Comparison of rhodamine dyes as matrices for matrix-assisted laser desorption/ionization mass spectrometry

✍ Scribed by K. Tang; S. L. Allman; R. B. Jones; C. H. Chen

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 383 KB
• Volume: 27
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210271211

✦ Synopsis

Comparison of Rhodamine Dyes as Matrices for ~a t n x -~i s t ~

Laser D ~o r p t i o n ~o n ~a t i o n

Mass Spectrometry

During the past few years, a tremendous effort has been applied to the mass spectrometric analysis of biopolymers. Hillenkamp and co-workers' developed the matrix-assisted laser desorption/ionization method (MALDI), which provides the capability of measuring the molecular masses of very large biopolymers. Recently, observations of protein ions with molecular masses greater than 1OOOOO Da without significant breakup have been reported.2 For a typical matrix-assisted laser desorption/ionization process, the biopolymer sample is mixed with a solution containing a molar excess of an organic acid. This solution is then dried on a metal substrate, which is subsequently placed into a mass spectrometer for the MALDI analysis. A short pulse ultraviolet (UV) or infrared (IR) laser beam is typically used for a MALDI process. Nd:YAG, N,, and excimer lasers"' are commonly used to produce a coherent ultraviolet beam. On the other hand, CO, and Er:YAG lasers have been chosen to produce the iR beam for MALDI.6.7 In general, the laser wavelength is selected for strong absorption of the matrix material to cause efficient desorption and ionization. The detailed mechanism of ionization is still not well understood.

Since most matrix materials used are small organic acids, a coherent UV beam is typically used to obtain strong absorption of matrix materials. At the same time, the absorption of UV light by biopolymers in the sample matrix mixture can possibly lead to the breakup of the biopolymer molecules. Romano and Levis' demonstrated the laser desorption of