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.     

Stereoselective syntheses of highly functionalized bicyclo[3.1.0]hexanes: a general methodology for the synthesis of potent and selective mGluR2/3 agonists

[Chemical reaction: See text] A Et3Al mediated intramolecular epoxide opening, cyclopropanation reaction is described. The transformation provided highly functionalized bicyclo[3.1.0]hexane systems in high efficiency and with perfect H or F endo selectivity. Application of this reaction to the synthesis of mGluR2/3 agonist 1 (43% overall yield) and a few intermediates suitable for the synthesis of other bicyclo[3.1.0]hexane mGluR2/3 agonists is discussed.     

Chain length effect of the counterion on the partial molal volume of alkanesulfonates

The partial molal volumes of two series of homologous surfactants, n-alkylammonium decanesulfonates and a, ?-alkanediammonium nonanesulfonates, were measured below and above their CMC in aqueous solution. Their counterions were n-alkylammonium and a, ?-alkanediammonium. The relationship between the partial molal volume and the chain length of the counterion below the CMC had an inflection point. The relationship between them, above the CMC, was almost linear. In the case of the alkylammonium salts, the values of the volume change of micellization were almost the same when the chain length of the counterions was shorter than the butyl, and increased with an increase in the chain length when it was longer than the propyl. In the case of the alkanediammonium salts, the volume change of micellization showed a small decrease with the chain length when it was shorter than octane, and was very large for the nonane ammonium salt. The large positive increase in the volume change with the increase in the chain length of the counterion can be explained by the hydrophobic interaction between the alkyl chain of the counterion and the hydrophobic core of the micelle.     

Nigellamines A3, A4, A5, and C, new dolabellane-type diterpene alkaloids, with lipid metabolism-promoting activities from the Egyptian medicinal food black cumin

New dolabellane-type diterpene alkaloids, nigellamines A(3), A(4), A(5), and C, were isolated from the methanolic extract of an Egyptian medicinal food, black cumin (the seeds of Nigella sativa). Their absolute configurations were determined on the basis of chemical and physicochemical evidence. Nigellamines were found to lower triglyceride levels in primary cultured mouse hepatocytes, and in particular, the activity of nigellamine A(5) was equivalent to that of the hypolipidemic agent, clofibrate.     

Ferromagnetic NiII-GdIII interactions in complexes with NiGd, NiGdNi, and NiGdGdNi cores supported by tripodal ligands

Dinuclear [(NiL)Gd(hfac)(2)(EtOH)](H(3)L = 1,1,1-tris(N-salicylideneaminomethyl)ethane, Hhfac = hexafluoroacetylacetone), trinuclear [(NiL)(2)Gd(NO(3))], and tetranuclear [(NiL)Gd(CH(3)CO(2))(2)(MeOH)](2) complexes, were prepared by treating [Ni(HL)] with [Gd(hfac)(3)(H(2)O)(2)], Gd(NO(3))(3).6H(2)O, and Gd(CH(3)CO(2))(3).4H(2)O, respectively, in the presence of Et(3)N. All the complexes show that ferromagnetic interactions occur between the Ni(II) and Gd(III) ions.     

Production of endohedral 133Xe-fullerene by ion implantation

Ion implantation was applied to the production of endohedral ¹³³Xe-fullerene. Using an isotope separator, ¹³³Xe ions were implanted into a fullerene target of C₆₀ and C₇₀ produced by vacuum evaporation on a Ni backing. An HPLC analysis following dissolution of the fullerene targets in o-dichlorobenzene corroborated the formation of ¹³³Xe@C₆₀ and ¹³³Xe@C₇₀, showing a strong correlation between C₆₀/C₇₀ and ¹³³Xe. The observed tailing following ¹³³Xe peaks in the elution curves suggests a possibility of the isolation of endohedral ¹³³Xe-fullerene from empty fullerene.     

Partialsynthese der Grandidone A, 7-Epi-A,B, 7-Epi-B,C, D und 7-Epi-D aus 14-Hydroxytaxodion

Partial Synthesis of Grandidones A, 7-Epi-A, B, 7-Epi-B, C, D and 7-Epi-D, from 14-Hydroxytaxodione Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U ( 6 ) to 14-hydroxytaxodione ( 5 ) in the presence of Fétizon's reagent mainly leads to grandidone A ( 1a ) and 7-epigrandidone A ( 1b ) (ca. 15:1), whereas coleon V ( 7 ) and 5 under the same conditions yield grandidone B ( 2a ) and 7-epigrandidone B ( 2b ) (ca. 3:1). Dimerization of 14-hydroxytaxodione ( 5 ) gives grandidone C ( 3 ; ca. 40%), grandidone D ( 4a ; ca. 50%) and 7-epigrandidone D ( 4b ; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C ( 3 ) to grandidone D ( 4a )/7-epigrandidone D ( 4b ) and interconversions of 4a and 4b were achieved.     

Synthesis and structural,electrochemical, and optical properties of Ru(II) complexes with azobis(2,2'-bipyridine)s

Two new ditopic ligands, 5,5"-azobis(2,2'-bipyridine) (5,5"-azo) and 5,5"-azoxybis(2,2'-bipyridine) (5,5"-azoxy), were prepared by the reduction of nitro precursors. Mononuclear and dinuclear Ru(II) complexes having one of these bridging ligands and 2,2'-bipyridine terminal ligands were also prepared, and their properties were compared with previously reported Ru(II) complexes having 4,4"-azobis(2,2'-bipyridine) (4,4"-azo). The X-ray crystal structure showed that 5,5"-azo adopts the trans conformation and a planar rodlike shape. The X-ray crystal structure of [(bpy)(2)Ru(5,5"-azo)Ru(bpy)(2)](PF(6))(4) (Ru(5,5"-azo)Ru) showed that the bridging ligand is in the trans conformation and nearly planar also in the complex and the metal-to-metal distance is 10.0 A. The azo or azoxy ligand in these complexes exhibits reduction processes at less negative potentials than the terminal bpy's due to the low-lying pi level. The electronic absorption spectra for the complexes having 5,5"-azo or 5,5"-azoxy exhibit an extended low-energy metal-to-ligand charge-transfer absorption. The ligands, 5,5"-azo and 5,5"-azoxy, and the mononuclear complex, [(bpy)(2)Ru(5,5"-azo)](2+), isomerize reversibly upon light irradiation. The low-energy MLCT state sensitizes the isomerization of the azo moiety in this complex. While [(bpy)(2)Ru(4,4"-azo)Ru(bpy)(2)](PF(6))(4) exhibits light switch properties, namely, significant electrochromism and a large luminescence enhancement, upon reduction, Ru(5,5"-azo)Ru does not show these properties. The radical anion formation upon reduction of these complexes has been confirmed by ESR spectroscopy.     

Plaunol A and B,new anti-ulcer diterpenelactones from Crotonsublyratus

Two new diterpenelactones named plaunol A ($\text{2}$) and B ($\text{3}$) exhibiting anti-Shay ulcer activity were isolated from Thai medicinal plant, $\text{Croton}$$\text{sublyratus}$. Structure of $\text{2}$ was determined by X-ray analysis of its $\text{p}$-bromobenzoate and structure of $\text{3}$ was deduced from the results of chemical correlation and the spectral data.     

Selective permeation of CO2 through poly 2-(N,N-dimethyl)aminoethyl methacrylate membrane prepared by plasma-graft polymerization technique

A membrane having an amine moiety was prepared by plasma-grafting 2-(N,N-dimethyl)aminoethyl methacrylate (DAMA) onto a microporous polyethylene substrate. Permselectivity of the membrane for CO₂ over N₂ was achieved in both dry and water swollen conditions. When the CO₂ partial pressure in the feed gas was 0.047 atm, the selectivity of CO₂ over N₂ reached 130 for the highly swollen water containing membrane. This value was found to agree with that obtained with a mobile carrier membrane (supported liquid membrane) using DAMA as the carrier. The effects of several experimental conditions such as degree of grafting, feed partial pressure and temperature on the membrane performance were studied. It was suggested that the membrane acted as a fixed carrier membrane for CO₂ facilitated transport in under the dry condition and acted as a fixed reaction site membrane in the water swollen condition. The carrier transport mechanism is discussed for dry and aqueous membranes.