preparation-of-homogeneous-maldi-samples-for-quantitative-applications

Preparation of Homogeneous MALDI Samples for Quantitative Applications

This protocol demonstrates a simple sample preparation to reduce spatial heterogeneity in ion signals during matrix-assisted laser desorption/ionization ...

an-efficient-sample-preparation-method-to-enhance-carbohydrate-ion

An Efficient Sample Preparation Method to Enhance Carbohydrate Ion Signals in Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Sample preparation is a critical process in mass spectrometry (MS) analysis of carbohydrates. Although matrix-assisted laser desorption/ionization (MALDI) ...

Academia Sinica

National Taiwan University

This work demonstrates a method to prepare homogeneous distributions of analytes to improve data reproducibility in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Natural-air drying processes normally result in unwanted heterogeneous spatial distributions of analytes in MALDI crystals and make quantitative analysis difficult. This study demonstrates that inducing Marangoni flows within drying droplets can significantly reduce the heterogeneity problem. The Marangoni flows are accelerated by changing substrate temperatures to create temperature gradients across droplets. Such hydrodynamic flows are analyzed semi-empirically. Using imaging mass spectrometry, changes of heterogeneity of molecules with the change of substrate temperature during drying processes are demonstrated. The observed heterogeneities of the biomolecules reduce as predicted Marangoni velocities increase. In comparison to conventional methods, drying droplets on a 5 °C substrate while keeping the surroundings at ambient conditions typically reduces the heterogeneity of biomolecular ions by 65%-80%. The observation suggests that decreasing substrate temperature during droplet drying processes is a simple and effective means to reduce analyte heterogeneity for quantitative applications. Graphical Abstract ᅟ.

Reducing Spatial Heterogeneity of MALDI Samples with Marangoni Flows During Sample Preparation.

The trimethylsilyl (TMS) derivative is one of the most widely utilized derivatives for analyzing polar compounds by gas chromatography. An ion two mass units higher than the protonated molecular ion was observed in analyzing TMS-monocarboxylic acids by using gas chromatography electrospray ionization mass spectrometry (GC-ESI/MS). The structure of the M + 2 compound was investigated using tandem mass spectrometry and high-resolution mass spectrometry. The results suggest that one methyl group bound to the silicon atom was replaced by a hydroxyl group during the ESI process. One possible mechanism for the formation of the M + 2 compound is proposed. This observation suggests the possibility of synthesizing an organic compound by using ESI.

Letter: The formation of a M + 2 compound in the analysis of a trimethylsilyl derivative of monocarboxylic acids by gas chromatography electrospray ionization mass spectrometry.

Quantitative analysis with mass spectrometry (MS) is important but challenging. Matrix-assisted laser desorption/ionization (MALDI) coupled with time-of-flight (TOF) MS offers superior sensitivity, resolution and speed, but such techniques have numerous disadvantages that hinder quantitative analyses. This review summarizes essential obstacles to analyte quantification with MALDI-TOF MS, including the complex ionization mechanism of MALDI, sensitive characteristics of the applied electric fields and the mass-dependent detection efficiency of ion detectors. General quantitative ionization and desorption interpretations of ion production are described. Important instrument parameters and available methods of MALDI-TOF MS used for quantitative analysis are also reviewed.This article is part of the themed issue 'Quantitative mass spectrometry'.

Critical factors determining the quantification capability of matrix-assisted laser desorption/ionization- time-of-flight mass spectrometry.

Carbohydrate analysis is challenging due to lack of sensitive detection and efficient separation methods. Although matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is a sensitive tool, the low ionization efficiency of carbohydrates makes mass analyses inefficient. This work systematically examines the correlation between MALDI-MS sensitivity and carbohydrate sample morphology. Depending on the properties of the matrix used, the morphology changes through sample recrystallization after drying or imposition of hydrodynamic flows during droplet drying. Observation shows that amorphous solids and finer crystals offer higher carbohydrate sensitivity and spatial homogeneity than larger crystals. Clear evidences of an inverse correlation between sensitivity and crystal size are obtained when various kinds of carbohydrates are mixed with different matrixes. Similar experiments on proteins and peptides showed a negative or negligible effect. The result serves as a general guideline for improving efficiency in routine carbohydrate analysis.

ArticleTotal : 2	Year
Publication title Cited by 10	2016
Publication title Cited by 4	2018

Article	Year
Reducing Spatial Heterogeneity of MALDI Samples with Marangoni Flows During Sample Preparation. Journal of the American Society for Mass Spectrometry\| PubMed ID: 27126469	2016
Letter: The formation of a M + 2 compound in the analysis of a trimethylsilyl derivative of monocarboxylic acids by gas chromatography electrospray ionization mass spectrometry. European journal of mass spectrometry (Chichester, England)\| PubMed ID: 27553737	2016
Critical factors determining the quantification capability of matrix-assisted laser desorption/ionization- time-of-flight mass spectrometry. Philosophical transactions. Series A, Mathematical, physical, and engineering sciences\| PubMed ID: 27644968	2016
Enhancing carbohydrate ion yield by controlling crystalline structures in matrix-assisted laser desorption/ionization mass spectrometry. Analytica chimica acta\| PubMed ID: 29126468	2017

Yu-Meng Ou

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