Poly -benzyl-L-glutamate

The intrinsic viscosity of poly(7-benzyl-L-glutamate) (Mq = 219) shows such a strong molecular weight dependence in dimethyl formamide that the polymer was suspected to exist as a helix which approximates a prolate ellipsoid of revolution in its hydrodynamic behaviorf ... 

Poly(7-benzyl-L-glutamate) is known to possess a helical structure in certain solvents. As part of an investigationf of this molecule, a fractionated sample was examined in chloroform (CHCI3) and chloroform saturated ( 0.5%) with dimethyl formamide (DMF). The following results were obtained ... 

Certain polymers will exhibit liquid crystal behaviour in solution. This phenomenon was first noted for natural polypeptides, but was found to be obtainable in synthetic systems initially for poly(7-benzyl L-glutamate)... 

Fig. 33. Zimm plot128) for a sample of poly-7-benzyl-L-glutamate in dimethyl formamide at 25 °C...

Figure 17. FTIR absorbance (lower), VCD (middle) and VCD noise estimate (upper) for the 1800-1500-cm" region of poly-7-benzyl-L-glutamate, 2 mg/ml in CHCI3, path length 0.5 mm, resolution 4 cm". (Reproduced by permission of Wiley, from ref. 99.)...

Fig. 4. Schematic representation of the structure of polymer-heme complexes the ferriheme complex with poly(4-vinylpyridine) (a), poly(L-lysine) (b), (c), or poly(7-benzyl-L-glutamate) with a pendant imidazole (d)...

When poly(7-benzyl-L-glutamate) containing a pendant imidazole at the chain end (PBLG Im)19 was used as the polymer ligand, the coordination number in... 

A particularly striking additive effect is observed in the case of certain synthetic polypeptides, e.g. poly(7 -benzyl-L-glutamate), which has a formula (-CO-CHR-NH-), R = -CH2-CH2-COO-CH2-C6H5. In solution this substance readily forms an ct-helix, maintained by hydrogen bonding, with an axial dipole moment per repeat unit of about 4.14 x 10 30 Cm. Since a typical molar mass is about 500 000, the total axial dipole moment for a molecule is about 10 000 x 10 30 Cm. 

Fig. 3. Intrinsic viscosity-molecular weight relationship of poly-7-benzyl-L-glutamates. The open circles represent the randomly coiled form and other symbols the a-helical form. The line of steeper slope is a plot of Simha s equation. Abbreviations dichloroacetic acid, DCA chloroform saturated with formamide, C-F dimethyl formamide, DMF light scattering, L.S. weight-average molecular weight, A/m. Reproduced from Doty et al. (1956).

Fiq. 1. Optical rotatory dispersions for ordered and disordered forms of two synthetic polypeptides and a globular protein, PBG poly-7-benzyl-L-glutamate. Helical... 

If the dispersion of an isolated helix is plotted from a Moflitt equation with the coefficients found by Doty and Lundberg, it shows a point of inflection and a maximum near 400 m/i and becomes progressively levorota-tory below 300 mju, indicating that the contribution of the helical form is indeed the anomalous variety of complex dispersion. The anomalous character of the dispersion of poly-7-benzyl-L-glutamate is especially evident in wi-cresol (Fig. 1), a solvent in which Downie et al. (19.57) suggest that... 

The rotatory behavior of poIy-/3-benzyl-L-aspartate presents an exception to the rule that L-residues favor helices of the same sense, for it has a bo of about - -600 (Blout and Karlson, 1958), as well as a far ultraviolet dispersion and changes in [to ]x on forming the random coil that are obviously opposite in sign to those of poly-7-benzyl-L-glutamate (Karlson et al., 1960). In addition, its enantiomorph, poly-/3-benzyl-D-aspartate behaves as a normal L-polypeptide (Blout and Karlson, 1958). The systematic investigations of Bradbury et al. (1959, 1960a, b) and Karlson et al. (1960) leave little doubt that helical poly-/8-benzyl-L-aspartate has a sense opposite to that of the standard polymers and that its rotatory parameters reflect this... 

Figure 33 shows similar dependences of [nj/lnl on M for solutions of poly(7-benzyl-L-glutamate) (PBLG) > (Curve 1). These are compared with data for poly(chk>rohexyl isocyanate) (Curve 2). Experimental values of In]/[r)J for PBLG do not permit the determination of the limiting value ((n]/[r)l)a. because they covet only the initial part of the curve [nJ/lnl = f (M). 

---