This proposal concerns the development and application of a resource technology capable of direct imaging of biomolecules with extremely good spatial resolution and sensitivity. In the best case, the spatial resolution will approach 1000 Angstroms. Increased spatial resolution will be the direct result of an increased sensitivity gained via the use of laser-based multiphoton ionization techniques combined with a liquid metal ion source. This imaging molecular microprobe, which may be constructed largely with commercially available components, is predicted to exhibit a nearly 2 order of magnitude improvement in resolution over existing molecular imaging techniques. Molecular imaging will be carried out using a liquid metal ion source for ion and neutral desorption from prepared surfaces with subsequent laser-based multiphoton ionization and mass analysis by time-of-flight mass spectrometry. This combination of chemical methodologies is uniquely suited to provide quantitative chemical identification with high spatial resolution, or conversely, spatial resolution at the few micron level with extremely good concentration sensitivity. Both high resolution and low resolution applications are planned. Applications of this technology will involve at least nine investigators at Penn State Univ., SUNY Buffalo and NIH. These applications will include imaging haptens to identify colonies that have been genetically manipulated to produce catalytic antibodies. Moreover, chemical imaging will be used to examine molecules bound to clusters of neurotransmitter receptors on nerve cell membranes and experiments are proposed to quantitate peptidergic neurotransmitters in single vesicles exposed by freeze fracture. In addition, the molecular microprobe will be developed for imaging phospholipids in erythrocyte, sperm and nerve cells to correlate membrane structure with function. The technology proposed complements existing capabilities in optical and electron microscopy, provides an ability to identify chemical species with extremely high resolution, and promises to revolutionize our ability to carry out experiments requiring bioimaging.
