Polybenzyl L-glutamate

A Some ambiguity must be attached to this statement in view of the conclusions reached by Luzzati el al. (1961) on the basis of small angle X-ray scattering studies from dilute solutions of polybenzyl-L-glutamate in dimethylformamide, pyridine, and TO-cresol. These authors conclude that the conformation of the polypeptide in these solutions is that of the 3io-helix (Donohue, 1953) and not that of the a-helix. The value of 6o = —630° in Eq. (13) was obtained from optical rotatory dispersion measurements with similar solutions, and therefore if the conclusions of Luzzati et al. are correct, this value characterizes the 3io-helix. It would then be necessary to determine whether the 6o value for the a-helix is significantly different. 

Figure 6.10. Square root of second harmonic intensity (O) versus electric field for y-polybenzyl-L-glutamate (33). The curved line is the best fit to equation 28 y and the straight line is the extrapolation of the low-field value obtained from Xxxx Table 6.4.

Many works deal with the variation of the helicoidal pitch in cholesteric phases as a function of temperature and composition. The best way to elucidate the origin of the twist seems to be to compare the pitch variations in lyotropic and in thermotropic systems. The first accurate work in this field is due to Robinson (1958-66) who studied PBLG (polybenzyl-L-glutamate) a synthetic polypeptide in organic solvents as dioxane, ethylic alcohol, chloroform etc. and Cano (1967) who made measurements of the pitches of nematic paraazoxyphenetol with different amounts of cholesterol benzoate. 

Completely different structures and properties are observed for polybenzyl-L-glutamate ( PBLG ), Figure 4.3 which is one of the most commonly used lyotropic cholesteric systems. The a-helix of the peptide backbone causes rodlike molecular shapes, which give chiral nematic orders in organic solvents. 

Fig. 5.29. The dependence of the shear rate on polymer concentration for solutions of PBLG (polybenzyl-L-glutamate) solutions (A) c < Ci (isotropic solution) and (B) c > cn (mesomorphic solution), from [104].

Quadrupole splittings of a covalent halogen compound in liquid crystals were first observed in Cl NMR spectra of CH2CI2 in polybenzyl-L-glutamate by Gill, Klein, and Kotowycs (14). Quadrupole splittings of halide ions in amphiphilic mesophases were first observed in 1971 by Lindblom, Winnerstrom, and Lindman (15). 

Polyaddition polymerization, 99 Poly(g-benzyl-L-glutamate), 202 Polybenzyl-trimethyl-ammoniom (PVBMA)-polystyiene sodium sulfonate (PNaSS), III... 

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