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Biomedical subjects

Tao Yang

Publications and source records attributed to Tao Yang.

At least 55 records · Page 3Linked to original sources
PubMed2006

[Fermentation and purification of Echistatin fusion protein expressed in Escherichia coli].

Lots of studies of Echistatin (Ecs) have proved its wide use in many aspects. However, the low yield of Ecs has impeded the relative researches of the protein. To establish the high-level expression system of Ecs, the fermentation and purification process of Ecs fusion protein expressed in E. coli were optimized. The Ecs gene was introduced into vector pTXB1 and placed under the control of highly efficient T7 promoter system. The cloned Ecs gene was expressed in E. coli BL21 (DE3) as soluble form. The Ecs production and biomass accumulation were optimized by examining medium composition, point of induction and induction time in fed-batch fermentation. Biomass accumulation was greatly affected by medium gradient, reaching 50.3g/L in 2 x YT medium. Ecs production was found to increase to 35% of total protein with 75g/L biomass accumulation after induced for 4h. Purification of Ecs from supernatant of sonication was done using one-step chromatographic procedure with chitin affinity chromatography and DTF cleavage, resulting in yields of 28mg/L and > 90% purity. The bioactivity of purified Ecs was determined and the result showed that purified Ecs could inhibit the aggregation of platelet in vitro with similar bioactivity to wild Ecs. This optimized method is readily scaled up for the expression and purification of Ecs in sufficient quantities for further structural and biological studies and applications.

Cloning, Molecular↗
PubMed2006

[Retrospective study on 116 unexpected sudden cardiac deaths in Yunnan, China].

OBJECTIVE: To identify the epidemiological and clinical features of unexpected sudden cardiac deaths (SUD) in Yunnan. METHODS: Choosing the old SUD cases from Xiangyun, Heqing, Nanjian and Dayao counties and using the standardized verbal autopsy Form, we interviewed the family members of the cases, witnesses and doctors as well as reviewing their medical files to get relative information. RESULTS: We identified 116 SUDs in 21 villages from 1984 to 2004. The village-specific annually standardized incidence rates were ranged from 0.2/1000 to 8.9/1000 (median = 0.8/1000). 66% and 29% of the SUDs occurred in July and August respectively. The incidence rates of SUD were higher (1.6/1000, chi(2) = 16, P < 0.01) in 10 - 39 year-olds, and higher in females than in males (RR = 1.6, 95% CI: 1.1 - 2.3). Seventy percent of SUD occurred in families having clustering nature and 60% of the additional cases in the family were occurred within 24 hours (median = 20 hours) after the first SUD identified in the family. SUD occurred in 23 families followed the first affected family in a village during the same season. In these 23 families, 61% of the first SUD occurred within 8 days after the first SUD in the first affected family. 68% and 66% of the SUDs did not have any complaints or signs during the last 3 weeks or from 3 weeks to 2 days prior to the onset of the disease. 63% of the SUDs had cardiac symptoms within the last 2 days prior to the onset with major symptoms as dizziness, nausea, faintness, unconsciousness, weakness and palpitation. The median duration from acute onset to death was 2 hours. CONCLUSIONS: The extreme time-space clustering of SUD in families and in villages suggested that the risk factors occurred in specific time and location. Familial clustered SUD cases had common exposure pattern. Sudden onset of acute cardiac symptoms often followed by sudden death. Epidemiological study on new cases was necessary to identify risk factors and to develop hypothesis for causation. In July 2005, we instituted a special SUD surveillance system for all the affected counties together with 10 counties which had no reported cases.

Adolescent↗
PubMed2005

DNA-network-templated self-assembly of silver nanoparticles and their application in surface-enhanced Raman scattering.

A large-scale lambda-DNA network on a mica surface was successfully fabricated with a simple method. Silver nanoparticles capped with the cationic surfactant cetyltrimethylammonium bromide (CTAB) were self-assembled onto a two-dimensional DNA network template by electrostatic interaction and formed nanoporous silver films, which can be used as active surface-enhanced raman scattering (SERS) substrates. Two probe molecules, Rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP), were studied on these substrates with very low concentrations, and great enhancement factors for R6G (0.21 x 10(10)-4.09 x 10(11)) and 4-ATP (approximately 1.70 x 10(5)) were observed. It was found that the enhancement ability was affected by the DNA concentration and the electrostatic absorption time of the CTAB-stabilized silver nanoparticles on the DNA strands. These SERS substrates formed by the self-assembly of silver nanoparticles on DNA network also show good stability and reproducibility in our experiments.

Aniline Compounds↗
PubMed2005

All-versus-nothing violation of local realism by two-photon, four-dimensional entanglement.

We develop and exploit a source of two-photon, four-dimensional entanglement to report the first two-particle all-versus-nothing test of local realism with a linear optics setup, but without resorting to a noncontextuality assumption. Our experimental results are in good agreement with quantum mechanics while in extreme contradiction to local realism. Potential applications of our experiment are briefly discussed.

Journal Article↗
PubMed2005

Synthesis, characterization, and catalytic performance of Cr-incorporated aluminoborate octahedral molecular sieves.

A series of Cr-incorporated PKU-1 molecular sieves (Cr-PKU-1) were synthesized by using boric acid as a flux, and the physicochemical properties were characterized by XRD, ICP, SEM, XPS, UV-vis, and NH3-TPD methods. The morphology of Cr-PKU-1 is a needlelike hexagonal prism with uniform size of about 2 microm in diameter and 20-50 microm in length. XRD and UV-vis provide direct evidence that Cr ions have been successfully incorporated into the framework of PKU-1. NH3-TPD shows a dramatic increase of acidic sites in the Cr-PKU-1 in comparison with PKU-1, indicating that the Cr incorporation can significantly modify the acidity of the compound. In addition, the incorporated Cr ions may act as redox centers, thus catalytic performance of Cr-PKU-1 molecular sieve was investigated by the selective oxidation of styrene under mild reaction conditions.

Journal Article↗
PubMed2005

New mechanism contributing to drug-induced arrhythmia: rescue of a misprocessed LQT3 mutant.

BACKGROUND: The cardiac sodium channel (SCN5A) mutation L1825P has been identified in a patient with drug-induced torsade de pointes precipitated by the IKr blocker cisapride. Although L1825P generates late sodium current typical of SCN5A-linked long-QT syndrome (LQT3) in vitro, the patient reported had a normal QT interval before administration of the drug. To address this discrepancy, we tested the hypothesis that this mutant channel is not processed normally. METHODS AND RESULTS: CHO cells transfected with L1825P displayed significantly reduced peak INa (209+/-36 versus 23+/-3 pA/pF, P<0.05). Confocal imaging and cell-counting studies using epitope-tagged constructs demonstrated that cell surface expression of the mutant was only approximately 9% of wild-type. Incubating transfected cells with cisapride partially rescued misprocessing to 30% of wild-type. As a result, "late" sodium current increased with cisapride from 1.2+/-0.11 to 5.04+/-0.77 pA/pF (P<0.05). CONCLUSIONS: L1825P fails to generate QT prolongation because it does not reach the cell surface. Moreover, the data suggest that cisapride caused torsade de pointes not only by blocking IKr but also by rescuing cell surface expression of the mutant channel, further exaggerating the LQT3 phenotype. This not only represents a new mechanism in the drug-induced long-QT syndrome but also strongly supports the concept that variable cell surface expression contributes to clinical variability in the LQT3 phenotype.

Action Potentials↗
PubMed2005

Genetic heterogeneity of deafness phenotypes linked to DFNA4.

Mutations in the heavy chain of the class II nonmuscle myosin, MYH14, cause autosomal dominant hearing loss in families linked to the DFNA4 locus. Consistent with this discovery, we identified an S120L mutation in MYH14 in a large German family segregating deafness that links to DFNA4. However, complete screening of the American family that originally defined the DFNA4 locus revealed no mutations in this gene. Furthermore, haplotyping of a single nucleotide polymorphism (SNP) 5' to MYH14 excludes this gene from the critical region in this family. Our results imply that mutations in another gene result in deafness at the DFNA4 locus. The newly defined candidate region encompasses a region of approximately 19 cM. Several candidate genes have been screened for disease-causing mutations.

Amino Acid Sequence↗
PubMed2005

Experimental quantum secret sharing and third-man quantum cryptography.

Quantum secret sharing (QSS) and third-man quantum cryptography (TQC) are essential for advanced quantum communication; however, the low intensity and fragility of the multiphoton entanglement source in previous experiments have made their realization an extreme experimental challenge. Here, we develop and exploit an ultrastable high intensity source of four-photon entanglement to report an experimental realization of QSS and TQC. The technology developed in our experiment will be important for future multiparty quantum communication.

Journal Article↗
PubMed2005

La4Cu(3-x)Zn(x)MoO12: zinc-doped cuprates with Kagomé lattices.

Two solid solutions, La4Cu(3-x)Zn(x)MoO12 (0.05 < or = x < or = 0.20, SS1) and La4Cu(3-x)Zn(x)MoO12 (0.30 < or = x < or = 2.40, SS2), were synthesized at ambient pressure and at temperatures from 1025 to 1200 degrees C by traditional solid-state reactions. Their structures were determined from X-ray powder diffraction with the help of electron and neutron diffraction. The atomic arrangements of SS1 and SS2 are similar, but their space groups are different, Pmnm for SS1 and P-1 for SS2, respectively. The copper, zinc, and molybdenum are coordinated by oxygen in corner-sharing trigonal bipyramids that are sandwiched between layers of lanthanum cations. In the transition metal cations layer of SS2, the copper and zinc cations order into a Kagomé-like lattice of triangular clusters. The magnetism has been measured from 2 to 300 K and is highly influenced by the geometric arrangement of the Cu(II) and Zn(II) cations. The number of free electrons per three Cu atoms is close to one for all samples in SS1 and SS2 indicating that the system can be well expressed by independent Cu(II)3 clusters. Spontaneous magnetization was observed in the system.

Copper↗
PubMed2005

Unmasking of brugada syndrome by lithium.

BACKGROUND: The characteristic ECG pattern of ST-segment elevation in V1 and V2 in the Brugada syndrome is dynamic; it is often intermittently present in affected individuals and can be unmasked by sodium channel blockers, including antiarrhythmic drugs and tricyclic antidepressants. We report here 2 patients who developed the Brugada ECG pattern after administration of lithium, a commonly used drug not previously reported to block cardiac sodium channels. METHODS AND RESULTS: Lithium induced transient ST-segment elevation (type 1 Brugada pattern) in right precordial leads at therapeutic concentrations in 2 patients with bipolar disorder. Lithium withdrawal in the patients resulted in reversion to type 2 or 3 Brugada patterns or resolution of ST-T abnormalities. In Chinese hamster ovary cells transfected with SCN5A, which encodes the cardiac sodium channel, lithium chloride caused concentration-dependent block of peak INa at levels well below the therapeutic range (IC50 of 6.8+/-0.4 micromol/L). CONCLUSIONS: The widely used drug lithium is a potent blocker of cardiac sodium channels and may unmask patients with the Brugada syndrome.

Adult↗
PubMed2005

Independently tunable 1.3 W femtosecond Ti:sapphire lasers passively synchronized with attosecond timing jitter and ultrahigh robustness.

A stable passively synchronized femtosecond laser has been realized by coupling two 1.3 W mode-locked Ti:sapphire lasers with a Kerr medium. An ultralong tolerance of 10 microm for the cavity length mismatch and a timing jitter of less than 0.4 fs were obtained. The relative carrier-envelope phase slip was directly observed by measuring the heterodyne output between the two lasers.

Journal Article↗
PubMed2005

Atrial fibrillation in KCNE1-null mice.

Although atrial fibrillation is the most common serious cardiac arrhythmia, the fundamental molecular pathways remain undefined. Mutations in KCNQ1, one component of a sympathetically activated cardiac potassium channel complex, cause familial atrial fibrillation, although the mechanisms in vivo are unknown. We show here that mice with deletion of the KCNQ1 protein partner KCNE1 have spontaneous episodes of atrial fibrillation despite normal atrial size and structure. Isoproterenol abolishes these abnormalities, but vagomimetic interventions have no effect. Whereas loss of KCNE1 function prolongs ventricular action potentials in humans, KCNE1-/- mice displayed unexpectedly shortened atrial action potentials, and multiple potential mechanisms were identified: (1) K+ currents (total and those sensitive to the KCNQ1 blocker chromanol 293B) were significantly increased in atrial cells from KCNE1-/- mice compared with controls, and (2) when CHO cells expressing KCNQ1 and KCNE1 were pulsed very rapidly (at rates comparable to the normal mouse heart and to human atrial fibrillation), the sigmoidicity of IKs activation prevented current accumulation, whereas cells expressing KCNQ1 alone displayed marked current accumulation at these very rapid rates. Thus, KCNE1 deletion in mice unexpectedly leads to increased outward current in atrial myocytes, shortens atrial action potentials, and enhances susceptibility to atrial fibrillation.

Action Potentials↗
PubMed2005

Experimental free-space distribution of entangled photon pairs over 13 km: towards satellite-based global quantum communication.

We report free-space distribution of entangled photon pairs over a noisy ground atmosphere of 13 km. It is shown that the desired entanglement can still survive after both entangled photons have passed through the noisy ground atmosphere with a distance beyond the effective thickness of the aerosphere. This is confirmed by observing a spacelike separated violation of Bell inequality of 2.45+/-0.09. On this basis, we exploit the distributed entangled photon source to demonstrate the Bennett-Brassard 1984 quantum cryptography scheme. The distribution distance of entangled photon pairs achieved in the experiment is for the first time well beyond the effective thickness of the aerosphere, hence presenting a significant step towards satellite-based global quantum communication.

Journal Article↗
PubMed2005

Experimental demonstration of a nondestructive controlled-NOT quantum gate for two independent photon qubits.

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum information processing. However, photons, one of the best candidates for qubits, suffer from a lack of strong nonlinear coupling, which is required for quantum logic operations. Here we show how this drawback can be overcome by reporting a proof-of-principle experimental demonstration of a nondestructive controlled-NOT (CNOT) gate for two independent photons using only linear optical elements in conjunction with single-photon sources and conditional dynamics. Moreover, we exploit the CNOT gate to discriminate all four Bell states in a teleportation experiment.

Journal Article↗
PubMed2005

A geraniol-synthase gene from Cinnamomum tenuipilum.

Geraniol may accumulate up to 86-98% of the leaf essential oils in geraniol chemotypes of the evergreen camphor tree Cinnamomum tenuipilum. A similarity-based cloning strategy yielded a cDNA clone that appeared to encode a terpene synthase and which could be phylogenetically grouped within the angiosperm monoterpene synthase/subfamily. After its expression in Escherichia coli and enzyme assay with prenyl diphosphates as substrates, the enzyme encoded by the putative C. tenuipilum monoterpene synthase gene was shown to specifically convert geranyl diphosphate to geraniol as a single product by GC-MS analysis. Biochemical characterization of the partially purified recombinant protein revealed a strong dependency for Mg2+ and Mn2+, and an apparent Michaelis constant of 55.8 microM for geranyl diphosphate. Thus, a new member of the monoterpene synthase family was identified and designated as CtGES. The genome contains a single copy of CtGES gene. Expression of CtGES was exclusively observed in the geraniol chemotype of C. tenuipilum. Furthermore, in situ hybridization analysis demonstrated that CtGES mRNA was localized in the oil cells of the leaves.

Acyclic Monoterpenes↗