Carbobenzoxy-L-lysine

Figure 4. NMR spectrum of a,N-carbobenzoxy-L-lysine having adenine moiety...

The oxidation of various alcohols by the poly(e-carbobenzoxy-L-lysine)-Cu complex was studied by Welch et aL127. The polymer catalyst showed selectivity in oxidation by virtually excluding alcohols of bulky structure such as diisopropyl and diisobutyl carbinol while admitting simple alcohols arch as n-butyl, iso-butyl, and sec-butyl. It was suggested from structural studies that the selectivity of the polymer catalyst resulted from the highly complex geometry of the molecular cage formed by the helix and the amino acid side chain around the coordinated Cu. The... 

Figure 6 shows how the transition of poly(e-carbobenzoxy L-lysine) (PCBL) in m-cresol is affected by the chain length of the sample (23). The trend displayed here is general and conforms to the theoretical prediction deduced from Fig. 1 the transition curve becomes sharper as chain length increases. Comparison with Fig. 5 indicates that in the same solvent, m-cresol, the direction of transition of PCBL is opposite to that of PBLA and the two transitions differ markedly in sharpness. This again illustrates the crucial importance of polymer-solvent interactions in the transitions of polypeptides. 

BG SG SC SL BCK SCK BK SK BE SE Polybutadiene-poly(benzyl-L-glutamate) Polystyrene-poly (benzyl-L-glutamate) Polystyrene-poly(cinnamyl-L-glutamate) Polystyrene-poly(L-leucine) Polybutadiene-poly(carbobenzoxy-L-lysine) Polystyrene-poly(carbobenzoxy-L-lysine) PoIybutadiene-poly(L-lysine) Polystyrene-poly(L-Iysine) Polybutadiene-poly(L-glutamic acid) Polystyrene-poly(L-glutamic acid)... 

The following copolymers have been prepared polybutadiene-poly(benzyl-L-glutamate) (BG), polystyrene-poly(benzyl-L-glutamate) (SG), polystyrene-poly(cinnamyl-L-glutamate) (SC), polystyrene-poly(L-leucine) (SL), polystyrene-poly(carbobenzoxy-L-lysine) (SCK) and polybutadiene-poly(carbobenzoxy-L-lysine) (BCK). 

Poly(e-carbobenzoxy-L-lysine)-Cu(II) complex is used in the selective dehydrogenation reaction of alcohol (138,139). X-Ray analysis shows that Cu(II) is coordinated with amide moiety in amino acid residue and peptide moiety in the helix chain, and gives the selectivity in the dehydrogenation (139). 

In (Section 8) we have considered kinetic phenomena encountered during the copolymerization of L- and D-enantiomorphs of a single type of NCA. Copolymerization of mixtures of NCAs of different a-amino acids to give random copolymers is readily realizable [2], one of the earliest examples reported being the synthesis of a DL-phenylalanine L-leucine copolymer by Woodward and Schramm [78]. However, there are few reports on the kinetics of random copolymerization. Shalitin and Katchalski [79] studied the copolymerization of the NCAs of 7-benzyl L-glutamate (A) and e,N-carbobenzoxy L-lysine (B) initiated by diethyl-amine in N,iV-dimethylformamide at 25°C and obtained the interesting result that the over-all rate of reaction (measured by the CO2 evolution) is equal to the sum of the rates of reaction of the individual monomers under similar conditions. The copolymerization is represented schematically in (60)... 

The following pairs of NCAs behaved similarly when copolymerized under the same conditions [79] L-phenylalanine + e,AT-carbo-benzoxy-L-lysine, L-phenylalanine + 7-benzyl-L-glutamate, glycine + e,A/ -carbobenzoxy-L-lysine, e,AT-carbobenzoxy-L-lysine + DL-alanine and 7-benzyl-L-glutamate + DL-alanine. On the other hand, copolymerization of 7-benzyl-L-glutamate and DL-alanine NCAs behaved in a different manner and showed retardation in the later stages. 

We have noticed for several systems examined that extrapolations of the Arrhenius plots for intermediate formation to ambient temperatures suggest that the rates of intermediate interconversion will be of the same order of magnitude at the temperatures at which the enzymes normally operate (12). The convergence of Arrhenius plots is shown for the papain-catalyzed hydrolysis of N-carbobenzoxy-L-lysine p-nitroanilide in Figure 3 (28). 

For reactions in which a chromophoric product is released part way through the catalytic reaction—for example, in protease catalysis where an acyl-enzyme intermediate is formed—it is often possible to see the release of an equivalent amount of the product formed concurrently to the formation of the enzyme-substrate intermediate. For example, as shown in Figure 4, in the reaction of papain with N -carbobenzoxy-L-lysine p-nitrophenyl ester in 60% dimethyl sulfoxide at pH 6.1 (the pH optimum) a stoichiometric "burst of p-nitrophenol is observed at temperatures below — 40°C as the acyl-enzyme is formed, followed by no further release of p-nitrophenol, indicating that no turnover is occurring... 

Synthesis. Using hexamethyl amine as initiator, we have copolymerized, in DNF solution, the N-carboxy-anhydride [NCA] of benzyl -L-glutamate with the NCAs of the following amino acids cinnamyl-L-glutamate, carbobenzoxy-L-lysine, L-leucine, dL-phenyl alanin, L-phenyl alanin. 

H909P9lyQ]ers of carbobenzGxy-L-lysine. We have studied homopolymers of carbobenzoxy-L-lysine with an average degree of polymerization between 50 and 500. They exhibit in dioxane solution different structures as it has already been reported for other solvents M1 ... 

If the hexagonal structure is particularly stable it is not the only structure possible for polymers of carbobenzoxy-L-lysine. For certain concentrations and temperatures a quadratic structure appears and it probably corresponds to a special conformation of the lateral chains. The elevation of the temperature increases the thermic agitation and destroys the asymmetry of the lateral chains leading to on hexagonal structure characterized by a cylindrical symmetry of the lateral chains around the peptidic chains. 

The fact that random and block copolymers of the same composition present the same hexagonal lattice with the same geometrical parameters means that the helices can slide along the direction of their axis and that there is no phase separation between the poly[carbobenzoxy-L-lysine] and the poly[y-benzyl-L-glutamate) blocks. 

On figure 8 we have plotted the variation of the parameter of the hexagonal lattice for homopoly[benzyl-L-glutamate curve D, for homopoly[carbobenzoxy-L-lysine) curve A and for random and block copolymers of different compositions curve B [copolymers containing 33 % of carbobenzoxy-L-lysine) and curve C [copolymers containing 66 % of carbobenzoxy-L-lysine). One can see that the distance between the axis of the helices increases with the carbo-benzoxy-lysine [CK) content of the copolymer. 

Polymerization of the polypeptide block. The polymerization of the NCA of Y benzyl L glutamate or of e-carbobenzoxy L lysine initiated by the primary amine function of the aminated polystyrene or polybutadiene is carried out in the absence of moisture, at room temperature in DMF solution in the case of polystyrene and in benzene solution in the case of polybutadiene. ... 

The number of folds of the polypeptide chains depends upon the nature of the polypeptide block the polyCe-carbobenzoxy-L-lysine) chains are less folded than the poly(y-benzyl-L-glutamate) chains. ... 

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