ABSTRACT
Photocaged complexes can control the availability of metal ions to interrogate cellular signaling pathways. We describe a new photocage, {bis[(2-pyridyl)methyl]amino}(9-oxo-2-xanthenyl)acetic acid (XDPAdeCage, 1), which utilizes a 2-xanthone acetic acid group to mediate a photodecarboxylation reaction. XDPAdeCage photolyzes with a quantum yield of 27%, and binds Zn2+ with 4.6 pM affinity, which decreases by over 4 orders of magnitude after photolysis. For comparison to our previous approach to Zn2+ release via photodecarboxylation, the analogous photocage {bis[(2-pyridyl)methyl]amino}(m-nitrophenyl)acetic acid (DPAdeCage, 2), which uses a m-nitrobenzyl chromophore, was also prepared and characterized. The advantages of the 2-xanthone acetic acid chromophore include red-shifted excitation and a higher extinction coefficient at the preferred uncaging wavelength. The neutral ternary complex of [Zn(XDPAdeCage)]+ with the anionic ligand pyrithione is membrane permeable, which circumvents the need to utilize invasive techniques to introduce intracellular Zn2+ fluctuations. Using fluorescent imaging, we have confirmed transport of Zn2+ across membranes; in addition, RT-PCR experiments demonstrate changes in expression of Zn2+-responsive proteins after photolysis.
Subject(s)
Acetic Acid/metabolism , Coordination Complexes/metabolism , Fibroblasts/metabolism , Fluorescent Dyes/metabolism , Xanthones/metabolism , Zinc/metabolism , Acetic Acid/chemistry , Cell Membrane/chemistry , Cell Membrane/metabolism , Cells, Cultured , Coordination Complexes/chemistry , Fibroblasts/chemistry , Fluorescent Dyes/chemistry , Humans , Molecular Structure , Optical Imaging , Permeability , Photochemical Processes , Photolysis , Xanthones/chemistry , Zinc/chemistryABSTRACT
Neurotransmission and sensory perception are shaped through metal ion-protein interactions in various brain regions. The term "metalloneurochemistry" defines the unique field of bioinorganic chemistry focusing on these processes, and zinc has been the leading target of metalloneurochemists in the almost 15 years since the definition was introduced. Zinc in the hippocampus interacts with receptors that dictate ion flow and neurotransmitter release. Understanding the intricacies of these interactions is crucial to uncovering the role that zinc plays in learning and memory. Based on receptor similarities and zinc-enriched neurons (ZENs) in areas of the brain responsible for sensory perception, such as the olfactory bulb (OB), and dorsal cochlear nucleus (DCN), zinc participates in odor and sound perception. Development and improvement of methods which allow for precise detection and immediate manipulation of zinc ions in neuronal cells and in brain slices will be critical in uncovering the synaptic action of zinc and, more broadly, the bioinorganic chemistry of cognition.
