W. Stephen McNeil

Reactivity of β-Methylamino-l-alanine in Complex Sample Matrixes Complicating Detection and Quantification by Mass Spectrometry

β-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.

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.

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

A series of square planar cobalt(II) compounds bearing tetradentate β-ketoaminato ligands with variation in the number of -CF(3) ligand substituents has been prepared and structurally and spectroscopically characterized. The fluorinated β-ketoamine ligands were prepared utilizing a multistep reaction sequence employing a silylenol protecting group. An additional tetrahedral cobalt compound bearing two bidentate β-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.

Cobalt(II) β-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 Alzheimers and Parkinsons 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 β-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.

Synthesis and characterisation of bis(β-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.

Cr(NAr)(O)(NPri2)(Ar): a strongly-bent monoimido complex resulting from nitrosyl ligand cleavage

The molecular structure of Cr(NAr)(O)(NPri2)(Ar) (Ar = 2-MeC6H4) is analysed by X-ray crystallographic and density functional theoretical techniques.