Matrix-Assisted Laser Desorption/Ionization

A modified Finnigan Mat MALDI/TOF-MS device is located in the Ultrafast Laser Facility for studies of the MALDI process. The MALDI process is initiated with a nitrogen laser for standard MALDI studies, and the nitrogen laser is replaced with nanosecond, picosecond, or femtosecond sources at wavelengths ranging from UV to mid-IR to study the MALDI process itself.

Typically, MALDI is conducted with nanosecond ultraviolet lasers because of their compact size and low cost. However, the number of matrices suitable for use in UV MALDI is limited. IR MALDI offers the advantage of having a wider range of possible matrices (virtually any acidic, strong IR absorber is a candidate). Often the large matrix signals are suppressed in IR MALDI allowing greater sensitivity with lower mass analytes. Since the picosecond laser is widely tunable we can study several matrix materials at many wavelengths.

Unfortunately, the ionization mechanisms of this popular technique are poorly understood. By using a short pulse, we hope to gain an understanding of the processes that may be occurring in the initial desorption and ionization event. These findings would provide insight into the nature of intermolecular and intramolecular interactions and laser interactions with condensed phases.