• Mass Spectrometry Letters
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• v.8 no.4
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• pp.105-108
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• 2017

Recently, deciduous teeth have been proposed as a promising biomatrix for estimating internal and external chemical exposures of an individual from prenatal periods to early childhood. Therefore, detection of organic chemicals in teeth has received increasing attention. Organic materials in tooth matrix are mostly collagen type proteins, but lipids and other small organic chemicals are also present in the tooth matrix. In this study, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) was employed to obtain lipid fingerprints from deciduous teeth. Phospholipids and triacylglcerols (TAGs) from deciduous teeth were successfully detected by MALDI MS with 2,5-dihydroxybenzoic acid (DHB) or gold nanoparticle (AuNP) as a matrix.

• Mass Spectrometry Letters
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• v.6 no.2
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• pp.27-30
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• 2015

This article reviews the fundamentals of sample preparation used in matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). MALDI is a soft ionization method used to generate analyte ions in their intact forms, which are then detected in MS analysis. MALDI-MS boasts fast analysis times and easy-to-use operation. The disadvantages of MALDI-MS include the occurrence of matrix-associated peaks and inhomogeneous distribution of analyte within the matrix. To overcome the disadvantages of MALDI-MS, various efforts have been directed such as using different matrices, novel matrix systems, various additives, and different sample preparation methods. These various efforts will be discussed in detail. This article will benefit those who would like to obtain basic knowledge of MALDI sample preparation and those who would like to use MALDI-MS in their chemical analyses.

• Analytical Science and Technology
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• v.8 no.4
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• pp.465-468
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• 1995

Matrix assisted laser desorption ionization in mass spectrometry is a fast and accurate method to determine the molecular weight of natural and synthetic polymers. Unknown peptides such as elastase inhibitor and $\small{D}$-hydantoinase were analyzed using sinapinic acid as matrix and their molecular weights were compared with the results from protein sequencer and gel filtration chomatography, respectively. Synthetic polymers such as polyethyleneglycol, polypropyleneglycol, polydimethylsiloxane, and polystyrene were analyzed using matrices such as 2,5-dihydroxybenzoic acid, 4-hdroxyazobenzenecarboxylic acid, and 2-nitrophenyl octyl ether. Average molecular weights of polystyrene were compared with molecular weights by gel permeation chromatography.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2293-2298
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• 2010

Focused electrospray (FES) deposition method is presented for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. FES ion optics consists of two cylindrical focusing electrodes capped with a truncated conical electrode through which an electrospray emitter passes along the cylindrical axis. A spray of charged droplets is focused onto a sample well on a MALDI target plate under atmospheric pressure. The shape and size distributions of matrix crystals are visualized by scanning electron microscope and the mass spectra are obtained by time-of-flight mass spectrometry. Angiotensin II, bradykinin, and substance P are used as test samples, while $\alpha$-cyano-4-hydroxycinnamic acid and dihydroxybenzoic acid are employed as matrices. FES of a sample/matrix mixture produces fine crystal grains on a 1-3 mm spot and reproducibly yields the mass spectra with little shot-to-shot and spot-to-spot variations. Although FES greatly stabilizes the signals, the space charge due to matrix ions limits the detection sensitivity of peptides. To avoid the space charge problem, we adopted a dual FES/FES mode, which separately deposits matrix and sample by FES in sequence. The dual FES/FES mode reaches the detection sensitivity of 0.88 amol, enabling ultrasensitive of peptides by homogeneously depositing matrix and sample under atmospheric pressure.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.370-372
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• 1999

• Mass Spectrometry Letters
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• v.3 no.1
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• pp.18-20
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• 2012

We report observation of laser desorption/ionization (LDI) of peptides from flat surfaces of tungsten silicide ($WSi_2$). In contrast to MALDI (matrix-assisted laser desorption/ionization) and SALDI (surface-assisted laser desorption/ionization) mass spectrometry, this study did not utilize any matrices and surface nanostructures. In this work, LDI on $WSi_2$ surfaces is demonstrated to cover a mass range up to 1,600 Da (somatostatin; monoisotopic mass = 1637.9 Da). In addition, it exhibited a high sensitivity, which could detect peptides, which could detect peptides of low femtomole levels (20 fmol for angiotensin II). The observed LDI process was discussed to be largely thermal, more specifically, due to laser-induced surface heating that is most likely promoted by the low thermal diffusivity (${\kappa}$) of $WSi_2$ substrate.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2955-2960
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• 2012

Product ion yields in the in- and post-source decays of three peptide ions, $[Y_5X+H]^+$ (X = Y (tyrosine), K (lysine), and R (arginine)), generated by matrix-assisted laser desorption ionization (MALDI) were measured at six wavelengths, 307, 317, 327, 337, 347, and 357 nm, using ${\alpha}$-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) as the matrices. The temperatures of the early and late plumes generated by MALDI were estimated via kinetic analysis of the product ion yield data. For both matrices, the temperature drop (${\Delta}T$), i.e. the difference in the temperature between the early and late plumes, displayed negative correlation with the absorption coefficient. This was in agreement with the previous reasoning that deeper laser penetration and larger amount of material ablation arising from smaller absorption coefficient would result in larger extent of expansion cooling. The results support the postulation of the expansion cooling occurring in the plume presented previously.

• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.763-768
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• 2005

An improved tandem time-of-flight (TOF) mass spectrometer for the photodissociation (PD) study of ions generated by matrix-assisted laser desorption ionization (MALDI), MALDI-TOF-PD-TOF, has been designed and constructed. Recording a full spectrum with better than unit mass resolution even in low mass range has been achieved without reflectron voltage stepping which was needed in the previous version. Other aspects of the improvement, such as those in the data system which now allow 10-100 times faster spectral acquisition than with the previous instrument, are described. Rationale for the ideas which have led to the improvements is presented also.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.427-431
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• 2007

In order to gain insight into the molecular changes at the protein level in plants exposed to low temperature for a long period of time (vernalization), proteome analyses of vernalization-treated Arabidopsis thaliana have been carried out by two-dimensional gel electrophoresis followed by matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry. Fourteen proteins including ATP binding/GTP binding/translation elongation factor and glycine-rich RNA-binding protein 7 (GRP7) showed differential expression in vernalization-treated Arabidopsis thaliana. GRP7 showed the most dramatic increase in expression suggesting its involvement in response to vernalization treatment.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1308-1312
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• 2003

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to observe folic acid and its derivatives such as tetrahydrofolate and 5-methyltetrahydrofolate in a vitamin tablet and in foods. Folic acid in a vitamin tablet was determined using angiotensin I as an internal reference. Tetrahydrofolic acid, 5-methyltetrahydrofolic acid, and an oxygenated folate were observed from a human blood sample using graphite plate. The results show that these mass spectrometric methods are useful for quickly obtaining a profile of folates.