Abstract
Redox biology is still looking for tools to monitor redox potential in cellular biology and, despite a large and sustained effort, reliable molecular probes have yet to emerge. In contrast, molecular probes for reactive oxygen and nitrogen have been widely explored. In this manuscript, three kinetically inert lanthanide complexes that selectively react with hypochlorous acid are prepared and characterized. The design is based on 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) and 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (DO2A) ligands appended with one or two redox active hydroquinone derived arms, thereby forming octadentate ligands ideally suited to complex trivalent lanthanide ions. The three complexes are found to react selectively with hypochlorous acid to form highly symmetric lanthanide(III) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacedic acid (DOTA) complexes. The conversion of the probe to [Ln.DOTA]− is followed by luminescence, absorption, and NMR spectroscopy in a model system comprised of a Triton-X modified HEPES buffer. It was concluded that the design principle works, and that simple caging units like hydroquinones can work well in conjugation with lanthanide(III) complexes.
Highlights
Reactive Oxygen Species (ROS), and Reactive Nitrogen Species (RNS) [1,2,3], are classes of compounds that include one- or two-electrons oxidants and play essential roles in living organisms [1,2].The most relevant ROS originate from a cascade started by the one electron reduction of O2 giving the superoxide radical (O2 − ) by means of either NADPH oxidases (NOXs) or by leakage in the electron transport chain inside the mitochondria [1,3,4,5,6,7,8]
ROS play numerous and diverse roles in biology: Biomolecules are responsive to redox conditions and many biological processes are regulated by redox chemistry [1,2,6,7]; the first understanding of ROS concerned either their deleterious action against lipids, proteins and nucleic acids or their role as antimicrobial agents, the importance of these reactive molecules has recently been revised, spurring the need for better probes to detect them [4,9,10]
Mass spectrometry and a plethora of fluorescent and luminescent probes have been proposed over the years [4,11,12,13,14]; these probes have been conjugated to units that can target specific organelles [4]; because of the complexity of both living organisms and redox processes in vivo, the selective and reliable detection of ROS has Molecules 2020, 25, 1959; doi:10.3390/molecules25081959
Summary
Reactive Oxygen Species (ROS), and Reactive Nitrogen Species (RNS) [1,2,3], are classes of compounds that include one- or two-electrons oxidants and play essential roles in living organisms [1,2].The most relevant ROS originate from a cascade started by the one electron reduction of O2 giving the superoxide radical (O2 − ) by means of either NADPH oxidases (NOXs) or by leakage in the electron transport chain inside the mitochondria [1,3,4,5,6,7,8]. Reactive Oxygen Species (ROS), and Reactive Nitrogen Species (RNS) [1,2,3], are classes of compounds that include one- or two-electrons oxidants and play essential roles in living organisms [1,2]. ROS play numerous and diverse roles in biology: Biomolecules are responsive to redox conditions and many biological processes are regulated by redox chemistry [1,2,6,7]; the first understanding of ROS concerned either their deleterious action against lipids, proteins and nucleic acids or their role as antimicrobial agents, the importance of these reactive molecules has recently been revised, spurring the need for better probes to detect them [4,9,10]. Mass spectrometry and a plethora of fluorescent and luminescent probes have been proposed over the years [4,11,12,13,14]; these probes have been conjugated to units (peptides or TTP) that can target specific organelles [4]; because of the complexity of both living organisms and redox processes in vivo, the selective and reliable detection of ROS has Molecules 2020, 25, 1959; doi:10.3390/molecules25081959 www.mdpi.com/journal/molecules
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