Poly a-amino add

From the CD spectra of PLL-A-67 (poly-L-lysine having 67% adenine units) in acidic aqueous solution, the residual elliptidty at 222 nm ([ I222) plotted against the pH of the system (Hg. 21). The value [0]222 is known to be related to the helix content of poly-(a-amino add) ... 

Catalytic Activity for Hydrolysis of p-Nitrophenyl Acetate and Heat Inactivation of Various Thermal Poly-a-Amino Adds°- ... 

The above conaderations ate described in fiiller detail in previous papers [6,7] and indicate that macromolecules assuming a single chirality conformation can show chiroptical properties characteristic of the conformation itself. Moreover, if chromophores are present in the side chains specific chiroptical properties can arise from dipole-dipole dectronic interactions among these chromophores disposed along the chirally arranged backbone. This situation is cleariy shown in poly-a-amino adds, in which spedfic and typical chiroptical properties are assodated with spedfic and typcal conformations (a-helix, -structures, random coil) [8]. 

Szwarc, M. The Kinetics and Mechanism of N-carboxy-a-amino-add Anhydride (NCA) Polymerization to Poly-amino Acids. Vol. 4, pp. 1—65. 

N-Carboxyanhydride of a-amino add is polymerized by the nucleophile-containing polymers such as poly(N-vinyl-2-ethylimidazole), poly(N-vinyl-2-ethylimidazole-co-acrylamide) and poly(N-vinyl-2-ethylimidazole-co-N-vinylpyrrolidone) (102, 103). The rate of polymerization increases with the order of pyrrolidone, amide and imidazole moieties. The order corresponds to the magnitude of the bond formation which is observed in 1R measurement. The rate also increases with the content of pyrrolidone moiety. The rate in N, N -dimethylformamide solution which is unfavorable to the hydrogen bond formation is lower than that in acetophenone. These results show that the hydrogen bond formation is notable as the binding. 

Katsarava R, Beridze V, Arabidi N, Kharadze D, Chu C C and Won C Y (1999), Amino add based bioanalogous polymers synthesis and study of regular poly (ester amide)s based on bis(a-amino add) a, co-alkylene diesters and aliphatic dicarboxyhc acids , / Polym Sci Polym Chem Ed, 37,391-407. 

Polydepsipeptides with N-alkyl-substituted a-amino add residues, such as poly(N-methylglydne-alt-D,L-lactic acid) and poly(N-isopropylglydne-alt-D,L-lactic acid), cannot be polymerized by a ring-opening reaction from the corresponding N-alkyl-substituted 2,5-morphohnediones [24]. 

By Naylor and Gilliam62, d (pT)6 was condensed in the presence of Poly A with carbodiimide to give d-(pT)12 with a yield of 5%. In the experiment of Shabarova and Prokofiev67, d-(pA)2 preactivated in the form of an amino add amidate was condensed on Poly U to give products with a yield of 10%. Uesugi and Ts o68 studied the condensation of (2 MeIp)6 or (2 MeIp)s in the presence of a Poly C template. The relative overall yield of the oligomer products was 43 to 71%. 

Several new amino acid residues were detected in irradiated poly-a, r glutamic acid, poly-D,h-alanine, and poly-irproline. The pH of the solution during irradiation affects the physical and chemical changes induced in the polyamino adds. 

There are also a few examples of poly-amino add catalyzed epoxidation of non-linear enones. These indude tetralone derivatives 47, which can be epoxidized with good yields and enantiomeric excesses the best results were achieved for R = p-02N-QH4 and n = 1 (85% 96% ee) [84]. Other examples are the epoxidation of "iso-chalcone 48 (78% 59% ee) [69] or of bis-benzylidene cyclohexanone 49, which affords the corresponding bis-epoxide of good optical purity [69]. 

The structural analysis has been carried out right up to the recognition of molecular Level (i, 2). a-Chymotrypsin is poly(amino acid) consisting of 245 amino adds, having relatively deep grooves. It catalyzes the hydrolysis of carboxylic acid derivatives such as protein, simple amides, esters, etc. The active site is composed of aspartic add, Asp (102). .. histidine, His (57). .. serine, Ser (195), and the distances between Asp. .. His and His... Ser are 2.8 A and 3.0 A, respectively. Electronic structures of these moieties depend on the pH of the reaction system. In the range of pH > 7 at which a-chymotrypsin is active, —COO" of Asp attracts N4 proton in imidazolyl of His, and Nj in the imidazolyl of His attracts the proton in OH of Ser. It is called charge-relay system . 

Brown MD, Gray AI, Tetley L, Santovena A, Rene J, Schatzlein AG, Uchegbu IF (2003) In vitro and in vivo gene transfer with poly(amino add) vesicles. J Contr Release 93(2) 193-211 Zhang L, Bartels C, Yu Y, Shen H, Eisenbeig A (1997) Mesosized crystal-Uke stmcture of hexagonally packed hollow hoops by solution self-assembly of diblock copolymers. Phys Rev Lett 79 5034-5037... 

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