Gold coating of non‐conductive membranes before matrix‐assisted laser desorption/ionization tandem mass spectrometric analysis prevents charging effect

Scherl, Alexander; Zimmermann‐Ivol, Catherine G.; Dio, Joel Di; Vaezzadeh, Ali R.; Binz, Pierre‐Alain; Amez-Droz, Michel; Cochard, Roland; Sanchez, Jean‐Charles; Glückmann, Matthias; Hochstrasser, Denis F.

doi:10.1002/rcm.1831

Cited by 40 publications

(42 citation statements)

References 26 publications

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“…The signal enhancement may be partially associated with decreased surface charging [24] but charging affects primarily the ion flight times and not the total ion signal. The coating process creates many microscopic regions of metal-matrix contact, all at the top of the sample where the laser intensity is highest.…”

Section: Metal Coating On Thick Samplementioning

confidence: 99%

Enhanced MALDI ionization efficiency at the metal-matrix interface: Practical and mechanistic consequences of sample thickness and preparation method

McCombie

Knochenmuss

2006

J. Am. Soc. Mass Spectrom.

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Electrosprayed spots of varying thickness were evaluated for use as reproducible, homogenous, high efficiency MALDI samples. Thin samples on stainless steel plates were found to give exceptionally strong signals, as did the last layers of thick samples, when ablated down to the steel substrate. A small enhancement was also observed for thin samples on a gold substrate, and with a few-nanometer gold coating on top of a thick sample. Ion yields and intensity ratios can be understood in the context of the previously described quantitative MALDI model including the matrix-metal interfacial ionization potential reduction effect (Knochenmuss, R.; Anal. Chem. 2004, 76, 3179 -3184). The absolute and relative stabilities of ion signals were found to be at least a factor of two better for the thin electrosprayed spots, , both the underlying ionization mechanisms and sample preparation methods remain objects of active study. These are coupled topics since mechanistic understanding can allow rational, rather than undirected, method development. Here, we make use of a recently developed quantitative model for UV-MALDI based on a two-step ionization process [2,3]. Primary laser-created matrix ions and analyte neutrals undergo ion-molecule reactions in the expanding ablation plume to yield secondary analyte ions. The observed mass spectrum is determined by the thermodynamics of these reactions. Because matrix and analyte are explicitly coupled, the model proved particularly suitable for understanding of practically relevant phenomena such as ion suppression effects [4 -6], which have been shown to be very common phenomena [7].A variant of this model has recently been developed for thin samples on metal substrates [8]. This was motivated by measurements of electron emission yields from MALDI samples on metallic versus insulating substrates [9], and suggestions that such electrons might neutralize (positive) analyte ions during the desorption process [10]. The model gave excellent agreement with the electron yield data, but this was not consistent with claims of higher analyte ion yields for samples on nonconductive versus conductive substrates [9]. The major difference between thick and thin samples is the interaction of matrix molecules with the substrate, which can lower the ionization potential of the combined system if the substrate is metal. It was, therefore, theoretically expected that thin samples on metal would yield higher, not lower, signals. The present study was undertaken to investigate this discrepancy and restore consistency to sample preparation strategy.The method selected here to prepare homogenous samples of variable thickness is electrospray (ES) deposition of analyte/matrix solution [11,12]. Electrospray produces more uniform, fine-grained sample spots than the more convenient and widespread dried droplet technique, which tends to form large matrix crystals in random locations. By varying the electrospray time, it is also possible to make samples as thin as a few hundred nanometers, but a few mm in diamete...

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Section: Metal Coating On Thick Samplementioning

confidence: 99%

Enhanced MALDI ionization efficiency at the metal-matrix interface: Practical and mechanistic consequences of sample thickness and preparation method

McCombie

Knochenmuss

2006

J. Am. Soc. Mass Spectrom.

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“…When the thickness of a slice is > 15 μ m, the sensitivity deteriorates, particularly when high molecular weight proteins are analyzed [66] (Figure 3.30 ). This difference can be attributed to a phenomenon referred to as the " charging effect " [67] . Generally, biological tissue sections have low intrinsic electric conductivity, and this tendency is considered more apparent with thicker tissue sections.…”

Section: Preparation Of Matrix Solutionmentioning

confidence: 99%

Imaging Mass Spectrometry (IMS) for Biological Application

Yao

Setou

2012

Mass Spectrometry Handbook

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“…Gold coating is beginning to find application in MALDI and LDI experiments (Scherl et al, 2005;Altelaar et al, 2006). A thin gold coating has reduced sample charging during mass analysis and thus increased the resolution and sensitivity of MS/MS experiments (Scherl et al, 2005). Other reports have demonstrated how the application of gold nano-particles (McLean, Stumpo, & Russell, 2005) or gold implantation of large gold clusters Tempez et al, 2005) followed by laser desorption can be used to generate peptide and protein ions, in the latter examples from tissue sections.…”

Section: Chemical Modificationmentioning

confidence: 99%

“…However, the high concentrations used in the latter experiment (1% and 10%) could simply indicate yield saturation and tangling of the larger molecules at the higher concentration. Gold coating is beginning to find application in MALDI and LDI experiments (Scherl et al, 2005;Altelaar et al, 2006). A thin gold coating has reduced sample charging during mass analysis and thus increased the resolution and sensitivity of MS/MS experiments (Scherl et al, 2005).…”

Section: Chemical Modificationmentioning

confidence: 99%

Imaging Mass Spectrometry

宮脇哲¹,

今井英明²,

早坂孝宏³

et al. 2010

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Imaging mass spectrometry combines the chemical specificity and parallel detection of mass spectrometry with microscopic imaging capabilities. The ability to simultaneously obtain images from all analytes detected, from atomic to macromolecular ions, allows the analyst to probe the chemical organization of a sample and to correlate this with physical features. The sensitivity of the ionization step, sample preparation, the spatial resolution, and the speed of the technique are all important parameters that affect the type of information obtained. Recently, significant progress has been made in each of these steps for both secondary ion mass spectrometry (SIMS) and matrix-assisted laser desorption/ionization (MALDI) imaging of biological samples. Examples demonstrating localization of proteins in tumors, a reduction of lamellar phospholipids in the region binding two single celled organisms, and sub-cellular distributions of several biomolecules have all contributed to an increasing upsurge in interest in imaging mass spectrometry. Here we review many of the instrumental developments and methodological approaches responsible for this increased interest, compare and contrast the information provided by SIMS and MALDI imaging, and discuss future possibilities. #

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Gold coating of non‐conductive membranes before matrix‐assisted laser desorption/ionization tandem mass spectrometric analysis prevents charging effect

Cited by 40 publications

References 26 publications

Enhanced MALDI ionization efficiency at the metal-matrix interface: Practical and mechanistic consequences of sample thickness and preparation method

Enhanced MALDI ionization efficiency at the metal-matrix interface: Practical and mechanistic consequences of sample thickness and preparation method

Imaging Mass Spectrometry (IMS) for Biological Application

Imaging Mass Spectrometry

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