Development of Chemical Probes for Studying Formaldehyde Biology
Formaldehyde (FA) is a reactive carbonyl species (RCS) produced in living systems through a diverse set of cellular pathways that span epigenetic regulation to metabolic processing of endogenous metabolites. At the same time, however, aberrant elevations in FA contribute to pathologies ranging from cancer and diabetes to heart, liver, and neurodegenerative diseases. Traditional methods for the detection of biological FA rely on sample destruction and/or extensive processing, resulting in a loss of spatiotemporal information. Disentangling the complex interplay between FA physiology and pathology motivates the development of chemical tools that can enable selective detection of this RCS in biological environments with spatial and temporal fidelity. This dissertation describes the design and applications of a FA-responsive homoallylamine trigger which undergoes imine condensation with FA, followed by 2-aza-Cope rearrangement and hydrolysis, irreversibly forming a diagnostic product. Importantly, this 2-aza-Cope reactivity-based trigger was found to discriminate FA from other RCS such as methylglyoxal, 4-hydroxynonenal, and glucosone as well as from simple carbonyl-containing species such as acetaldehyde and pyruvate.
Throughout this body of work, emphasis was placed on the design of FA probes whose responsiveness and readout could be applied to interrogate FA biology in a number of biological systems. To this end, the FA-reactive trigger was appended to a variety of useful diagnostic readouts, including intensity-based fluorescence (FA Probe-1), excitation-ratiometric fluorescence (Ratiometric FA Probe-1 and Ratiometric FA Probe-2), bioluminescence (FA Luciferin-1), and immunohistochemistry (Puromycin FA Probe-1). All of these probes were shown to be responsive and selective toward FA in vitro and subsequently characterized in various cell culture model systems. This work established the utility of the 2-aza-Cope reaction as a FA detection platform and demonstrated its versatility for generating many functional imaging probes, paving the way for future interrogation of FA biology in living, intact systems.