Isotactic oligopeptides

Cenemtion of Isotactic Oligopeptides via Polymerization in Racemic Crystals 213... 

Figure 8.10 Cartoon representing a racemic template, composed of isotactic oligopeptide chains [shown as sequences ofleft- and right-hands], exerting a regioenantioselective incorporation of new monomers (shown as single isolated left- and right-hands) during the chain-elongation step of the polymerization.

Isotactic Oligopeptides from the Polymerization of Racemic VaINCA or LeuNCA in Aqueous Solution... 

Figure 8.18 MALDI-TOF MS partial spectra of the oligopeptides obtained from the polymerization, with 25 mol% n-butylamine initiator of RS-VaiNCA in (a) aqueous solution and (b) in THF. Isotactic oligopeptides are labeled R13, Rm, S13, Si4, and arrows point to the strong signals in water (a) or to their absence in THF (b).

Isotactic Oligopeptides from the Polymerization of Racemic ValNCA or LeuNCA in Aqueous Solution 222 Racemic -Sheets in the Polymerization of a-Amino-Acids in Aqueous Solutions Homochiral Ohgopeptides and Copeptides via the Ehler-Orgel Reaction 224... 

The extension of the term isotactic to condensation polymers was made by Natta in his first article discussing poly-L-a-amino acids (22). In itself the term isotactic is redundant here as the configuration of the repeating unit is sufficient to identify the macromolecular stmcture. It is, however, useful to distinguish a system, racemic or not, in which each macromolecule is composed of only l or only D residues from a mixture of macromolecules made up of random or alternate sequences of L or d units. Similarly the term syndiotactic serves in the identification of oligopeptides or polypeptides composed of alternate sequences of D and L units, like those synthesized by Lorenzi and Tomasic (77). 

Scheme 8.4 Schematics of a 2-D-crystallization process at the air-water interface of a nonracemic mixture of OJ -stearyl-glutamic acid-N -carboxyanhydride (R>S) as a mixture of racemic and (R)-enantiomorphous 2-D-crystals followed by polymerization yielding a mixture of syndiotactic and isotactic (R)-oligopeptides.

Colloidal particles composed from mixtures of IsotactIc and atactic racemic short oligopeptides assembled as either racemic 8-sheets like or rippled 8-sheets... 

Figure 8.23 Schematic representation of a racemic 8-sheet architecture composed of isotactic (R)- (black) and (S)- (red) oligopeptide chains, showing the enantioselective reaction with a (R)-thio-ester-monomer molecule only at the left-side rim. The monomer molecule is prevented from reacting at the right-side rim.

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