Our research is in the area of instrument development and applications of laser desorption mass spectrometry. The main focus areas are creating new methods for laser desorption ionization, coupling liquid separations and laser desorption mass spectrometry, bioaerosol and biological agent detection and applications of new biological mass spectrometry methods to peptide and protein identification.

Infrared Laser Desorption Ionization

High speed photograph of a laser desorption plume.

The Murray Group is developing novel ionization methods for biological mass spectrometry using infrared lasers. In contrast to the ultraviolet lasers typically used for matrix-assisted laser desorption ionization (MALDI), infrared lasers have unique characteristics that can be advantageous for bioanalytical applications. One of the most significant advantages of infrared lasers is the ability to ionize without the addition of a matrix. Another characteristic of pulsed infrared lasers interacting with biological samples is the large depth of penetration and the propensity to remove large quantities of material with each laser shot. These properties can be put to use effectively in the ionization of biomolecules directly from polyacrylamide gels, tissue sections, and bacterial cells without the addition of a matrix. In addition to developing new mass spectrometric approaches, we are also investigating the fundamental chemical and physical processes of laser desorption and ionization. These include the effect of wavelength and energy on desorption, ablation and the production of ions from biological samples.

Laser Desorption for Microfluidic Chip Readout

Bacteria culturing microfluidic chip configured for deposition onto a MALDI target.

This project is a collaboration with the Prof. Steven Soper and is aimed at developing an interface that allows microfluidic chip devices to be "read" by a mass spectrometer. Microfluidic chips are small devices with systems of micrometer sized channels etched into glass, silicon, or molded in plastic. The channels are enclosed by bonding to a flat substrate. Various microfluidic components have been developed to perform valving, mixing, filtering, electrophoresis, liquid chromatography, polymerase chain reaction and other procedures. Sample transport is typically by electroosmosis and/or electrophoresis. In analogy to electronic integrated circuits, multiple components can be combined to form microscale total analysis systems. The advantages of such devices compared to conventional chemical analysis include low cost, small size, low sample consumption, high sensitivity, and rapid analysis. 

Isolation of Antimicrobial Peptides from the American Alligator

LSU Graduate Student Lancia Darville and Dr. Mark Merchant.

Alligators and crocodiles live in environments with large concentrations of pathogenic microbes, yet their wounds typically heal without infection. This is thought to be due to cationic peptides in their white blood cells. In a collaboration with Prof. Mark Merchant at McNeese State University, we are working to isolate these peptides in alligator blood using a mass spectrometry and proteomics based approach. One and two-dimensional gel electrophoresis, reversed phase high-performance liquid chromatography and nano-electrospray tandem mass spectrometry are used for separation, detection and peptide identification.

Bioaerosol and Biological Agent Detection

Ion mobility MALDI mass spectrum of B. subtilis bacteria with the UV MALDI mass spectrum  shown at bottom.

Our work with aerosol mass spectrometry has focused on generating ions from large biological molecules contained in small particles. The Murray Group is working to develop methods for bioaerosol analysis using both on-line and off-line approaches. We are also collaborating with the small business Ionwerks in Houston, Texas, to develop an ion mobility MALDI mass spectrometer for biological agent detection. This research will pave the way for portable instruments that can be used in homeland security and public health applications.