J. Mass Spectrom. Soc. Jpn., 48(2), 71-78, 2000
Isotope effects of some elements in chemical exchange reaction were investigated by use of liquid-liquid extraction, liquid membrane or chromatographic separation. Cyclic polyether was used for every method. All polyethers used in a series of the studies were made clear that they distinguished the isotopes not only by their nuclear masses but also by their nuclear sizes and shapes. Chromium isotopes, for example, were recognized to have enrichment factors being proportional to d<r2> which is a parameter to show field shift or the nuclear size and shape of the isotope. It follows that the chromium isotopes are separated not by their masses but by their field shift effects. Nuclear spin also played a great role to separate odd mass number isotopes from even mass number isotopes in even atomic number elements. Contribution of the nuclear spin (I=3/2) of 53Cr to total enrichment factor, e53/52=-0.00028, for 53Cr to 52Cr was observed to be, espin=-0.0025.
J. Mass Spectrom. Soc. Jpn., 48(2), 79-93, 2000
Protonation of organic compounds and fragmentations of resulting protonated molecules are reviewed. In chemical ionization (CI) mass spectrometry, the amount of protonation and the extent of bond cleavages of typical functional groups are evaluated by using appropriate test compounds. A new parameter, protonation susceptibility (PS), is introduced, which is not directly related to the ordinary proton affinity (PA) of organic compounds. CI mass spectra of a series of compounds are quantitatively analyzed, and prediction of an unknown spectrum is shown to be successful. The principal modes of bond cleavages in even-electron ions are also formulated. These results are compared to the protonation in fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectra, where the protonation takes place in condensed phase-like environment and in solution, respectively.
J. Mass Spectrom. Soc. Jpn., 48(2), 94-100, 2000
In order to understand the protein function in detail, it is important to have information on tertiary structure of the protein. Protein tertiary structure has generally been studied using X-ray crystallography and NMR. However, these techniques require a large scale sample preparation. On the other hand, mass spectrometry requires a smaller sample amount and is much faster than X-ray crystallography or NMR. These are great advantages of MS in the structural characterization of a protein. In the present commentary, it will be described how to study the tertiary structure of proteins using hydrogen-deuterium exchange in conjunction with mass spectrometry.
J. Mass Spectrom. Soc. Jpn., 48(2), 101-107, 2000
As the development of X-ray crystallography and NMR, tertiary structure of proteins has come to be investigated more precisely than before. Mass spectrometry is also an effective tool to analyze the structure of large biomolecules. In addition, computational chemistry enables to study the protein-ligand interaction. This commentary explains how effective mass spectrometry and computational chemistry are in the analysis of structure-function relationships of biomolecule networks, indicating the resutls of mass spectrometric characterization of immunoglobulin G2b and analysis of computational chemistry of the binding of immunoglobulin G2b and its receptor.
J. Mass Spectrom. Soc. Jpn., 48(2), 108-118, 2000
The improved sensitivity and soft ionization characteristic of ESI-MS/MS and MALDI-TOF-MS were applied to the identification of characteristic fragment ions from C-terminal GPI-anchored peptides of bovine liver 5'-nucleotidase and other several GPI-anchored proteins. In the CID spectrum of ESI-MS/MS, characteristic fragment ions such as m/z 162 (glucosamine) and m/z 286 (mannose-phosphate-ethanolamine) were effectively identified. In matrix-assisted laser desorption/ionization (MALDI)-TOF-MS analysis, heterogeneous peaks of GPI-anchored peptides caused by sugar side chains were detected as single charged ions in positive mode analysis. In PSD analysis most of the expected product ions succeeding from the precursor GPI-anchored peptide were fully obtained. Thus ESI-MS/MS and PSD of MALDI-TOF-MS proved to be fairly effective in analyzing small amount of GPI-anchored structure less than 10 pmol. By LC-ESI-MS analysis, C-terminal peptides bearing the products of GPI were effectively detected by combination with in-source decay and multi-functional scanning for the several characteristic fragment ions from GPI-anchor structure. Existence of microheterogeneity was observed in the C-terminal GPI-anchored peptides from the 42 kDa and 40 kDa protein of bovine erythrocytes. By LC-ESI-MS, C-terminal GPI-anchor structure can be easily identified from the target protein even if its amino acid sequence data are not available.
J. Mass Spectrom. Soc. Jpn., 48(2), 119-123, 2000
Presolar grains are defined as grains which had formed in the circumstellar envelope or supernova ejecta and remain intact during the formation of the solar system. They have been extensively studied during the last 10 years. They exhibit huge isotopic anomalies, confirming their stellar origin. SIMS (Secondary Ion Mass Spectrometry) has proved itself to be a very powerful tool to study presolar grains. Isotopic ratios of more than one elements can be measured if grains are 1mm or larger in size. Several kinds of stars have been identified as stellar sources of presolar grains. One type is AGB (Asymptotic Giant Branch) stars and another type is supernovae (SNe). Most presolar SiC grains (about 93%) exhibit12C/13C ratios ranging from 30 to 100 and are called mainstream SiC grains. Their C and N isotopic ratios generally agree with what is expected from the evolution of AGB stars. Silicon isotopic ratios of the grains show excesses in 29Si and 30Si. To explain the Si-isotopic ratios, Galactic chemical evolution or inhomogeniety of the ISM (Interstellar Medium) has to be invoked. Silicon carbide of type X (about 1% of total SiC), low-density graphite, and silicon nitride are most likely to have formed in supernova ejecta. Many grains have 28Si excesses and a few grains show the presence of 44Ti. These features are considered to be a proof of their supernova origin. The comparison with theoretical calculations of nucleosynthesis in supernova suggests that extensive and heterogeneous mixing occurs when supernovae explode.
J. Mass Spectrom. Soc. Jpn., 48(2), 124-130, 2000
It has been well known that the isotopic ratios of the elements in our solar system are very uniform unless there is any special reason such as radioactive decay, cosmic ray spallation, fractionation effect etc. This suggests that all material had been vaporized and well mixed at an early stage of the formation of our solar system, which is the so-called "isotope mixing". All the material had lost their past memories at this stage. However, some material survived during the vaporization at the early stage of the solar system. We can detect this material by measuring the isotopic composition that is different from the value in our solar system matters (isotopic anomaly). This material preserves the memory before the formation of our solar system, and is called "presolar grain" or "star dust". These materials are found to be diamond, silicon carbide, and graphite etc., almost all of which were initially isolated by chemical treatment of meteorite by using the isotope anomaly of noble gases as a guide. Here, I briefly introduce isotopic anomalies of noble gases (Ne-E, Xe-HL, Xe-S, Kr-S) and their host phases.
J. Mass Spectrom. Soc. Jpn., 48(2), 131-133, 2000
A technique for realizing in situ isotope-ratio is reported for measuring small isotopic ratio by the use of the ion-microprobe. In the case of inhomogeneous insulator-samples, such as the primitive meteorites, the difference in conductivity of each grain causes considerable amount of instrumental mass discrimination. As a preliminary step to solve this problem, a metal channel is embedded and the analysis is taken along it. The method is effective to homogenize the surface ionization condition, and the 26Mg/24Mg ratio of individual spot with the size of 40 microns was measured with the error of less than ±3%. This is a step to realize 2-dimensional isotopic ratio imaging.
J. Mass Spectrom. Soc. Jpn., 48(2), 134-140, 2000
The quality control of the data and instruments on the analysis of drugs by mass spectrometry should be controlled by analytical section of pharmaceutical company. ICH, FDA, EMEA, and Ministry of Health and Welfare guidelines related the criteria of quality control of analytical method have been published. The purity and stability of the drugs are analyzed according to Validation of Analytical Procedures (ICH, 1994.10). The clinical pharmacokinetics samples are analyzed according to Guidance for Industry; Bioanalytical Methods Validation for Human Studies (FDA, 1998.12). Toxicokinetics samples are analyzed according to Validation of Analytical Procedures for toxicokinetics (Japan Pharmaceutical Manufacturers Association (JPMA), 1997.3). In this report, I write the actual quality control of analytical instrument and procedure by mass spectrometry in the pharmaceutical companies and compare the above described guideline.
J. Mass Spectrom. Soc. Jpn., 48(2), 141-144, 2000
Hydrogen bonding host-guest complex ions between chiral crown ethers and chiral amino acid ester salts, detected by matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) with a DHBA or MSA matrix, were studied on the view point of chiral recognition properties of the chiral crown hosts. The chiral recognition property (IR/IS-dn
value
1.0) obtained by the present MALDI-MS is sharply different from the IR/IS-dn value obtained by FAB-MS or
ESI-MS (
1.0) in the same host-guest combinations. The direct comparison on the basis of the IR/IS-dn values suggests that MALDI-MS is not a suitable measurement tool for chiral host-guest interactions probably because of the particular way of sample preparation involving a crystallization process.
J. Mass Spectrom. Soc. Jpn., 48(2), 145-149, 2000
Urinary leukotriene E4 (LTE4) levels in healthy volunteers were determined using liquid chromatography/tandem mass spectrometry (LC/MS-MS). LTE4 and its internal standard were extracted by simple solid-phase extraction and analyzed using LC/MS-MS in the selected reaction monitoring (SRM) mode by monitoring the transitions between m/z 438 and m/z 333 for LTE4 and between m/z 441 and m/z 336 for LTE4-d3. We detected LTE4 (64.7±8.3 pg/mg creatinine, n=13) in healthy human urine. Then, we determined the intra- (within one day) and inter-day (for two weeks) variation of the excretion rates of LTE4 in healthy volunteers (n=5). No significant variations in urinary LTE4 excretion rates were observed in both examinations. In conclusion, LC/MS-MS is a rapid, accurate and sensitive method for determination of urinary LTE4. The present results about urinary LTE4 levels and variation of LTE4 excretion in healthy volunteers can be helpful in evaluating the role of cysteinyl LTs in pathophysiological conditions.
J. Mass Spectrom. Soc. Jpn., 48(2), 150-154, 2000
Determination of low molecular weight compounds by MALDI-TOF MS was developed using emedastine, an anti-allergic drug, as model compound. It was found that a-cyano-4-hydroxycinnamic acid is suitable as matrix and a mixture of acetonitrile and water (7 : 3) as solvent for the measurement. Emedastine in rat plasma was extracted with mixture of hexane and chloroform (7 : 3). Calibration curve of emedastine in rat plasma was linear over the range 5-100 ng/mL with coefficient of 0.997. It seems that MALDI-TOF MS is useful for the determination of a drug in plasma.
J. Mass Spectrom. Soc. Jpn., 48(2), 155-159, 2000
A simultaneous and high sensitivity determination method of emedastine and its major metabolites, 5- and 6-hydroxy emedastine, in human plasma was developed. Plasma samples were extracted by Extrelut-1 column. Extracts were separated by reverse phase C18 column under stepwise gradient conditions. An atmospheric pressure chemical ionization interface was used in positive ionization mode. The analytes were detected using a tandem mass spectrometer operated selected reactant monitoring mode. The method was linear over the range 50-5,000 pg/mL (r=0.999). This method is suitable for therapeutic drug monitoring of unchanged drug and its major metabolites.
J. Mass Spectrom. Soc. Jpn., 48(2), 160-168, 2000
The drift tube method, which is known as one of the powerful techniques for low energy atomic collision experiments, is explained with description on the history of this method. A new selected ion drift tube mass spectrometer, which has been developed for ion swarm experiments at very low temperature, is presented. Gas temperature of 2 K in the drift tube as the lowest one for this apparatus is achieved by liquid helium cooling. Details of this set-up are described, and several technical points for the low temperature experiment, which are concerned in the development of this apparatus, are discussed: analysis of the heat flow rates into the drift tube, thermal contraction of metallic parts, temperature measurements of gas and solid surfaces, and gas pressure correction with respect to the thermal transpiration effect because of large temperature difference between the drift tube and the capacitance manometer. Mass spectra with the injection of doubly charged rare gas ions, Ar2+ and Kr2+, into helium gas are shown as examples of experimental results with this apparatus. Charge transfer, ion-molecule and atomic association reactions take place in the drift tube. Structure of large helium cluster ions K2+Hen (n<40), which have been observed to have magic numbers n=12 and n=32, is discussed.
J. Mass Spectrom. Soc. Jpn., 48(2), 169-173, 2000
In the last decade, electron cyclotron resonance ion sources (ECRISs) have been developed from complex prototype to compact and high perfromance ion source. They can produce the intense beams of heavy ions from most elements of the periodic table with high ionization efficiency. These features are great advantages as an ion source for trace element analysis. Futhermore, when we accelerate the highly charged heavy ions produced from ECRIS with using heavy ion linear accelerator, we can identify many kinds of trace elements simulteneously with very low background. In this paper, we demonstrate the new experimental method for trace element analysis using ECRIS and heavy ion linear accelerator.
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