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Volume 58 (2010)
- Issue 6 Pages 195-
- Issue 5 Pages 167-
- Issue 4 Pages 123-
- Issue 3 Pages 93-
- Issue 2 Pages 35-
- Issue 1 Pages 1-
Volume 58, Issue 4
Displaying 1-4 of 4 articles from this issue
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Regular Papers
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Issey OSAKA, Koji OKUMURA, Naoki MIYAKE, Takehiro WATANABE, Kazuyoshi ...2010 Volume 58 Issue 4 Pages 123-127
Published: August 01, 2010
Released on J-STAGE: August 15, 2010
JOURNAL FREE ACCESSThe applicability of matrix-free surface-assisted laser desorption/ionization mass spectrometry using porous silicon (DIOS-MS) and TiO2 nanoparticles (TiO2-SALDI-MS) was examined by analyzing an antioxidant added to insoluble polypropylene (PP) materials. The optimized solvent extraction, which involved freezing and crushing the PP, results in a good recovery, 89±4 and 97±8% for 0.5 wt% of the added antioxidant, tetrakis[methylene3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (commercial name; Irganox1010) in laboratory-produced and commercial PP composites, respectively. The positive ion measurements in DIOS and TiO2-SALDI-MS yielded sodium adduct ions without any interference from other signals. Using an internal standard with a similar structure, a good calibration curve linearity was established in the Irganox1010 concentration range of 0.01-2.0 mg/mL in PP, which was sufficient for monitoring the plastic additives. However, TiO2-SALDI-MS was superior to DIOS-MS in terms of mass resolution and easiness of sample preparation. A solvent extraction method followed by TiO2-SALDI-MS appears to be a anticipated method for the analysis of additives in insoluble plastics.View full abstractDownload PDF (273K) -
Yutaka KYONO, Naoyuki SUGIYAMA, Koshi IMAMI, Shota MIYAZAKI, Masayoshi ...2010 Volume 58 Issue 4 Pages 129-138
Published: August 01, 2010
Released on J-STAGE: August 15, 2010
JOURNAL FREE ACCESSTitanium dioxide, titania, is used as an affinity support for enriching phosphopeptides in mass spectrometry-based phosphoproteomics. In this study, a variety of titania particles were prepared by calcination at different temperatures or were obtained from different manufacturers, and relationships between their physico-chemical properties and the selectivity in phosphopeptide enrichment was examined. Tryptic peptides from three phosphoproteins were employed for phosphopeptide enrichment by aliphatic hydroxyl acid-modified metal oxide chromatography (HAMMOC) using titania in the presence of lactic acid. The recovery of phosphopeptides increased with increasing calcination temperature, up to 500°C, while the number of identified non-phosphopeptides decreased. For titania calcined at 800°C, the retention of phoshopeptides as well as non-phosphopeptides was significantly reduced in the presence of lactic acid. Various physico-chemical parameters, such as crystalline form, pore size and surface area were examined for these calcined titania beads, as well as commercial titania beads. The findings indicate that the weight-loss from 130°C to 800°C, as determined by thermal analysis, was well correlated with the selectivity of phosphopeptides by HAMMOC. Based on these results, optimized titania beads were prepared and applied to 100 μg of a HeLa cell extract. More than 1,000 phosphorylation sites were successfully identified with a false positive rate of 1.4%, whereas 455 phosphorylation sites were identified with a false positive rate of 4.1% when commercially available titania beads were used for HAMMOC.View full abstractDownload PDF (2315K)
REVIEW
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—Fundamentals of Electrospray—Kenzo HIRAOKA2010 Volume 58 Issue 4 Pages 139-154
Published: August 01, 2010
Released on J-STAGE: August 15, 2010
JOURNAL FREE ACCESSElectrospray is an ultimate phenomenon that occurs when the liquid is exposed to the high electric field. In order to fully exploit electrospray for the analytical science and technology, it is mandatory to understand the mechanisms for the formation of charged droplets and the following formation of gas phase ions. This article will explain the basic aspects of electrospray from various points of view. The contents are as follows: (i) electrospray ionization (ESI) is based on electrochemical reactions, (ii) what is the Taylor cone? (iii) disintegration of charged liquid droplets, (iv) mechanism for the formation of gas-phase ions from the charged liquid droplets, (v) effect of surface tension of liquid on electrospray, (vi) positive- and negative-mode of ESI, (vii) suppression effect by the presence of salts, (viii) down-sizing of electrospray, ESI→nanoESI→Probe ESI, (ix) field desorption, (x) field ionization, (xi) formation of multiple-charge ions, (xii) application of electrospray.View full abstractDownload PDF (3590K)
COMMENTARY
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—Analysis of Structure and Function of a Protein by the pH Titration Using ESI-MS—Kazuo HIRAYAMA2010 Volume 58 Issue 4 Pages 155-165
Published: August 01, 2010
Released on J-STAGE: August 15, 2010
JOURNAL FREE ACCESSAn analysis of the pH-dependent dissociation and denaturation of a heterodimeric protein is described. Electrospray ionization mass spectrometry (ESI-MS) was utilized to analyze the dissociation and denaturation of the heterodimeric yeast killer toxin SMKT. The two distinct subunits of SMKT noncovalently associate with one another under acidic conditions, but dissociate and are then denatured under neutral and basic conditions. In order to understand the mechanism that controls the unique pH-dependent denaturation mechanism of this protein, a pH titration was performed using ESI-MS. In this report, the MS conditions for the pH-titration and data-analysis procedures are described.View full abstractDownload PDF (1310K)
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