Reactivity of ß-methylamino-L-alanine in complex sample matrixes complicating detection and quantification by mass spectrometry.

ß-methylamino-l-alanine (BMAA) is a naturally occurring nonprotein amino acid originally discovered in cycad seeds and traditional foods of the Chamorro people of Guam. Recent research has implicated BMAA as a potential factor in neurodegenerative disease and described the production of BMAA in cyanobacteria, but conflicting results have complicated the interpretation of data. We hypothesized that the reactivity of BMAA with metal ions in the sample matrix and the formation of metal adducts in electrospray ionization mass spectrometry (MS) analysis confound results. Dilute solutions of TCA, MgCl(2), NaCl, CuCl(2), ZnCl(2) (0.01 M), or artificial ocean water (Instant Ocean, 3.5 g/L) reduced the signal attributable to the BMAA M + H(+) peak by 78-99.7%. The degree of adduct formation was significantly affected by MS settings such as induction voltage. A number of the detected ion peaks in BMAA standards were consistent with the formation of metal-BMAA complexes in addition to the adduct formation. A standard of Zn(BMAA)(2) was synthesized, and the effects of sample preparation, derivatization, column chromatography, pH, and interactions with serine were determined. Together, these data demonstrate that sample matrix, formation of adducts, and mass spectrometry settings complicate analysis of BMAA, that analysis by detection of the parent ion and daughter ion fragmentation patterns are highly susceptible to false negative findings, and that failure to detect BMAA cannot be considered proof of absence of the compound.

Cobalt(II) ß-ketoaminato complexes as novel inhibitors of neuroinflammation.

Neuroinflammation contributes to the pathogenesis of neurological disorders including stroke, head trauma, multiple sclerosis, amyotrophic lateral sclerosis as well as age-associated neurodegenerative disorders including Alzheimer's and Parkinson's diseases. Therefore, anti-inflammatory drugs could be used to slow the progression of these diseases. We studied the anti-neuroinflammatory activity of four novel square planar cobalt(II) compounds bearing tetradentate ß-ketoaminato ligands with variation in the number of CF(3) ligand substituents, as well as their corresponding unmetallated organic ligands. Cobalt (Co) complexes were consistently more active than their corresponding ligands. One of the complexes, L(3)Co at concentrations (1-10 µM) that were not toxic to cells, significantly reduced cytotoxic secretions by human monocytic THP-1 cells, astrocytoma U-373 MG cells, and primary human microglia. This anti-neurotoxic action of L(3)Co was reduced by SP600125 and PD98059, selective inhibitors of c-Jun NH2-terminal kinase (JNK) and extracellular signal regulated kinase (ERK) kinase (MEK)1/2 respectively. L(3)Co had no effect on secretion of monocyte chemotactic protein-1 (MCP-1) by THP-1 cells, but it inhibited the NADPH oxidase-dependent respiratory burst activity of differentiated human HL-60 cells. L(3)Co upregulated heme oxygenase-1 (HOX-1) expression by THP-1 cells, which may be one of the molecular mechanisms responsible for its anti-inflammatory properties. Two of the Co compounds tested showed activity only at high concentrations (50 µM), but L(2)Co was highly toxic to all cell types used. Select Co complexes, such as L(3)Co, may exhibit pharmacological properties beneficial in human diseases involving neuroinflammatory processes. Further studies of the in vivo efficacy, safety and pharmacokinetics of L(3)Co are warranted.

The synthesis and characterization of a series of cobalt(II) ß-ketoaminato complexes and their cytotoxic activity towards human tumor cell lines.

A series of square planar cobalt(II) compounds bearing tetradentate ß-ketoaminato ligands with variation in the number of -CF(3) ligand substituents has been prepared and structurally and spectroscopically characterized. The fluorinated ß-ketoamine ligands were prepared utilizing a multistep reaction sequence employing a silylenol protecting group. An additional tetrahedral cobalt compound bearing two bidentate ß-ketoaminato ligands was also prepared and characterized. Cytotoxic activity of the cobalt-containing complexes was evaluated using six human cell lines; including two different prostate cancer cell lines (PC-3 and VCaP), acute monocytic leukemia (THP-1), astrocytoma (U-373 MG), hepatocellular carcinoma (HepG2), and neuroblastoma (SH-SY5Y) cells. The cobalt compounds are more active than their corresponding ligands. The activity is cell type specific; the cobalt compounds exhibit strong activity against human prostate cancer and monocytic leukemia cells but weak or no activity against neuroblastoma, astrocytoma, and liver carcinoma cells. Activity generally increases with a greater number of -CF(3) substituents, and square planar complexes exhibit greater activity than the tetrahedral derivative. The mechanisms of activity against human PC-3 prostate cancer cells involve caspase-3 and two different mitogen-activated protein kinases. The addition of a thiol antioxidant reduced cytotoxicity, suggesting the possible involvement of reactive oxygen species. These cobalt complexes may represent a novel class of cytotoxic drugs selective towards certain types of tumors.

Exploration and characterisation of novel bronze patinas derived from simple coordination complexes.

The chemical reactions of aqueous solutions containing simple transition-metal salts and bidentate nitrogen ligands on bronze surfaces results in a series of brightly coloured patinas. Chemically and physically robust patinas involve a chemical oxidation of the copper atoms within the bronze surface, either by an applied ferric salt or atmospheric dioxygen. The combination of Fe(NO(3))(3)·9H(2)O and 2,2'-bipyridine produces a coloured patina that is either red or blue, depending on whether oxygen was present during application, due to the presence of [Fe(bpy)(3)](2+) or [Fe(bpy)(3))](3+), respectively. Application of pyrazine produces a bright orange patina, due to the formation of Cu(i) coordination polymers on the bronze surface. Application of Fe(NO(3))(3)·9H(2)O and tetramethylethylenediamine (TMEDA) yields a forest green coloration, believed to be due to a bimetallic copper-iron complex, while TMEDA alone affords the sapphire blue of [Cu(TMEDA)(2)](2+). These patinas were characterized with ESI-TOF MS, UV-Vis spectrophotometry, and IR spectrophotometry, to determine the molecular basis for the patina chromophores.

Controlled radical polymerisation of methyl acrylate initiated by a well-defined cobalt alkyl complex.

Cobalt-mediated radical polymerisation of methyl acrylate is effected at moderate temperature by both a square planar bis(beta-ketoaminato)cobalt(II) complex in the presence of V-70 diazo radical initiator, and by a well-defined cobalt(III) alkyl derivative in the absence of a diazo complex. Polymerisation rates suggest that both reversible termination and degenerative transfer mechanisms are operative.

Synthesis and characterisation of bis(beta-ketoaminato) complexes of cobalt(II).

Condensation of 1-phenyl-1,3-butanedione with various substituted anilines affords N-aryl substituted beta-ketoamines PhC(O)CHC(CH(3))Naryl, which, when deprotonated and reacted with Co(OAc)(2).4H(2)O yields a series of bis(beta-ketoaminato)cobalt(II) complexes 1b to 6b (aryl = Ph, 1b; p-CH(3)C(6)H(4), 2b; 2,6-(CH(3))(2)C(6)H(3), 3b; 3,5-(CH(3))(2)C(6)H(3), 4b; p-CF(3)C(6)H(4), 5b; p-CH(3)OC(6)H(4), 6b). All six cobalt compounds were characterised by (1)H NMR, elemental analysis, magnetic susceptibility, and X-ray crystallography, indicating a uniform tetrahedral geometry in all cases. Electrochemical oxidation potentials indicate sensitivity to aryl substitution at the ortho- and para- positions, but not to meta-substitution, a conclusion supported by DFT calculations.

Electronic and steric ligand effects in the radical polymerization of vinyl acetate mediated by beta-ketoiminate complexes of cobalt(II).

Complexes Co[OC(Ph)CHC(Me)NAr](2) [Ar=Ph, 1; o,o'-C(6)H(3)Me(2) (Xyl), 2; p-C(6)H(4)CF(3), 3] are tested in the polymerization of vinyl acetate (VAc) initiated by V-70 (0.8 equiv) at 30 degrees C. Polymerization occurs without any notable induction time yielding PVAc with relatively low polydispersity, but with higher than expected M(n) values, which indicates inefficient trapping processes. The apparent polymerization rate constant varies in the order 2>1>3. Controlled polymer growth is also observed when the polymerization is conducted in the presence of a much higher V-70/1 ratio, demonstrating that this system can also function as a transfer agent in a degenerative transfer process. Competition between chain growth and catalyzed chain transfer (CCT) is also observed, the latter prevailing at higher temperatures. Comparison of these results with previous reports on bis(beta-diketonato) complexes allows a separate assessment of ligand electronic and steric effects in the ability to control polymerization.

Direct observation of the phenomenology of a solid thermal explosion using time-resolved proton radiography.

We present a new phenomenology for burn propagation inside a thermal explosion based on dynamic radiography. Radiographic images were obtained of an aluminum cased solid cylindrical sample of a plastic bonded formulation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. The phenomenology observed is ignition followed by cracking in the solid accompanied by the propagation of a radially symmetric front of increasing proton transmission. This is followed by a further increase in transmission through the sample, ending after approximately 100 micros. We show that these processes are consistent with the propagation of a convective burn front followed by consumption of the remaining solid by conductive particle burning.

Toward binary nitrosyls: distinctly bent Fe[bond]N[bond]O linkages in base-stabilized Fe(NO)3+ complexes.

Air- and moisture-sensitive Fe(NO)(3)(eta(1)-PF(6)) (1) may be conveniently prepared by treating Fe(NO)(3)Cl with 1 equiv of [Ag][PF(6)] in CH(2)Cl(2) or by reacting [NO][PF(6)] with excess iron filings in MeNO(2). Complex 1 is thermally sensitive both as a solid and in solutions, and is best handled below -20 degrees C. To isolate 1 reproducibly from MeNO(2) solutions it is necessary to remove all traces of propionitrile, which often occurs as an impurity in MeNO(2), because it reacts with Lewis-acidic 1 to form [Fe(NO)(3)(EtCN)][PF(6)] (2). If trace H(2)O is present during the synthesis of 1, some of the PF(6)(-) is converted to PO(2)F(2)(-), which is sufficiently Lewis basic that it captures two Fe(NO)(3)(+) fragments and forms [(ON)(3)Fe(mu-PO(2)F(2))Fe(NO)(3)][PF(6)] (3). Finally, Fe(NO)(3)(eta(1)-BF(4)) (4) can be obtained as a green microcrystalline powder by employing the same synthetic methodologies used to prepare 1. The new complexes 1-4 have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2, 3, and 4 and their parent compound, Fe(NO)(3)Cl, have been established by X-ray diffraction methods. The iron centers in the Fe(NO)(3) fragments in all these structures exhibit approximately tetrahedral coordination geometries, and the Fe-N-O linkages are distinctly nonlinear with bond angles in the range of 159 to 169 degrees. DFT calculations on Fe(NO)(3)(eta(1)-BF(4)) (4) confirm that its bent Fe-N-O links have an electronic origin and need not be attributed to other factors, such as packing forces in the crystal. Interestingly, the bending of the NO ligands results in an increase in the energy of the HOMO, relative to the linear case, but at the same time causes a decrease in energy of the HOMO-1 and the HOMO-2 molecular orbitals. This more than compensates for the higher energy of the HOMO, resulting in a lower energy structure.

The elusive 16-electron Cp*M(NO)Me(2)(M = Mo, W) complexes and their spontaneous conversions to Cp*M(NMe)(O)Me isomers.

Treatment of [Cp*Mo(NO)Cl(mu-Cl)](2) with magnesium (Me(2)Mg.dioxane, MeMgCl) or aluminum (Me(3)Al) methylating reagents affords the known compound [Cp*Mo(NO)Me(mu-Cl)](2) (1). Similar treatment of the dichloro precursor with MeLi in ethereal solvents generates an equimolar mixture of 1 and the trimethyl "ate" complex, Cp*MoMe(3)(NO-Li(OEt(2)(n)), (2-Et(2)O). Reaction of 2-Et(2)O with a source of [Me](+) forms Cp*MoMe(3)(=N-OMe)(3), a rare terminal alkoxylimido complex. Metathesis of the chloro ligands of [Cp*Mo(NO)Cl(mu-Cl)](2) by MeLi in toluene at low temperatures produces the target dimethyl complex, Cp*Mo(NO)Me(2) (4), in 75% isolated yield. In solution, 4 is predominantly a monomeric species, whereas in the solid state it adopts a dimeric or oligomeric structure containing isonitrosyl bridges as indicated by IR and (15)N/(13)C NMR spectroscopies. Hydrolysis of 4 affords meso- and rac-[Cp*Mo(NO)Me](2)(mu-O) (5), and the reactions of 4 with a range of Lewis bases, L, to form the 18e adducts Cp*Mo(NO)(L)Me(2) (e.g., Cp*Mo(NO)(PMe(3))Me(2) (7)), have established it to be the most electrophilic complex of its family. Acidolysis of the methyl groups of 4 is also facile. Most notably, 4 is thermally unstable in solution and undergoes isomerization via nitrosyl N-O bond cleavage to its oxo(imido) form, Cp*Mo(NMe)(O)Me (11), which is isolable from the final reaction mixture as the mu-oxo-bridged adduct formed by 4 and 11, i.e., Cp*Mo(NO)Me(2)(mu-O)Cp*Mo(NMe)Me (4 <-- 11). The rate of this isomerization is significantly faster for the tungsten dimethyl complex; hence, Cp*W(NO)Me(2) (12) is not isolable free of a supporting donor interaction and can only be isolated as Cp*W(NO)Me(2)(mu-O)Cp*W(NMe)Me (12 <-- 13) or Cp*W(NO)Me(2)(PMe(3)) (14) adducts.

Schwannoma of the vagus nerve.

A case is described in which severe bradycardia complicated removal of a Schwannoma of the vagus nerve in the parapharyngeal space. The presentation of this rare tumour is discussed.

Lidar polarization studies of the troposphere.

The polarization properties of lidar backscattering from the atmosphere have been measured using a ruby system operating at 694.3 nm and 347.2 nm. Linearly polarized signals are transmitted, and multiple receiver channels simultaneously sample the return with polarizers oriented parallel and perpendicular to the transmitted polarization. It is found that the polarization of the scattered signal varies substantially with meteorological conditions and that the signals can be employed to derive useful information about the atmospheric conditions.