Infrared Desorption of Neutral Molecules Embedded in Transparent Matrices

Abstract

I n f r a r e d D e s o r p tio n o f N e u t r a l M o le c u le s E m b e d d e d in T r a n s p a r e n t M a tr ic e s R.C. Beavis, J. Lindner, J. Grotemeyer, and E.W. Schlag Institut für Physikalische und Theoretische Chemie, Technische Universität München Z. Naturforsch. 43a, 1083Naturforsch. 43a, -1090Naturforsch. 43a, (1988; received July 25, 1988 The desorption of intact molecules by pulsed IR irradiation is shown to depend on the IR absorption of the matrix. IR transparent matrices, such as NaCl or NH4N03, increase the total yield and the shot-to-shot stability of the sample. IR absorbing matrices decrease the yield of intact molecules and increase the amount of pyrolysis products.Using semi-transparent sugar matrices with dipeptide samples, the most intense fragment, i.e. the parent molecule having lost 18 u, is suppressed. This fragment is formed by pyrolysis during IR desorption. Three other prominent fragments are caused by the UV photoionization step.The experimental results suggest that a model involving bulk stresses and strain may be necessary to explain the observations.

Photomechanical Processes and Effects in Ablation

“…Many explanations have been put forward, including models related to mechanical fragmentation , and laser-induced acoustic desorption that are relevant within the context of the present review. The possibility that laser-induced thermomechanical stress contributes to the disintegration of MALDI matrices with IR lasers, where beam penetration in the matrix is deeper than with UV lasers, was put forward by Beavis et al and elaborated upon by Vertes and Levine . The basis of this suggestion appears to be earlier experimental studies on the laser desorption mass spectrometry of nonvolatile molecules reported by Lindner and Seydel .…”

Optimization of Sample Preparation for Peptide Sequencing by MALDI-TOF Photofragment Mass Spectrometry

“…Numerous papers have addressed issues of matrix-analyte preparation methods that result in improved sensitivity by reducing the internal energies of the ions. For example, Wilkins and co-workers 3,4 used a method originally discovered by Beavis and co-workers, 5 which involved mixing sugars with the sample to increase the stability of protonated peptides and proteins and, thus, enhance the resolution for Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. Becker and co-workers 6 showed that careful selection of the matrix increases the sensitivity of MALDI-TOFMS analysis of DNA, and they attributed the observed effects to internal energies of the MALDI formed ions.…”

Ion spray-tandem mass spectrometry of supramolecular coordination complexes

“…The formation of polynuclear helical complexes with heterocyclic nitrogen ligands is particularly attractive [2], especially for the development of luminescent chemical probes and sensors [3][4][5][6], but the characterization of the resulting supermolecules is often difficult. Mass spectrometry is a powerful technique, but for many systems studied, the low volatility and the tendency of the complexes to undergo reduction during the ionization process have limited the application of conventional techniques of mass spectrometry [7,8]. Fast-atom-bombardment (FAB) has been successfully applied to many cases as exemplified by the observation of molecular peaks for double-helical [2,[9][10][11][12][13][14] and triple-helical complexes [6,[15][16][17][18], for a trefoil molecular knot [19], and for the first deoxyribonucleohelicates [20].…”