Poly alanines

B. Poly alanine Extension in Oculopharyngeal Muscular Dystrophy... 

A genuine example of enantiomer discrimination has been reported for polypeptides by Malcolm (108,109). Mixed monolayers of enantiomerically related samples of isotactic poly (alanine), poly(7-benzylglutamate), poly(/3-benzylaspartate), and poly(e-benzyloxycarbonyllysine) were studied to shed some light on the... 

Rathoie O, Sogah DY. Self-assembly of j8-sheets into nanostructmes by poly(alanine) segments incorporated in multiblock copolymers inspired by spider silk. J Am Chem Soc 2001 123 5231-5239. 

Plate 11 Poly alanine model of ALBP built into electron-density map. This section of the final ALBP model is shown in Plate 2. (For discussion, see Chapter 7.)... 

Vener MV, Egorova AN, Fomin DP, Tsirelson VG (2007) QTAIM study of the closed-shell interactions in peptide secondary structures A cluster treatment of oligo- and poly alanines. Chem Phys Lett... 

In the 1980s, Julia and Colonna discovered that the Weitz-Scheffer epoxidation of enones such as chalcone (4, Scheme 2) by alkaline hydrogen peroxide is catalyzed in a highly enantioselective fashion by poly-amino acids such as poly-alanine or poly-leucine (Julia et al. 1980, 1982). The poly-amino acids used for the Julia-Colonna epoxidation are statistical mixtures, the maximum length distribution being around 20-25 mers (Roberts et al. 1997). The most fundamental question to be addressed refers to the minimal structural element (i.e. the minimal peptide length) required for catalytic activity and enantioselectiv-ity. To tackle this question, we have synthesized the whole series of L-leucine oligomers from 1- to 20-mer on a solid support (Berkessel... 

High-molecular-weight polymers of low polydispersity are formed [180]. BuONa initiates the isomerization polymerization of acrylamide, producing poly ( -alanine) (see also Chap. 5, Sect. 6.6). This initiation can be described as addition of the CH2=CHCONH anion to the monomer double bond [181]. The anion is formed by the reversible reaction... 

Trossarelli et al. studied the formation of poly-/ -alanine by the polymerization of acrylamide with ter/.-BuNa. The initiating anion is in equilibrium with the monomer [24]... 

The shapes of the pressure-area isotherms of monolayers of synthetic polypeptides in the a-helical conformation depend on the nature of the side chain interactions. Poly(y-n-decyl-iu-glutamate), poly(i.-leucine), poly(iu-norleucine), and poly(iu-methionine) show differences related to side chain flexibility and dipolar interactions. Comparison of the isotherms of monolayers of the enantiomorphic and racemic forms of polymers [poly(alanine), poly(y-benzyl-glutamate), poly( /3-benzyl-aspartate), poly( e-benzyloxycarbonyllysine )] similarly show features related to side chain properties. The results support the view that when a monolayer consists of a-helices, the shape of the isotherm depends on the difference between the energies of interaction of parallel and antiparallel molecules. These conclusions are discussed in relation to proteins. 

Monolayers of Racemic Mixtures Poly (alanine), Poly (y-benzyl Glutamate), Poly ( -benzyl Aspartate), Poly (Benzyloxy carbonyl Lysine). Experimental Results. The pressure-area and surface potential results for the two enantiomorphic forms of a given polymer were virtually identical except for poly (benzyl aspartate) where the plateau of poly( -benzyl-D-aspartate) was about 2 dynes/cm higher than that of the L enantiomorph (Figure 6). This may result from the incomplete ben-zylation of the o-aspartate. 

Electron diffraction patterns have been obtained from collapsed monolayers of poly (alanine) and poly (y-benzyl glutamate). The enantiomorphic forms of the other two polymers give patterns with very poor crystallinity, and their racemic mixtures have not therefore yet been investigated. The principal features of the diffraction pattern of poly-... 

Figure 6. Surface pressure (P) and surface potential (V) vs. area for mono-layers on distilled water, pH 5.6-5.7. (a) poly-alanine, (b) poly(e-benzyloxy-carbonyl lysine), (c) poly(y-benzyl-glutamate), (d) poly(P-benzyl-aspartate).

This phenomenon is in remarkable contrast to the cases of alanine NCA and 7-glutamate NCA, where a selection of monomer antipodes by a-helical polymer chain is observed. The lack of selectivity of the growing poiy(valine) chains cannot be attributed to the heterogeneity of the reaction mixture due to the insolubility of the polymer, since the polymerization of alanine NCA in tetrahydrofuran does demonstrate the selectivity, as mentioned previously, despite the heterogeneous reaction observed. The determining factor seems to be the different conformation acquired by the growing poly(valine) as compared to the a-helices of poly(7-benzyl glutamate) and poly(alanine), both in solution and solid state. 

Acrylamide. The dienes, acrolein, ketene, and the dialdehydes represent monomers that are obviously polyfunctional. Acrylamide, on the other hand, was not thought until recently to be capable of any polymerization reactions other than at the vinyl group e,g., with free-radical catalysts). Breslow and Matlack demonstrated, however, that under anhydrous conditions and in the presence of strong bases the product obtained is poly- -alanine (nylon-3) (6). These structures are shown in Reaction 20. 

The silk produced by these worms displayed — 15% labeling of the poly-alanine chains, while the glycine-rich domains only reached a five times lower labeling fraction. For these samples, double-quantum correlation spectroscopy (DOQSY) experimentswere performed. The 2D DOQSY spectra prove to be highly sensitive to the peptide... 

Anionic polymerization of unsubstituted acrylamide, catalyzed by strong bases, does not yield typical vinyl polymers. Instead, the product is a 1,3-adduct, poly -alanine). " Two alternate reaction paths were originally proposed " ... 

The simplest member of the nylon 3 series is poly( -alanine), with the monomeric unit - NH—CH2—CH2—CO. It is obtained by polymerization of acrylamide with strong bases ... 

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