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Biomedical subjects

Yan Zhao

Publications and source records attributed to Yan Zhao.

At least 37 records · Page 2Linked to original sources
PubMed2006

An amphiphilic molecular basket sensitive to both solvent changes and UV irradiation.

A molecular basket was obtained by linking four cholate units to a cone-shaped calix[4]arene scaffold through azobenzene spacers. The molecule turns its polar faces inward in nonpolar solvents to bind polar molecules such as sugar derivatives. In polar solvents, the nonpolar faces turn inward, allowing the binding of hydrophobic guests such as pyrene. The molecule can also respond to UV irradiation by trans-cis isomerization of the azobenzene spacers. Response toward both solvents and UV light is fully reversible.

Journal Article↗
PubMed2006

A density functional that accounts for medium-range correlation energies in organic chemistry.

It has recently been pointed out that current density functionals are inaccurate for computing stereoelectronic effects and energy differences of isomerization reactions and isodesmic reactions involving alkanes; this has been interpreted as an incorrect prediction of medium-range correlation energies. This letter shows that the recently published M05-2X functional has good accuracy for all three of the recently highlighted problems and should be useful for a wide variety of problems in organic chemistry. [structure: see text]

Journal Article↗
PubMed2006

hTERT/re-caspase-3 system induce apoptosis in hTERT-positive cancer cells.

Apoptosis induction is a promising approach for the treatment of human cancer. To achieve this purpose, the design of an expression system capable to induce apoptosis specifically in cancer cells is essential. Telomerase is an attractive target for delivery of apoptotic genes as an overwhelming majority of cancers have telomerase activity whereas most normal cells have low or an absence of telomerase activity. Activation of telomerase is tightly regulated at the transcriptional level of human telomerase reverse transcriptase (hTERT). In the present study, we developed a telomerase-specific delivery system of apoptosis-inducible gene re-Caspase-3, through utilizing the promoter of the hTERT gene, and then investigated its antitumor effect on cancer cells and tissues. The reason we used the re-Caspase-3 gene is that it is capable of autocatalytic processing and inducing apoptosis independent of the initiator Caspases. Here, we demonstrated that the hTERT/re-Caspase-3 system induced apoptosis in hTERT-positive cancer cells: CNE1 (nasopharyngeal carcinoma), HRT-18 (colonic carcinoma), MGC (stomath carcinoma), but not in hTERT-low Hacat (human normal keratinize epithelium) cells. In addition, the growth of s.c. tumors in nude mice was suppressed significantly by the treatment with the hTERT/re-Caspase-3 system. Results suggested that the telomerase-specific transfer of there-Caspase-3 gene may be an effective and promising targeting approach for the treatment of cancer.

Animals↗
PubMed2006

A new local density functional for main-group thermochemistry, transition metal bonding, thermochemical kinetics, and noncovalent interactions.

We present a new local density functional, called M06-L, for main-group and transition element thermochemistry, thermochemical kinetics, and noncovalent interactions. The functional is designed to capture the main dependence of the exchange-correlation energy on local spin density, spin density gradient, and spin kinetic energy density, and it is parametrized to satisfy the uniform-electron-gas limit and to have good performance for both main-group chemistry and transition metal chemistry. The M06-L functional and 14 other functionals have been comparatively assessed against 22 energetic databases. Among the tested functionals, which include the popular B3LYP, BLYP, and BP86 functionals as well as our previous M05 functional, the M06-L functional gives the best overall performance for a combination of main-group thermochemistry, thermochemical kinetics, and organometallic, inorganometallic, biological, and noncovalent interactions. It also does very well for predicting geometries and vibrational frequencies. Because of the computational advantages of local functionals, the present functional should be very useful for many applications in chemistry, especially for simulations on moderate-sized and large systems and when long time scales must be addressed.

Journal Article↗
PubMed2006

Thermodynamic basis for cluster kinetics: Prediction of the fragility of marginal metallic glass-forming liquids.

Due to the inaccessibility of the supercooled region of marginal metallic glasses (MMGs) within the experimental time window, we study the cluster kinetics above the liquidus temperature, Tl, to acquire information on the fragility of the MMG systems. The thermodynamic basis for the stability of locally ordered structure in the MMG liquids is discussed in terms of the two-order-parameter model. It is found that the Arrhenius activation energy of clusters, Deltah, is proportional to the chemical mixing enthalpy of alloys, DeltaH(chem). Fragility of the MMG forming liquids can be described by the ratio of the absolute DeltaH(chem) value to the glass transition temperature, Tg. The manner of vitrification during rapid solidification is an important factor for the discrepancy between the data presented in this paper and the prediction of the two-order-parameter model concerning the relation between Delta h and the liquid fragility.

Journal Article↗
PubMed2006

Comparison of various kinds of bone marrow stem cells for the repair of infarcted myocardium: single clonally purified non-hematopoietic mesenchymal stem cells serve as a superior source.

A variety of adult stem cells have been used to transplant into the infarcted (MI) heart, however, comparative studies are lacking to show more suitable source of cells for transplantation. We have identified a single non-hematopoietic mesenchymal stem cell subpopulation (snMSCs) isolated from human bone marrow and clonally purified, that over 99% of them expressed MSC marker proteins and cardiomyocyte marker proteins when induction in vitro. We also compared the effects of the snMSCs with unpurified MSC (uMSCs), mononuclear cells (BMMNCs), or peripheral blood mononuclear cells (PBMNCs) on myocardial repair after induction of MI in rats. Ninety days later, we observed a better cardiac function assessed by ejection fraction, fraction of shortening and lung wet/dry weight ratios, less remodeling of left ventricle (LV), lower collagen density in the LV, and more vessels in the ischemic wall in the snMSCs transplantation group than in other cell-transplanted groups. Furthermore, the transplanted cells expressing cardiomyocyte specific proteins or vascular endothelial cell marker proteins were more in the snMSCs group than in other ones. We conclude that transplantation with single clonally purified MSCs seems to be more beneficial to the cardiac repair than with other stem cells after MI.

Adult↗
PubMed2006

Detection of Hg2+ in aqueous solutions with a foldamer-based fluorescent sensor modulated by surfactant micelles.

[structure: see text] A hybrid foldamer constructed from six cholate units and two methionines was labeled with a DANSYL (DNS) group. The foldamer was solubilized by surfactant micelles to allow its usage as a fluorescent sensor for mercury ions present in the micromolar range in aqueous solutions. Its sensitivity was largely independent of the concentration of nonionic surfactants but was strongly influenced by both the nature and the concentration of ionic surfactants.

Fluorescent Dyes↗
PubMed2006

[Detection of anti-SSA/Ro antibody by ELISA, double immunodiffusion, and immunoblotting: a comparative study].

OBJECTIVES: To compare the specificity and sensitivity of ELISA, double immunodiffusion (ID), and immunoblotting (IB) in detection of anti-SSA/Ro antibodies in the sera of patients with connective tissue disease (CTD). METHODS: ELISA, double ID, and IB were used to detect the serum levels of anti-SSA/Ro antibodies in 7736 patients undergoing screening of CTD, 122 healthy blood donors, and 166 CTD patients positive in antinuclear antibody (ANA) and/or anti-extractable nuclear antigen (ENA). RESULTS: (1) The sera of the 122 healthy blood donors were all negative in anti-SSA/Ro antibodies by these three methods. (2) 1085 of the 7736 sera undergoing screening of CTD were positive in the anti-SSA/R0 antibody of the relative molecular quantity of 52,000. Ninety-two of the 1085 patient, ANA and/or anti-ENA negative, were all confirmed by ELISA and ID to be negative in anti-SSA/R0 antibodies. And 993 of these 1085 patients were positive in ANA and/or anti-ENA antibody, 917 of which were shown to be anti-SSA/R0 antibodies positive by ELISA (92.3%, 917/993), and 860 of which were shown to be anti-SSA/R0 antibodies positive by ID (86.6%, 860/993). (3) The prevalence rates of anti-SSA/Ro antibodies in the 166 CTD patients detected by ELISA, ID, and IB respectively were 76.5% (127/166), 65.1% (108/166), and 49.4% (82/166) respectively. (4) 127 of the 166 sera of the CTD group were anti-SSA/Ro antibody positive By ELISA, and 108 of the 166 sera were anti-SSA/R0 antibody positive by ID, with a coincidence rate of ELISA and ID of 88.6% (147/166), and there was a significant difference in positive rate of anti-SSA/Ro antibody between these two methods (P < 0.001). 81 of the 166 CTD sera were anti-SSA/Ro antibody positive with a positive rate of 63.8%. The coincidence rate of ID and IB was 75.9% (126/166) and there was a significant difference in positive rate of anti-SSA/Ro antibody between ID and IB methods too (P < 0.001). (5) Spearman's rank correlation study showed that the correlation coefficient between ELISA and ID was 0.828 (P < 0.001). CONCLUSIONS: (1) ELISA and ID are more specific than IB in detection of anti-SSA/Ro antibody. (2) The specificity of IB was lower, however, when ANA and/or other anti-ENA are positive, its specificity would be improved markedly. (3) ELISA is more sensitive than ID, and ID is more sensitive than IB in detection of anti-SSA/Ro antibody. (4) There is a significant positive correlation between ELISA and ID quantitatively.

Antibodies, Antinuclear↗
PubMed2006

Solvent-induced amphiphilic molecular baskets: unimolecular reversed micelles with different size, shape, and flexibility.

Amphiphilic molecular baskets were obtained by attaching facially amphiphilic cholate groups to a covalent scaffold (calix[4]arene or 1,3,5-2,4,6-hexasubstituted benzene). In a solvent mixture consisting of mostly a nonpolar solvent (i.e., CCl4) and a polar solvent (i.e., DMSO), the hydrophilic faces of cholates turned inward to form a reversed-micelle-like conformer whose stability was strongly influenced by the number of the cholates and the topology of the scaffold. Preferential solvation of the hydrophilic faces of cholates within the molecule by the polar solvent was cooperative and gave the fundamental driving force to the conformational change. The reversed-micelle-like conformer was most stable in structures that allowed multiple cholates to form a microenvironment that could efficiently enrich the polar solvent molecules from the bulk solvent mixture.

Journal Article↗
PubMed2006

Assessment of density functionals for pi systems: Energy differences between cumulenes and poly-ynes; proton affinities, bond length alternation, and torsional potentials of conjugated polyenes; and proton affinities of conjugated Shiff bases.

Woodcock et al. [J. Phys. Chem. A 2002, 106, 11923] pointed out that no density functional was able to obtain the correct sign of the relative energies of the allene and propyne isomers of C3H4 and that density functional theory (DFT) predicts that poly-ynes are insufficiently stabilized over cumulenes for higher homologues. In the present work, we show that the recent M05 density functional predicts the correct ordering of allene and propyne and gives a mean unsigned error (MUE) of only 1.8 kcal/mol for the relative energies of the two isomers of C3H4, C5H4, and C7H4. Two other recent functionals, M05-2X and PWB6K, also give reasonably low MUEs, 2.7 and 3.0 kcal/mol, respectively, as compared to 6.2 kcal/mol for the popular B3LYP functional. Another challenging problem for density functionals has been a tendency to overpolarize conjugated pi systems. We test this here by considering proton affinities of conjugated polyenes and conjugated Schiff bases. Again M05-2X performs quite well, with MUEs of 2.1 and 3.9 kcal/ mol, respectively, as compared to 5.8 and 5.9 kcal/mol for B3LYP. Averaged over the three problems, M05-2X has a MUE of 3.0 kcal/mol, the BMK functional of Boese et al. has an MUE of 3.2 kcal/mol, and M05 has an MUE of 5.1 kcal/mol. Twenty-two other tested functionals have MUEs of 5.2-8.1 kcal/mol averaged over the three test problems. Both M05 and M05-2X do quite well, compared to other density functionals, for torsion potentials in butadiene and styrene, and M05 does very well for bond length alternation in conjugated polyenes. Since the M05 functional has broad accuracy for main group and transition metal chemistry and M05-2X has broad accuracy for main group chemistry, we conclude that significant progress is being made in improving the performance of DFT across a wide range of problem types.

Journal Article↗
PubMed2006

Tuning the sensitivity of a foldamer-based mercury sensor by its folding energy.

A fluorescent sensor for Hg2+ was obtained by incorporation of two methionine units into a cholate hexamer and by attaching a Dansyl group at the chain end. Folding could be made highly favorable or unfavorable in different solvents. Because folding was required to bring the sulfur groups together to chelate the mercury ion, binding affinity of the foldamer and, thus, its sensitivity as a sensor, could be tuned over broad ranges (at least 5 orders of magnitude) by solvent changes.

Biopolymers↗
PubMed2006

alpha-Tocopheryl succinate-induced apoptosis in human gastric cancer cells is modulated by ERK1/2 and c-Jun N-terminal kinase in a biphasic manner.

Gastric neoplastic disease is one of the most frequent causes of cancer-associated deaths with poor prognosis. Here we studied the effect of the redox-silent analogue alpha-tocopheryl succinate (alpha-TOS), a strong apoptogen and anti-cancer agent, on the gastric cancer cell line SGC-7901. alpha-TOS inhibited proliferation of the cells and induced their apoptosis in a concentration- and time-dependent manner, while succinate or alpha-tocopherol showed no effect. The effect of alpha-TOS was modulated by components of the MAPK signaling network, including ERK1/2 and c-Jun N-terminal kinase (JNK), but not p38. Activation of ERK1/2 occurred early and increased until 12h, coinciding with an in crease in apoptosis in the cells, after which it dropped abruptly, while activation of JNK rose steadily, reaching a plateau at 12h of alpha-TOS treatment. The effects of ERK1/2 and JNK on the apoptosis outcome are transmitted via c-Jun, since transfection of the cells with c-Jun antisense oligodeoxynucleotide inhibited alpha-TOS-induced apoptosis. We conclude that ERK1/2 and JNK positively regulate apoptosis induced in gastric cancer cells by alpha-TOS.

Apoptosis↗
PubMed2006

[Ultrasound-guided minimally invasive neurosurgery in treatment of cranial tumors: clinical study].

OBJECTIVE: To explore the applicability of ultrasound-guided minimally invasive neurosurgery in treatment of intracranial tumors. METHODS: Thirty five patients with intracranial tumors diagnosed with preoperative CT and MRI underwent craniotomy. Intraoperative real-time monitoring ultrasound was conducted to detect the location, size and depth of the cerebral masses so as to determine the appropriate approach. At the end of operation, ultrasonography was used to explore the range of residue tumors. RESULTS: All the 35 patients acquired exact location of the tumors with ultrasound manifesting different levels of echo. According to the pathological results, the lesions of 32 patients (91%) were totally removed and 3 patients (9%) underwent subtotal resection. No infection was found. CONCLUSION: Ultrasound-guided minimally invasive neurosurgery is an effective real-time tool to localize brain tumors. It will provide a significant guidance for minimally invasive neurosurgery.

Adult↗
PubMed2006

Activation and sensitization of C and Adelta afferent fibers mediated by P2X receptors in rat dorsal skin.

The present study investigated the activation and sensitization effects of local injection of P2X receptor agonist alpha,beta-methylene ATP (alphabeta-meATP) into the receptive fields of afferent fibers innervating dorsal hairy skin in anesthetized rats. Single unit activities of afferent fibers were recorded by means of isolation of the fiber filaments from the dorsal cutaneous nerve branch. A total of 237 fibers were obtained. Of these, 67 were classed as C fibers, 104 as Adelta fibers and 66 as Abeta fibers. When alphabeta-meATP (0.1-100 microM, 10 microl) was injected subcutaneously into the receptive fields of these units, C and Adelta fibers demonstrated a dose-related increase in the discharge rates of the response. The activated proportion of C and Adelta fibers with a response to the drug also increased with dose. However, Abeta fibers did not exhibit significant activation. Furthermore, injection of alphabeta-meATP (10 microl) at a concentration of 100 microM resulted in a significant decrease of mechanical thresholds in C and Adelta fibers compared with pre-injection baseline (P < 0.05). In control experiments, injection of the vehicle phosphate-buffered saline (PBS, 10 microl) had no effect on all units tested. alphabeta-meATP (100 microM, 10 microl) followed by pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), a P2X receptor antagonist, successfully blocked the activation and sensitization effects of alphabeta-meATP on C and Adelta fibers tested. These results suggest that peripheral P2X receptors are involved in mediating peripheral excitation of C and Adelta fibers.

Action Potentials↗
PubMed2006

Comparative assessment of density functional methods for 3d transition-metal chemistry.

In the present study, we comparatively assessed the newly developed M05 functional against a data set of reaction energies for transition-metal chemistry. The functionals to which we compare are BLYP, B3LYP, B97-2, MPWLYP1M, TPSS, and TPSSh. We draw the following conclusions: (1) TPSS gives the best performance for calculating the binding energies of three transition-metal dimers (Sc(2), Ni(2), and V(2)) that have severe multireference character, (2) B97-2 gives the best performance for calculating the binding energies of the nine metal-ligand diatomics (three monohydrides, three monoxide, and three monofluorides), and (3) M05 gives the overall best performance for all 18 data in the assessment, and it has a mean unsigned error 55% lower than the popular B3LYP functional. Since the M05 functional also gives good performance for main-group thermochemistry, for noncovalent chemistry, and for calculating barrier heights, M05 can be applied to a wide range of problems where nonhybrid functionals or functionals designed for kinetics fail.

Algorithms↗
PubMed2006

Simulation of leaky Rayleigh wave at air-solid cylindrical interfaces by finite element method.

The finite element method is used to simulate the laser-excited leaky Rayleigh wave at air-solid cylindrical interfaces. A whole arithmetic of fluid-solid interaction is presented, which includes a coupling matrix that describing the process of the interaction between fluid and solid, the Arbitrary Lagrangian-Eulerian (ALE) formulation for treating the variation of fluid domain, which results from the Rayleigh wave propagating on the cylindrical interface, etc. Typical calculation is executed and the results show that the polarity of leaky Rayleigh waveform gradually changes as it propagates on the air-solid cylindrical interface.

Journal Article↗
PubMed2006

Artemisinin: current state and perspectives for biotechnological production of an antimalarial drug.

Artemisinin isolated from the aerial parts of Artemisia annua L. is a promising and potent antimalarial drug which has a remarkable activity against chloroquine-resistant and chloroquine-sensitive strains of Plasmodium falciparum, and is useful in treatment of cerebral malaria. Because the low content (0.01-1 %) of artemisinin in A. annua is a limitation to the commercial production of the drug, many research groups have been focusing their researches on enhancing the production of artemisinin in tissue culture or in the whole plant of A. annua. This review mainly focuses on the progresses made in the production of artemisinin from A. annua by biotechnological strategies including in vitro tissue culture, metabolic regulation of artemisinin biosynthesis, genetic engineering, and bioreactor technology.

Antimalarials↗