Epsilon -N,N,N-trimethyllysine-specific ions in matrix-assisted laser desorption/ionization-tandem mass spectrometry

Epsilon -N,N,N-trimethyllysine (K(me3)) is a component of a number of proteins and plays an important role in the expression of their biological functions. Trimethylation, which causes an incremental increase in mass of 42.0470 Da from that of the corresponding MH(+) ion, cannot be distinguished from the acetylation (+42.0106 Da), which also occurs on epsilon-amino groups of Lys or alpha-amino groups in many proteins, without high-accuracy mass measurement which is accurate to within the second decimal place. MALDI-MS and MS/MS have been applied for the analyses of post-translational modifications of histone H3, which is known to contain both multiple acetylation and methylation sites in its sequence. During the measurements of the modified peptides, a novel fragmentation which involves the loss of trimethylamine from K(me3) was found. This characteristic fragmentation, which was observed to produce ions separated by 59 Da from the conventional precursor ion or sequence ions, would be useful for probing K(me3) units in the sequence.     

Ultraviolet derivatization of steroidal saponin in garlic and commercial garlic products as p-nitrobenzoate for liquid chromatographic determination

A method is described for determination of the steroidal saponin, eruboside B, originating in garlic and garlic products as the p-nitrobenzoyl chloride (PNBC) derivative by reversed-phase liquid chromatography (with ultraviolet detection at 260 nm. Proto-eruboside B was extracted from garlic (Allium sativum L.); subjected to solid-phase extraction (SPE) with a C18 cartridge, Florisil column chromatography, and silica gel column chromatography; and then enzymatically converted to eruboside B, which was applied as an external standard. Steroidal saponins in garlic and commercial garlic products were extracted with methanol and purified by SPE cartridges, followed by enzymatic treatment. A frostanol saponin such as proto-eruboside B is enzymatically transformed to a spirostanol saponin, eruboside B. After the derivatization with PNBC, the saponin derivative was chromatographed on a C8 column with a gradient elution of (A) 80% aqueous acetonitrile and (B) 100% acetonitrile. The detection limit of the developed method was 1 microg/g for the samples. The method was applied to the analysis of garlic and garlic health food products available in Japan.     

Collisional activation mass spectra of pentene and hexene molecular ions

The collisional activation spectra of the molecular ions from fourteen pentene and hexene isomers show substantial differences, some of which can be rationalized using known ion fragmentation mechanisms. These differences, and their negligible dependence on ion internal energy, are advantageous for the structural characterization of such isomeric ions, including those produced by fragmentation of larger molecules. The decompositions of metastable ions of the pentenes were nearly identical, but those of the hexenes showed some differences useful for structural charactrization.     

Preferential Uniplanar Orientation of Cellulose Microfibrils Reinvestigated by the FTIR Technique

A simple detection method to observe the uniplanar orientation behavior of native cellulose microfibrils to the cell wall surface by using Fourier transform infrared (FTIR) spectroscopy in the transmission mode is reported. Four bands at 1372, 1355, 1337, and 1317 cm⁻¹ (the latter two have been mentioned previously by Liang and Marchessault (1960, J. Polym. Sci. 43: 85–100)) were found to be sensitive to such orientation: the two middle bands at 1355 and 1337 cm⁻¹ increase remarkably when the 0.60–61 nm lattice planes lie parallel to the cell wall surfaces. The reverse was true when the 0.53–54 nm lattice planes oriented preferentially. Polarization of the two bands at 1372 and 1355 cm⁻¹ was parallel, while that of the other two bands at lower wavenumbers, i.e., at 1337 and 1317 cm⁻¹, was perpendicular to the molecular axis of cellulose. These bands were assigned to OH-related motion, probably to in-plane OH bending, as reported by Maréchal and Chanzy (2000, J. Mol. Spectrosc. 523: 183–196).     

Homoleptic cyclometalated iridium complexes with highly efficient red phosphorescence and application to organic light-emitting diode

Phosphorescence studies of a series of facial homoleptic cyclometalated iridium(III) complexes have been carried out. The complexes studied have the general structure Ir(III)(C-N)(3), where (C-N) is a monoanionic cyclometalating ligand: 2-(5-methylthiophen-2-yl)pyridinato, 2-(thiophen-2-yl)-5-trifluoromethylpyridinato, 2,5-di(thiophen-2-yl)pyridinato, 2,5-di(5-methylthiophen-2-yl)pyridinato, 2-(benzo[b]thiophen-2-yl)pyridinato, 2-(9,9-dimethyl-9H-fluoren-2-yl)pyridinato, 1-phenylisoquinolinato, 1-(thiophen-2-yl)isoquinolinato, or 1-(9,9-dimethyl-9H-fluoren-2-yl)isoquinolinato. Luminescence properties of all the complexes at 298 K in toluene are as follows: quantum yields of phosphorescence Phi(p) = 0.08-0.29, emission peaks lambda(max) = 558-652 nm, and emission lifetimes tau = 0.74-4.7 micros. Bathochromic shifts of the Ir(thpy)(3) family [the complexes with 2-(thiophen-2-yl)pyridine derivatives] are observed by introducing appropriate substituents, e.g., methyl, trifluoromethyl, or thiophen-2-yl. However, Phi(p) of the red emissive complexes (lambda(max) > 600 nm) becomes small, caused by a significant decrease of the radiative rate constant, k(r). In contrast, the complexes with the 1-arylisoquinoline ligands are found to have marked red shifts of lambda(max) and very high Phi(p) (0.19-0.26). These complexes are found to possess dominantly (3)MLCT (metal-to-ligand charge transfer) excited states and have k(r) values approximately 1 order of magnitude larger than those of the Ir(thpy)(3) family. An organic light-emitting diode (OLED) device that uses Ir(1-phenylisoquinolinato)(3) as a phosphorescent dopant produces very high efficiency (external quantum efficiency eta(ex) = 10.3% and power efficiency 8.0 lm/W at 100 cd/m(2)) and pure-red emission with 1931 CIE (Commission Internationale de L'Eclairage) chromaticity coordinates (x = 0.68, y = 0.32).     

Determination of trace amounts of vanadium in air samples with 2-(8-quinolylazo)-5-N,N-diethylaminophenol by reversed-phase liquid chromatography

A reversed-phase liquid chromatographic method for the determination of trace amounts of vanadium is described. Metal ions are converted into 2-(8-quinolylazo)-5-N,N-diethylaminophenol chelates in an off-line system. The chelates are injected onto a Zorbax CN column and separated with an aqueous acetonitrile mobile phase containing no chromogenic reagent. Unter these conditions, only vanadium(V) is spectrophotometrically detected at 540 nm among the metal ions Al(III), Ba(II), Ca(II), Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ga(III), Hg(II), Mg(II), Mn(II), Ni(II), Pb(II), V(V) and Zn(II). Amounts of 8.0–200 pg of vanadium(V) in 100-μl injections can be determined without interference from 10-fold molar excesses of many cations. At 0.001 a.u.f.s., the detection limit (twice the peak-to-peak noise) for vanadium(V) is 8.0 pg in 100 μl of injected solution and the relative standard deviation at 120 pg of vanadium(V) in a 100-μl injection is 3.5%. The proposed method is applied to the determination of vanadium in rain water and airborne particulates.     

Profiling analysis of oligosaccharides in antibody pharmaceuticals by capillary electrophoresis

Carbohydrate chains in glycoprotein pharmaceuticals have important roles for the expression of their biological activities. Therefore, development of an assessment method for the carbohydrate chains is an important parameter for quality control of glycoprotein pharmaceuticals such as newly developed therapeutic antibodies. In this report, we applied capillary electrophoresis with laser-induced fluorescence detection to the analysis of carbohydrate chains after releasing with glycoamidase followed by derivatization with 3-aminobenzoic acid. We found that four major oligosaccharides present in antibody pharmaceuticals were successfully separated with good resolution. The present method showed good precision in both migration times and relative peak areas, and gave comparable accuracy with that using a derivatization method with 8-aminopyrene-1,3,6-trisulfonate.     

Cover Picture

The cover picture shows a section of the electron charge density of the first metal carbide endohedral metallofullerene (Sc(2)C(2))@C(84) obtained from a synchrotron X-ray powder diffraction study by the maximum entropy method (MEM). The several density maxima, which correspond to scandium and carbon atoms, are clearly seen inside the C(84) carbon cage. The MEM charge density distribution also reveals that the C(84) cage has D(2d) symmetry (no. 23) and that the C(2) axis is parallel to the <100> face-centered cubic (fcc) direction of the unit cell. As a consequence of the site symmetry being 4mm, the C(2) axis of (Sc(2)C(2))@C(84) is oriented to six equivalent <100> directions and shows a merohedral disorder. The resultant Sc small middle dot small middle dot small middle dotSc distances and C-C bond lengths of the Sc(2)C(2) cluster are 0.429(2) and 0.142(6) nm, respectively. The observed C-C bond length is between that of a typical single and a double bond, and is very close to that of the C-C bond (0.143 nm) combining two pentagons in a C(60) molecule. More about this fascinating structure can be found in the contribution by Shinohara and co-workers on p. 397 ff.     

NLO‐active maleimide copolymers with ­high glass transition temperatures

We synthesized some novel rigid NLO‐active maleimide copolymers bearing DR‐1 moieties ( PMPD , PHSD and PHND ). All copolymers exhibited high T_g's (190～197 °C), good solubilities for common solvents and excellent film‐forming properties. Dependence of film thickness on the d₃₃ value for the poled copolymer films induced by corona poling was investigated and it was demonstrated that in less than thickness of 0.3 µm decrease of the thickness gives rise to remarkable increase in the d₃₃ value. The poled copolymer films exhibited large d₃₃ values (270 × 10^?9 esu (film thickness 0.13 µm) for PMPD , 290 × 10^?9 esu (0.12 µm) for PHSD and 350 × 10^?9 esu (0.08 µm) for PHND ) as well as large r₃₃ values (51.0 pmV^?1 for PMPD and 60.4 pmV^?1 for PHND ) which are significantly large compared to the value of LiNbO₃ (31 pmV^?1) as a typical EO material. The d₃₃ values of the poled copolymers were kept constant even after standing 1000h at 80 °C, although a small decrease was observed at an initial stage. Further, the d₃₃ values did not change up to ca. 123 °C upon heating at the rate of 10 °C/min in all cases. Copyright © 2002 John Wiley & Sons, Ltd.