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The improved ester substrates, which are cleaved in the presence of catalytic amounts of [Cu.sup.2+], are described. The studies have shown that the hydrolytic chemical reaction is used for sensitive and selective detection of [Cu.sup.2+] by using both absorption and fluorescence spectroscopy.

The concept of fluorescent metal ion sensing with an easily tunable emission wavelength is described and its principle is demonstrated by detection of Cu(super 2+) ions. The intensity of sensor emission at 624 nm is strongly dependent on the Cu(super 2+) concentration, with a 20 nM detection limit.

A series of conjugates of peptide nucleic acids(PNA) and Zr(IV) complexes were prepared. The efficient artificial restriction enzyme found that PNA conjugate with a Zr(IV) complexes of tris(hydroxymethyl)-aminomethane, cleavage DNA targets sequence selectively in close proximity to the Zr(IV) complex.

A concept of fluorescent metal ion sensing with an easily tunable emission wavelength is presented and its principle demonstrated by detection of Cu2+. A fluorescein dye was chemically modified with a metal chelating group and then attached to the terminus of ss-DNA. This was combined with a complementary ss-DNA modified with another fluorescent dye (ATTO 590), emitting at a longer wavelength. In the assembled duplex, fluorescence resonance energy transfer (FRET) between the fluorescein donor (excited at 470 nm) and the ATTO 590 acceptor (emitting at 624 nm) is observed. Proper positioning within the rigid DNA double helix prevents intramolecular contact quenching of the two dyes. Coordination of paramagnetic Cu2+ ions by the chelating unit of the sensor results in direct fluorescence quenching of the fluorescein dye and indirect (by loss of FRET) quenching of the ATTO 590 emission at 624 nm. As a result, emission of the acceptor dye can be used for monitoring of the concentration of Cu2+, with a 20 nM detection limit. The emission wavelength is readily tuned by replacement of ATTO-DNA by other commercially available DNA-acceptor dye conjugates. Fluorescent metal ion sensors emitting at >600 nm are very rare. The possibility of tuning the emission wavelength is important with respect to the optimization of this sensor type for application to biological samples, which usually show broad autofluorescence at <550 nm. [ABSTRACT FROM AUTHOR]

Hydrolysis of activated esters, e.g., picolinic acid and a-amino acid esters, in the presence of Cu2+ salts is a stoichiometric process because products of this reaction bind the catalytic metal ion substantially stronger than starting materials do. Herein we report improved ester substrates, which are cleaved in the presence of catalytic amounts of Cu2+; 55 turnovers of hydrolysis are observed for the best substrate, acetic acid 2-hydroxypyridine ester. We demonstrate that this reaction can be used for sensitive and selective detection of Cu2+ by using both absorption and fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]