Biomedical subjects
Publications and source records attributed to Xiao-Ming Chen.
The synthesis and crystal structures of two new NLO-active coordination polymers, [Zn(2-pc)(4-pc)] and [Cd(2-pc)(4-pc)(H(2)O)]xN(2)H(4) (2-pc = 2-pyridine carboxylate, 4-pc = 4-pyridine carboxylate), bridged by in situ generated mixed ligands under solvothermal treatment is described.
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The planar coordination complexes [Ag2L2] (L = ophen or obpy, where Hophen = 1H-[1,10]phenanthrolin-2-one and Hobpy = 1H-[2,2']bipyridinyl-6-one) contain both hydrophilic and hydrophobic functional groups. Crystallization of these structurally related complexes in an aqueous medium gives [Ag2(ophen)2]2 x 6H2O (1), [Ag2(obpy)2]3 x 18H2O (2), and [Ag2(obpy)2]2 x 14.5H2O (3). Novel water morphologies are observed in these crystalline hydrates, similar 2D metal-organic layers in which the planar [Ag2L2] complexes as building blocks are stacked alternately together and provide hydrogen bond acceptor sites (O atoms) for anchoring 1D water chains or 2D water layers on their surfaces. In the wavelike metal-organic framework of 1, the wide hydrophobic region renders the formation of 1D water tapes containing four- and six-membered water rings, whereas more complex 2D water layers are sandwiched in 2 and 3, owing to the fact that the surfaces of the supporting layers are more hydrophilic than 1.
One-pot solvothermal treatments of organonitriles, ammonia, and Cu(II) salts yielded Cu(I) and 3,5-disubstituted 1,2,4-triazolates. The organic triazolate components were derived from copper-mediated oxidative cycloaddition of nitriles and ammonia, in which a key intermediate 1,3,5-triazapentadienate was isolated as [Cu(II)(4-pytap)(2)] (4-Hpytap = 2,4-di(4-pyridyl)-1,3,5-triazapentadiene) via controlled solvothermal conditions. This intermediate could also be synthesized by Ni(II)-mediated reactions; however, the final triazoles were obtained only when Cu(II) was employed. Therefore, the reaction mechanism of these reactions was elucidated as follows: nitrile was first attacked by ammonia to form the amidine, which further reacted with another nitrile or self-condensed to yield 1,3,5-triazapentadiene, which was coordinated to two Cu(II) ions in its deprotonated form. A two-electron oxidation of the 1,3,5-triazapentadienate mediated by two Cu(II) ions gave one triazolate and Cu(I) cations. Other in situ ligand reactions, such as C-C bond cleavage and hydrolysis, were also found for the nitriles under these solvothermal conditions. Another remarkable feature of these crystalline Cu(I) triazolates is their simple, typical 3- or 4-connected network topologies. The self-assembly of these nets is presumably controlled by steric hindrance, which is subsequently applied to the rational design of the close-packed 2D networks [Cu(I)(tz)](infinity) and [Ag(I)(tz)](infinity) (Htz = 1,2,4-triazole), as well as the porous 3D network [Cu(I)(etz)](infinity) (Hetz = 3,5-diethyl-1,2,4-triazole). The interesting photoluminescence properties of these coinage d(10) metal complexes were also investigated.
The solvent effect of different polarities in hydro(solvo)thermal reaction of Cu(II) and 2-ethylimidazole leads to the generation of two supramolecular isomers of triple-stranded helical and zigzag chain-like structures of Cu(I) 2-ethylimidazolate.
Discrete dinuclear and polymeric heterometallic copper(II)-lanthanide(III) complexes have been synthesized upon variation of pH and characterized by X-ray diffraction analysis. Reactions of the ligand Htza (tetrazole-1-acetic acid) with copper(II) and lanthanide(III) salts gave dinuclear [CuLn(tza)4(H2O)5Cl] complexes at the low pH of 3.5 and 2D heterometallic coordination polymers with high-nuclearity [{Cu2(OH)2}2{Cu12Ln6(mu3-OH)24(Cl)(1/2)(NO3)(1/2)(tza)12(H2O)18}](NO3)(9).8H2O (Ln = Gd or Nd) at a higher pH of 6.6. The acidity of the reaction solution can cause drastic changes in the structures of the products. In the dinuclear complexes, each pair of adjacent dinuclear molecules is linked through hydrogen bonds and pi-pi stacking interactions, and the whole structure is a hydrogen-bonded three-dimensional cubic net. In the coordination polymers, the connecting nodes are [Cu12Ln6] units, which are interconnected by [Cu2O2] units into two-dimensional structures. Magnetic studies exhibit the existence of weak exchange interactions between the Cu(II) and Ln(III) ions bridged by carboxylate and hydroxy ligands.
A predesigned metal-organic building-block [Cu(I)(2-pytz)](2-Hpytz = 3,5-di-2-pyridyl-1,2,4-triazole) has been successfully used to synthesize four genuine supramolecular isomers.
To verify whether attractive metallophilic interactions exist in the dimer-of-dimers [Cu(2)(ophen)(2)](2) (Hophen=1H-[1,10]phenanthrolin-2-one) (1), we designed and synthesized a series of such [M(2)L(2)](2) structures by varying the d(10) metal and/or the ligand (M=Cu(I) or Ag(I), L=ophen or obpy; Hobpy=1H-[2,2']bipyridinyl-6-one), and have successfully obtained three dimers-of-dimers: [Ag(2)(ophen)(2)](2).6 H(2)O (2), [Cu(2)(obpy)(2)](2) (3), and [Ag(2)(obpy)(2)](2).4.5 H(2)O.0.5 DMF (4). X-ray analyses of these structures show that interdimer M-M separations in [Ag(2)-(ophen)(2)](2) (3.199 A) are remarkably shorter than those in [Cu(2)(ophen)(2)](2) (3.595 A). Shorter interdimer M-M separations are found in the structures of [M(2)(obpy)(2)](2) (2.986 and 2.993 A in [Cu(2)(obpy)(2)](2), 3.037 to 3.093 A in [Ag(2)(obpy)(2)](2)), in which the pi systems are smaller than in the complexes with the ophen ligand. Detailed structural comparison of these dimers-of-dimers indicates that the interdimer, face-to-face pi-pi interactions repulse rather than support the interdimer metal-metal attractive interactions. This study also yields qualitative comparison of the strengths between argentophilic, cuprophilic, and face-to-face pi-pi interactions. DFT calculations on the four dimers-of-dimers further support the above deduction. The structure of a trimer-of-dimers [Ag(2)(obpy)(2)](3) (Ag-Ag 3.171 to 3.274 A) is further evidence that the oligomerization of the [M(2)L(2)] molecules is favored by stronger metallophilic and weaker face-to-face pi-pi interactions.
Homochiral/heterochiral crystallizations of helical chiral polymer chains bridged by achiral poly-pyridyl ligands dependent on the structures of the bridging ligands and independent on the solvent are described, implying a possible strategy to design achiral crystals of helical chains using chiral bridging ligands.
OBJECTIVE: To investigate the immunological function of a yeast expression system for thymosin alpha1 (Talpha1). METHODS: A constructed Talpha1 yeast expression system was used to investigate the immunological function of orally administered Talpha1. Dried yeast containing three different concentration of Talpha1 was fed to normal Balb/c mice and other Balb/c mice whose immunities were inhibited in advance by cyclophosphamide. Synthesized Talpha1 peptide was used as positive control and dried yeast with empty plasmid was used as negative control. CD4(+) and CD8(+) levels were detected by flow cytometry assay. TNF-alpha, IFN-gamma, IL-2, IL-6 and IL-10 levels were detected by liquid chip. RESULTS: In normal Balb/c mice or immune inhibition Balb/c mice, CD8(+) levels were significantly increased. Especially in immune inhibition Balb/c mice, CD8(+) levels in synthesized Talpha1 group (18.77%+/-4.72%), small dose group (13.48%+/-6.17%) and large dose group (22.74%+/-1.09%) were significantly higher than that in empty yeast control group (7.49%+/-2.14%). CONCLUSION: Orally administered Talpha1 has its certain immunomodulatory function.
We want to construct a yeast expression system for thymosin alpha1 (Talpha1) to make the orally administered Talpha1 preparation possible. The whole Talpha1 DNA fragment was obtained by PCR. After being digested with restriction enzymes, it was cloned into pYES2 vector. Sequencing was performed to identify the recombinant. The sequence of Talpha1 in recombinant coincided with the original one reported in Genbank. When pYES2-Talpha1 plasmid was transformed into yeast, galactose instead of glucose was used to induce Talpha1 expression. Western blot was performed to identify the quality of the expressed Talpha1. Dried yeast containing pYEST2-Talpha1 was fed to Balb/c mice whose immunities were inhibited by cyclophosphamide in advance. Synthesized Talpha1 peptide was used as positive control and empty yeast was used as negative control. Compared with the negative control group, both dried yeast containing pYEST2-Talpha1 and synthesized Talpha1 peptide can significantly increase the CD8+ level (22.74 +/- 1.09 and 18.77 +/- 4.72 vs 7.49 +/- 2.14, p < 0.01), while both of them had little effect on the CD4+ lymphocytes (61.86 +/- 6.94 and 65.91 +/- 4.78 vs 57.93 +/- 10.40,p > 0.05). We concluded that a high effective yeast expression system for Talpha1 was constructed successfully and the Talpha1 protein expressed by this system can improve CD8+ level in immune inhibited mice.
Reaction of di-2-pyridyl ketone (dpk) with nickel acetate and azide in the presence of potassium tert-butylate as a catalytic base generates the title compound, which contains the largest [Ni(mu(1,1)-N3)]6 circles in the discrete ferromagnetically-coupled M(II)-azide cluster family, and shows an unprecedented in situ cyanomethylation of ketone.
Cyclic water hexamers containing 1-D metal--water chains have been observed in the complexes of [M(H(2)biim)(2)(OH(2))(2)](ina)(2) x 4H(2)O [M = Zn (1) and Co (2), H(2)biim = 2,2'-biimidazole, ina = isoniconate]. The water clusters are trapped by the cooperative association of coordination interactions as well as hydrogen bonds.
A new facile synthetic strategy successfully leads to the isolation of two polygons of high numbers of sides constructed by simple, bent imidazolate bridging ligands and two-coordinate CuI ions upon templating of circular organic molecules, which were characterized by crystallography.
Single crystals of a neutral, microporous, laminated metal-organic framework (MOF)[Fe(pydc)(4,4'-bipy)]xH(2)O (1xH(2)O)(H(2)pydc = 2,5-dicarboxypyridine, 4,4'-bipy = 4,4'-bipyridine) were generated by hydrothermal synthesis, and its crystal structure was determined. 1xH(2)O retains the framework robustness to ca. 370 degrees C and is insoluble in common organic solvents. By soaking in MeOH and EtOH solutions, 1xH(2)O was transformed directly from the parent single crystals into single crystals of 1xMeOH or 1xEtOH, respectively. Meanwhile, 1xH(2)O shrank to the guest-free framework (h) or (v), respectively, under appropriate heating (up to 160 degrees C in N(2)) or vacuum treatment (10 mmHg) at room temperature. Compared to that of 1xH(2)O, the unit-cell volume of 1xEtOH slightly increases by 2.9%, whereas those of (h) or (v) are reduced by 8.2 and 6.6%, respectively. The anhydrous (v) was found to be highly chemically reactive, taking up ethanol vapor to furnish the solvated crystal structure of an 'expanded' framework 1xEtOH. In a mixture of ethanol-DMF or ethanol-benzene, a selective exchange process was observed, with only ethanol molecules exchanged into the structure due to the limited free size of the channels in the framework of. All the transformed crystals have also been characterized by X-ray single-crystal diffraction to understand the crystal-to-crystal transformation, which have different free volumes (6.5-20.4%).
A new metal-valence tuning synthetic approach has been utilized to generate two new mixed-valence Cu(I,II) coordination polymers Cu(2)(im)(3) and Cu(3)(im)(4)(Him = imidazole), which are an unprecedented uninodal 4-connected 4.8(5) topological net and a 4-connected (4,4) net, respectively.
The free solvated ligand, H(2)bna.CH(3)OH.H(2)O (1), and its dimeric complex, [Cd(2)(bna)(2)(H(2)O)(6)] (2) (bna = 2,2'-dihydroxy-[1,1']-binaphthalene-3,3'-dicarboxylate), were obtained by evaporation of the solutions, while two new d(10) metal-hydroxy cluster-based coordination polymers, namely [Cd(8)(OH)(4)(H(2)O)(10)(bna)(6)].17H(2)O (3) and [Hpy](2)[Zn(4)(OH)(2)(H(2)O)(2)(bna)(4)].2H(2)O.2CH(3)CN (4), were obtained by a hydrothermal route. All the compounds have been characterized by X-ray crystallography and photoluminescence measurements. Compound 1 consists of a three-dimensional, hydrogen-bonded supramolecular array, 2 exhibits a dimeric molecule featuring a square motif organized by two Cd(II) atoms and two bna ligands each at the corner, and 3 contains unprecedented [Cd(8)(micro(3)-OH)(2)(micro-OH)(2)(micro-H(2)O)(2)](12+) octanuclear metallacrown cores which are interlinked through bna to afford a two-dimensional structure, while 4 features layers with butterfly-shaped [Zn(4)(micro(3)-OH)(2)](6+) clusters. All the complexes display photoluminescent properties in the blue/green range. The manifestation of photoluminescence, as probed by molecular orbital calculations performed on the complexes and also on hypothetical multinuclear complexes, is attributed to a ligand-to-metal charge-transfer mechanism. In addition to presenting a new approach for the study of the photoluminescent properties of metal-cluster-based coordination polymers by using simple model compounds, the study also reveals the dominant role of the structure of the ligand over that of the d(10) metal-hydroxy (or oxy) cluster and the presence of the cluster significantly increasing the emission lifetime.
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