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Biomedical subjects

Song Gao

Publications and source records attributed to Song Gao.

At least 55 records · Page 3Linked to original sources
PubMed2005

Synthesis, crystal structures, and magnetism of cobalt coordination polymers based on dicyanamide and pyrazine-dioxide derivatives.

Three coordination polymers of Co(II) with dicyanamide (dca) were obtained by adding coligands of 2,5-dimethylpyrazine-dioxide (2,5-dmpdo), 2,3,5-trimethylpyrazine-dioxide (2,3,5-tmpdo), or 2,3,5,6-tetramethylpyrazine-dioxide (2,3,5,6-tmpdo) to the binary system of Co-dca. Co2(dca)(4)(2,5-dmpdo)2 (1) crystallizes in the triclinic space group P with a=7.4962(2), b=9.0364(2), c = 10.4783(4) A, alpha = 72.567(1), beta = 72.557(1), gamma = 68.814(2) degrees , V = 616.61(3) A(3), Z = 1, and R1 = 0.0345. [Co3(dca)6(H2O)4].2(2,3,5-tmpdo) (2) is in the monoclinic space group C2/c with a = 29.477(1), b = 7.3735(2), c = 17.4631(7) A, beta = 93.652(1) degrees , V = 3787.9(2) A(3), Z = 4, and R1 = 0.0532. [Co(dca)2(H2O)2].2(2,3,5,6-tmpdo) (3) is in the monoclinic space group P2(1)/c with a = 9.4739(3), b = 11.3876(3), c = 12.1778(3) A, beta = 98.967(1) degrees , V = 1297.74(6) A(3), Z = 4, and R1 = 0.0481. 1 contains an unusual (4,4) Co-dca layer, representing a rare example of metal-dca coordination polymers with mixing 1,3-mu(2)- and 1,5-mu2-dca bridges. The Co-dca (4, 4) layers are connected by 2,5-dmpdo to give an alpha-Po-type network, which displays antiferromagnetic ordering below 10.8 K. 2 is a unique 3D framework composed of 2D twinned 1,5-mu2-dca bridged layers, which are connected by Co-H2O-Co linkages. The noncoordinated 2,3,5-tmpdo units and the coordination water molecules form hydrogen-bonded chains that thread the framework. 3 has alternating stacks of usual Co-dca (4, 4) layers through 1,5-mu2-dca bridges and organic layers of noncoordinated 2,3,5,6-tmpdo. Weak antiferromagnetic and weak ferromagnetic coupling was observed in 2 and 3, respectively.

Journal Article↗
PubMed2005

Assembly of hydrogen bonded diamondoid networks based on synthetic metal-organic tetrahedral nodes.

Reaction of Mn(ClO4)2 or Co(PF6)2 with 4,4'-dipyridine-dioxide (dpdo) produced novel molecular species [M(dpdo)4(H2O)2]2+, which hold a tetrahedral configuration notwithstanding their octahedral environment around the metal centers. The tetrahedral moieties are further assembled through hydrogen bonds between peripheral NO ends of dpdo ligands and coordinated water molecules, giving rise to 3D diamondoid networks.

Journal Article↗
PubMed2005

Formate--the analogue of azide: structural and magnetic properties of M(HCOO)2(4,4'-bpy).nH2O (M = Mn, Co, Ni; n = 0, 5).

Reaction of transition metal formate M(HCOO)(2).2H2O (M = Mn, Co, Ni) with 4,4'-bpy (4,4-bipyridine) has led to four new compounds with the formula M(HCOO)2(4,4'-bpy).nH2O (M = Mn, Co (1.Mn, 2.Co), n = 0; M = Co, Ni (3.Co, 4.Ni), n = 5). Compounds 1.Mn and 2.Co are isomorphous and crystallized in the tetragonal crystal system with the chiral space group P4(1)2(1)2. They are of three-dimensional diamondoid structure connected by anti-anti formate with 4,4'-bpy in the cavities of the framework reinforcing the intermetallic connections; the diamond-like net was observed also in their azide analogue (Mn(N3)2(4,4'-bpy)). Compounds 3.Co and 4.Ni are isomorphous also but crystallized in the monoclinic crystal system with the space group Cc. Both structures are uninterpenetrated 3D "CdSO4" type with big channels, constructed by anti-anti formate and 4,4'-bpy. This type of net was not observed in their azide analogue. Residing in the channels, water molecules form a new type of 1D tape constructed by vertex-sharing cyclic pentamers. Magnetic measurements were performed on all of these four compounds. 1.Mn and 2.Co are weak ferromagnets with the critical temperature Tc = 5.3 and 7.4 K, respectively. 3.Co is an antiferromagnet with Neel temperature TN = 3.0 K, and 4.Ni is a weak ferromagnet below 20 K. Hysteresis loop can be observed for 2.Co and 4.Ni at 1.8 K. As an analogue of azide, formate can be used to construct molecular architectures, which structurally and magnetically have great similarities to and also differences from those of azide. This offers a promising method for the design of new molecular architectures with formate.

Journal Article↗
PubMed2005

Five new cytotoxic triterpenoid saponins from the roots of Symplocos chinensis.

Five new triterpenoid saponins, named symplocososides G-K, were isolated from the roots of Symplocos chinensis. Their structures were elucidated by spectral and chemical methods as symplocososide G, 3beta-O-{[beta- D-glucopyranosyl(1-->2)][alpha-L-arabinofuranosyl(1-->4)]-beta-D-(3-O-acetyl)-glucuronopyranosyl}-21beta- O-[(2 Z)-3,7-dimethyl-2,6-octadienoyl]-22 alpha-O-(2-methylbutanoyl)-R1-barrigenol, symplocososide H, 3beta-O-{[beta-D-glucopyranosyl(1-->2)][alpha-L-arabinofuranosyl(1-->4)]- beta-D-(3-O-acetyl)-glucuronopyranosyl}-21beta-O-[(2E)3,7-dimethyl-2,6-octadienoyl]-22alpha-O-(2-methylbutanoyl)-R1-barrigenol, symplocososide I, 3beta-O-{[beta-D-glucopyranosyl(1-->2)][ alpha-L-arabinofuranosyl(1-->4)]-beta-D-(3- O-acetyl-6-O-methyl)-glucuronopyranosyl}-21beta-O-[(2 Z)3,7-dimethyl-2,6-octadienoyl]-22alpha-O-(2-methylbutanoyl)-R1-barrigenol, symplocososide J, 3 beta-O-{[ beta-D-glucopyranosyl(1-->2)][alpha-L-arabinofuranosyl(1-->4)]-beta-D-(3- O-acetyl)-glucuronopyranosyl}-21beta-O-[(2 Z)3,7-dimethyl-2,6-octadienoyl]-22alpha-O-benzoyl-R1-barrigenol, and symplocososide K, 3beta-O-{[beta-D-glucopyranosyl (1-->2)][alpha-L-arabinofuranosyl(1-->4)]- beta-D-(3-O-acetyl-6-O-methyl)-glucuronopyranosyl}-21beta-O-[(2Z)3,7-dimethyl-2,6-octadienoyl]-22alpha-O-benzoyl-R1-barrigenol. Symplocososides G-K showed significant cytotoxicity against cancer cell lines KB, HCT-8, Bel-7402, BGC-823 and A549 with IC50 values ranging from 0.82 microM to 5.09 microM, except for symplocososide I against cancer cell lines KB, BGC-823, A549 and symplocososide K against cancer cell line BGC-823 with IC50 values >10.00 microM.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Image segmentation and selective smoothing by using Mumford-Shah model.

Recently, Chan and Vese developed an active contour model for image segmentation and smoothing by using piecewise constant and smooth representation of an image. Tsai et al. also independently developed a segmentation and smoothing method similar to the Chan and Vese piecewise smooth approach. These models are active contours based on the Mumford-Shah variational approach and the level-set method. In this paper, we develop a new hierarchical method which has many advantages compared to the Chan and Vese multiphase active contour models. First, unlike previous works, the curve evolution partial differential equations (PDEs) for different level-set functions are decoupled. Each curve evolution PDE is the equation of motion of just one level-set function, and different level-set equations of motion are solved in a hierarchy. This decoupling of the motion equations of the level-set functions speeds up the segmentation process significantly. Second, because of the coupling of the curve evolution equations associated with different level-set functions, the initialization of the level sets in Chan and Vese's method is difficult to handle. In fact, different initial conditions may produce completely different results. The hierarchical method proposed in this paper can avoid the problem due to the choice of initial conditions. Third, in this paper, we use the diffusion equation for denoising. This method, therefore, can deal with very noisy images. In general, our method is fast, flexible, not sensitive to the choice of initial conditions, and produces very good results.

Algorithms↗
PubMed2005

[Identification of genomic differences in avian pathogenic Escherichia coli using suppression subtractive hybridization analysis].

To identify unique DNA fragments associated with avian pathogenic Escherichia coli strains, suppression subtractive hybridization (SSH) was used. The genome of nonpathogenic E. coli K-12 strain MG1655 was subtracted from the genome of avian highly pathogenic strain E037 (serotype O78) resulting in the identification of 17 specific fragments. And the genome of avian low pathogenic E. coli strain E526 (serotype O2) was subtracted from the genome of avian highly pathogenic strain E058 (serotype O2) resulting in the identification of 32 specific fragments. Sequence homology analysis was done and four types of fragments were identified: plasmid sequences, phage sequences, sequences with known function and sequences without any currently known function. And 12 specific fragments that were not found in E. coli K-12 were identified from two avian E. coli strains. The results suggested that there were some genetic differences between the highly pathogenic strains and low pathogenic or nonpathogenic strains.

Animals↗
PubMed2004

Particle phase acidity and oligomer formation in secondary organic aerosol.

A series of controlled laboratory experiments are carried out in dual Teflon chambers to examine the presence of oligomers in secondary organic aerosols (SOA) from hydrocarbon ozonolysis as well as to explore the effect of particle phase acidity on SOA formation. In all seven hydrocarbon systems studied (i.e., alpha-pinene, cyclohexene, 1-methyl cyclopentene, cycloheptene, 1-methyl cyclohexene, cyclooctene, and terpinolene), oligomers with MW from 250 to 1600 are present in the SOA formed, both in the absence and presence of seed particles and regardless of the seed particle acidity. These oligomers are comparable to, and in some cases, exceed the low molecular weight species (MW < 250) in ion intensities in the ion trap mass spectra, suggesting they may comprise a substantial fraction of the total aerosol mass. It is possible that oligomers are widely present in atmospheric organic aerosols, formed through acid- or base-catalyzed heterogeneous reactions. In addition, as the seed particle acidity increases, larger oligomers are formed more abundantly in the SOA; consequently, the overall SOA yield also increases. This explicit effect of particle phase acidity on the composition and yield of SOA may have important climatic consequences and need to be considered in relevant models.

Aerosols↗
PubMed2004

Genetic structure of Hmong-Mien speaking populations in East Asia as revealed by mtDNA lineages.

Hmong-Mien (H-M) is a major language family in East Asia, and its speakers distribute primarily in southern China and Southeast Asia. To date, genetic studies on H-M speaking populations are virtually absent in the literature. In this report, we present the results of an analysis of genetic variations in the mitochondrial DNA (mtDNA) hypervariable segment 1 (HVS1) region and diagnostic variants in the coding regions in 537 individuals sampled from 17 H-M populations across East Asia. The analysis showed that the haplogroups that are predominant in southern East Asia, including B, R9, N9a, and M7, account for 63% (ranging from 45% to 90%) of mtDNAs in H-M populations. Furthermore, analysis of molecular variance (AMOVA), phylogenetic tree analysis, and principal component (PC) analysis demonstrate closer relatedness between H-M and other southern East Asians, suggesting a general southern origin of maternal lineages in the H-M populations. The estimated ages of the mtDNA lineages that are specific to H-M coincide with those based on archeological cultures that have been associated with H-M. Analysis of genetic distance and phylogenetic tree indicated some extent of difference between the Hmong and the Mien populations. Together with the higher frequency of north-dominating lineages observed in the Hmong people, our results indicate that the Hmong populations had experienced more contact with the northern East Asians, a finding consistent with historical evidence. Moreover, our data defined some new (sub-)haplogroups (A6, B4e, B4f, C5, F1a1, F1a1a, and R9c), which will direct further efforts to improve the phylogeny of East Asian mtDNAs.

Asia, Southeastern↗
PubMed2004

Downregulation of lysyl oxidase and upregulation of cellular thiols in rat fetal lung fibroblasts treated with cigarette smoke condensate.

Lysyl oxidase (LO), a copper-dependent enzyme, plays a critical role in the formation and repair of the extracellular matrix (ECM) by catalyzing the crosslinking of elastin and collagen. To better understand mechanisms of cigarette smoke (CS)-induced emphysema, we examined changes in LO and its substrates, i.e., elastin and collagen type I, the major components of cellular thiols, i.e., metallothionein (MT) and glutathione (GSH), and gamma-glutamylcysteine synthetase (gamma-GCS), a key enzyme for GSH biosynthesis, in cigarette smoke condensate (CSC)-treated rat fetal lung fibroblasts (RFL6). Exposure of RFL6 cells to CSC decreased levels of LO catalytic activity, mRNA, and protein, i.e., the 46 kDa preproenzyme, the 50 kDa proenzyme and the 32 kDa mature enzyme in a dose-dependent manner. In addition, CSC also inhibited the expression of collagen type I and elastin, substrates of LO and important components of the lung ECM. Meanwhile, cellular thiols including MT and GSH as well as gamma-GCS were markedly upregulated in CSC-treated cells. To evaluate modulation of LO expression by cellular thiols, we further examined the effect of increased levels of GSH on LO expression at protein and catalytic levels. Interestingly, exposure of cells to glutathione monoethyl ester, a GSH delivery system, effectively elevated cellular GSH levels and induced a dose-dependent decrease in levels of the protein species and catalytic activity of LO. These results suggest that upregulation by CSC of cellular thiols may play an important role in the downregulation of LO and subsequently destabilization of the lung ECM in CS-induced emphysema.

Aminoacyltransferases↗
PubMed2004

Interweaving 3D network with double helical tubes filled by 1D coordination polymer chains.

The hydrothermal reaction of mellitic acid, 4,4'-bipydine, and Cu(CH(3)COO)(2).H(2)O gave rise to a novel 3D supramolecular architecture interpenetrated by three types of coordination polymer motifs. Two independent [[Cu(2)(mellitate)(4,4'-bpy)(H(2)O)(2)](2)(-)] 3D polymers incorporating helical substructures were interwoven into a 3D network with double-stranded helical tubes that host 1D linear polymers [Cu(4,4'-bpy)(H(2)O)(4)](2+)](n).

Journal Article↗
PubMed2004

Prevalence of serogroups and virulence factors of Escherichia coli strains isolated from pigs with postweaning diarrhoea in eastern China.

This study was undertaken to determine the present distribution of serogroups, hemolytic activity and virulence factors among Escherichia coli strains isolated from pigs with postweaning diarrhoea from eight provinces in eastern China. Two hundred and fifteen E. coli isolates were serogrouped with O-antisera, investigated for hemolytic activity, assessed for F4, F5, F6, F18 and F41 fimbrial antigens by monoclonal antibodies and detected for genes of enterotoxins and shiga-toxin-two-variant (Stx2e) by a multiplex polymerase chain reaction (PCR). Among these E. coli isolates, 140 were determined to be placed in serogroups, 52 were unable to be serogrouped and the rest 23 auto-agglutinated. These isolates distributed in 45 serogroups and 64.3% (90/140) belonged to 12 O serogroups: O8, O9, O11, O20, O32, O91, O93, O101, O107, O115, O116 and O131. Hemolytic activity was detected in 11.6% (25/215) of all isolates. Several uncommon O serogroups were discovered in this study. Agglutination tests showed that 50.2% (108/215) of these isolates were positive for one or more of the five fimbrial antigens. Seventy-two E. coli strains expressed single fimbria and 36 strains expressed two or more fimbriae. Among these 215 E. coli isolates, strains expressing F18, F4, F6, F6 + F18 or F5 + F41 occurred more frequently. PCR analysis showed that 60.5% (130/215) of the isolates only harboured the gene of estI (STI) while 6.0% (13/215) strains possessed the genes of stx2e, estI and estII and 5.6% (12/215) of strains had the genes of estI/estII. Of all these isolates, 107 (49.8%) were negative for the fimbrial antigens examined. The fimbria-negative isolates usually possessed genetic determinant of estI (78, 72.9%).

Agglutination Tests↗
PubMed2004

New route to the mixed valence semiquinone-catecholate based mononuclear FeIII and catecholate based dinuclear MnIII complexes: first experimental evidence of valence tautomerism in an iron complex.

The semiquinone-catecholate based mixed valence complex, [FeIII(bispicen)(Cl4Cat)(Cl4SQ)] x DMF (1), and catecholate based (H2bispictn)[Mn2III(Cl4Cat)4(DMF)2] (2) (bispicen = N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine, bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, Cl4Cat = tetrachlorocatecholate dianion, and Cl4SQ = tetrachlorosemiquinone radical anion) were synthesized directly utilizing a facile route. Both the complexes have been characterized by single crystal X-ray diffraction study. The electronic structures have been elucidated by UV-vis-NIR absorption spectroscopy, cyclic voltammetry, EPR, and magnetic properties. The structural as well as spectroscopic features support the mixed valence tetrachlorosemiquinone-tetrachlorocatecholate charge distribution in 1. The ligand based mixed valence state was further confirmed by the presence of an intervalence charge transfer (IVCT) band in the 1900 nm region both in solution and in the solid. The intramolecular electron transfer, a phenomenon known as valence tautomerism (VT), has been followed by electronic absorption spectroscopy. For 1, the isomeric form [FeIII(bispicen)(Cl4Cat)(Cl4SQ)] is favored at low temperature, while at an elevated temperature, the [FeII(bispicen)(Cl4SQ)2] redox isomer dominates. Infrared as well as UV-vis-NIR spectral characterization for 2 suggest that the MnIII(Cat)2- moiety is admixed with its mixed valence semiquinone-catecholate isomer MnII(SQ)(Cat)-, and the electronic absorption spectrum is dominated by the mixed charged species. The origin of the intervalence charge transfer band in the 1900 nm range is associated with the mixed valence form, MnII(Cl4Cat)(Cl4SQ)-. The observation of VT in complex 1 is the first example where a mixed valence semiquinone-catecholate iron(III) complex undergoes intramolecular electron transfer similar to manganese and cobalt complexes.

Journal Article↗
PubMed2004

The observation of superparamagnetic behavior in molecular nanowires.

Using the anionic precursor [(Tp)Fe(CN)3]-, a new one-dimensional Ising cyanide-bridged chain, [(Tp)2FeIII2(CN)6Cu(CH3OH).2CH3OH]n, has been prepared. The crystal structure and magnetic studies demonstrate that it is a single-chain magnet and the blocking temperature is ca. 6 K.

Journal Article↗
PubMed2004

Two polymorphs of cobalt(II) imidazolate polymers synthesized solvothermally by using one organic template N,N-dimethylacetamide.

Two structurally different polymorphs of cobalt(II) imidazolate frameworks are solvothermally synthesized by using N,N-dimethylacetamide as a template: The polymorph 6 (a = 9.797 (4) angstroms, b = 15.301(6) angstroms, c =14.902(6) angstroms, beta = 98.904(6) degrees, monoclinic, P21/n) shows structures of silicate CaAl2Si2O8 with CrB4 topology, while polymorph 7 (a = 15.173(4) angstroms, b = 15.173(4) angstroms, c = 19.089(5) angstroms, Pbca) shows CaGa2O4-related topological structures. In addition, the 7' (a = 15.9712(18) angstroms, b = 15.9253(19) angstroms, c = 18.475(2) angstroms, Pbca), a compound isostructural with 7, is synthesized by using cyclohexanol as a template. Thus, these cobalt(II) imidazolate polymers are reminiscent of the zeolite syntheses in that not only the same topological structure can be synthesized by using the different organic templates, but also different topological structures can be synthesized by using the same organic template.

Journal Article↗
PubMed2004

Perovskite-like Metal Formates with Weak Ferromagnetism and as Precursors to Amorphous Materials.

Three isomorphous compounds M(CHOO)3[NH2(CH3)2] (M = Mn(1 x Mn), Co(2 x Co), Ni(3 x Ni)) have been synthesized in solvothermal conditions. Single-crystal X-ray diffraction shows that they are all crystallized in the trigonal space group R c with small differences in the lattice parameters. Bridged by the three-atom single-bridge CHOO-, M ions form a three-dimensional distorted perovskite-like structure with dimethylamine (DMA) cations located in the cages of the network. Based on the magnetic data, these three 3D compounds are weak ferromagnets with the critical temperature Tc = 8.5 K (1 x Mn), 14.9 K (2 x Co), and 35.6 K (3 x Ni), and for 2 x Co and 3 x Ni, spin reorientation might take place at 13.1 and 14.3 K, respectively. At 1.8 K, hysteresis loops can be observed for all three compounds with the coercivity field ca. 90 Oe (1 x Mn), 920 Oe (2 x Co), and 320 Oe (3 x Ni). The canting angles are estimated to be 0.08 degrees, 0.5 degrees, and 0.6 degrees for 1 x Mn, 2 x Co, and 3.Ni, respectively. The magnetic coupling between MnII ions in 1.Mn was estimated based on the model developed by Rushbrook and Wood for a Heisenberg antiferromagnet on a simple cubic lattice and the best fit gives J = -0.23 cm(-1). At the same time, according to molecular field theory of antiferromagnetism, the J values for compounds 1 x Mn, 2 x Co, and 3 x Ni were estimated to be -0.32 cm(-1), -2.3 cm(-1), and -4.85 cm(-1), respectively. The spin cant in these compounds may originate from the noncentrosymmetric character of the three-atom single-bridge CHOO-. Furthermore, amorphous materials 4 x Mn238, 5 x Mn450, 6 x Co320, and 7 x Ni300 were prepared from precursors 1-3 under an argon atmosphere at different temperatures according to the thermogravimetric analyses. As an interesting result, 5 x Mn450 was confirmed to be an amorphous form of Mn3O4 with a considerably large coercivity field HC = 4.1 kOe at 30 K compared to that value (250 Oe) for bulk Mn3O4.

Journal Article↗