The interaction of ultraintense, ultrafast radiation with van der Waals bound condensed phase systems results in a useful approach for sample introduction to an electrospray source, namely transfer of molecules into the gas phase without decomposition. We have explored laser vaporization as a means to deliver sample directly into an electrospray source for subsequent mass spectral analysis. We have found that molecules as large as tobacco mosaic virus may be transferred from the solution phase into the gas phase not only without decomposition, but also maintaining biological activity after interacting with a laser pulse of duration 50 femtoseconds and intensity 10^13 W cm^-2.
This talk will introduce the method of laser electrospray mass spectrometry (LEMS) and will explore the use of LEMS to measure condensed phase tertiary structure of protein, measurement of enzyme substrate dissociation constant, and classification materials including improvised explosive devices (IED), black powder manufacturer, and gunshot residue manufacturer from the quantitative, direct analysis of complex mixtures. The universal detection of molecules using a single electrospray solvent composition, either polar or nonpolar, for either hydrophilic or hydrophobic samples will be presented. The ability to perform an ESI measurement approximately every second will be discussed, and this provides the ability to perform many thousands of ESI measurements per day. Finally, we will discuss the use of LEMS as a means to chemically image mouse brain to identify new biomarkers for traumatic brain injury.
Traumatic brain injury (TBI) is a complex injury involving multiple physiological and biochemical alterations to tissue. The potentially thousands of relevant biomarkers spread over a volume of thousands of mm3 inherently makes the spatially-resolved chemical analysis of brain a big data problem. LEMS was employed to image TBI mouse brain sample and assess the spatial distribution of biomarkers after trauma. The imaging experiment was performed using a 100 µm laser spot size rastered over a 4 x 4 mm area of a mild TBI brain tissue section to generate 100 Gbytes of data. Species identified by mass spectra were spatially mapped and compared to corresponding optical images of the brain sample. A present challenge for the method is the development of data mining techniques to identify relevant biomarkers for TBI.
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