Synthesis of New Polymer‐Bound Adenine Nucleotides Using Starburst PAMAM Dendrimers

Abstract

Two types of new polymer-bound adenine nucleotides were synthesized by coupling adenine nucleotides (ATP and ADP) with starburst polyamidoamine (PAMAM) dendrimers. The first type was obtained by coupling native adenine nucleotides directly with a carboxy-terminated PAMAM dendrimer. In the second type, the nucleotides were modified by introducing a spacer arm containing a carboxylic end group (N(6)-R-ATP and N(6)-R-ADP) and coupled with an amine-terminated PAMAM dendrimer. Both types of the dendrimers were coupled with native or the modified nucleotides using the well-known carbodiimide activation technique. The optimum coupling pH and temperature were 4 and 30 degrees C, respectively, for preparing the carboxy-terminated PAMAM-bound ATP or ADP, and were 9 and 50 degrees C, respectively, for preparing the amine-terminated PAMAM-bound N(6)-R-ATP or N(6)-R-ADP. The ATP or ADP contents in the synthesized polymers were found to be 4 mol of ATP or of ADP/mol of carboxy-terminated PAMAM-bound ATP or ADP and 25 mol of ATP or of ADP/mol of amine-terminated PAMAM-bound N(6)-R-ATP or N(6)-R-ADP. The coenzymatic activities relative to the native ATP of the carboxy-terminated PAMAM-bound ATP against glucokinase and hexokinase were 16 and 7%, respectively, and those of the amine-terminated PAMAM-bound N(6)-R-ATP 2 and 1%, respectively. The coenzymatic activities relative to the native ADP of the carboxy-terminated PAMAM-bound ADP and the amine-terminated PAMAM-bound N(6)-R-ADP against acetate kinase were 24 and 3.5%, respectively.

Complexes of Poly(ethylene glycol)-Based Cationic Random Copolymer and Calf Thymus DNA: A Complete Biophysical Characterization

“…[11][12][13][14][15][16] Common cationic polymers such as polylysine, polyethylenimine, and polyamidoamine dendrimers have been extensively used for this purpose. [17][18][19][20][21][22][23][24] Electroneutral polyplexes that contain equivalent amounts * To whom correspondence should be addressed. E-mail: souvik2maiti@yahoo.com.…”

“…Successful delivery of therapeutic genes to intended targets remains a challenge for researchers. Viral vectors efficient in gene transfection in vivo pose safety concerns unlikely to abate soon, rendering nonviral delivery systems an attractive alternative. − One promising approach is to use DNA−polycation complexes (polyplexes) formed as a result of ionic interactions between the cationic groups of the polymer and the negatively charged phosphate groups of DNA. − Common cationic polymers such as polylysine, polyethylenimine, and polyamidoamine dendrimers have been extensively used for this purpose. − Electroneutral polyplexes that contain equivalent amounts of polyion units and negatively charged phosphate groups of DNA are insoluble in water and hence unsuitable for application as gene delivery vehicles. Conjugation of the cationic polymer to hydrophilic segments of poly(ethylene glycol) (PEG), dextran (Dx), and other glucose molecules markedly improves the solubility of the polyplexes. − For example, grafting of poly( l -lysine) (PLL) with PEG results in the formation of soluble polyplexes in a 40 μg/mL DNA solution, while nonsoluble aggregated polyplexes form when a PLL homopolymer is used .…”

Study of enzymatic G6P synthesis using polymer‐bound ATP in membrane reactors

“…Recently, we succeeded in synthesizing the polymer‐bound ATP and ADP by binding native ATP and ADP to a carboxy‐terminated polyamidoamine dendrimer 23. When the polymer‐bound ATP and ADP were used as cofactors, the rates of reactions catalyzed by B. stearothermophilus GK and AK were well correlated by the same rate equations as shown above (Eqs.…”

“…These calculations were based on the assumption that the reactor was continuously operated for 1 month without the activity loss of the enzymes and polymer‐bound ATP. This assumption is valid when the highly stable B. stearothermophilus GK and AK and the highly stable polymer‐bound ATP prepared in our previous work23 are used. Moreover, based on the simple polymer‐bound ATP synthesis procedures developed in our previous work,23 it becomes possible to overcome the cost barrier of the polymer‐bound ATP synthesis, which is more advantageous for using polymer‐bound ATP in the case of G6P production requiring ATP as a cofactor.…”