A zinc(II) complex‐conjugated polymer for selective recognition and separation of phosphates

Abstract

AbstractA new polymer, Zn2+–cyclen complex‐conjugated polymer 4 (cyclen = 1,4,7,10‐tetraazacyclododecane), was synthesized by copolymerization of a Zn2+–(4‐vinyl)benzylcyclen complex (3, ZnL2) with ethylene glycol dimethacrylate (EGDMA). The contents of the zinc(II) ions in Zn2+–cyclen polymer 4 were determined as 36–42 μmol g−1, utilizing a Zn2+‐selective fluorophore, dansylamidoethylcyclen 10 (L3). It was found that 31% of deoxyadenosine 5′‐monophosphate (5′‐dAMP) (50 μM) is adsorbed on 4 (corresponding to 50 μM) in 20 mM HEPES (pH 7.0) with I = 0.1 (NaNO3) at 25°C. The apparent complexation constants for the 1:1 complex of ZnL2 on 4 with 5′‐dAMP and 4‐NPP, logKapp(ZnL–S2−) (S2− denotes a phosphomonoester dianion), at pH 7.0 and 25°C were determined as 4.1±0.1, which was larger than that (3.5) for the 1:1 complex of 3 (ZnL2) with 5′‐dAMP in homogeneous aqueous solution at pH 7.0 and 25°C. Deoxyadenosine (dA) and adenosine 3′,5′‐cyclic‐monophosphate (3′,5′‐cAMP), a cyclic phosphodiester monoanion, were negligibly adsorbed on Zn2+–cyclen polymer 4, implying that 4 interacts selectively with phosphomonoester dianions. For reference, Zn2+‐free polymer 8 (prepared from 4) and control polymer 9 (prepared by copolymerization of styrene with EGDMA) hardly adsorbed 5′‐dAMP, dA and 3′,5′‐cAMP. High‐performance liquid chromatography (HPLC) of mononucleotides such as 5′‐dAMP, cytidine 5′‐monophosphate (5′‐CMP), guanosine 5′‐monophosphate (5′‐GMP), and thymidine 5′‐monophosphate (5′‐dTMP) was achieved using 4 as a stationary phase and continuous gradient elution with 10:90 MeOH–1 mM HEPES (pH 7.0) and 10:90 MeOH–1 mM HEPES+10 mM (NH4)2HPO4 (pH 7.0). As expected, the retention times of mononucleotides were larger than those of the corresponding nucleosides, owing to the Zn2+‐phosphate interactions. These results indicated that Zn2+–cyclen‐conjugated polymer 4 affords a strong methodology to detect and separate biologically important phosphates. Copyright © 2004 John Wiley & Sons, Ltd.