Biomedical subjects

Jin An

Publications and source records attributed to Jin An.

6 recordsLinked to original sources

PubMed2006

Coexistence of f-wave superconductivity, charge order, and spin antiferromagnetism around nonmagnetic impurities in Na0.33CoO2.1.3H2O.

To check whether charge dynamics is responsible for the superconductivity in NaxCoO2.yH2O, we investigate local electronic and magnetic structure around nonmagnetic impurities embedded in this material at x=0.33 in the vicinity of charge instability, by using a phenomenological model within the slave-boson framework including competitions among a square root of 3 x square root of 3 charge order, antiferromagnetism, and f-wave superconductivity. Around the repulsive impurities, it is found that both local charge and spin orders are induced. Furthermore, the f-wave pairing order parameter is decreased on one sublattice but increased on another honeycomb sublattice. If the charge dynamics is responsible for the superconductivity, the predicted local electronic and magnetic structure could be observed by the STM and spatial resolved NMR experiments.

Journal Article↗

PubMed2006

Electronic configuration of high-spin imidazole-ligated iron(II) octaethylporphyrinates.

The preparation and characterization of two new five-coordinate, imidazole-ligated, high-spin iron(II) octaethylporphyrinates is described. [Fe(OEP)(1,2-Me2Im)] and [Fe(OEP)(2-MeHIm)] have been characterized by X-ray structure determinations and temperature-dependent Mössbauer spectroscopy in zero and applied magnetic fields. The distinction between imidazole-ligated and other ligands in high-spin iron(II) porphyrinates, noted for a series of tetraarylporphyrinate derivatives (Hu, C.; Roth, A.; Ellison, M. K.; An, J.; Ellis, C. M.; Schiltz, C. E.; Scheidt, W. R. J. Am. Chem. Soc. 2005, 127, 5675), is seen here as well. The sign of the quadrupole-splitting constant is again negative, which is unique to the imidazole-ligated derivatives and suggests a distinct electronic structure. The derivatives again display a remarkable temperature dependence in the quadrupole splitting, which is also seen for deoxymyoglobin and -hemoglobin. Structural features for the two new derivatives are similar to those seen earlier, although the core conformations show somewhat more doming character.

Crystallography, X-Ray↗

PubMed2005

Electronic configuration assignment and the importance of low-lying excited states in high-spin imidazole-ligated iron(II) porphyrinates.

The synthesis and characterization of six new high-spin deoxymyoglobin models (imidazole(tetraarylporphyrinato)iron(II)) are described. These have been intensively studied by temperature-dependent Mossbauer spectroscopy from 295 to 4.2 K. All complexes show a strong temperature dependence for the quadrupole splitting consistent with low-lying excited states of the same or lower multiplicity. An analysis of the data obtained in applied magnetic fields leads to the assignment of the sign of the quadrupole splitting. All model compounds as well as those of deoxymyoglobin and deoxyhemoglobin, previously studied, have a negative sign for the quadrupole splitting. Although not previously predicted, this experimental observation leads to the assignment of the ground-state electronic configuration for all high-spin imidazole-ligated iron(II) porphyrinates as (d(xz)())(2)(d(yz)())(1)(d(xy)())(1)(d(z)()()2)(1)(d(x)()()2(-)(y)()()2)(1). This is a distinctly different ground-state electronic configuration from other high-spin iron(II) porphyrinates; differences in structural details for the two classes of high-spin complexes are also discussed. The apparent anomaly of differing signs for the zero-field splitting constant between previously studied model complexes and the heme proteins is addressed; the difference appears to result from the fact that the assumptions used in the spin Hamiltonian approach that has been applied to these complexes are not adequately satisfied. Structures of four of the new five-coordinate species have been determined. Core conformations in these derivatives show variation, but these and previously studied compounds reveal a limited number of conformational patterns. The bond lengths and other geometrical parameters such as porphyrin core size and iron out-of-plane displacement support a high-spin state assignment for the iron(II).

Biomimetic Materials↗

PubMed2004

Anionic Fischer-type carbene complexes as bidentate (N,O) ligands.

New polynuclear complexes, (L1)3M2 [M2 = Cr(III) (4a,4b), Fe(III) (5), Co(III) (8)], (L1)2M2(L2)2 [M2 = Co(II) (7), Ni(II) (9)], (L1)2M2(O)L2 [M2 = V(IV) (6)] and L1M2Cp2 [M2 = Ti(III) (10)] with L1 = (CO)5M1=C[C=NC(CH3)=CHS](O-)(M1 = Cr or W) and L2 = 4-methylthiazole or THF, are described. The molecular structures of these complexes determined by X-ray diffraction show that the Fischer-type carbene complexes act as bidentate ligands towards the second metal centre, coordinating through C(carbene)-attached O-atoms and imine N-atoms of the thiazolyl groups to form five-membered chelates with the oxygen atoms in the mer configuration. Isostructural complexes have similar characteristic band patterns in their far-IR spectra. Cyclic voltammetry of selected complexes reveals the oxidation of the carbene complex ligand between 1.01 and 1.29 V. Oxidation of the central metal (M2) takes place at 0.56 and 0.86 V for 7 and 9, respectively. Three stepwise reductions of Cr(III) to Cr(0) occur for 4a and 4b in the region -0.51 to -1.58 V. These new ligand types and other variants thereof should find application in ligand design with the first metal -- and other ligands attached thereto -- in the carbene complex ligand, playing an important role.

Journal Article↗

PubMed2002

[Cloning and identification of human tissue-type plasminogen activator gene].

OBJECTIVE: To acquire the gene fragments coding for human tissue-type plasminogen activator (ht-PA). METHOD: Total RNA was extracted from Bowes Melanoma cell line and reverse transcriptase-"touchdown" PCR was employed to amplify ht-PA cDNA that underwent digestion with the restriction enzymes and was subsequently cloned into vector pSP72 for transforming E.coli TG1. The cloned fragment was subjected to restriction mapping and sequence analysis for confirmation. RESULT: The restriction maps of the selected clones were consistent with those generated by computer-based analysis and was identical with that of reported ht-PA cDNA. CONCLUSION: The gene fragment encoding ht-PA was successfully cloned, which lays a foundation for further study and artificial modification of this gene.

Base Sequence↗

PubMed2002

[Techniques for producing transgenic animals and the recent development].

In this article the author reviews the currently prevailing techniques in producing transgenic animals with recount of those employing microinjection, retrovirus infection, embryonic stem cells, sperm vectors and nuclei transfer of somatic cells. The prospective of these techniques are also dealt with in brief.

Animals↗