A high pressure matrix-assisted laser desorption ion source for Fourier transform mass spectrometry designed to accommodate large targets with diverse surfaces

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Metastable decomposition of ions generated in matrix-assisted laser desorption/ionization (MALDI) mass spectrometers complicates analysis of biological samples that have labile bonds. Recently, several academic laboratories and manufacturers of commercial instruments have designed instruments that introduce a cooling gas into the ion source during the MALDI event and have shown that the resulting vibrational cooling stabilizes these labile bonds. In this study, we compared stabilization and detection of desorbed gangliosides on a commercial orthogonal time-of-flight (oTOF) instrument with results we reported previously that had been obtained on a home-built Fourier transform mass spectrometer. Decoupling of the desorption/ ionization from the detection steps resulted in an opportunity for desorbing thin-layer chromatography (TLC)-separated gangliosides directly from a TLC plate without compromising mass spectral accuracy and resolution of the ganglioside analysis, thus coupling TLC and oTOF mass spectrometry. The application of a declustering potential allowed control of the matrix cluster and matrix adduct formation, and, thus, enhanced the detection of the gangliosides. during matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analyses of molecules having labile bonds. Although this phenomenon can be used for obtaining analyte structural information for small peptides, oligosaccharides, and some glycolipids [1-5] for larger or more fragile molecules, it can limit the mass accuracy and resolution and complicate interpretation of the spectra of heterogeneous samples. Thus, it is important to develop methods that allow control of the extent of metastable decay. In addition to the pressure of the background gas and extraction field strength in the MALDI technique, the major factors affecting metastable fragmentation are laser wavelength/pulse width and the choice of the MALDI matrix [6,7]. In addition, the presence of electrons may play a role in analyte fragmentation and may cause suppression of multiply charged ions in a spectrum [8,9].Control of the metastable fragmentation in MALDI by increasing the pressure in the ionization source and reduction of the ions internal energy was first introduced by Loboda et al. on orthogonal time-of-flight (oTOF) instruments [10] and later extended to Fourier transform mass spectrometry (FTMS) [11] and to the operation at atmospheric pressure on various types of instruments [12]. These methods have since been used for stabilization of glycolipids [13,14] and peptides and proteins [11,15]. The term vibrational cooling (VC) MALDI recently has been introduced to describe desorption in the pressure range where cooling of the excess bond energy is achieved [12]. Stabilization of the labile bonds under these conditions allows for control of the extent of fragmentation, which is particularly

Section: Discussionmentioning

confidence: 99%

Ganglioside analysis by thin-layer chromatography matrix-assisted laser desorption/ionization orthogonal time-of-flight mass spectrometry

Ivleva

Sapp

O’Connor

et al. 2005

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“…Due to the high mass accuracy and resolving power of an FTMS, MALDI-FTMS [5][6][7] and ESI-FTMS [8,9] are becoming the instruments of choice for proteomics [10], and experiments on proteins and large fragments of proteins, so called "top-down" [11][12][13][14] mass spectrometry. These experiments tend to slow down due to the lack of sophisticated methods for automatic spectrum analysis.…”

Section: T He Wide Employment Of Fourier Transform Massmentioning

confidence: 99%

Algorithms for automatic interpretation of high resolution mass spectra

Kaur

O’Connor

2006

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Automated interpretation of high-resolution mass spectra in a reliable and efficient manner represents a highly challenging computational problem. This work aims at developing methods for reducing a high-resolution mass spectrum into its monoisotopic peak list, and automatically assigning observed masses to known fragment ion masses if the protein sequence is available. The methods are compiled into a suite of data reduction algorithms which is called MasSPIKE (Mass Spectrum Interpretation and Kernel Extraction). MasSPIKE includes modules for modeling noise across the spectrum, isotopic cluster identification, charge state determination, separation of overlapping isotopic distributions, picking isotopic peaks, aligning experimental and theoretical isotopic distributions for estimating a monoisotopic peak's location, generating the monoisotopic mass list, and assigning the observed monoisotopic masses to possible protein fragments. The method is tested against a complex top-down spectrum of bovine carbonic anhydrase. Results of each of the individual modules are compared with previously published work. (J Am Soc Mass Spectrom 2006, 17, 459 -468)

“…We recently reported an optimized procedure for (Ϫ)nanoESI-QTOF MS and tandem MS for the characterization of a native ganglioside mixture from brain tissue [27][28][29][30]. This procedure requires elevated parameter values for ionization, and an extended time for MS/MS signal acquisition, which suggests that relatively high sample consumption is needed for identification and structural elucidation.…”

mentioning

confidence: 99%

Fully-automated chip-based nanoelectrospray tandem mass spectrometry of gangliosides from human cerebellum

Zamfir

Vukelić

Bîndilă

et al. 2004

The introduction of chip-based electrospray (ESI) ion sources into biological mass spectrometry (MS) addressed the fundamental issue of how to analyze minute amounts of complex biological systems. The automation of sample delivery into the MS combined with the chip-based ESI allows for high quality bioanalysis in a high-throughput fashion. These advantages have already been demonstrated in proteomics, direct screening of drugs and drug discovery. As part of our continuing effort to implement automated chip-based mass spectrometry into the field of complex carbohydrate analysis, we hereby report the development of a chipESI MS and MS/MS methodology for the screening of gangliosides. A strategy to characterize a complex ganglioside mixture from human cerebellar tissue, by automated ESIchip-quadrupole time-of-flight (QTOF) MS and MS/MS is presented here. The feasibility of this method, and the general experimental requirements for automated chipESI MS analysis of these carbohydrate species is