Biomedical subjects

Chen Fang

Publications and source records attributed to Chen Fang.

9 recordsLinked to original sources

PubMed2026

Haplotype-resolved genome of Forsythia suspensa reveals the reticulate evolution in Oleaceae and a novel gene cluster regulating stamen development.

The olive family (Oleaceae) comprises numerous species of economic, horticultural, and medicinal importance. Despite its significance, the evolutionary history of this complex family remains enigmatic. Here, we generated a high-quality haplotype-resolved genome of Forsythia suspensa, a distylous species that occupies a key phylogenetic position in Oleaceae. The 2 haplotypes exhibit significant allelic divergence with potential allele-specific regulation. We reconstructed the polyploidization history of Oleaceae by confirming and precisely dating a shared whole-genome triplication and an independent whole-genome duplication event. We revealed a complex reticulate evolution that gave rise to the tribe Oleeae: an initial hybridization between Forsythieae (♂) and Jasmineae (♀), a subsequent backcrossing event, and a final whole-genome duplication. We identified a novel tandemly duplicated pectin methylesterase inhibitor gene cluster that regulates filament length and pollen size via restricting cell elongation in the long-styled morph. Dosage augmentation via stepwise cluster formation (0.99 to 3.83 Mya) may contribute to maintaining stamen traits of the long-styled morph. These FsPMEIs are co-expressed with many cell wall-related genes, suggesting a functional link in cell wall modification. Our study reveals the reticulate evolution in Oleaceae and a novel gene cluster controlling stamen development in F. suspensa and provides valuable haplotype-resolved genomic resources for heterostylous species, offering novel framework and molecular pathways to understand plant adaptive evolution.

Forsythia↗

PubMed2006

Methotrexate-immobilized poly(ethylene glycol) magnetic nanoparticles for MR imaging and drug delivery.

We report the development of a biostable methotrexate-immobilized iron oxide nanoparticle drug carrier that may potentially be used for real-time monitoring of drug delivery through magnetic resonance imaging. Methotrexate (MTX) was immobilized on the nanoparticle surface via a poly(ethylene glycol) self-assembled monolayer (PEG SAM). The cytotoxicity of the nanoparticle-drug conjugate (NP-PEG-MTX) to target cells was studied with 9L glioma cells. Cellular uptake experiments showed that the uptake of NP-PEG-MTX conjugates by glioma cells was considerably higher than that of control nanoparticles. Magnetic resonance imaging in 9L cells cultured with NP-PEG-MTX of various concentrations showed significant contrast enhancement. NP-PEG-MTX demonstrated higher cytotoxicity in 9L cells to free MTX in vitro. Leucovorin, an MTX antidote, was used to rescue the cells that had been exposed to NP-PEG-MTX or free MTX, and the experiment verified the biocompatibility of NP-PEG-MTX conjugates and the MTX on NP-PEG-MTX conjugates to be the true source of the cytotoxicity to the target cells. TEM results showed that NP-PEG-MTX conjugates were internalized into the 9L cellular cytoplasm and retained its crystal structure therein for up to 144 h, as identified by electron diffraction. This prolonged particle retention may allow physicians to image tumor cells exposed to the NP-PEG-MTX conjugate over an extended therapeutic time course.

Adsorption↗

PubMed2006

Characterization of a new stearoyl-acyl carrier protein desaturase gene from Jatropha curcas.

A new full-length cDNA of stearoyl-acyl carrier protein desaturase was obtained by RT-PCR and RACE techniques from developing seeds of Jatropha curcas. Sequence alignment showed that its deduced amino acid sequence had high similarity with other stearoyl-acyl carrier protein desaturases. The gene was functionally expressed in E. coli and the desaturating activity of recombinant protein was easily detected when assayed in vitro with added spinach ferredoxin. Southern blot analysis indicated that the gene was a member of a small gene family. Northern blot analysis revealed it was highly expressed in developing fruits of J. curcas.

Amino Acid Sequence↗

PubMed2005

An enhanced polarization mechanism for the metal cations modified amorphous TiO2 based electrorheological materials.

In the present work, we developed a new kind of electrorheological (ER) materials, metal cations modified amorphous TiO(2) gels. The static yield stress of Sn(4+) modified amorphous TiO(2) gel based ER fluid with a volume fraction Phi = 38% reaches 26.2 kPa at E = 3.5 kV/mm. The result shows that metal cations can significantly enhance the ER activity of amorphous TiO(2) gels. We then proposed a novel ER effect mechanism (metal cations enhanced polarization mechanism) to clarify the experimental results. We believe that it is the metal cations that enhanced the polarization of the polar groups (-OH) which results in the corresponding enhancement of the interfacial polarization.

Journal Article↗

PubMed2005

Preparation and electrorheological property of rare earth modified amorphous BaxSr1-xTiO3 gel electrorheological fluid.

In this paper, we present a newly developed rare earth modified amorphous barium strontium titanate (Ba(x)Sr(1-x)TiO3) gel/silicone oil electrorheological (ER) fluid. The ER behaviors of suspensions of pure and rare earth modified amorphous Ba(x)Sr(1-x)TiO3 particles in silicone oil have been investigated under a dc electric field. The shear yield stress of the rare earth modified amorphous BaTiO3 gel/silicone oil ER fluid could reach 14.9 kPa at E=3.5 kV/mm while the leaking current density was very low, about 7.64 microA/cm2. The ER fluids with a higher volume fraction had a higher current density and a higher shear yield stress under the same electric field. The ER fluid has a long-term stability against sedimentation. The problem of caking was not serious and the agglomerated particles could be easily broken up by strongly stirring.

Journal Article↗

PubMed2005

Expression of a ribosome inactivating protein (curcin 2) in Jatropha curcas is induced by stress.

The open reading frame (ORF) encoding curcin 2 was cloned from total genomic and cDNA of Jatropha curcas leaves, which were treated by drought, temperature stress and fungal infection, by polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR amplification. The ORF has 927 bp that encodes a precursor protein of 309 amino acid residues. There are high similarities with curcin and the conserved domain of ribosome inactivating proteins (RIPs). Antiserum to curcin recognized one band of 32 kDa on Western blot of the leaves treated by temperature stresses at 4 degree C and 50 degree C and by fungal infections of Pestalotia funerea, Curvularia lunata (Walk) Boed, Gibberelle zeae (Schw.) Petch. Two bands of 32 kDa and 65 kDa were recognized on Western blot of the leaves treated by 10--40 percent polyethylene glycol (PEG). In addition, the 32 kDa band is nearly the molecular weight of curcin 2. This finding suggests that the protein of 32 kDa should be related to curcin 2. The presence of this protein molecular marker under stresses may provide an experimental foundation to study the stress proteins in J. curcas.

Amino Acid Sequence↗

PubMed2003

Cloning and expression of a new Tibetan hulless barley (Hordeum vulgare) beta-1,3-glucanase gene.

A new full-length beta-1,3-glucanase cDNA was obtained by RT-PCR and RACE techniques from Tibet hulless barley and its complete gene sequence obtained by DNA Walking. Sequence alignment with the BLAST program showed that cDNA has high similarity with barley beta-1,3-glucanase II. The gene was functionally expressed in E. coli and the recombinant protein catalysed the hydrolysis of beta-1,3-glucan with an action pattern characteristic of a beta-1,3-glucan endohydrolase (EC 3.2.1.39). Southern blot analysis indicated that the gene is a member of a small gene family. RT-PCR and northern blot analysis indicated it is constitutively expressed in barley shoots.

Amino Acid Sequence↗

PubMed2002

[Effects on fine particles by the continued high temperature weather in Beijing].

The continued high temperature weather (CHTW) appeared in Beijing since June 23 1999. The measurements showed the PM2.5 mass concentrations were 2 to 3 times of that in non-CHTW period. However the diffusion conditions were still fine in these days. Both the highest hourly concentrations of O3 and the SO4(2-) composition in PM2.5 can identify that the photochemical action was very active. It is the very reason to produce more fine particles in atmosphere.

Air Pollutants↗

PubMed2002

[Source apportionment on fine particles in Beijing].

The positive matrix factorization(PMF) method was used to apportion the sources for fine particles in Beijing. The data were obtained from four samplings from 1999 to 2000. The number of this data set was 40. The chemical compositions used in analysis include element carbon(EC), organics, SO4(2-), F-, Cl-, Fe, Ca, K, Mg, Al, Na, Zn, Mn, Ti, Pb, Ba and P. Six main sources, soil dust, construction dust, secondary source (by photochemical action), biomass burning, motor vehicle and coal burning were found.

Air Pollutants↗