have been vortices determining permanent sign directions in primordial times. 

The growing interest in supramolecular chirality stems not only from the intrinsic relevance of such studies for the origin of chirality in life processes, but also from the potential technological applications, such as the separation of optical isomers for the pharmaceutical or food industries. 

Thermodynamics has in this case to do with the specificity of the protein structure that determines the binding selectivity to one another, for example actin and 

Another complex macromolecular aggregate that can reassemble from its components is the bacterial ribosome. These ribosomes are composed of 55 different proteins and by 3 different RNA molecules, and if the individual components are incubated under appropriate conditions in a test tube, they spontaneously form the original structure (Alberts et al., 1989). It is also known that even certain viruses, e.g., tobacco mosaic virus, can reassemble from the components this virus consists of a single RNA molecule contained in a protein coat composed by an array of identical protein subunits. Infective virus particles can self-assemble in a test tube from the purified components. 

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