Chi-Wi Ong

Synthesis, crystal structure and biological activity of thiophene-2-carboxaldehyde thiosemicarbazone and its tin complexes

Abstract Thiophene-2-carboxaldehyde thiosemicarbazone, C 4 H 3 S–CHN–NH–C(S)NH 2 (tctscH) obtained by the condensation reaction of thiophene-2-carboxaldehyde with thiosemicarbazide forms SnPh 2 Cl(tctsc), 1 and SnCl 2 (tctsc) 2 , 2 with SnPh 2 Cl 2 and SnPhCl 3 in 1:1 and 1:2 tin:ligand molar ratios, respectively. The crystal structure determination shows that in both 1 and 2 , tctscH is deprotonated and functions as an anionic bidentate ligand, co-ordinating to the tin atom through its azomethine- N and thiol- S atoms. The geometry about the tin atom for complex 1 is distorted trigonal bipyramidal whereas for complex 2 is distorted octahedral. Note that dephenylation occurs during the formation of complex 2 . Fungitoxicity and cytotoxicity of the two tin complexes and tctscH have been evaluated and the biological activity is more remarkable in complex 1 in comparison to the other.

Effect of Various Organic Precursors on the Performance of LiFePO4 ∕ C Composite Cathode by Coprecipitation Method

The goal of this research was to study the effect of organic precursors with functionalized aromatic anhydrides or aromatic diketones on the performance of the LiFePO 4 /C composite. A coprecipitation method was applied to prepare a series of LiFePO 4 /C materials by calcinating amorphous LiFePO 4 with 5 wt % organic precursors at 750°C. The materials were characterized by X-ray diffraction, scanning electron microscopy, particle size analysis, thermal analysis, Brunauer-Emmett-Teller specific surface area and electrochemical methods. The obtained LiFePO 4 /C composites showed a well-ordered olivine-type LiFePO 4 structure with a minor Fe 2 P impurity. The occurrence of the Fe 2 P phase can be attributed to the relatively high temperature of 750°C. The LiFePO 4 /C composites produced by pyrolysis of an aromatic diketone with a longer alkoxy branch exhibited a better capacity compared to other types of organic compounds. The longer alkoxy aromatic diketone showed a better performance because its decomposition temperature was close to the temperature of the LiFePO 4 phase transformation resulting in a fine particle size and uniform carbon distribution on the composite surface. The performance of different organic precursors showed a strong relationship with its decomposition temperature, but was not in correlation with its weight loss. According to Raman spectral analysis, longer alkoxy aromatic diketones have a larger (D + G)/PO 4 peak ratio indicating higher uniform and carbon content coating on LiFePO 4 /C particles.

SYNTHESIS, CRYSTAL STRUCTURE AND BIOLOGICAL ACTIVITY OF BIS(ACETONE THIOSEMICARBAZONE-S)DICHLORODIPHENYLTIN(IV)

The reaction between diphenyltin(IV) dichloride and thiosemicarbazide using acetone–ethanol as solvent resulted in the formation of bis(acetone thiosemicarbazone-S)dichlorodiphenyltin(IV), SnPh 2 Cl 2 (atsc) 2 . The crystal structure determination of the compound revealed it to be a monomeric six-co-ordinated organotin(IV) complex. Each of the two atsc functions as a monodentate ligand, co-ordinating to the tin atom through the sulfur atom and conferring a distorted-octahedral geometry upon the tin. The Sn–S bond length is 2.712(1) A. The antifungal activity of the complex, atsc and SnPh 2 Cl 2 against four plant pathogens has been evaluated. The complex displays marked fungitoxicity against these fungi and is more fungitoxic than free atsc and SnPh 2 Cl 2 . It has also shown significant cytotoxicity against human colon adenocarcinoma, breast adenocarcinoma, hepatocellular carcinoma and acute lymphoblastic leukaemia.

Reaction cell inductively coupled plasma mass spectrometry-based immunoassay using ferrocene tethered hydroxysuccinimide ester as label for the determination of 2,4-dichlorophenoxyacetic acid

The high sensitive dynamic reaction cell inductively coupled plasma mass spectrometry (DRC ICP-MS)-based immunoassay using ferrocene (Fc) tethered hydroxysuccinimide ester as label for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) was presented. Ferrocene tethered hydroxysuccinimide ester was directly or via horse radish peroxidase (HRP) as a bridge coupled to monoclonal antibody (mAb) of 2,4-D. Competitive immunoreactions were completed in microtiter plate and the signal of 56 Fe in the bound ferrocene labeled conjugate was detected by DRC ICP-MS. The potentially interfering 40 Ar 16 O + at the iron mass m/z 56 was reduced in intensity significantly by using NH 3 as the reaction gas. The optimization process of the immunoassay was greatly simplified in the aid of enzyme linked immunosorbent assay (ELISA) procedure. The 2,4-D was determined in the dynamic range of 0.1–1000 ng/ml and the detection limits of the assays using the two ferrocene labeled conjugates were found to be 0.044 and 0.055 ng/ml, respectively. The relative standard deviation for six measurements were within 5.5–15.3%.

Chemical synthesis, DNA cleavage and antitumor activity of molecules with (Z)-7-sulfonyl-3-hexene-1,5-diyne functionalities

Abstract Compounds 20a-d, 21a, 21d and 22 were synthesized from the corresponding (Z)-1,2-dichloroethylene, 1,2-diiodobenzene and 2,3-naphthylene bistriflate respectively and exhibited DNA cleaving properties at 37 °C in pH 8.0 as well as potent cytotoxicity against human carcinoma cells with no additive.

A comparative study on the binding characteristics of the tight serum biliverdin-protein complexes in two fishes: Anguilla japonica and Clinocottus analis

The binding characteristics of biliverdin to its carrier protein in the blue-green blood of Clinocottus analis (woolly sculpin) and Anguilla japonica (freshwater eel) were operationally defined by various chemical probing methods and spectra analysis. The biliverdin in C. analis is a rotatable coiled molecule enveloped in a hydrophobic pocket of its carrier protein. The biliverdin in A. japonica is an open form molecule with external hydrogen bond or weak ester bond interacting with the carrier protein. This, for the first time, shows that the novel firm binding biliprotein complexes in the blood of different species are biochemically different. Their comparative and evolutionary significance is discussed.

Antitumor antibiotics drug design. Part I. Synthesis of a 6-chloro-2-methoxy-9-triethylenetetraaminoacridine iron complex which binds to DNA and causes strand scissioning in vitro

Abstract 6-Chloro-2-methoxy-9-triethylenetetraaminoacridine iron complex has been synthesized and was found to bind to duplex DNA and to cause strand scissioning in the presence of a reducing agent in vitro. The advantage of this compound is its high water solubility.

Impact of pyrrolidine-bispyrrole DNA minor groove binding agents and chirality on global proteomic profile in Escherichia Coli.

BackgroundThere is great interest in the design of small molecules that selectively target minor grooves of duplex DNA for controlling specific gene expression implicated in a disease. The design of chiral small molecules for rational drug design has attracted increasing attention due to the chirality of DNA. Yet, there is limited research on the chirality effect of minor groove binders on DNA interaction, especially at the protein expression level. This paper is an attempt to illustrate that DNA binding affinity might not provide a full picture on the biological activities. Drug interacting at the genomic level can be translated to the proteomic level. Here we have illustrated that although the chiral bispyrrole-pyrrolidine-oligoamides, PySSPy and PyRSPy, showed low binding affinity to DNA, their influence at the proteomic level is significant. More importantly, the chirality also plays a role. Two-dimensional proteomic profile to identify the differentially expressed protein in Escherichia coli DH5α (E coli DH5α) were investigated.ResultsE coli DH5α incubated with the chiral PySSPy and PyRSPy, diastereomeric at the pyrrolidine ring, showed differential expression of eighteen proteins as observed through two dimensional proteomic profiling. These eighteen proteins identified by MALDI_TOF/TOF MS include antioxidant defense, DNA protection, protein synthesis, chaperone, and stress response proteins. No statistically significant toxicity was observed at the tested drug concentrations as measured via MTT assay.ConclusionThe current results showed that the chiral PySSPy and PyRSPy impact on the proteomic profiling of E coli DH5α, implicating the importance of drug chirality on biological activities at the molecular level.