Poly-y-benzyl-D-glutamates

Racemic complex (racemic PBG), composed of PBLG and its enantiomer poly(y-benzyl D-glutamate) (PBDG), takes an a-helical conformation in the solid state and has different physical properties from those of PBLG or... 

Polymers. Poly (L-leucine) and poly( -benzyl-D-aspartate) were kindly provided by E. M. Bradbury, Portsmouth Polytechnic. Poly(L-alanine), poly(D-alanine), and poly(L-methionine), MW 40,000, were obtained from Sigma Chemical Co. A further sample of poly(L-methio-nine), MW 36,000, (Van Slyke method) was obtained from Mann Research Labs. Poly( -benzyl-L-aspartate), MW 210,000, poly(c-benzyl-oxycarbonyl-L-lysine), MW 400,000, poly (c-benzyloxycarbonyl-o-lysine), MW 900,000, poly(y-n-decyl-L-glutamate), MW 860,000, and poly(y-benzyl-D-glutamate), MW 235,000, were all obtained from Pilot Chemicals. The remaining polymers were the same as those used previously (12, 14). 

One of the best measures of twist is thought to be the cholesteric pitch. The temperature dependence of cholesteric pitch is then measured for poly-y-benzyl-L-, and poly-y-benzyl-D-glutamates ( PBLG, and PBDG ) and poly-y-alky1-L-glutamates, in various sol-ven-t systems. The temperature dependence of some physical properties were also measured. 

Panar, M., Phillips, W. D. Magnetic ordering of poly-y-benzyl-L-glutamate solutions. /. Am. Chem. Soc. 1968, 90, 3880-3882. 

Lotz and coworkers have used poly (y-benzyl-D-L-glutamate) as a stereochemical model to study the conformation of gramicidin A89. 

Saba,R.G., Sauer,J. A., Woodward,A.E. Dynamic shear behavior of poly (y-benzyl L-glutamate), poly(D, L-propylene oxide), and polyfethyl vinyl ether). J. Polymer Sd. A1, 1483 (1963). 

In fact, for random-coil conformations, b in Equation 41 is explicitly related to the exponent in the Mark-Houwink equation by 3b = a 1. In this way values of M may be determined directly from measurements of D° provided KD and b are known. Although both these parameters could in principle be calculated from a detailed knowledge of the geometry of the solute, it is usual to regard them as experimentally determinable parameters. A similar relationship has also been found to hold true for the polypeptide poly(y-benzyl L-glutamate) (PBLG) dissolved both in 1,2-dichloroethane and in dichloroacetic acid. These results are shown in Figures 6 and 7, respectively. 

Figure 6. Graph of D° vs. molecular weight for poly(y-benzyl-L-glutamate) (PBLG) in 1,2-dichloroethane. PBLG is in a helical conformation.

Fig. 8. Poly-y-benzyl-L-glutamates from polymerizations in dioxane solution with n-hexyiamine initiator, A with sodium hydroxide initiator, B degree of polymerization (D. P.) as a function of anhydride-initiator ratio (A/X). The molecular weights were obtained from reduced specific viscosities at concentrations of 0.2% in dichloroacetic acid. [Reprinted from paper by E. R. Blout and R. H Karlson J. Am. Chero. Soc. 78...

Figure 4-26. Specific rotation [o]d a poly(y-benzyl-L-glutamate) (M, = 350,000 g mol) in ethylene dichloride-dichloroacetic acid mixtures at 20° C (after J. T. Yang).

Tang D, Lin J, Lin S, Zhang S, Chen T, Tian X (2004) Self-assembly of poly(y-benzyl L-glutamate)-graft-poly(efhylene glycol) and its mixtures with poly(y-benzyl L-glutamate) homopolymer. Macromol Rapid Commun 25 1241-1246... 

Figure 4-24. Specific rotation [a]o of poly(y-benzyl-L-glutamates) of various degrees of polymerization Xn as a function of the temperature difference T — in 1,2-dichloroethane-dichloroacetic acid (20 80) mixture. is defined as the inflection point of the [ ]d = f T) curve for the probe with the highest degree of polymerization. Tj,c = 30°C. (After P. Doty and J. T. Yang, and B. H. Zimm, P. Doty, and K. Iso.)...

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