Proteins, self-assembly tertiary protein structure

In addition to self-assembly of protein structures, in living systems the complex maneuvers needed to achieve properly folded tertiary structures are facilitated by the function of a pre-existing protein machinery, of which, ihe molecular chaperones are an illustrative example. Chaperones are proteins that bind to and stabilize an otherwise unstable conformer of another protein, and by controlled binding and release, facilitate its correct fate in vivo. Molecular chaperones may be said to be the natural... 

Hydrophobicity is believed to play a major role in organizing the self-assembly of protein molecules. Patterns of hydrophobic versus hydrophilic side chains are very in predicting secondary and tertiary structure simply by virtue of their preferential occurrence on the inside versus outside of various structural features. Those hydrophobicity patterns... 

Several laboratories have described systems by which synthetic linear peptide chains self-assemble into desirable secondary and tertiary structures. One self-assembly approach has been the creation of a peptide-amphiphile, whereby a peptide head group has the propensity to form a distinct structural element, while a lipophilic tail serves to align the peptide strands and induce secondary and tertiary structure formation, as well as providing a hydrophobic surface for self-association and/or interaction with other surfaces. The preparation of a dialkyl ester tail first involves the acid-catalyzed condensation of H-Glu-OH with the appropriate fatty acid alcohol to form the dialkyl ester of H-Glu-OH a typical example is shown in Scheme 7. The assembly of peptide-amphiphiles with mono- and dialkyl ester tails is shown in Scheme 8. A series of studies have demonstrated that triple-helical and a-helical protein-like molecular architecture is stabilized in the peptide-amphiphile 44,63-65 ... 

Important differences between DNA and RNA appear in their secondary and tertiary structures, and so we shall describe these structural features separately for DNA and for RNA. Even though nothing in nucleic acid structure is directly analogous to the quaternary structure of proteins, the interaction of nucleic acids with other classes of macromolecules (for example, proteins) to form complexes is similar to the interactions of the subunits in an oligomeric protein. One well-known example is the association of RNA and proteins in ribosomes (the polypeptide-generating machinery of the cell) another is the self-assembly of tobacco mosaic virus, in which the nucleic acid strand winds through a cylinder of coat-protein subunits. 

One of the most remarkable properties of self-assembly is its ability to generate exceedingly coinplica ted supramolecular structures from fairly simple components. Perhaps the most elegant embodiment of this phenomenon is protein stmcture. Proteins exhibit at least four hierarchies of stmcture primary, secondary, tertiary, and quaternary stmctures. Primary stmcture describes the covalent connections making up the sequence of amino acids in each strand. Secondary stmcture involves local architectural elements created when portions of a strand... 

In reeent years, polypeptides have been intensively studied as stimulus-responsive polymers owing to their obvious attractive features such as their inherent ionizable groups Le., NH2 and COOH), hierarchical self-assembly, and multiple secondary or tertiary structures. The biocompatibility and bio-degradability of hybrid pol)q)eptides or proteins have attracted great attention for possible clinical use some have entered clinical trials. 

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