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

Anew 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(11) ions in Zn2+-cyclen polymer 4 were determined as 36-42 mumol g(-1), utilizing a Zn2+- selective fluorophore, dansylamidoethylcyclen 10 (L-3). It was found that 31% of deoxyadenosine 5'-monophosphate (5'-dAMP) (50 mum) is adsorbed on 4 (corresponding to 50 pm) in 20 mm HEPES (pH 7.0) with I = 0.1 (NaNO3) at 25 degreesC. The apparent complexation constants for the 1:I complex of ZnL2 on 4 with 5-dAMP and 4-NPP, logK(app)(ZnL-S2-) (S2- denotes a phosphomonoester dianion), at pH 7.0 and 25 degreesC 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 degreesC. 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)(2)HPO4 (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 (C) 2004 John Wiley Sons, Ltd.