Displaying publications 341 - 360 of 396 in total

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  1. Servati Gargari M, Stilinović V, Bauzá A, Frontera A, McArdle P, Van Derveer D, et al.
    Chemistry, 2015 Dec 1;21(49):17951-8.
    PMID: 26489982 DOI: 10.1002/chem.201501916
    Three solid materials, [Pb(HL)(SCN)2 ]⋅CH3 OH (1), [Pb(HL)(SCN)2 ] (2), and [Pb(L)(SCN)]n (3), were obtained from Pb(SCN)2 and an unsymmetrical bis-pyridyl hydrazone ligand that can act both as a bridging and as a chelating ligand. In all three the lead center is hemidirectionally coordinated and is thus sterically optimal for participation in tetrel bonding. In the crystal structures of all three compounds, the lead atoms participate in short contacts with thiocyanate sulfur or nitrogen atoms. These contacts are shorter than the sums of the van der Waals radii (3.04-3.47 Å for Pb⋅⋅⋅S and 3.54 Å for Pb⋅⋅⋅N) and interconnect the covalently bonded units (monomers, dimers, and 2D polymers) into supramolecular assemblies (chains and 3D structures). DFT calculations showed these contacts to be tetrel bonds of considerable energy (6.5-10.5 kcal mol(-1) for Pb⋅⋅⋅S and 16.5 kcal mol(-1) for Pb⋅⋅⋅N). A survey of structures in the CSD showed that similar contacts often appear in crystals of Pb(II) complexes with regular geometries, which leads to the conclusion that tetrel bonding plays a significant role in the supramolecular chemistry of Pb(II) .
  2. Heng MP, Sinniah SK, Teoh WY, Sim KS, Ng SW, Cheah YK, et al.
    PMID: 26057090 DOI: 10.1016/j.saa.2015.05.095
    Testosterone thiosemicarbazone, L and its nickel (II) complex 1 were synthesized and characterized by using FTIR, CHN, (1)H NMR, and X-ray crystallography. X-ray diffraction study confirmed the formation of L from condensation of testosterone and thiosemicarbazide. Mononuclear complex 1 is coordinated to two Schiff base ligands via two imine nitrogens and two tautomeric thiol sulfurs. The cytotoxicity of both compounds was investigated via MTT assay with cisplatin as positive reference standard. L is more potent towards androgen-dependent LNCaP (prostate) and HCT 116 (colon). On the other hand, complex 1, which is in a distorted square planar environment with L acting as a bidentate NS-donor ligand, is capable of inhibiting the growth of all the cancer cell lines tested, including PC-3 (prostate). It is noteworthy that both compounds are less toxic towards human colon cell CCD-18Co. The intrinsic DNA binding constant (Kb) of both compounds were evaluated via UV-Vis spectrophotometry. Both compounds showed Kb values which are comparable to the reported Kb value of typical classical intercalator such as ethidium bromide. The binding constant of the complex is almost double compared with ligand L. Both compounds were unable to inhibit the action topoisomerase I, which is the common target in cancer treatment (especially colon cancer). This suggest a topoisomerase I independent-cell death mechanism.
  3. Liu L, Han ZB, Wang SM, Yuan DQ, Ng SW
    Inorg Chem, 2015 Apr 20;54(8):3719-21.
    PMID: 25849722 DOI: 10.1021/acs.inorgchem.5b00185
    Herein, two stable lead(II) molecular-bowl-based metal-organic frameworks and their micro- and nanosized forms with open metal sites were presented. These materials could act as Lewis acid catalysts to cyanosilylation reaction. Moreover, the catalytic performances are size-dependent, with the catalyst with nanosized form being 1 order of magnitude more efficient than those with micro- and millisized forms.
  4. Ng CH, Lim CW, Teoh SG, Fun HK, Usman A, Ng SW
    Inorg Chem, 2002 Jan 14;41(1):2-3.
    PMID: 11782136
    Treatment of vanadium(V) oxide with an ethanol-concentrated sulfuric acid mixture, followed by the addition of an equimolar amount of beta-alanine and sodium hydroxide, and finally raising the pH to 3.9 with sodium carbonate solution, under continuous heating in a water bath and in the presence of air, leads to the polyionic sodium cyclo-[mu(6)-(sulfato-O,O',O'')tris[mu-(beta-alanine-O,O')-mu-oxo]tris(mu-hydroxo-mu-oxo)hexa[oxovanadium(V)]] sulfate tridecahydrate which crystallizes in the monoclinic P2(1)/n space group [a = 9.5192(4), b = 20.1185(9), c = 22.6174(9) A, beta = 97.011(1) degrees; Z = 4]. The crown-shaped polyoxovanadium(V) cluster cation, with carboxylate-bridging amino acid ligands, has an Anderson structure with two unique capping sulfato ligands. Its structural analysis, together with IR, UV-vis, and preliminary data on its solution properties, is presented.
  5. Tong ML, Ye BH, Cai JW, Chen XM, Ng SW
    Inorg Chem, 1998 Jun 01;37(11):2645-2650.
    PMID: 11670398
    In the presence of guest 2,4'-bpy molecules or under acidic conditions, three compounds, [Cd(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(2).(2,4'-bpy)(2).H(2)O (1), [Zn(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(2).(2,4'-bpy)(2).H(2)O (2), and [Cu(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(4).(4,4'-H(2)bpy) (3), were obtained from the reactions of the metal salts and 4,4'-bpy in an EtOH-H(2)O mixture. 1 has a 2-D square-grid network structure, crystallizing in the monoclinic space group P2/n, with a = 13.231(3) Å, b = 11.669(2) Å, c = 15.019(3) Å, beta = 112.82(3) degrees, Z = 2; 2 is isomorphous with 1, crystallizing in the monoclinic space group P2/n, with a = 13.150(3) Å, b = 11.368(2) Å, c = 14.745(3) Å, beta = 110.60(3) degrees, Z = 2. The square grids superpose on each other into a channel structure, in which each layer consists of two pairs of shared edges, perfectly square-planar with an M(II) ion and a 4,4'-bpy at each corner and side, respectively. The square cavity has dimensions of 11.669(2) x 11.788(2) and 11.368(2) x 11.488(2) Å for 1 and 2, respectively. Every two guest 2,4'-bpy molecules are clathrated in each hydrophobic host cavity and are further stabilized by pi-pi stacking and hydrogen bonding interactions. The NMR spectra clearly confirm that both 1 and 2 contain 4,4'-bpy and 2,4'-bpy molecules in a 1:1 ratio, which have stacking interaction with each other in the solution. 3 crystallizes in the orthorhombic space group Ibam, with a = 11.1283(5) Å, b = 15.5927(8) Å, c = 22.3178(11) Å, Z = 4. 3 is made up of two-dimensional square [Cu(4)(4,4'-bpy)(4)] grids, where the square cavity has dimensions of 11.13 x 11.16 Å. Each [4,4'-H(2)bpy](2+) cation is clathrated in a square cavity and stacks with one pair of opposite edges of the host square cavity in an offset fashion with the face-to-face distance of ca. 3.95 Å. Within each cavity, the [4,4'-H(2)bpy](2+) cation forms twin three-center hydrogen bonds with two pairs of ClO(4)(-) anions. The results suggest that the guest 2,4'-bpy molecules and protonated [4,4'-H(2)bpy](2+) cations present in the reaction systems serve as structure-directing templates in the formation of the crystal structures and exclude self-inclusion of the networks having larger square cavities.
  6. Ng SW, Shanmuga Sundara Raj S, Fun HK, Razak IA, Hook JM
    Acta Crystallogr C, 2000 Aug;56 ( Pt 8):966-8.
    PMID: 10944291
    catena-Poly[dicyclohexylammonium [tributyltin-mu-(4-oxo-4H-pyran-2,6-dicarboxylato-O(2):O( 6))]], (C(12)H(24)N)[Sn(C(7)H(2)O(6))(C(4)H(9))(3)], consists of 4-oxo-4H-pyran-2,6-dicarboxylato groups that axially link adjacent tributyltin units into a linear polyanionic chain. The ammonium counter-ions surround the chain, and each cation forms a pair of hydrogen bonds to the double-bond carbonyl O atoms of the same dianionic group. The chain propagates in a zigzag manner along the c axis of the monoclinic cell. In catena-poly[methyl(phenyl)ammonium [tributyltin-mu-(pyridine-2,6-dicarboxylato-O(2):O(6))]], (C(7)H(10)N)[Sn(C(7)H(3)NO(4))(C(4)H(9))(3)], the pyridine-2, 6-dicarboxylato groups also link the tributyltin groups into a chain, but the hydrogen-bonded chain propagates linearly on the ac face of the monoclinic cell.
  7. Ng SW, Yang Farina AA, Othman AH, Baba I, Sivakumar K, Fun HK
    Acta Crystallogr C, 2000 Mar 15;56(Pt 3):E84-5.
    PMID: 15263206
    The title compound, [Sn(CH(3))(2)(C(5)H(10)NO(2)S(2))(2)], has crystallographic mirror symmetry (C-Sn-C on mirror plane) and the coordination polyhedron around the Sn atom is a tetrahedron [C-Sn-C 139.3 (2) degrees and S-Sn-S 82.3 (1) degrees ] distorted towards a skew-trapezoidal bipyramid owing to an intramolecular Sn.S contact [3.0427 (6) A]. The molecules are linked into a linear chain by intermolecular O-H.O hydrogen bonds [O.O 2.646 (3) A].
  8. Low KS, Muniandy S, Naumov P, Shanmuga Sundara Raj S, Fun HK, Razak IA, et al.
    Acta Crystallogr C, 2000 Mar 15;56(Pt 3):E113-4.
    PMID: 15263222
    Bis(N,N-dimethylthiocarbamoylthio)acetic acid, [(CH(3))(2)NC(=S)S](2)CHC(=O)OH or C(8)H(14)N(2)O(2)S(4), exists as a centrosymmetric hydrogen-bonded dimer [O.O 2.661 (3) A].
  9. Xu LL, Zhang HF, Li M, Ng SW, Feng JH, Mao JG, et al.
    J Am Chem Soc, 2018 09 19;140(37):11569-11572.
    PMID: 30141923 DOI: 10.1021/jacs.8b06725
    Chiroptical activity is observed from an achiral adenine-containing metal-organic framework (MOF) named ZnFDCA. Such a seemingly counterintuitive phenomenon can, in fact, be predicted by the intrinsic crystal symmetry of 4̅2 m point group. Although theoretically allowed, examples of optically active achiral crystals are extremely rare. ZnFDCA is the first reported achiral MOF showing optical activity, as demonstrated by a pair of circular dichroism signals with opposite signs and enhanced intensity. Moreover, simply through adding an amino substituent to adenine, the chiroptical activity, as well as nonlinear optical activity, of the analogous MOF, namely ZnFDCA-NH2, disappears due to diverse packing pattern giving rise to centrosymmetric crystal symmetry.
  10. Zhan SZ, Li JH, Zhang GH, Liu XW, Li M, Zheng J, et al.
    Chem Commun (Camb), 2019 Oct 03;55(80):11992-11995.
    PMID: 31498358 DOI: 10.1039/c9cc05236d
    A luminescent edge-interlocked heteroleptic metallocage based on Cu3(pyrazolate)3 was prepared through a ligand replacement reaction from a homoleptic metallocage and a new ligand. Its structure was confirmed by XRD and MALDI-TOF mass spectrometry. Theoretical calculations revealed the new ligand was evidently responsible for the bathochromic shift of the optimal excitation. This work provides a heteroleptic strategy to regulate the interlocking fashion and photophysical mechanism of metallocages based on Cu3(pyrazolate)3.
  11. Ng SW, Selvarajah GT, Hussein MZ, Yeap SK, Omar AR
    Biomed Res Int, 2020;2020:3012198.
    PMID: 32596292 DOI: 10.1155/2020/3012198
    Feline infectious peritonitis (FIP) is an important feline viral disease, causing an overridden inflammatory response that results in a high mortality rate, primarily in young cats. Curcumin is notable for its biological activities against various viral diseases; however, its poor bioavailability has hindered its potential in therapeutic application. In this study, curcumin was encapsulated in chitosan nanoparticles to improve its bioavailability. Curcumin-encapsulated chitosan (Cur-CS) nanoparticles were synthesised based on the ionic gelation technique and were spherical and cuboidal in shape, with an average particle size of 330 nm and +42 mV in zeta potential. The nanoparticles exerted lower toxicity in Crandell-Rees feline kidney (CrFK) cells and enhanced antiviral activities with a selective index (SI) value three times higher than that of curcumin. Feline-specific bead-based multiplex immunoassay and qPCR were used to examine their modulatory effects on proinflammatory cytokines, including tumour necrosis factor (TNF)α, interleukin- (IL-) 6, and IL-1β. There were significant decrements in IL-1β, IL-6, and TNFα expression in both curcumin and Cur-CS nanoparticles. Based on the multiplex immunoassay, curcumin and the Cur-CS nanoparticles could lower the immune-related proteins in FIP virus (FIPV) infection. The single- and multiple-dose pharmacokinetics profiles of curcumin and the Cur-CS nanoparticles were determined by high-performance liquid chromatography (HPLC). Oral delivery of the Cur-CS nanoparticles to cats showed enhanced bioavailability with a maximum plasma concentration (Cmax) value of 621.5 ng/mL. Incorporating chitosan nanoparticles to deliver curcumin improved the oral bioavailability and antiviral effects of curcumin against FIPV infection. This study provides evidence for the potential of Cur-CS nanoparticles as a supplementary treatment of FIP.
  12. Huang SL, Zhang WH, Ling Y, Ng SW, Luo HK, Hor TS
    Chem Asian J, 2015 Oct;10(10):2117-20.
    PMID: 25965032 DOI: 10.1002/asia.201500231
    Four porous coordination networks have been synthesized from 1,4-benzenedicarboxylate with Cl, Br, I, and NO2 substituents whose different spatial differences are sufficient to influence the coordination mode of adjacent carboxyl moieties to unlock an inter-penetrating framework to give isostructural structures. Their size and polarity differences account for the diverging CO2 adsorption performances.
  13. Von ST, Seng HL, Lee HB, Ng SW, Kitamura Y, Chikira M, et al.
    J Biol Inorg Chem, 2012 Jan;17(1):57-69.
    PMID: 21833656 DOI: 10.1007/s00775-011-0829-0
    By inhibiting only two or three of 12 restriction enzymes, the series of [M(phen)(edda)] complexes [M(II) is Cu, Co, Zn; phen is 1,10-phenanthroline; edda is N,N'-ethylenediaminediacetate] exhibit DNA binding specificity. The Cu(II) and Zn(II) complexes could differentiate the palindromic sequences 5'-CATATG-3' and 5'-GTATAC-3', whereas the Co(II) analogue could not. This and other differences in their biological properties may arise from distinct differences in their octahedral structures. The complexes could inhibit topoisomerase I, stabilize or destabilize G-quadruplex, and lower the mitochondrial membrane potential of MCF7 breast cells. The pronounced stabilization of G-quadruplex by the Zn(II) complex may account for the additional ability of only the Zn(II) complex to induce cell cycle arrest in S phase. On the basis of the known action of anticancer compounds against the above-mentioned individual targets, we suggest the mode of action of the present complexes could involve multiple targets. Cytotoxicity studies with MCF10A and cisplatin-resistant MCF7 suggest that these complexes exhibit selectivity towards breast cancer cells over normal ones.
  14. Asiri AM, Faidallah HM, Sobahi TR, Ng SW, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2015 Nov 1;71(Pt 11):e4.
    PMID: 26617187 DOI: 10.1107/S2056989015019271
    In the paper by Asiri et al. [Acta Cryst. (2012), E68, o1154], the title and the chemical name of one of the reagents used in the synthesis are corrected.[This corrects the article DOI: 10.1107/S1600536812011579.].
  15. Liu M, Li H, Bai L, Zheng K, Zhao Z, Chen Z, et al.
    J Hazard Mater, 2021 07 05;413:125291.
    PMID: 33588337 DOI: 10.1016/j.jhazmat.2021.125291
    Real-time and visual monitoring of pollutants in the air is of great importance since they are usually cannot be seen, smelled, or touched. Lanthanide nano-cluster is a kind of luminescent sensor for various species. However, controlling synthesis of lanthanide nano-cluster remains experimentally challenging. In this work, four series of lanthanide-barium (Ln-Ba) nano-clusters of Dy2Ba (1), Tb2Ba2 (2), Ln4Ba3 (Ln = Tb, 3a; Eu, 3b), Tb4Ba4 (4) were assembled through precisely controlling the pH of the reactant solutions. The work features the first example that the number of cluster's nuclei changes regularly with the pH. Moreover, investigation reveals that nano-cluster 3a is a highly selective and sensitive sensor towards acetylacetone (acac) and aniline. Interestingly, easy-to-use sensing devices of test paper, agarose gel, and five kinds of film on CaCO3, polyfoam, coin, mask, and wall that based on 3a were fabricated by facile methods. The seven sensing devices showed remarkable ability to sense aniline and acac vapors with visibility to the naked eyes. This is the first work on multiple real-time and visual sensing devices based on the lanthanide nano-cluster.
  16. Chan Y, Ng SW, Mehta M, Gupta G, Chellappan DK, Dua K
    Future Med Chem, 2020 11;12(21):1887-1890.
    PMID: 33054387 DOI: 10.4155/fmc-2020-0206
  17. Safi N, Haghani A, Ng SW, Selvarajah GT, Mustaffa-Kamal F, Omar AR
    BMC Vet Res, 2017 Apr 07;13(1):92.
    PMID: 28388950 DOI: 10.1186/s12917-017-1019-2
    BACKGROUND: There are two biotypes of feline coronavirus (FCoV): the self-limiting feline enteric coronavirus (FECV) and the feline infectious peritonitis virus (FIPV), which causes feline infectious peritonitis (FIP), a fatal disease associated with cats living in multi-cat environments. This study provides an insight on the various immune mediators detected in FCoV-positive cats which may be responsible for the development of FIP.

    RESULTS: In this study, using real-time PCR and multiplex bead-based immunoassay, the expression profiles of several immune mediators were examined in Crandell-Reese feline kidney (CRFK) cells infected with the feline coronavirus (FCoV) strain FIPV 79-1146 and in samples obtained from FCoV-positive cats. CRFK cells infected with FIPV 79-1146 showed an increase in the expression of interferon-related genes and pro-inflammatory cytokines such as MX1, viperin, CXCL10, CCL8, RANTES, KC, MCP1, and IL8. In addition, an increase in the expression of the above cytokines as well as GM-CSF and IFNγ was also detected in the PBMC, serum, and peritoneal effusions of FCoV-positive cats. Although the expression of MX1 and viperin genes was variable between cats, the expression of these two genes was relatively higher in cats having peritoneal effusion compared to cats without clinically obvious effusion. Higher viral load was also detected in the supernatant of peritoneal effusions compared to in the plasma of FCoV-positive cats. As expected, the secretion of IL1β, IL6 and TNFα was readily detected in the supernatant of peritoneal effusions of the FCoV-positive cats.

    CONCLUSIONS: This study has identified various pro-inflammatory cytokines and interferon-related genes such as MX1, viperin, CXCL10, CCL8, RANTES, KC, MCP1, IL8, GM-CSF and IFNγ in FCoV-positive cats. With the exception of MX1 and viperin, no distinct pattern of immune mediators was observed that distinguished between FCoV-positive cats with and without peritoneal effusion. Further studies based on definitive diagnosis of FIP need to be performed to confirm the clinical importance of this study.

  18. She W, Qi T, Cui M, Yan P, Ng SW, Li W, et al.
    ACS Appl Mater Interfaces, 2018 May 02;10(17):14698-14707.
    PMID: 29638107 DOI: 10.1021/acsami.8b01187
    A family of two-dimensional salen-type lanthanide complexes was synthesized through a facile solution diffusion method. The two-dimensional lanthanide complexes were characterized by single-crystal X-ray diffraction (SCXRD) and X-ray photoelectron spectroscopy (XPS) analytical techniques. The SCXRD and XPS analyses reveal that the obtained two-dimensional structures are rich in uncoordinated imine (-CH═N-) groups located on the skeleton of the salen-type organic ligand, which retain strong coordination ability with metal ions. On the basis of this unique feature, a highly dispersed CeO2-supported Ni catalyst (Ni/CeO2-CAS) with highly strong metal-support interaction was first synthesized via a coordination-assisted synthesis (CAS) method, which exhibits a much better catalytic activity in the hydrogenation of nitrobenzene than the traditional Ni/CeO2-IWI catalyst prepared by incipient wetness impregnation (IWI). The origin of the improved catalytic activity of Ni/CeO2-CAS as well as the role of Ni@Ce-H2salen was revealed by using diverse characterizations. On the basis of the comparative characterization results, the superior catalytic performance of Ni/CeO2-CAS to Ni/CeO2-IWI could have resulted from the smaller and highly dispersed Ni nanoparticulates, the intensified Ni-CeO2 interaction, the enhanced NiO reducibility, and the higher concentration of oxygen vacancies, favoring the H2 dissociation and adsorption of the nitrobenzene reactant. The Ni/CeO2-CAS catalyst also exhibits high catalytic performance for reduction of diverse nitroarenes to their corresponding functionalized arylamines. We anticipated that this coordination-assisted strategy may provide a new way for preparing other highly oxide-supported catalysts with potential applications in various catalytic reactions.
  19. Cai H, Xu LL, Lai HY, Liu JY, Ng SW, Li D
    Chem Commun (Camb), 2017 Jun 27.
    PMID: 28654101 DOI: 10.1039/c7cc03350h
    A new adenine-containing metal-organic framework (MOF), [Zn4O(adenine)4(benzene-1,3-dicarboxylate)4Zn2] (named as ZnBDCA), was synthesized solvothermally. ZnBDCA possesses high quantum yield (>50%) and nano-channels that can encapsulate acriflavine molecules to build a host-guest chemopalette for approaching white-light emission.
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