Poly L-lysine -Based Copolymers

ZHA Zhao, C., Zhuang, X., He, C., Chen, X., and ling, X., Synthesis of novel thermo- and pH-responsive poly(L-lysine)-based copolymer and its micellization in water, Macromol. Rapid Commun., 29, 1810, 2008. 

Poly(L-lysine)-Based Copolymers Synthetic Strategies and Biomedical Applications... 

With thymine and uracil derivatives, graft reactions proceed almost quantitatively while in the case of the adenine derivative, its activated ester hardly reacts with poly-L-lysine, and only the copolymer with low adenine content is obtained, probably owing to the instability of the activated ester. Hypochromidty of the copolymer based... 

Conformations of the polymers were studied by CD and optical rotation measurements. Poly-L-lysine is known to exist in disordered, helical and -conformation, depending on the temperature, pH of the system and the solvent used. The side chain of the polymer has a significant effect on the backbone conformation. At neutral pH, poly-L-lysine exists in a random coil structure while at pH above 10, the e-amino group becomes a neutral form and the polymer undergoes transition to a helical structure. In order to elucidate the effect of base substituents on the conformation of poly-L-lysine, CD spectra of the copolymer were measured. 

Encapsulation and delivery of DNA has also been investigated with poly(amino acid) (poly(AA)) based polymer vesicles. Brown and coworkers synthesized an amphiphilic triblock copolymer from methoxy-poly(ethylene glycol) (mPEG), hydrophobic palmitic acid chains in block segments along a poly-L-lysine (PLL) or... 

A new polymeric amphiphile based on cationic poly(L-lysine), which was partially modified with hydrophobic palmitoyl chains and hydrophilic neutral methoxy-poly(ethylene glycol) (Fig. 7e), was introduced by Uchegbu et al. [38,39], In water in the presence of cholesterol, these copolymers assembled into vesicles with diameters ranging from 200 to 600 nm (DLS, freeze-fracture TEM), depending on the chemical composition of the copolymer and the length of the polypeptide backbone. More detailed information about the secondary structure of chains and the structure of vesicle membranes were not given. 

Two older reviews summarize work in this field [124,125]. The following derivatives have been employed as porphyrins Fe(II,III) protoporphyrin-EX (heme, hemin), Fe(II,III) or Co(II) protoporphyrin-IX-diester, chlorophyllins with different metal ions in the core, Fe(II) tetraphenylporphyrin, Mg(II) or Fe(II,III) octaethylporphyrin, Fe(II,III) tetrakis[o-(alkylamido)phenyl]-porphyrin. Polymers with N-donor groups are based on proteins such as poly(L-lysine), poly(L-histidine), poly(Y-benzyl-L-glutamate) or synthetic polymers such as homopolymers and copolymers with vinylpyridine, iV-vinylimidazole or ethyleneimine. 

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