Search PubMed⌕ Search

Biomedical subjects

Fei Ding

Publications and source records attributed to Fei Ding.

At least 19 recordsLinked to original sources
PubMed2007

Supramolecular assemblies of sulfonatocalixarenes with phenanthroline: factors governing capsule formation versus bilayer arrangements.

Four crystalline complexes were prepared by the inclusion complexation of the 1,10-phenanthrolinium ion (Phen) with p-sulfonatothiacalix[4]arene (TCAS) (2 from a solution at pH 1-2 and 4 from 1 M HCl) and with p-sulfonatocalix[5]arene (C5AS) (3 from a solution at pH 1-2 and 5 from 1 M HCl) upon varying the acidity of the solution. By combining the results obtained for complexes 2-5 with those for our previously reported complex (1), p-sulfonatocalix[4]arene (C4AS) complexed to Phen, it was revealed that p-sulfonatocalixarenes (CASs) form "bis-molecular" capsules (1, 2, and 3) around Phen at pH 1-2, whereas complexes 4 and 5 display distinct host-guest inclusion behavior at higher acid concentrations. The degree of compactness of the capsules increases with the enlargement of the calixarene cavity, which is affected significantly by both the penetration depth of Phen and the structure of the Phen dimer. Furthermore, the complexation behavior of TCAS/C5AS with Phen in 1 M DCl was investigated by using NMR spectroscopy, and was discussed in comparison with the previously reported results obtained from solutions at pH 2.0.

Journal Article↗
PubMed2006

Biocompatibility evaluation of silk fibroin with peripheral nerve tissues and cells in vitro.

Silk-based materials have been used in the field of bone or ligament tissue engineering. In order to explore the feasibility of using purified silk fibroin to construct artificial nerve grafts, it is necessary to evaluate the biocompatibility of silk fibroin material with peripheral nerve tissues and cells. We cultured rat dorsal root ganglia (DRG) on the substrate made up of silk fibroin fibers and observed the cell outgrowth from DRG during culture by using light and electron microscopy coupled with immunocytochemistry. On the other hand, we cultured Schwann cells from rat sciatic nerves in the silk fibroin extract fluid and examined the changes of Schwann cells after different times of culture. The results of light microscopy, MTT test and cell cycle analysis showed that Schwann cells cultured in the silk fibroin extract fluid showed no significant difference in their morphology, cell viability and proliferation as compared to that in plain L15 medium. Furthermore, no significant difference was found in expression of the factors secreted by Schwann cells, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and S-100, between Schwann cells cultured in the silk fibroin extraction fluid and in plain L15 medium by the aid of immunocytochemistry, RT-PCR and Western analysis. Collectively, these data indicate that silk fibroin has good biocompatibility with DRG and is also beneficial to the survival of Schwann cells without exerting any significant cytotoxic effects on their phenotype or functions, thus providing an experimental foundation for the development of silk fibroin as a candidate material for nerve tissue engineering applications.

Animals↗
PubMed2006

Expression and distribution of trihydrophobin 1 in postnatal developing mouse testis.

The human trihydrophobin 1 (TH1) is a highly conserved and widely expressed protein. It is clear that TH1 serves as a new specific negative regulator of A-Raf kinase. In this study, we found that TH1 associated with A-Raf in mouse testis by using coimmunoprecipitation analysis. Then we characterized the gene expression of TH1 in mouse testis and analyzed the changes of TH1 protein during postnatal development. The protein expression of TH1 in mouse testis was further analyzed by immunohistochemistry staining. Strong signals were detected in the seminiferous tubules and the distribution patterns varied with the different ages of postnatal mouse testis. TH1 was distributed in spermatocytes and Sertoli cells at 2 weeks postnatal, and was abundant in spermatogonia at 8 weeks postnatal. Leydig cells were positive to TH1 throughout testicular development. A high expression of TH1 in both Leydig cells and mouse Leydig tumor cells (mLTC-1cells) was found to be concentrated in the cytoplasm. The colocalization of TH1 and A-Raf in mLTC-1 cells or in adult testis was also observable.

Animals↗
PubMed2006

Investigation of differentially expressed proteins in rat gastrocnemius muscle during denervation-reinnervation.

To have a better insight into the molecular events involved in denervation-induced atrophy and reinnervation-induced regeneration of skeletal muscles, it is important to investigate the changes in expression levels of a great multitude of muscle proteins during the process of denervation-reinnervation. In this study, we employed an experimental model of rat sciatic nerve crush to examine the differentially expressed proteins in the rat gastrocnemius muscle at different time points (0, 1, 2, 3, 4 weeks) after sciatic nerve crush by using two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS), collectively referred to as the modern proteomic analysis. The results showed that 16 proteins in the rat gastrocnemius muscle exhibited two distinct types of change pattern in their relative abundance: (1) The relative expression levels of 11 proteins (including alpha actin, myosin heavy chain, etc.) were decreased either within 1 or 2 weeks post-sciatic nerve injury, followed by restoration during the ensuing days until 4 weeks. (2) The other 5 proteins (including alpha enolase, beta enolase, signal peptide peptidase-like 3, etc.) displayed an up-regulation in their relative expression levels within 1 week following sciatic nerve injury, and a subsequent gradual decrease in their relative expression levels until 4 weeks. Moreover, the significance of the changes in expression levels of the 16 proteins during denervation-reinnervation has been selectively discussed.

Animals↗
PubMed2006

Expression of myostatin RNA transcript and protein in gastrocnemius muscle of rats after sciatic nerve resection.

Myostatin, a member of the transforming growth factor-beta (TGF-beta) superfamily, has been identified as an inhibitor of skeletal muscle mass. To have an insight into the expression pattern of myostatin and its potential role in skeletal muscle atrophy induced by denervation, we used an animal model of peripheral nerve resection to examine the time-dependent changes in myostatin mRNA and protein levels in the denervated gastrocnemius muscle of rats after sciatic neurectomy by the aid of quantitative real-time RT-PCR and Western blotting, respectively. We also conducted morphometric analyses to measure the wet weight ratio of the denervated muscle (the operated side/contralateral non-operated side) and the cross sectional area of muscle fibers and to observe muscle morphology. The experimental results showed that myostatin mRNA and protein levels in rat gastrocnemius muscle persistently elevated after denervation, despite a fluctuation of myostatin mRNA level at day 3 after denervation, reached their respective peaks at day 28 after denervation, and then depressed slightly until day 56 after denervation. Furthermore, a significant negative linear correlation was found between myostatin abundance and muscle atrophy degree, suggesting that myostatin might probably play an important role in denervation-induced muscle atrophy. Our present study perhaps provides a new window into myostatin regulation in association with a specific type of muscle atrophy.

Animals↗
PubMed2006

EST-based identification of genes expressed in brain and spinal cord of Gekko japonicus, a species demonstrating intrinsic capacity of spinal cord regeneration.

In the present study, a brain and spinal cord cDNA library of Gekko japonicus was constructed, and 2349 unique expressed sequence tags (ESTs), composed of 494 clusters and 1855 singletons, were determined from 4108 randomly selected clones. Of these sequences, 54.8% (1287/2349) ESTs are identified as known genes and 45.2% (1062/2349), as unknown genes. The identified ESTs were classified with respect to their functional categorization; both the housekeeping genes and the nervous system-related genes were well represented in the library. The complete open reading frame (ORF)-containing clones derived from the library were identified as well; 303 clones were obtained to date. Finally, two clones with sequence homology to endothelial differentiation-related factor 1 (EDF-1) and to myelin-associated glycoprotein (MAG) precursor were selected, and their expression patterns in normal and regenerating spinal cord were analyzed by RT-PCR. Both of them were expressed in the spinal cord, and the expression level decreased significantly after tail amputation. This study provides a preliminary view of the gene expression profiles of the central nervous system in gecko, and it might accelerate the process of gene discovery and function analysis in this organism, which demonstrates an intrinsic capacity of spinal cord regeneration.

Animals↗
PubMed2006

Tpc1808 increases expression of NF-H in PC12 cells.

Tpc1808 is a candidate chemotropic factor induced by nerve injury, and we report here the role of rat Tpc1808 in the expression of high-molecular-weight neurofilament (NF-H) in PC12 cells. A full-length Tpc1808 cDNA encoding the 275-amino-acid protein was constructed into pcDNA-HA and transfected into PC12 cells. The increased expression of NF-H was detectable in PC12-Tpc1808 clones by semi-qRT-PCR, real-time PCR, Western blot, and immunofluorescence. Such an increase could also be observed in PC12 cells subjected to recombinant Tpc1808 protein by real-time PCR and immunohistochemistry. At a concentration of 0.1 microg/mL, Tpc1808 protein, similar to NGF, could promote the expression of NF-H in a time-dependent manner. Our findings suggest that Tpc1808 is the gene related to promotion of nerve growth, and both the Tpc1808 gene and the Tpc1808 recombinant protein up-regulate the expression of NF-H in PC12 cells.

Amidohydrolases↗
PubMed2005

Spectrophotometric study of fluorescence sensing and selective binding of biochemical substrates by 2,2'-bridged bis(beta-cyclodextrin) and its water-soluble fullerene conjugate.

A bis(beta-cyclodextrin)-fullerene conjugate (3) linked at the secondary hydroxyl side was prepared in a good yield from its precursor N,N'-bis(2-(2-aminoethylamino)ethyl)malonamide-bridged bis(beta-cyclodextrin) (2). Spectrophotomeric studies on the conformation and the inclusion complexation behavior of 3 with a variety of organic and biochemical substrates by means of UV-vis, FT-IR, NMR, fluorescence, and circular dichroism spectroscopy showed that the bis(beta-cyclodextrin)-fullerene conjugate displayed an intramolecular capsule-type conformation in aqueous solution. Because of the multiple binding of bis(beta-cyclodextrin) with substrates, 2 can act as an efficient fluorescence sensor for biochemical substrates, while its fullerene conjugate 3 displays a capability of cleaving DNA under visible-light irradiation.

Benzyl Compounds↗
PubMed2005

Cyclodextrins as carriers for cinchona alkaloids: a pH-responsive selective binding system.

A series of cyclodextrin-cinchona alkaloid inclusion complexes were prepared from beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and four cinchona alkaloids in ca. 90% yields, and their inclusion complexation behavior was investigated at pH 7.2 and 1.5 by means of fluorescence, UV/Vis and 2D NMR spectroscopy. The results showed that the cinchona alkaloids can be efficiently encapsulated in the cyclodextrin cavity in an acidic environment and sufficiently released in a neutral environment, which makes these cyclodextrin derivatives the potential carriers for cinchona alkaloids. The binding ability and molecular selectivity of cyclodextrins toward cinchona alkaloids were discussed from the viewpoint of the size-fit concept and multiple recognition mechanism between host and guest.

Binding Sites↗
PubMed2005

FTIR spectroscopic investigations of supersaturated NaClO4 aerosols.

Supersaturated NaClO4 aerosols have been studied using a Fourier transform infrared (FTIR) spectrometer coupled with an aerosol flow tube (AFT). Compared with previous Raman results, the water O-H stretching envelope in the supersaturated solutions of NaClO4 aerosols was more structured in response to changing RH, revealing at the same time the existence of water monomers weakly hydrogen-bonded with ClO4- at extremely high concentrations. Due to enhanced ion interactions in the supersaturated solutions of NaClO4 aerosols, the formation of contact ion pairs (CIPs) could be observed without component decomposition for the nondegenerate nu1 band of ClO4-, and the degenerate nu3 band of ClO4- was successfully related to the formation of CIPs in NaClO4 solutions. Based on these observations, a new mechanism featured by the attack of ClO4- upon hydrated Na+ for CIPs formation in the supersaturated solutions of NaClO4 aerosols was further proposed. The anhydrous NaClO4, characterized by the upper limit deliquescence relative humidity (DRH) of approximately 43% and the disappearance of the nu1 band of ClO4- in the infrared spectra, was observed to form on the silicon windows at low RHs.

Aerosols↗
PubMed2005

Spectrophotometric study on the controlling factor of molecular selective binding of dyes by bridged bis(beta-cyclodextrin)s with diselenobis(benzoyl) linkers.

A series of beta-cyclodextrin (beta-CD) dimers with 4,4'-diselenobis(benzoyl) linkers, that is, 6,6'-[4,4'-diselenobis(benzoyloxyl)]-bridged bis(beta-CD) (1a), 6,6'-[4,4'-diselenobis[2-(benzoylamino)ethyleneamino]]-bridged bis(beta-CD) (2a), and 6,6'-[4,4'-diselenobis[2-(benzoylamino)-3,6-diazaoctylamino]]-bridged bis(beta-CD) (3a), were synthesized in moderate yields by the reaction of 4,4'-diselenobis(benzoic acid) with beta-CD or oligo(ethylenediamino)-6-deoxy-beta-CD. Their binding behaviors with some structure-related substrates, such as acridine red (AR), neutral red (NR), rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonate (ANS), and 6-p-toluidino-2-naphthalenesulfonic acid (TNS), were investigated in aqueous phosphate buffer solution (pH 7.20) at 298.15 K by means of fluorescence, NMR, as well as circular dichroism spectroscopy and compared with those of their 2,2'-diselenobis(benzoyl)-linked analogues, that is, 6,6'-[2,2'-diselenobis(benzoyloxyl)]-bridged bis(beta-CD) (1b), 6,6'-[2,3'-diselenobis[2-(benzoylamino)ethyleneamino]]-bridged bis(beta-CD) (2b), and 6,6'-[2,2'-diselenobis[2-(benzoylamino)-3,6-diazaoctylamino]]-bridged bis(beta-CD) (3b). The results showed that bis(beta-CD)s 1a-3a, whose Se-Se bonds were located at the para position of the carboxyl group, gave stronger binding abilities toward nonlinear guests (RhB and ANS) than their analogues 1b-3b, whose Se-Se bonds were located at the ortho position relative to the carboxyl group. The molecular binding ability and selectivity of model substrates by these ditopic hosts were sufficiently discussed to reveal not only the cooperative contributions of the linker group and CD cavities upon inclusion complexation with dye guest molecules but also the controlling factors for the molecular selective binding.

Journal Article↗
PubMed2005

Molecular recognition thermodynamics of bile salts by beta-cyclodextrin dimers: Factors governing the cooperative binding of cyclodextrin dimers.

The complex stability constants (K(S)), standard molar enthalpy (DeltaH degrees), and entropy changes (DeltaS degrees) for the inclusion complexation of two families of beta-cyclodextrin (beta-CD) dimers, i.e. beta-CD dimers Se1-Se4 bearing 2,2'-diselenobis(benzoyl) tether (Se-dimers) and beta-CD dimers Py1-Py4 bearing 2,2'-bipyridine-4,4'-dicarboxy tether (Py-dimers), with four bile salt guests, i.e. sodium cholate (CA), sodium deoxycholate (DCA), sodium glycocholate (GCA), and sodium taurocholate (TCA), were determined at 25 degrees C in Tris buffer solution (pH 7.4) at 298.15 K by means of isothermal titration microcalorimetry. The thermodynamic parameters obtained, together with the ROESY spectra of interactions between beta-CD dimers and bile salts, consistently suggest that the length, flexibility, and structure of spacers linking the two beta-CD cavities not only determine the binding modes but also significantly alter the molecular selectivity of beta-CD dimers.

Calorimetry↗
PubMed2005

Efficient fluorescent sensors of oligopeptides by dithiobis(2-benzoylamide)-bridged bis(beta-cyclodextrin)s: structure in solution, binding behavior, and thermodynamic origin.

Two 6,6'-bis(beta-cyclodextrin)s linked by 2,2'-dithiobis[2-(benzoylamino)ethyleneamino] and 2,2'-dithiobis[2-(benzoylamino)diethylenetriamino] bridges (1 and 2) have been synthesized as cooperative multipoint recognition receptor models for non-aromatic oligopeptides. Their structures in solution and inclusion complexation mechanism are comprehensively investigated by means of circular dichroism, 2D NMR spectra and temperature-dependent fluorescence titrations. The results show that the cooperative 'host-linker-guest' binding mode and the extensive desolvation effect jointly contribute to the guest-induced fluorescence enhancement of bis(beta-cyclodextrin)s. Further examinations on the binding behavior of hosts 1-2 with a series of di- and tri-peptides demonstrate that bis(beta-cyclodextrin) 1 can recognize not only the size/shape of oligopeptides but also the dipeptide sequence, giving an exciting residue selectivity up to 37.5 for Gly-Gly-Gly/Glu-Glu pair and a high sequence selectivity up to 5.0 for Gly-Leu/Leu-Gly pair. These fairly good selectivities are discussed from the viewpoint of cooperative binding, multiple recognition and induced-fit interactions between host and guest.

Fluorescent Dyes↗
PubMed2005

[Cooperative luminescence in Yb:YAG crystals].

Cooperative luminescence phenomenon of Yb:YAG crystals was studied. Up-converted blue luminescence was obviously observed in Yb:YAG under excitation in the near-infrared region with a wavelength 940 nm. Experimental evidence was provided by the fact that the intensity of 498 nm luminescence shows a quadratic dependence on excitation power, and the intensity of blue luminescence increased with the increase in Yb ion concentration. It is concluded that this luminescence is due to a cooperative process resulting from a strong interaction of Yb ions. The cooperative luminescence is possiblely assigned to the strong interaction of 4f(13) electrons and neighboring Yb3+ ions in a covalent host lattice such as YAG. Theoretical cooperative luminescence spectrum was calculated.

Aluminum Oxide↗
PubMed2004

Stereoselective tandem 1,4-addition reactions for benzenes: a comparison of Os(II), Re(I), and W(0) systems.

The arene ligand in the complex TpRe(CO)(MeIm)(eta2-benzene) (Tp = hydridotris(pyrazolyl)borate; MeIm = N-methylimidazole) undergoes tandem electrophile/nucleophile 1,4-addition reactions. Subsequent oxidative demetalation affords cis-3,6-disubstituted 1,4-cyclohexadienes (46-84%). Common organic electrophiles such as acetals and Michael acceptors were successfully added to the bound benzene to generate eta3-benzenium complexes, which then were treated with a silyl ketene acetal, silyl vinyl ether, phenyllithium, or malonate ester to afford 1,4-dialkylated dihydrobenzene complexes. The d6 transition metal analogues TpW(NO)(PMe3)(eta2-benzene) and [Os(NH3)5(eta2-benzene)]2+ also undergo 1,4-dialkylation reactions, and the relative ability of all three metals to activate arenes is compared.

Benzene Derivatives↗
PubMed2004

Biquinolino-modified beta-cyclodextrin dimers and their metal complexes as efficient fluorescent sensors for the molecular recognition of steroids.

A series of bridged beta-cyclodextrin (beta-CyD) dimers possessing functional tethers of various lengths was synthesized in moderate yield by the treatment of 2,2'-biquinoline- 4,4'-dicarboxylic dichloride with beta-CyD or mono[6-oligo(ethylenediamino)-6-deoxy]-beta-CyDs. The products were 2,2'-biquinoline-4,4'-dicarboxy-bridged bis(6-O-beta-CyD) (8), N,N'-bis(2-aminoethyl)-2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CyD) (9), and N,N'-bis(5-amino-3-azapentyl)-2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CyD) (10). The reaction of 8-10 with copper perchlorate give their copper(II) complexes 11-13 in satisfactory yields of over 77 %. All the bis(beta-CyD)s 8-13 act as efficient fluorescent sensors and display remarkable fluorescence enhancement upon addition of optically inert steroids. The inclusion complexation behaviors of 8-13 when treated with the representative steroids cholate (14), deoxycholate (15), and glycocholate (16) in aqueous solution at 25 degrees C were investigated by means of UV/Vis spectroscopy, conductivity and fluorescence measurements, circular dichroism spectroscopy, and 2D NMR spectroscopy. The tether length of bis(beta-CyD) 9 allows it to adopt a cooperative host-tether-guest binding mode in which the spacer and guest are co-included in the two CyD cavities. As a result of this cooperation, 9 has a stability constant (K(s)) about 2x10(2) times higher than that of monomodified beta-CyD 4 for inclusion complexation with cholate. Metallooligo(beta-CyD)s with four beta-CyD units have enhanced binding abilities compared with monomodified beta-CyDs. These metallo compounds have binding affinities for guest steroids that are up to 50-4.1x10(3) times higher than those of CyDs 2-4. The guest-induced fluorescence enhancement of bis(CyD)s opens a new channel for the design of sensor materials. The complex stability constants of these compounds are discussed from the viewpoint of induced-fit interaction and cooperative multiple binding between host and guest.

Circular Dichroism↗
PubMed2004

Interaction between beta-cyclodextrin and 1,10-phenanthroline: uncommon 2:3 inclusion complex in the solid state.

The crystallographic structure of the complex formed by beta-cyclodextrin with 1,10-phenanthroline has been studied by X-ray diffraction. The result shows that the complex adopts an uncommon 2:3 stoichiometry in solid state, that is, every complex unit contains three 1,10-phenanthroline molecules and two beta-cyclodextrin molecules, where two 1,10-phenanthroline molecules individually occupy two cyclodextrin cavities, and the third guest molecule is located in the interstitial space between two head-to-head cyclodextrin molecules. The intermolecular hydrogen bonds between the adjacent complex units further link these individual monomers to a channel-type assembly. Furthermore, 1H and 2D NMR spectroscopy has been employed to investigate the inclusion behavior between the host beta-cyclodextrin and guest 1,10-phenanthroline in aqueous solution.

Carbohydrate Conformation↗