Tohru Yamagaki

Rhamnan sulfate from cell walls of Monostroma latissimum

Abstract Rhamnan sulfate from cell walls of Monostroma latissimum was purified through subsequent chromatographic systems. The purified polysaccharide consisted of large amounts of rhamnose residues and appeared to be an entire homopolysaccharide. Antithrombin activity was lower than rhamnan sulfate previously obtained from M. nitidum but similar to standard heparin. Studies of the major structural parts of the rhamnan sulfate by periodate oxidation, Smith degradation and permethylation, showed it to consist of 1,3- and 1,2-linked rhamnose residues in a ratio of 3 : 2. Sulfate was mainly substituted at C-3 or C-4 in the 1,2-linked rhamnose residue. The detection of oligosaccharides by matrix-assisted laser desorption\ionization time-of-flight mass spectrometry supports this structure. These results suggested that rhamnan sulfate from the Monostromaceae has quite different structural properties from ulvan from the Ulvaceae.

Post‐source Decay Fragment Spectra of Cyclomalto‐octaose and Branched Cyclomalto‐hexaose by Matrix‐assisted Laser Desorption/Ionization Time‐of‐flight Mass Spectrometry

gamma-Cyclodextrin, maltosyl-alpha-cyclodextrin and diglucosyl-alpha-cyclodextrin were analyzed using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. All of these compounds have the same molecular weight (M.W. = 1297.15) and consist of only D-glucopyranose. From a comparison of the intensities in the post-source decay (PSD) fragment spectra of these cyclodextrin derivatives, correlation between the chemical structures and the relative intensities in the PSD fragment ions was found. The correlation is considered to be caused by the difference in the number of cleavage sites at the glycosyl binding. It was found that the intensity of the PSD ion resulting from one cleavage is higher than that resulting from two cleavages at a glycosyl bond. The results show that PSD fragment-ion spectrum method used in MALDI-TOF mass spectrometry is a very powerful technique for the structural analyses of the sugar-substituted cyclodextrins.

Analysis of Glycosidic Linkages in Saccharide Compounds by Post-source Decay Fragment Methods in Matrix-assisted Laser Desorption/Ionization Time-of-Flight Mass Spectroscopy

Maltotriosyl- and panosyl-alpha-cyclodextrins and the nonaose of pullulan were analyzed by post-source decay (PSD) fragment methods of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy. By the mass number analysis, it was found that all of the PSD fragment ions were produced by cleavages of glycosidic linkages. Comparison of the relative intensities of the ions in those compounds enabled us to distinguish two kinds of glycosidic linkages, alpha 1-4 and alpha 1-6, by MALDI-TOFMS with a new type of ion reflector: the curved field reflectron.

Hydrogen Radical Removal Causes Complex Overlapping Isotope Patterns of Aromatic Carboxylic Acids in Negative-ion Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

We studied the ionization process of aromatic carboxylic acids, including ones with or without hydroxy groups in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), because many natural products, metabolites, and drags contain those structural units. In the actual experimental data, benzoic acid was ionized as only deprotonated molecule [M-H](-). In contrast, both of negative molecular ion M(-) and deprotonated molecule [M-H](-) were generated from 2-naphthoic acid and 2-anthracenecarboxylic acid, and the ratio of negative molecular ion to deprotonated molecule M(-)/[M-H](-) was increased in 2-anthracenecarboxylic acid. In addition, the ratio of 2-anthracenecarboxylic acid was much higher than those of 1- and 9-anthracenecarboxylic acids among the three isomers. Therefore, 2-substitution induced the generation of the negative molecular ion M(-), which can made us prediction of the substituted positions from their overlapping peak isotope patterns. 2,5-Dihydroxybenzoic acid (2,5-DHBA) showed two deprotonated molecules, [M-H](-) and [M-H*-H](-), which was generated from a neutral hydrogen radical (H*) removal from a phenolic hydroxy group. The deprotonated molecule [M-H*-H](-) of 2,5-DHBA was the most abundant among six DHBAs and three hydroxybenzoic acids (hBAs). This observation raises the possibility that such a property of 2,5-DHBA could be a clue to explain its highest efficiency as a MALDI matrix. The order of the hydrogen radical removal from the phenolic hydroxy groups was the 3-<4-≪5-positions in the DHBAs, and the 3-<4-positions in hBAs. We can distinguish among six DHBA isomers and three hBA isomers from their spectral pattern around the deprotonated molecules [M-H*-H](-) and [M-H](-). The intra-molecular hydrogen bonding between 1-carboxy and 2-hydroxy groups was an important factor in hydrogen radical removal in the hydroxylbenzoic acids and dihydroxybenzoic acids.

A Special Issue for The International Biological Mass Spectrometry (BMS) Symposium 2016 in Tokyo

is symposium, which was held on 14 and 15 October 2016 in the Nihonbashi Life Science Building in Tokyo, was organized by the biological mass spectrometry (BMS) division of the Mass Spectrometry Society of Japan. e subtitle of this symposium was “Advanced research in direct detection of metabolites and proteins in biological tissues and cells with ambient MS, imaging MS, and single-cell MS.” Recent developments and improvements of MS techniques have helped clarify the relationship between metabolites and proteins and allowed interesting biological phenomena to be observed directly. Imaging MS and single-cell MS can show us when and where the target metabolites are in biological tissues, the organs, and the body. Omics studies can reveal the function of untargeted molecules that we have not focused on. Ambient MS can develop new applications of the direct detection of metabolites, even for living targets. We invited the leading professors and researchers in these elds as keynote lectures.

Mechanism for Odd‐electron Anion Generation of Dihydroxybenzoic Acid Isomers in Matrix‐assisted Laser Desorption/Ionization Mass Spectrometry with Density Functional Theory Calculations.

Rationale Proton and radical are transferred between matrices and matrix and analyte in matrix‐assisted laser desorption/ionization (MALDI) and these transfers drive ionization of analytes. The odd‐electron anion [M–2H]•– was generated in dihydroxybenzoic acids (DHBs) and the ion abundance of the 2,5‐DHB was the highest among six DHB isomers. We were interested in the mechanism of the ion generation of the odd‐electron anion. Methods The observed [M–2H]•– and [M–3H]− ions, which were generated with the hydrogen radical removed from the phenolic hydroxyl groups (OH) in DHB isomers, were analyzed using negative‐ion MALDI‐MS. The enthalpy for ion generation and their stable structures were calculated using the density functional theory (DFT) calculation program Gaussian 09 with the B3LYP functional and the 6–31+G(d) basis set. Results The number of observed [M–2H]•– and [M–3H]− ions of the DHB isomers was dependent on the positions of the phenolic OH groups in the DHB isomers because the carboxy group interacts with the ortho OH group due to neighboring group participation, as confirmed from the stable structures of the [M–2H]•– anions calculated with the Gaussian 09 program. The DHB isomers were placed into three categories according to the number of the ions. Conclusions Odd‐electron anions ([M–2H]•–) and [M–2H•–H]− ([M–3H]−) ions were generated from DHB isomers due to removal of the hydrogen radical from the phenolic groups. The enthalpy for ion generation revealed that ion formation proceeds via a two‐step pathway through the [M–M]− ion as an intermediate.

Special Issue: Advanced techniques of MALDI-TOF MS in ionization, instrumentation and applications

I am glad to share with the many contributors and readers of this journal a special issue highlighting recent advances in MALDI-MS, which is the first published issue of a new journal from the Mass Spectrometry Society of Japan entitled Mass Spectrometry. I thank the editors, Prof. Yoshinao Wada and Prof. Toshifumi Takao, for providing me with the opportunity to highlight this important aspect of science of mass spectrometry. Over twenty years have passed already since the first report of soft ionization in matrix-assisted laser desorption/ionization (MALDI) MS. These days, researchers can identify target molecules by using MALDI-MS without having to consider what actually happens during the MALDI process. Moreover, life scientists desire to know when, where, and how various biomolecules are expressed and work in cells, tissues, and organs. Material scientists also want to investigate solid-surface chemistry of their materials, and their studies may require time and space resolving analytical instruments. To provide an ideal molecular imaging system, MALDI-MS has been developed as an imaging MS system in biology and material sciences. Polymer scientists require highly sensitive and high-resolution instruments to estimate the fine distributions within mixtures and the degree of polymerization. MALDI-MS has proven to be an essential tool in all of these fields, and it has great potential for scientists who hope to develop new applications and basic technologies, and to gain further scientific knowledge. This special issue contains articles describing new applications of imaging mass spectrometry in cell and plant biology. The combination of MALDI-MS and other scientific techniques such as micro-scale manipulation systems and microscopes, will be critical to develop and improve innovative new techniques and applications. On the other hand, important and essential aspects of developing new MALDI applications include basic studies of ionization mechanisms, matrices, fragmentation processes, and so on. For instance, both in-source and post-source decay in the MALDI process are significant topics because we can obtain additional and/or complementary structural information from each other. Interestingly, in-source and post-source decay of analytes depend on the matrix properties. Even matrices themselves are an important research target, and mechanisms of co-crystal formation are also of great interest. Finally I would like to express my sincere appreciation to all contributors of this special issue of the new journal Mass Spectrometry to reach to readers in wide ranging fields.

Structural Analyses of Sugar Branched Cyclodextrin Derivatives by the Post-Source Decay Fragment Method in MALDI-TOF Mass Spectrometry

Post-source decay fragment analyses by MALDI-TOFMS were applied to the sugar-branched s-cyclodextrin (CD) derivatives. In the fragment spectra, all possible fragment ions larger than trisaccharide produced by the cleavage of glycosidic linkage were clearly observed. The detailed ion intensity analyses enable us to distinguish the ions produced from branched and CD moieties because the ion intensities were influenced by the structure. The relative intensities of the ions produced from s-CD moiety have the characteristically cleavaged pattern which was common in the branched s-CDs.