MALDI-MS Direct Tissue Analysis of Proteins:  Improving Signal Sensitivity Using Organic Treatments

Lemaire, R.; Wisztorski, Maxence; Desmons, Annie; Tabet, Jean‐Claude; R, Day; Salzet, Michel; Fournier, Isabelle

doi:10.1021/ac060565z

Cited by 175 publications

(167 citation statements)

References 35 publications

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“…It has previously been shown that washing the tissue sections with organic solvents such as chloroform and EtOH before matrix deposition increases the number and intensities of protein signals up to 20 kDa [27][28][29]. To test if the increased high mass sensitivity and charge capacity of the high mass HM1 detector may benefit imaging MS of higher mass proteins, mouse brain tissue sections were washed with chloroform and ethanol, prepared with a matrix solution of 20 mg/mL SA in AcN:0.1% TFA (7:3, vol/vol), and then analyzed using an AutoFlex III MALDI-ToF equipped with an MCP and a HM1 detector.…”

Section: Resultsmentioning

confidence: 99%

MALDI imaging and profiling MS of higher mass proteins from tissue

Remoortere

Zeijl

Oever

et al. 2010

J. Am. Soc. Mass Spectrom.

113

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MALDI imaging and profiling mass spectrometry of proteins typically leads to the detection of a large number of peptides and small proteins but is much less successful for larger proteins: most ion signals correspond to proteins of m/z Ͻ 25,000. This is a severe limitation as many proteins, including cytokines, growth factors, enzymes, and receptors have molecular weights exceeding 25 kDa. The detector technology typically used for protein imaging, a microchannel plate, is not well suited to the detection of high m/z ions and is prone to detector saturation when analyzing complex mixtures. Here we report increased sensitivity for higher mass proteins by using the CovalX high mass HM1 detector (Zurich, Switzerland), which has been specifically designed for the detection of high mass ions and which is much less prone to detector saturation. The results demonstrate that a range of different sample preparation strategies enable higher mass proteins to be analyzed if the detector technology maintains high detection efficiency throughout the mass range. The detector enables proteins up to 70 kDa to be imaged, and proteins up to 110 kDa to be detected, directly from tissue, and indicates new directions by which the mass range amenable to MALDI imaging MS and MALDI profiling MS may be extended. (J Am Soc Mass Spectrom 2010, 21, 1922-1929) © 2010 American Society for Mass Spectrometry S ince its inception ϳ10 y ago, MALDI imaging mass spectrometry (imaging MS) has developed into a powerful and versatile tool for biomedical research [1,2]. It is now routinely used for analyzing peptides and small proteins up to 25 kDa [3-6], administered drugs and their metabolites [7], and recently major improvements have been reported for lipids [8]. Despite this success, proteins exceeding 25 kDa are not routinely detected. Proteins larger than 25 kDa include many proteins with important biological activities, such as most cytokines, growth factors, enzymes, receptors, proproteins, and neuropeptide precursors. Increasing the mass range of proteins amenable to MALDI imaging MS might enable these biologically crucial proteins to be included in current applications, e.g., biomarker discovery.The most common technique currently used to access larger proteins in MALDI imaging MS analyses is based on proteolytic digestion of the tissue's proteins followed by MALDI imaging MS of their tryptic peptides. Note on-tissue digestion has the additional advantage that it can be applied to formalin fixed tissues as proteolytic peptides can be generated that are not bound within the cross-linked protein matrix. For example, Djidja et al. used on-tissue digestion to determine that the 78 kDa protein GRP78 may be a new candidate protein biomarker of pancreatic adenocarcinoma [9]. In principal, this 'bottom-up' strategy could enable proteins of any mass to be detected. In practice the large increase in complexity associated with proteolysing the entire tissue's protein content will cause many tryptic peptides to have identical nominal mass [1], thus under...

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Section: Resultsmentioning

confidence: 99%

MALDI imaging and profiling MS of higher mass proteins from tissue

Remoortere

Zeijl

Oever

et al. 2010

J. Am. Soc. Mass Spectrom.

113

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“…Tissues were then submitted to washing procedures prior to matrix application for improved detection of peptides/proteins. Washing was performed by two washing steps using first washing with cold 95% EtOH for 15 s followed by a washing step with chloroform for 1 min according to previously published protocols [11,34].…”

Section: Frozen Tissuesmentioning

confidence: 99%

“…Since then, many improvements in MALDI-MSI performance have been achieved, including improvements related to tissue preparation [10][11][12], data processing and imaging software [13,14], and spatial resolution [15,16]. Biomarker discovery and identification has been a field of intense research over the past 10 years, and MALDI-MSI has been proven to provide an interesting and promising strategy for such investigations [17][18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Multivariate analyses for biomarkers hunting and validation through on-tissue bottom-up or in-source decay in MALDI-MSI: application to prostate cancer

Bonnel

Longuespée

Franck³

et al. 2011

Anal Bioanal Chem

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The large amount of data generated using matrixassisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) poses a challenge for data analysis. In fact, generally about 1.10 8 -1.10 9 values (m/z, I) are stored after a single MALDI-MSI experiment. This imposes processing techniques using dedicated informatics tools to be used since manual data interpretation is excluded. This work proposes and summarizes an approach that utilizes a multivariable analysis of MSI data. The multivariate analysis, such as principal component analysis-symbolic discriminant analysis, can remove and highlight specific m/z from the spectra in a specific region of interest. This approach facilitates data processing and provides better reproducibility, and thus, broadband acquisition for MALDI-MSI should be considered an effective tool to highlight biomarkers of interest. Additionally, we demonstrate the importance of the hierarchical classification of biomarkers by analyzing studies of clusters obtained either from digested or undigested tissues and using bottom-up and in-source decay strategies for in-tissue protein identification. This provides the possibility for the rapid identification of specific markers from different histological samples and their direct localization in tissues. We present an example from a prostate cancer study using formalinfixed paraffin-embedded tissue.

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“…The washing method should be optimized for the target imaging molecules. Several washing protocols using organic solvents have been reported Andersson et al, 2008;Groseclose et al, 2007;Lemaire et al, 2006;Schwartz et al, 2003).…”

Section: Washingmentioning

confidence: 99%

Application of Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry

Zaima¹

2012

Pharmacology

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MALDI-MS Direct Tissue Analysis of Proteins: Improving Signal Sensitivity Using Organic Treatments

Cited by 175 publications

References 35 publications

MALDI imaging and profiling MS of higher mass proteins from tissue

MALDI imaging and profiling MS of higher mass proteins from tissue

Multivariate analyses for biomarkers hunting and validation through on-tissue bottom-up or in-source decay in MALDI-MSI: application to prostate cancer

Application of Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry

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