Chemical vapour deposition of In2O3 thin films from a tris-guanidinate indium precursor.

A new homoleptic sublimable indium(III) guanidinate, (In[(N(i)Pr)(2)CNMe(2)](3) (1), was synthesized from a facile high-yield procedure. Compound 1 crystallized is a P1 space group; a = 10.5989(14) Å, b = 11.

Use of saliva for early dengue diagnosis.

Background: The necessity of a venous blood collection in all dengue diagnostic assays and the high cost of tests that are available for testing during the viraemic period hinder early detection of dengue cases and thus could delay cluster management. This study reports the utility of saliva in an assay that detects dengue virus (DENV)-specific immunoglobulin A (Ig A) early in the phase of a dengue infection.

Methods And Findings: Using an antigen capture anti-DENV IgA (ACA) ELISA technique, we tested saliva samples collected from dengue-confirmed patients.

Amine-linked N-heterocyclic carbenes: the importance of an pendant free-amine auxiliary in assisting the catalytic reaction.

We have successfully expanded the library of amino-NHCs with varying substituents on the amine group, leading to insight about the instability of NHCs arising from the intermolecular interaction of the dangling amine side-arm. However, the pendant amine plays an important role with respect to the catalytic process, resuscitating the catalytic activity of unsaturated NHC's through a synergistic effect invoked by the secondary amine. This proof of concept allows us to expand the spectrum of catalysis to C-C, as well as C-B bond formation.

Epidemiological characteristics of the 2005 and 2007 dengue epidemics in Singapore - similarities and distinctions.

Introduction: We investigated the epidemiological features of the 2007 dengue outbreak to determine the factors that could have triggered it two years after the previous large outbreak in 2005.

Methods: All laboratory-confirmed cases of dengue reported during the year, as well as entomological and virological data, were analysed.

Results: A total of 8826 cases including 24 deaths were reported in 2007, giving an incidence of 192.

Interplay between the diamine structure and absolute helicity in Ni-salen metallofoldamers.

The nature of internal chiral diamines can greatly influence the ratio of helical diastereomers for Ni-salen based metallofoldamers. The diastereomer ratio is small for metallofoldamers derived from (1R, 2R)-cyclohexanediamine, (11R, 12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine, or (1R, 2R)-cyclopentanediamine. By contrast, the foldamer from (1S, 2S)-1,2-diphenylethylenediamine provides a relatively large bias (6 : 1) for the P-helical diastereomer as evidenced by NMR studies, chiroptical data, and X-ray studies.

Enhanced stereoselectivity of a Cu(II) complex chiral auxiliary in the synthesis of Fmoc-L-γ-carboxyglutamic acid.

L-γ-Carboxyglutamic acid (Gla) is an uncommon amino acid that binds avidly to mineral surfaces and metal ions. Herein, we report the synthesis of N-α-Fmoc-L-γ-carboxyglutamic acid γ,γ'-tert-butyl ester (Fmoc-Gla(O(t)Bu)(2)-OH), a suitably protected analogue for Fmoc-based solid-phase peptide synthesis. The residue was synthesized using a novel chiral Cu(II) complex, whose structure-based design was inspired by the blue copper protein rusticyanin.

A family of four-coordinate iron(II) complexes bearing the sterically hindered tris(pyrazolyl)borato ligand Tp(tBu,Me).

A new family of 14-electron, four-coordinate iron(II) complexes of the general formula [Tp(tBu,Me)FeX] (Tp(tBu,Me) is the sterically hindered hydrotris(3-tert-butyl-5-methyl-pyrazolyl) borate ligand and X=Cl (1), Br, I) were synthesized by salt metathesis of FeX(2) with Tp(tBu,Me)K. The related fluoride complex was prepared by reaction of 1 with AgBF(4). Chloride 1 proved to be a good precursor for ligand substitution reactions, generating a series of four-coordinate iron(II) complexes with carbon, oxygen, and sulphur ligands.

Trigonal bi- and monopyramidal cobalt(II) complexes of a novel guanidine-based tripodal ligand.

The novel ligand DIG(3)tren has three N',N''-diisopropylguanidinyl (DIG) moieties. We report on the structures of two cobalt complexes that show how an isopropylamino group from each DIG acts as a flap that can either close over the metal or rotate away from the metal to open up a site for auxiliary ligand binding. Two of the -NH(iPr) flaps are open in pink [Co(DIG(3)tren)(OAc)]OAc (1), and each of these flaps provides a hydrogen bond to stabilize acetate binding to trigonal bipyrimidal cobalt.

Harnessing low-valent metal centers through non-bonding orbital interactions.

The synthesis, characterization, and computational analysis of a series of low-valent, In(I) complexes bearing the bis(imino)pyridine scaffold, {Ar'N=CPh}(2)(NC(5)H(3)), is reported. A stepwise steric reduction of the aryl groups on the imine substituents around the coordination site, (Ar' = 2,5-(t)Bu(2)C(6)H(3), 2,6-(i)Pr(2)C(6)H(3), 2,6-(CH(3)CH(2))(2)C(6)H(3)) is explored through the spectroscopic and crystallographic examination of complexes [{Ar'N=CPh}(2)(NC(5)H(3))]In(+)(OTf)(-) (1-3). Compounds 1-3 displayed long In-N and In-OTf distances indicating only weak or no coordination.

Minimalist end groups for control of absolute helicity in salen- and salophen-based metallofoldamers.

(S)-1-Methylindan end groups are effective controllers of absolute helicity in Ni-salen- and Ni-salophen-based foldamers derived from (R,R)-trans-1,2-cyclohexanediamine and 1,2-phenylenediamine, respectively. Evidence for the helicity of the described complexes was provided through X-ray crystallography and study of chiroptical properties in solution. The chiral end groups control the absolute sense of helicity for the salen complexes, even in a case where the helical bias of the end group is mismatched relative to that of the internal diamine.

Heteroleptic iminopyrrolidinates of aluminium.

A series of iminopyrrolidine (ip) compounds were synthesized with excellent yields as potential ligands for novel organometallic precursors for atomic layer deposition. The idea behind these ligands was that carbodiimide (CDI) deinsertion would not occur as the quaternary carbon was tethered to one chelate nitrogen. To our advantage a melting point trend was evident within the ip ligands and reflected in the family of heteroleptic aluminium species when the ip ligands were reacted with TMA or TEA.

Bimetallic nickel aluminum mediated para-selective alkenylation of pyridine: direct observation of eta2,eta1-pyridine Ni(0)-Al(III) intermediates prior to C-H bond activation.

We have presented new amino-NHC Ni-Al complex mediated para C-H bond activation for pyridine and quinolin, and isolated for the first time the intermediate structure of a bimetallic eta(2),eta(1)-pyridine nickel aluminum complex prior to its C-H activation, which serves as key evidence for bimetallic catalysis.

Evaluation of Chikungunya diagnostic assays: differences in sensitivity of serology assays in two independent outbreaks.

Background: The sensitivity and specificity of two in-house MAC-ELISA assays were tested and compared with the performance of commercially-available CTK lateral flow rapid test and EUROIMMUN IFA assays for the detection of anti-Chikungunya virus (CHIKV) IgM. Each MAC-ELISA assay used a whole virus-based antigen derived from genetically distinct CHIKV strains involved in two chikungunya disease outbreaks in Singapore (2008); a January outbreak strain with alanine at amino acid residue 226 of the E1 glycoprotein (CHIKV-A226) and a May-to-September outbreak strain that possessed valine at the same residue (CHIKV-226V). We report differences in IgM detection efficacy of different assays between the two outbreaks.

Disubstituted 1,8-diamidonaphthalene ligands as a flexible, responsive, and reactive framework for tantalum complexes.

Deprotonated N,N'-disubstituted 1,8-diaminonaphthalenes (R(2)DAN(2-); R = (CH(3))(2)CH, C(6)H(5), 3,5-Me(2)C(6)H(3)) were incorporated into Ta(V) complexes employing two methods. The direct proton transfer reaction of the parent amine, 1,8-(RNH)(2)C(10)H(6), with TaMe(3)Cl(2) led to elimination of methane and formation of TaCl(3)[1,8-(RN)(2)C(10)H(6)] (1, 2). Reaction of the dilithiated amido species, Li(2)R(2)DAN, with TaMe(3)Cl(2) or [Ta(NEt(2))(2)Cl(3) ] yielded TaMe(3)[1,8-(RN)(2)C(10)H(6)] (3, 4) and TaCl(NEt(2))(2)[1,8-(RN)(2)C(10)H(6)] (5, 6), respectively.

The chiral crown conformation in paddlewheel complexes.

Bimetallic paddlewheel complexes derived from imides of (S)-tert-leucine adopt 'chiral crown' configurations in which the four imide groups are projected in a chiral arrangement on one face, and the four tert-butyl groups are projected on the opposite face. In this contribution, the generality of the chiral crown conformation is examined through crystallographic studies where the metal and the nature of the chiral ligands are altered. Based upon these observations, a model is proposed to explain the factors which create bias for the chiral crown configuration.

Comparative analysis of fecal microbiota in infants with and without eczema.

Eczema is a chronic form of childhood disorder that is gaining in prevalence in affluent societies. Previous studies hypothesized that the development of eczema is correlated with changes in microbial profile and composition of early life endemic microbiota, but contradictory conclusions were obtained, possibly due to the lack of minimization of apparent non-health related confounders (e.g.

Water-based oxygen-sensor films.

The luminescent cyclometalated iridium complex [Ir(fppy)(2)(t-Bu-iCN)(2)]CF(3)SO(3), 1 (fppy = 4-(2-pyridyl)benzaldehyde, and t-Bu-iCN = tert-butyl isocyanide), was synthesized and characterized by X-ray crystallography and (1)H NMR, absorption, and emission spectroscopies. Complex 1 was quantitatively bound to the water-soluble amine-functionalized polymer Silamine D208-EDA by reductive amination, to produce 2. The quantum yield of emission and excited state lifetime of 2 (varphi(em) = 0.

Differential regulation of effector- and central-memory responses to Toxoplasma gondii Infection by IL-12 revealed by tracking of Tgd057-specific CD8+ T cells.

Production of the pro-inflammatory cytokine IL-12 by innate phagocytes drives the differentiation of IFN-gamma-producing effector T cells during Toxoplasma gondii infection. However, the role of IL-12 in the regulation of memory CD8+ T cell differentiation and function during murine toxoplasmosis is unclear. To track memory CTL development, we identified a novel H-2K(b)-restricted CTL population specific for the Toxoplasma antigen tgd057.

A Series of Cyanide-Bridged Binuclear Complexes.

A series of cyanide-bridged binuclear complexes, ('S(3)')Ni-CN-M[Tp(tBu)] ('S(3)' = bis(2-mercaptophenyl)sulfide, Tp(tBu) = hydrotris(3-tert-butylpyrazolyl)borate, M = Fe (2-Fe), Co (2-Co), Ni (2-Ni), Zn (2-Zn)) was prepared by the coupling of K[('S(3)')Ni(CN)] with [Tp(tBu)]MX. The isostructural series of complexes was structurally and spectroscopically characterized. A similar coupling strategy was used to synthesize the anionic copper(I) analogue, Et4N{('S3')Ni-CN-Cu[Tp(tBu)]}, 2-Cu.

Disproportionation and radical formation in the coordination of "GaI" with bis(imino)pyridines.

Attempted coordination of "Ga(I)I" with two new sterically bulky, aryl substituted bis(imino)pyridine ligands lead to Ga(III) species [2,6-{ArN=CPh}(2)(NC(5)H(3))]GaI(2)(+)GaI(4)(-) (Ar = 2,5-(t)Bu(2)C(6)H(3), 2,6-(i)Pr(2)C(6)H(3) = Dipp) arising from thermodynamically favorable disproportionation reactions. Examination of these reactions lead to isolation of a neutral radical species [2,6-{DippN=CPh}(2)(NC(5)H(3))]GaI(2). Both EPR spectroscopy and DFT calculations on this compound indicate that the unpaired electron is localized in a di(imino)pyridine pi* orbital of an anionic ligand with nearly zero contribution from the Ga or I centers.

Molecular characterization of two hantavirus strains from different rattus species in Singapore.

Background: Hantaviruses cause human disease in endemic regions around the world. Outbreaks of hantaviral diseases have been associated with changes in rodent population density and adaptation to human settlements leading to their proliferation in close proximity to human dwellings. In a parallel study initiated to determine the prevalence of pathogens in Singapore's wild rodent population, 1206 rodents were trapped and screened.

A family of heteroleptic titanium guanidinates: synthesis, thermolysis, and surface reactivity.

A family of new mixed-ligand titanium guanidinate compounds was synthesized as potential atomic layer deposition precursors, and the surface chemistry on silica of a promising candidate (Cp(2)Ti[(N(i)Pr)(2)CN(H)(i)Pr]) was explored. Generally, these compounds have very good thermal stability with onsets of volatility between 127 and 168 degrees C, with melting points generally ranging from 147 to 165 degrees C. The reactivity of [(i)PrN(H)C(N(i)Pr)(2)]TiCp(2) was studied with high surface area silica between 180 and 330 degrees C.

Seroepidemiology of dengue virus infection among adults in Singapore.

Introduction: To determine the seroepidemiology of dengue virus infection in a representative sample of the adult resident population aged 18 years old to 74 years old in Singapore and to estimate the proportion of asymptomatic dengue infection during the 2004 epidemic.

Materials And Methods: The study was based on 4152 stored blood samples collected between September and December 2004 from participants aged 18 years old to 74 years old during the 2004 National Health Survey. Sera were tested for IgG and IgM antibodies using a commercial test kit (PanBio Capture/Indirect ELISA).

Synthetic analogs for evaluating the influence of N-H...S hydrogen bonds on the formation of thioester in acetyl coenzyme A synthase.

A series of square planar methylnickel(II) complexes, (dppe)Ni(Me)(SAr) (dppe = 1,2-bis(diphenylphosphino)ethane); 2. Ar = phenyl; 3. Ar = pentafluorophenyl; 4.

A high-spin organometallic Fe-S compound: structural and Mössbauer spectroscopic studies of [phenyltris((tert-butylthio)methyl)borate]Fe(Me).

The synthesis and structure of the pseudotetrahedral, sulfur-rich, high-spin organoiron(II) [phenyltris((tert-butylthio)methyl)borate]Fe(Me), [PhTt(tBu)]Fe(Me), 1, are reported. Low-temperature Mössbauer spectroscopic studies reveal an isomer shift of delta = 0.60(3) mm/s and DeltaE(Q) = 0.