Sarah Trimpin Title Assistant Professor Division Analytical Education Diplom Universität Konstanz, 1999 (Germany) Doctor rerum naturalium Max-Planck-Institute for Polymer Research (degree granting institution: Universität Mainz), 2002 (Germany) Postdoctoral Fellow, Oregon State University/Oregon Health&Science University, 2002-2006 Research Associate, Indiana University, 2007-2008 Office Chem 61 Phone (313) 577-9823 E-Mail Group http://sarah.trimpin.googlepages.com/publications22

The organizing theme for our research is the exploration of approaches to chemical analyses that avoid the use of solvents to the greatest extent possible. This new area of research, which we term total solvent-free analysis, has yielded novel methods in sample preparation, ionization, separation, and mass spectrometry (MS) analysis. While solvent-based approaches are ideal for many types of chemical analysis, there is a host of reasons for developing methods that avoid solvents. The justification for exploring solvent-free approaches to chemical analysis relate to several factors that include: 1) the need to perform chemical analysis on molecules that are difficult or impossible to solubilize, known collectively as the "insolubleome"; 2) the need to avoid chemical reactions that can spontaneously change the structures of certain types of molecules when they are in solution; 3) the need to address problems associated with extreme loss of certain analytes in solution during sample preparation; and, 4) diffusion of analytes within a complex matrix such as tissue sections for MS imaging, where spatial distribution of analytes is a major variable in the analysis. The two primary goals of our research are the following.

Insolubleome. The "insolubleome" presents a unique challenge for traditional omics technology (both MS and gel based) due to the hydrophobic nature of particular biological constituents such as membranes, certain proteins, and lipids. The difficulty stems from the need for solubilization of analytes in traditional analytical techniques along with the incompatibility of detergents with mass spectrometry methods and, thus, the inherent need of detergent removal prior to mass analysis. Omic analysis aims at profiling the expression of proteins, metabolites, or lipids, etc. in a particular biological compartment (preferably an easily accessible body fluid) by a comparative analysis of different samples to identify differentially expressed molecules among healthy, diseased, and/or drug-treated populations. Scheme 1 provides an overview of stimuli affecting human health and current research areas intended at understanding molecular changes. Technologies employed for expression profiling aim at providing a maximum degree of accuracy and comprehensiveness by minimizing the analytical variability and increasing the sensitivity for all compounds present in large or minute amounts and independent of the degree of hydrophobicity and hydrophilicity.

The most important protein class for drug action are membrane proteins which serve as targets for approximately 70% of all drugs. On average, about 70% of all amino acids (aa) of an integral membrane protein are imbedded in the lipid bilayer and thus are intrinsically hydrophobic and not amenable for conventional proteolytic (tryptic) digestion. Current proteomics approaches aim at analyzing soluble domains which constitute about 25% of the primary sequence of membrane proteins. Alternative technologies are needed that improve/overcome the biases of present methods of analysis of hydrophobic proteins and other solubility-restricted compounds ideally also in a high-throughput fashion. Our current interest is to establish total solvent-free analysis for the characterization of the insolubleome. These fundamental developments in membrane proteomics, lipidomics and other metabolomic areas (including drugs) will be augmented by capabilities for analyses of in particularly protein modifications (phosphorylation, alkylation, etc) required to obtain a better understanding of protein interactions and functions (functional analysis).

Scheme 1. Molecular level and health effects.

Imaging of tissue samples. The localization of signaling molecules within specific brain circuits is crucial information for determining their functions. A vast literature has been devoted to determining the localization of signaling molecules in small diameter cells (SDC) within the dorsal root ganglion (DRG) that contains the cell bodies of peripheral sensory nerve fibers. SDC bodies are of particular interest because these cells evoke pain sensations when activated by noxious stimuli or under pathological conditions in chronic pain. Identifying signaling cascades unique to small caliber DRG cells offers promise for developing novel pharmacotherapies for chronic pain that lack the serious side-effects of current medicines. Despite the central role of lipids in cell signaling, their localization within neural circuitry is unknown because there is no way to visualize them at the cellular level; major obstacles are low-abundance and complexity while maintaining total tissue integrity. Imaging mass spectrometry offers the means to provide this crucial information for the first time, but the application of liquid matrix normally containing organic solvents can lead to diffusion of lipids in tissue sections and blur their distribution. We are interested in developing total solvent-free analysis for imaging of tissue sections in order to determine the localization of lipid signaling molecules and other components of intracellular signaling cascades in brain, spinal cord, and peripheral tissues.



REPRESENTATIVE PUBLICATIONS

^* Denotes corresponding authorship

Trimpin, S., Plasencia, M.D., Isailovic, D., and Clemmer, D.E.* Resolving Oligomers from Fully Grown Polymers with IMS-MS Resolving Oligomers from Fully Grown Polymers with IMS-MS. Anal. Chem. 79: 7965-7974, 2007.(accelerated publication)

Trimpin, S.*, Weidner, S.M., Falkenhagen, J., and McEwen, C.N. Fractionation and Solvent-free MALDI-MS Analysis of Polymers using Liquid Adsorption Chromatography at Critical Conditions in Combination with a Novel Multi-Sample On-Target Homogenization/Transfer Sample Preparation Method. Anal. Chem. 79: 7565-7570, 2007.

Trimpin, S.,* Clemmer, D.E., and McEwen, C.N. Charge-Remote Fragmentation of Lithiated Fatty Acids on a TOF-TOF Instrument Using Matrix-Ionization. J. Am. Soc. Mass Spectrom. 18: 1967-1972, 2007. (accelerated short communication)

Trimpin, S.* and Deinzer, M. L. Solvent-free MALDI-MS for the Analysis of β-Amyloid Peptides via the Mini-Ball Mill Approach: Qualitative and Quantitative Improvements. J. Am. Soc. Mass Spectrom. 18: 1533-1543, 2007.

Trimpin, S.* and McEwen, C.N. A Multi-Sample On-Target Homogenization/Transfer Method for Solvent-free MALDI-MS Analysis of Synthetic Polymers. J. Am. Soc. Mass Spectrom. 18(3):377-381, 2007.

Trimpin, S.* and Deinzer, M.L. Solvent-free MALDI-MS for the Analysis of a Membrane Protein via the Mini-Ball Mill Approach: a Case Study of Bacteriorhodopsin. Anal. Chem. 79(1):71-78, 2007.

Book Chapter

Trimpin, S. Solvent-free Matrix-Assisted Laser Desorption Ionization. Encyclopedia of Mass Spectrometry: Molecular Ionization, Vol. 6, Elsevier by Editor Dr. Michael L. Gross; 2006.