CHANNEL MIMETIC SENSING MEMBRANES FOR NUCLEOTIDES BASED ON MULTITOPICHYDROGEN-BONDING

Nucleotide-induced permeability changes of oriented monolayers compose d of the nucleotide receptors 4-amino-1-octadecyl-2-(1H)-pyrimidinone (1), 5-methyl-1-octadecyl-2,4(1H,3H)-pyrimidinedione (2), and decyl)-4 -(8-(3-methylureido)-2-naphthyl)-amide-2-( VI)-pyrimidinone (3) were e xamined. These molecules are capable of binding guanosine, adenosine, and guanosine nucleotides, respectively, by multitopic hydrogen bondin g. Monolayers were first formed at the air/water interface and then di rectly contacted with a highly oriented pyrolytic graphite (HOPG) elec trode. The permeabilities of these membranes were evaluated with cycli c voltammetry, using [Fe(CN)(6)](4-) as permeability marker. Selective ly 5'-GMP-induced decreases in the permeability of the membranes based on receptor 1 or 3 were observed. On the other hand, decreases in the permeability of membranes based on receptor 2 were larger in the pres ence of 5'-AMP than of 5'-GMP. The permeability changes thus observed can be ascribed to repulsive electrostatic interaction between the mar ker anions and the negatively charged nucleotides that selectively bin d to the electrically neutral membrane receptors. The ratios of the ox idation current decreases for solutions containing 3.0 mM 5'-GMP and f or solutions containing 3.0 mM 5'-AMP were 1.30, 0.76, and 1.85 for mo nolayers based on receptors 1, 2, or 3, respectively. The monolayer ba sed on receptor 3, which is capable of binding the guanine base by fiv e hydrogen bonds, showed a higher 5'-GMP selectivity than the monolaye r of receptor 1 with the cytosine residue. Similar nucleotide-induced permeability changes were observed for mixed multilayers of receptor 1 and octadecanol (4), as well as for mixed monolayers with receptor 2 and 4.