Abstract
Two near-infrared fluorescent probes (A and B) containing hemicyanine structures appended to dipicolylamine (DPA), and a dipicolylamine derivative where one pyridine was substituted with pyrazine, respectively, were synthesized and tested for the identification of Zn(II) ions in live cells. In both probes, an acetyl group is attached to the phenolic oxygen atom of the hemicyanine platform to decrease the probe fluorescence background. Probe A displays sensitive fluorescence responses and binds preferentially to Zn(II) ions over other metal ions such as Cd2+ ions with a low detection limit of 0.45 nM. In contrast, the emission spectra of probe B is not significantly affected if Zn(II) ions are added. Probe A possesses excellent membrane permeability and low cytotoxicity, allowing for sensitive imaging of both exogenously supplemented Zn(II) ions in live cells, and endogenously releases Zn(II) ions in cells after treatment of 2,2-dithiodipyridine.
Highlights
After iron, zinc is the most abundant metal ion in the human body
This may be due to less delocalization of the lone pair from the reduction in the fluorescence background of the probes if an acetyl group is attached to the hydroxyl oxygen atom directly bonded to the acyl/hemicyanine fluorophore resulting in less charge delocalization group on the hemicyanine platform
Zn(II) ions coordinate with probe A and promote acetyl hydrolysis that yields a significant increase hemicyanine fluorophore in both solution and live cells
Summary
Zinc is the most abundant metal ion in the human body. Zn occurs strongly bonded within metalloproteins providing structural support and accomplishing various catalytic functions [1,2,3,4,5,6,7]. We find a significant probes A and B, see Schemes 1 and 2, and utilize these to determine Zn(II) concentrations in live cells reduction in the fluorescence backgroundligands of the on probes if an acetylplatform. Group is We attached to the hydroxyl by coordinating different Zn(II)-binding the hemicyanine find a significant group on the hemicyanine platform This may be due to less delocalization of the lone pair from the reduction in the fluorescence background of the probes if an acetyl group is attached to the hydroxyl oxygen atom directly bonded to the acyl/hemicyanine fluorophore resulting in less charge delocalization group on the hemicyanine platform. Zn(II) ions coordinate with probe A and promote acetyl hydrolysis that yields a significant increase hemicyanine fluorophore in both solution and live cells.
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