Polypeptide blocks

Dimitrov I, Schlaad H (2003) Synthesis of nearly monodisperse polyst3Tene-polypeptide block copolymers via polymerisation of N-carboxyanhydrides. Chem Commun 2944—2945... 

Kim KT, Vandermeulen GWM, Winnik MA, Manners I (2005) Organometallic-polypeptide block copolymers synthesis and properties of poly(ferrocenyldimethylsilane)-b-poly (gamma-benzyl-L-glutamate). Macromolecules 38 4958 961... 

Elastin-like polypeptide block copolymer ELP(ViAaG7-n] I ELPBfs-nl... 

The preparation of polypeptide and polypeptide hybrid vesicles with predictable properties begins with proper synthesis of a primary structure. This section focuses on three different classes of procedures that are used to synthesize polypeptides. Although conjugation between the polypeptide and non-polypeptide blocks to form polypeptide hybrids is discussed briefly with the third class of synthesis procedures (Sect. 2.3), more detailed information regarding the synthesis and generation of polypeptide hybrid macromolecules are reviewed elsewhere [22-26]. 

Lin J, Zhang S, Chen T et al (2007) Micelle formation and drug release behavior of polypeptide graft copolymer and its mixture with polypeptide block copolymer. Int J Pharm 336 49-57... 

Rod-coil copolymers are good candidates for the formation of rodlike or vesicular structures and can be built from polypeptide-block-containing copolymers, as previously discussed in Sect. 6. 

TTie C-terminal polypeptide block A (residues 462-497) has also been synthesized and its three dimensional structure in solution (90% H2O/10%D2O) was determined by two-dimensional NMR-spectroscopy with a 600 MHz instrument 28. According to this analysis the peptide has a wedge-like shape with dimensions 3 x 1.8 x 1.0 nm. This wedge probably represents the last part in the SAXS model which has a length of about 4 nm and a maximum diameter of 1.4 nm. The principle element of the secondary structure in this part is the conformation. Three antiparallel short jS-sheets composed of residues 466 to 470 ()5j), 485 to 489 and 493 to 496... 

These polypeptide block copolymers have attracted particular attention because of their tendency to form liquid crystals and because they can be selectively degraded by enzymolysis. 

Fig. 37. Example of an electron micrograph of copolymers with a polyvinyl block and a polypeptide block. Copolymer polybutadiene-poly(benzyl-L-glutamate) BG.530 containing 33% polypeptide with polydiene chains have been stained with osmium tetroxide...

In biological membranes, integral proteins are amphipatic molecules their hydro-phobic moiety is embedded in the lipid bilayer and their hydrophilic moiety protrudes from the surface of the membrane279. So, it was interesting to prepare polymeric models of such amphipatic proteins. For that purpose, two new classes of block copolymers have been synthetized in Orleans, namely copolymers with a polyvinyl block and a polypeptide block and copolymers with a saccharide and a peptide block. We shall give some information concerning the preparation of these copolymers and then describe their structure. 

A) Synthesis of Copolymers with a Polyvinyl Block and a Hydrophobic Polypeptide Block... 

Block copolymers with a hydrophobic polyvinyl block and a hydrophobic polypeptide block (BG, SG, SC, SL, BCK and SCK copolymers) exhibit well organized meso-phases in dioxane, 1,2-dichloroethane, 2,3-dichloro 1-propene, etc., solutions. These mesophases are observed for solvent concentrations smaller than about 60% and for dry samples obtained by evaporation of the solvent at a slow rate. 

The Fig. 37 gives an example of electron micrographs of such lamellar structure. It is characterized by alternating black (containing the polydiene blocks stained by osmium) and white (containing the polypeptide blocks) parallel stripes. 

Fig. 38. Example of variation of the geometrical parameters of the lamellar structure of copolymers with a polyvinyl block and a hydrophobic polypeptide block. Copolymer BG.530 in dioxane solution22 ...

Copolymers with a hydrophobic polyvinyl block and a hydrophilic polypeptide block like polybutadiene-poly(L-lysine) (BK), polystyrene-poly(L-lysine) (SK),poly-butadiene-poly(L-glutamic acid) (BE), and polystyrene-poly(L-glutamic acid) (SE) are obtained by action of HC1 and HBr on copolymers BCK, SCK, BG, and SG, respectively23. ... 

The behaviour of copolymers SK is typical for the behaviour of copolymers with a hydrophobic polyvinyl block and a hydrophilic polypeptide block. They exhibit mesophases in water for water concentration ranging from 0 to 50% and the structure of the mesophases is lamellar23. The special feature of this lamellar structure consists in the conformation of the polylysine chains which are roughly to 15% in a 0-chain conformation, to 35% in an a-helix conformation and to 50% in a coiled conformation23, so that the hydrophilic block of such amphipatic copolymers has the same type of conformation as the hydrophilic part of the membrane proteins. 

The study by low-angle X-ray diffraction of these mesophases provides X-ray patterns exhibiting a set of sharp lines with Bragg spadngs characteristic of a layered structure. This lamellar structure results from the superposition of plane, parallel, and equidistant sheets each sheet contains two layers one of thickness dA formed by the carbohydrate blocks, the other of thickness dB formed by the polypeptide blocks, there is a partition of the solvent between the two blocks 70% DMSO is localized in the carbohydrate layer284. Furthermore, the polypeptide chains are in a a-helix conformation as is demonstrated by infrared spectroscopy and X-ray diffraction and are oriented perpendicular to the plane of the sheets and assembled in a bidimensional hexagonal lattice as is revealed by X-rays284. ... 

The lamellar structure of saccharide-peptide block copolymers presents many analogies with the structure of copolymers with a hydrophobic polyvinyl block and a hydrophobic polypeptide block and exhibits a similar behaviour as a function of the solvent concentration. When the solvent concentration increases the total thickness of a sheet and the thickness of the carbohydrate layer both increase while the thickness of the polypeptide layer remains nearly constant284. ... 

Not all monomers are anionically pol5anerizable. Nevertheless, one can take advantage of the activity of the living ends to introduce reactive end groups at the extremity of homopolymers and then use arch end groups to initiate the polymerization of anionically non polymerizable monomers. This method has been applied to the synthesis of copolymere with polyvinyl and polylactone blocks and of copolymers with polyvinyl and polypeptide blocks One can at last use both anionic and cationic polymerization to prepare block copolymers of tetrahydrofuran with styrene or methylstyrene ... 

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