Panoptic electrochemical probe for next-generation mass spectrometry based-lipidomics

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PROJECT SUMMARY/ABSTRACT Lipids play a vital role in maintaining cellular function. Altered lipid metabolism is currently considered a hallmark characteristic of many diseases such as malignancies, neurodegenerative diseases, cardiovascular diseases, and diabetes. This has led to a demand for new technologies with comprehensive capabilities for revealing lipid structure and composition. Such technology is essential for the study of lipid structure-function relationships and the development of methods to diagnose and treat pathologies. Recent efforts in mass spectrometry (MS)-based lipidomics, including ion activation methods and chemical derivatization, have expanded the toolbox for lipid analysis. However, there is no single method at present that is capable of resolving all types of lipid structures since lipids are structurally diverse and often contain mixtures of isomers. The lack of efficient and reliable analytical approaches for discerning lipid isomers in biological samples directly leads to the fact that the physiological roles and functions of lipid isomers remain largely unknown. The central vision of my research program is to address the deficiencies in lipid structural analysis technology using the unique microdroplet electrochemical (ME) methods, which take advantage of voltage-controlled electrochemical derivatization of lipid isomers and the dramatically accelerated rates of electrochemical transformations at microdroplet interfaces to achieve structural elucidation. The proposed voltage-triggered ME reactions will be performed in a modified electrospray emitter taking the form of a probe and using standard commercial MS instrumentation. Derivatized products will generate diagnostic ions specific to particular lipid isomers in tandem mass spectra, allowing characterization of detailed structures. During the next five years, my research group aims to develop ME probes for lipid analysis with particular emphasis on isomer identification and quantification so as to realize the promise of ME as a practical research tool for understanding, diagnosing, and treating diseases. A toolbox of ME reactions will be developed to characterize various lipid isomers including lipid class, acyl chain length, double- bond positions, geometries, and sn(stereospecific numbering)-positions, the key information needed for accurate lipid structure annotation. The ME reactions are diverse and can be triggered by voltage changes, so they will be cascaded into a single system (a panoptic ME probe) to identify lipid structures at all levels of isomer specificity in a single experimental run. The ME probe will be used for studying the lipidome of pre-diabetic mouse heart to reveal the initial lipidomic signature in the heart in response to a Western diet and to define the deleterious effects of lipid isomers on the development of cardiac pathology. The expected outcome of this project is to provide a widely applicable approach with enhanced capabilities in lipid structural analysis, which will uncover structure-function relationships in lipid homeostasis and pathology invisible to current lipid profiling.