School of Pharmacy UNIVERSITY OF WISCONSIN - MADISON Research Research in my laboratory focuses on developing and implementing an array of novel mass spectrometry based strategies to answer questions about the most complex and elusive set of signaling molecules, the neuropeptides, and gain new insights into the roles of peptide hormones and neurotransmitters play in the plasticity of neural circuits and behavior. While significant effort has been directed to analytical technique and method development, it is the biomedical importance of understanding the neuropeptidergic system that drives our research to continuously refine and improve the analytical capabilities to address challenging neuroscience problems. Specifically, we are interested in understanding the roles that neuropeptides play in food intake, neural network development and response to environmental stresses. We have chosen to work with a simpler and well-defined crustacean nervous system to both facilitate technology development and address fundamental neuroscience problems related to neuromodulation and network plasticity. We have developed several unique sample preparation strategies and instrumentation protocols that enable sensitive analysis of neuropeptides directly from minute quantities of neural tissues. By combining chemical labeling, micro-scale separation and tandem mass spectrometry sequencing techniques, we have discovered a large number of novel neuropeptides used in crustacean nervous systems. The physiological effects of these new peptides at the cellular and network levels are evaluated in collaboration with laboratories of Eve Marder and Michael Nusbaum. Furthermore, both mass spectrometric imaging techniques and in vivo microdialysis sampling tools have been implemented to follow neuropeptide distribution and secretion with unprecedented details. Finally, a differential display strategy in conjunction with isotopic labeling technique is being developed to allow functional discovery of neuropeptides in response to various physiological changes. While the technology is developed using crustacean model system as a test-bed, the technology advancement resulting from our research is widely applicable to the large-scale analysis of peptides and proteins in many biological systems, including those of mammalian and humans. Towards this end, we have established several exciting collaborations targeted at neurochemical analysis in mammalian systems. These collaborative projects include the discovery of prion disease biomarkers in cerebral spinal fluids and serum (in collaboration with Judd Aiken and David Page), proteomic analysis neuroprotective factors secreted by astrocytes (in collaboration with Jeff Johnson), and proteomic study of dioxin-induced cardiotoxicity in developing zebrafish (in collaboration with Warren Heideman and Dick Peterson). We are also interested in developing new collaborations to help transform advances in analytical tools into important findings that lead to new diagnosis and therapeutic strategies. Li Group Ongoing Projects Quantitative MS Strategies iTRAQ (isobaric tag for relative and absolute quantitation) has become a widely utilized, but expensive labeling tool. We are developing an efficient, less expensive iTRAQ alternative that uses dimethylated amino acid labeling. Comparative Neuropeptidomic Study Neuropeptide expression changes induced by food intake, environmental stress and nanoparticle exposure in crustacean models are profiled and compared in this project. Monitoring of Neuropeptide Release via Microdialysis Microdialysis is performed to monitor neuropeptide secretion in live animals. Current effort has been focused on developing affinity-based enrichment strategy to improve peptide recovery and sensitivity. Biomarker Discovery We use large scale proteomic techniques to mine the proteome and peptidome of neurologically relevant cells, tissues, and biofluids for biomarker discovery and disease diagnosis. Mass Spectrometric Imaging Mass spectrometric imaging enables scientists to obtain 2D and 3D maps of biological analytes in their native tissues without the need for antibodies. The Li group implements this technology to examine distribution patterns of neuropeptides, proteins, lipids, and metabolites in a variety of tissues. Ion Mobility-Mass Spectrometry Ion mobility-mass spectrometry separates gas-phase ions by mass, charge, size and shape through collisions with inert gas molecules. The Li group is using it in novel ways to improve peptide identification and quantitation. When combined with theoretical modeling, it can be used to probe 3D molecular structures. Capillary Electrophoresis MS Capillary zone electrophoresis and capillary isoelectric focusing are being developed to couple with MS detection both off-line and on-line for enhanced neuropeptidomics. Available Instruments: Thermo Orbitrap Fusion Lumos Thermo Q-Exactive HF Thermo Q-Exactive Thermo Orbitrap Elite Thermo MALDI LTQ Orbitrap Waters Synapt G2 QTOF Bruker amaZon ETD Ion Trap Bruker ultrafleXtreme MALDI-TOF/TOF Bruker maXis 4G QTOF AB Sciex 5500 Q-Trap Group Achievements: Graduate students in our lab have received more than 60 awards, including various training grants (BTP, CBI, CNTP), fellowships and travel awards; Our lab members have given more than 150 research presentations at national and international meetings We have published more than 140 peer-reviewed research journal articles in the past eleven years.