Biomedical subjects

Sheng Zhang

Publications and source records attributed to Sheng Zhang.

At least 19 recordsLinked to original sources

PubMed2025

A chromosome-level genome assembly of Guimi No. 2 (Actinidia chinensis).

In this study, we report a high-quality chromosome-level genome assembly of Actinidia chinensis var. chinensis 'Guimi No. 2'. This cultivar, discovered in Guizhou karst ecosystems, exhibits resistance to Pseudomonas syringae pv. actinidiae (Psa). Using a combination of MGI short-read sequencing, PacBio HiFi long-read sequencing, and Hi-C technology, we generated a genome assembly of 608.43 Mb with a contig N50 of 20.70 Mb, and 99.70% of the assembly was successfully anchored onto 29 pseudochromosomes. The quality value (QV) and the LTR Assembly Index (LAI) of the assembled genome were 72.23 and 10.10. The BUSCO analysis indicated that the genome assembly and gene model prediction were 98.40% and 96.56% complete, respectively. A total of 251.15 Mb of repetitive sequences and 45,986 protein-coding genes were annotated. This genome assembly provides critical insights into A. chinensis's genomic architecture and serves as a foundational resource for elucidating disease resistance mechanisms against Psa, while enabling comparative phylogenomic studies across the Actinidia genus.

Actinidia↗

PubMed2006

Self-assembly of C(60) pi-extended tetrathiafulvalene (exTTF) dyads on gold surfaces.

The first self-assembly of a C60 pi-extended tetrathiafulvalene (exTTF) dyad on a gold surface is reported. Four fullerene derivatives, two of them containing p-quinonoid pi-extended tetrathiafulvalenes (exTTFs), have been synthesized, and their solution electrochemistry has been investigated by means of cyclic voltammetry. Fullerene-containing SAMs of thioctic acid derivatives 3 and 6 have also been investigated by cyclic voltammetry. The cyclic voltammograms of both compounds exhibit three reversible reduction waves, and for compound 6, one irreversible oxidation process corresponding to the oxidation of the exTTF subunit is observed. Stable self-assembled monolayers (SAMs) of fullerene derivative 3 were formed on gold surfaces, whereas dyad 6 does not present a very clear electrochemical response, most probably as a result of structural rearrangements on the monolayer or charge transfer between the C60 and exTTF moieties.

Electrochemistry↗

PubMed2006

Selective anion sensing based on tetra-amide calix[6]arene derivatives in solution and immobilized on gold surfaces via self-assembled monolayers.

Two anion receptors, 1 and 2, based on the calix[6]crown-4 architecture were synthesized and characterized by NMR (1H, 13C, COSY), UV-vis, and MALDI-MS. 1H NMR measurements demonstrate that receptors 1 and 2 exhibit the highest binding affinity for fluoride ions compared to other anions including Cl-, Br-, NO3-, HSO4-, H2PO4-, and AcO-. The binding constants of 1 with F- and AcO- are 326 (+/-32) and 238 (+/-23) M-1, whereas those of 2 with F- and AcO- are 222 (+/-25) and 176 (+/-21) M-1. The fluorescent titration of 2 with various anions such as Cl-, Br-, NO3-, HSO4-, and H2PO4- led to essentially no change in excimer emission and a slight enhancement of monomer emission. In contrast, a dramatic change was observed in the fluorescence spectra upon the addition of F- and AcO- to 2. Self-assembled monolayers (SAMs) of 1 were formed on gold surfaces and characterized by reductive desorption and other techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy were used to monitor anion recognition by the SAM-modified gold electrodes. The gold electrodes modified by SAMs of 1, upon binding with the F- anion, exhibit a dramatic increase in charge-transfer resistance (Rct) values. This is due to the repulsion between the negatively charged electrode surfaces and the negatively charged Fe(CN)6(3-/4-) redox probe in the electrolyte solution. In contrast, smaller increases in Rct values were observed in the cases of other monovalent anions investigated.

Journal Article↗

PubMed2006

Increased expression of angiogenin in gastric carcinoma in correlation with tumor angiogenesis and proliferation.

AIM: To investigate the implication of angiogenin (ANG) in the neovascularizaton and growth of human gastric carcinoma (HGC). METHODS: ANG mRNA expression in HGC specimens obtained by surgical resection from patients with HGC were examined by RT-PCR. ANG, Ki-67, VEGF protein expression and microvessel density (MVD) in HGC specimens were detected by immunohistochemistry. RESULTS: RT-PCR showed significantly higher ANG mRNA expression (0.482 +/- 0.094) in HGC tissues than in the surrounding nontumorous tissues (0.276 +/- 0.019, P = 0.03). MVD within tumorous tissues increased significantly with ANG mRNA expression (r = 0.380, P = 0.001) and ANG protein expression (P < 0.01). The ANG expression levels of cancer tissues were positively correlated with VEGF (P < 0.01) and the proliferation index of cancer cells (P < 0.01). CONCLUSION: ANG is one of the neovascularization factors of HGC. ANG may work in coordination with VEGF, and promote the proliferation of HGC cells.

Aged↗

PubMed2006

Triply fused Zn(II)-porphyrin oligomers: synthesis, properties, and supramolecular interactions with single-walled carbon nanotubes (SWNTs).

The photophysical, electrochemical, and self-assembly properties of a novel triply fused Zn(II)-porphyrin trimer were investigated and compared to the properties of a triply fused porphyrin dimer and the analogous monomer. The trimer exhibited significantly red-shifted absorption bands relative to the corresponding monomer and dimer. Electrochemical investigations indicated a clear trend in redox properties amongst the three porphyrin structures, with the lowest oxidation potential and the lowest HOMO-LUMO gap exhibited by the triply fused trimer. This electrochemical behavior is attributed to the extensive pi-electron delocalization in the trimeric structure relative to the monomer and dimer. Additionally, it was found that the trimer forms extremely strong and nearly irreversible supramolecular interactions with single-walled carbon nanotubes (SWNTs), resulting in stable solutions of porphyrin-nanotube complexes in THF. Formation of these complexes required the addition of trifluoroacetic acid (TFA) to the solvent. This allowed the oligomers to make close contact with the nanotubes, enabling the formation of stable supramolecular assemblies. Atomic force microscopy (AFM) was used to observe the supramolecular porphyrin-nanotube complexes and revealed that the porphyrin trimer formed a uniform coating on the SWNTs. Height profiles indicated that nanotube bundles could be exfoliated into either individual tubes or very small bundles by exposure to the porphyrin trimer during sonication.

Journal Article↗

PubMed2006

Fullerene polypyridine ligands: synthesis, ruthenium complexes, and electrochemical and photophysical properties.

Fullerene coordination ligands bearing one bipyridine or terpyridine unit were synthesized, and their coordination to ruthenium(II) formed linear rod-like donor-acceptor systems. Steady-state fluorescence of [Ru(bpy)(2)(bpy-C(60))](2+) showed a rapid solvent-dependent, intramolecular quenching of the ruthenium(II) MLCT excited state. Time-resolved flash photolysis in CH(3)CN revealed characteristic transient absorption changes that have been ascribed to the formation of the C(60) triplet state, suggesting that photoexcitation of [Ru(bpy)(2)(bpy-C(60))](2+) results in a rapid intramolecular transduction of triplet excited state energy. The electrochemical studies on both [Ru(bpy)(2)(bpy-C(60))](2+) and [Ru(tpy)(tpy-C(60))](2+) indicated electronic coupling between the metal center and the fullerene core.

Journal Article↗

PubMed2006

Synthesis of fullerene adducts with terpyridyl- or pyridylpyrrolidine groups in trans-1 positions.

Two C(60) hexakis-adducts (2 and 3) were synthesized by using a protection-deprotection strategy. The symmetric fullerene tetrakis-adduct 8 was obtained by anthracene removal from the hexakis-adduct 7. Reaction of 8 with terpyridylglycine or pyridylglycine afforded two hexakis-adducts, 2 and 3. By using the retro-cyclopropanation reaction, the four malonate addends located on the equatorial belt of the hexakis-adducts were removed to afford two trans-1 bis-adducts, 4 and 5, with terpyridyl- or pyridylpyrrolidine groups. The structures of 2 and 3 were confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and (1)H, (13)C, and COSY NMR, and UV-visible spectroscopy. The cyclic voltammograms of fullerene multiadducts 2, 3, and 9 show irreversible reductions. Self-assembled monolayers (SAMs) of 1 and 3 were formed on gold surfaces through nitrogen adsorption. SAMs of 3 represent the first example of a fullerene hexakis-adduct formed on gold surfaces through nitrogen adsorption. Controlled potential electrolyses (CPE) were conducted to prepare trans-1 bis-adducts 4 and 5 modified with terpyridyl and pyridyl groups.

Electrochemistry↗

PubMed2006

A thiamin-bound, pre-decarboxylation reaction intermediate analogue in the pyruvate dehydrogenase E1 subunit induces large scale disorder-to-order transformations in the enzyme and reveals novel structural features in the covalently bound adduct.

The crystal structure of the E1 component from the Escherichia coli pyruvate dehydrogenase multienzyme complex (PDHc) has been determined with phosphonolactylthiamin diphosphate (PLThDP) in its active site. PLThDP serves as a structural and electrostatic analogue of the natural intermediate alpha-lactylthiamin diphosphate (LThDP), in which the carboxylate from the natural substrate pyruvate is replaced by a phosphonate group. This represents the first example of an experimentally determined, three-dimensional structure of a thiamin diphosphate (ThDP)-dependent enzyme containing a covalently bound, pre-decarboxylation reaction intermediate analogue and should serve as a model for the corresponding intermediates in other ThDP-dependent decarboxylases. Regarding the PDHc-specific reaction, the presence of PLThDP induces large scale conformational changes in the enzyme. In conjunction with the E1-PLThDP and E1-ThDP structures, analysis of a H407A E1-PLThDP variant structure shows that an interaction between His-407 and PLThDP is essential for stabilization of two loop regions in the active site that are otherwise disordered in the absence of intermediate analogue. This ordering completes formation of the active site and creates a new ordered surface likely involved in interactions with the lipoyl domains of E2s within the PDHc complex. The tetrahedral intermediate analogue is tightly held in the active site through direct hydrogen bonds to residues His-407, Tyr-599, and His-640 and reveals a new, enzyme-induced, strain-related feature that appears to aid in the decarboxylation process. This feature is almost certainly present in all ThDP-dependent decarboxylases; thus its inclusion in our understanding of general thiamin catalysis is important.

Amino Acid Substitution↗

PubMed2006

A receptor-modifying deamidase in complex with a signaling phosphatase reveals reciprocal regulation.

Signal transduction underlying bacterial chemotaxis involves excitatory phosphorylation and feedback control through deamidation and methylation of sensory receptors. The structure of a complex between the signal-terminating phosphatase, CheC, and the receptor-modifying deamidase, CheD, reveals how CheC mimics receptor substrates to inhibit CheD and how CheD stimulates CheC phosphatase activity. CheD resembles other cysteine deamidases from bacterial pathogens that inactivate host Rho-GTPases. CheD not only deamidates receptor glutamine residues contained within a conserved structural motif but also hydrolyzes glutamyl-methyl-esters at select regulatory positions. Substituting Gln into the receptor motif of CheC turns the inhibitor into a CheD substrate. Phospho-CheY, the intracellular signal and CheC target, stabilizes the CheC:CheD complex and reduces availability of CheD. A point mutation that dissociates CheC from CheD impairs chemotaxis in vivo. Thus, CheC incorporates an element of an upstream receptor to influence both its own effect on receptor output and that of its binding partner, CheD.

Amidohydrolases↗

PubMed2006

Regulated phosphorylation of budding yeast's essential myosin V heavy chain, Myo2p.

The tail of the yeast myosin V encoded by Myo2p is known to bind several receptors for cargo delivery along polarized actin cables. However, it is not known how Myo2p activity is regulated or how it selects between cargoes. Here we show that Myo2p is reversibly phosphorylated in vivo. A short peptide at the N-terminal end of the cargo-binding domain contains three residues contributing to single or doubly phosphorylated species. We confirm that the tail consists of two proteolytically resistant subdomains and identify a functionally important region N-terminal to subdomain 1 that includes the phosphorylation sites. Mutagenesis of the phosphorylation sites to alanine abolished a mobility shift diagnostic of phosphorylation, whereas mutagenesis to glutamic acid produced the shift and the formation of an additional phosphorylated species. These substitutions did not affect overall cell growth. However, one of the sites is predicted to be a substrate of cAMP-dependent protein kinase (PKA), and yeast expressing Myo2p with alanine substitutions is resistant to otherwise lethal overexpression of PKA, whereas the glutamic acid mutant is supersensitive to overexpression of PKA. These results suggest that in yeast, Myo2p is subject to phosphoregulation involving a PKA-related signaling pathway.

Alanine↗

PubMed2006

[Correlation between the expression of angiopoietins and their receptor and angiogenesis in gastric cancers].

OBJECTIVE: To explore the effects of angiopoietins (Ang-1 and Ang-2) and Tie-2 expression on microvessel density (MVD) in gastric cancers. METHODS: By using semiquantitative RT-PCR, immunohistochemistry and image analysis system, the expression of Ang-1, Ang-2, Tie-2 mRNA and their proteins were detected in 68 primary gastric cancers and their adjacent normal tissues. Microvessel density (MVD) was figured out based on CD34 immunohistochemical staining. RESULTS: The expression of all Ang-1, Ang -2, Tie-2 mRNA and their proteins was detected in gastric cancers and their paired adjacent gastric mucosa tissues. A negative correlation between Ang-1 protein, Tie-2 mRNA and MVD in gastric cancers was observed (r = -0.440, r = -0.267; P < 0.05), while the relation between Ang-2 mRNA and its protein, Ang-2/Ang-1 protein ratio with MVD were positive (r = 0.319, r = 0.729, r = 0.739; P < 0.05). It was found that MVD in groups with Ang-2 mRNA T/N ratio over 1.2 (the ratio of Ang-2 mRNA in gastric cancers and its adjacent normal mucosa) was higher than that in those with a ratio under 1.2, revealed by analysing the effects of Ang-1 and Ang-2 mRNA T/N ratio on MVD in gastric cancers. CONCLUSION: Ang-1 activates Tie-2 receptor, whereas Ang-2 antagonizes Ang-1 in the angiogenesis, and the Ang-2/Ang-1 ratio determines angiogenesis and tumor growth in gastric cancers. When the expression of Ang-2 is high and Ang-1 is low, the angiogenesis in gastric cancers is promoted, otherwise oppositely. The role of Ang-2 is dominant in the effect of Angs and their receptor on angiogenesis in gastric cancers.

Angiopoietin-1↗

PubMed2006

[Distribution features of nutrient and phytoplankton in incipient Three Gorges reservoir].

The distribution features of nutrient and chlorophyll a were determined by cruise during 2003-09-08 approximately 2003-09-15 with 11 sites in the Three Gorges reservoir. The results showed that the concentration of nitrogen was exceed the national surface water body quality standard III. The concentration of nitrogen range 1.01 approximately 1.35 mg x L(-1); Total phosphorus range 0.028 approximately 0.054 mg x L(-1); Kalium range 2.80 approximately 3.44 mg x L(-1); Total organic carbon range 1.92 approximately 2.59 mg x L(-1); Chlorophyll a range 1.58 approximately 7.53 mg x m(-3). The average concentration of chlorophyll a was 4.69 mg x m(-3) at surface layer. The correlation of nutrient and chlorophyll a were researched. It indicated there was a significant positive correlation (r = 0.7287) between chlorophyll a and NO3(-)-N. There was a significant negative correlation (r = -0.9207) between chlorophyll a and turbidity. Using the method of system cluster, it showed there was distinct distribution features which can be divided into three clusters. The upper river areas cluster included Changshou, Fuling,Fengdu, Zhongxian; The middle river areas cluster included Wanzhou, Yunyang and Fengjie; The down river areas included Wushan. The rate of diatom in phytoplankton was about 86%. Diatom was absolute predominance on 4 monitoring sites. The average of diatom was 129844 cells x L(-1). Amount of phytoplankton was increased along the river flow direction.

China↗

PubMed2006

[Antioxidant enzyme activities and proline content in maize seedling and their relationships to cold endurance].

This paper studied the catalase (CAT) and peroxidase (POD) activities and proline (Pro) content in the seedling's root, mesocotyl (including coleoptile node) , and coleoptile (including infancy leaf) of two maize inbred lines Huang C (cold-endurance) and Mo17 (cold-sensitive), and their relationships to cold endurance under low temperature stress (5 degrees C, 3 d). The results showed that under the low temperature stress, Huang C had a significantly higher relative growth rate of mesocotyl and coleoptile than Mo17, and the change rates of CAT and POD activities and Pro content in the root, mesocotyl and coleoptile of Huang C were higher than those of Mo17. The plasma membrane permeability of the three segments of both inbred lines was significantly increased, but Huang C had significantly lower plasma membrane permeability than Mo17. Compared with those under normal temperature, the seedlings under low temperature stress had higher CAT activity and Pro content, and the increment was higher in Huang C than in Mo17. The POD activity in the three segments of the seedlings under low temperature stress was reduced, and the decrement was lower in Huang C than in Mo17. Stepwise regression analysis showed that under low temperature stress, the dry matter accumulation in cold-endurance line Huang C was mainly related to Pro content, while that in cold-sensitive line Mo17 was mainly related to POD activity. Mesocotyl was the most responsive tissue to low temperature. The change rate of Pro content in mesocotyl was more closely correlated with the cold endurance of maize inbred lines than the other physiological parameters.

Adaptation, Physiological↗

PubMed2006

[Synthesis and characterizations of poly (ethylene glycol)-block-poly (glutamate)].

Amine-terminated poly (ethylene glycol) (PEG) was prepared by two steps. Firstly, potassium naphthalene was added to a solution of methoxypolyethylene glycol 5,000 in benzene until the solution maintains green in half of an hour, then excess tosylchloride was introduced; secondly, the conversion of the tosylate into an amine was carried out by Gabriel synthesis. The block copolymer poly (ethylene glycol)-co-poly (gamma-benzyl L-glutamate ) could be obtained by ring-opening polymerization of gamma-benzyl-L-glutamate N-carboxy anhydride with amine-terminated PEG as macroinitiator. And the benzyl group could be removed by sodium hydroxide. The product structure was characterized by IR, 1HNMR, GPC. The cisplatin-loaded micelle was observed by transmission electron microscope (TEM). And the block copolymer is expected to be useful as functional materials including carrier systems in drug controlled delivery applications.

Drug Carriers↗

PubMed2005

Supramolecular incorporation of fullerenes on gold surfaces: comparison of C60 incorporation by self-assembled monolayers of different calix[n]arene (n = 4, 6, 8) derivatives.

[reaction: see text] Two new calix[6]arene derivatives 3 and 4 in a 1,4-anti conformation and one calix[8]arene derivative 5 were synthesized. SAMs of calix[n]arene (n = 4, 6, 8) derivatives 1-5 were formed on gold bead electrodes. Cyclic voltammetry with Ru(NH3)6(3+/2+) as a redox probe, together with impedance spectroscopy and reductive desorption, indicates that SAMs of 5 have a higher coverage than those of 3 and 4 due to the presence of hydrogen bonding and possibly its conformation. Noncovalent immobilization of C60 on gold surfaces was achieved with SAMs of calix[8]arene derivative 5 but not with those of 1-4.

Journal Article↗

PubMed2005

Bcl-xL inhibits T-cell apoptosis induced by expression of SARS coronavirus E protein in the absence of growth factors.

One of the hallmark findings in patients suffering from SARS (severe acute respiratory syndrome) is lymphopenia, which is the result of massive lymphocyte death. SARS-CoV (SARS coronavirus), a novel coronavirus that has been etiologically associated with SARS cases, is homologous with MHV (murine hepatitis coronavirus), and MHV small envelope E protein is capable of inducing apoptosis. We hypothesized that SARS-CoV encodes a small envelope E protein that is homologous with MHV E protein, thus inducing T-cell apoptosis. To test this hypothesis, a cDNA encoding SARS-CoV E protein was created using whole gene synthesis. Our results showed that SARS-CoV E protein induced apoptosis in the transfected Jurkat T-cells, which was amplified to higher apoptosis rates in the absence of growth factors. However, apoptosis was inhibited by overexpressed antiapoptotic protein Bcl-xL. Moreover, we found that SARS-CoV E protein interacted with Bcl-xL in vitro and endogenous Bcl-xL in vivo and that Bcl-xL interaction with SARS-CoV E protein was mediated by BH3 (Bcl-2 homology domain 3) of Bcl-xL. Finally, we identified a novel BH3-like region located in the C-terminal cytosolic domain of SARS-CoV E protein, which mediates its binding to Bcl-xL. These results demonstrate, for the first time, a novel molecular mechanism of T-cell apoptosis that contributes to the SARS-CoV-induced lymphopenia observed in most SARS patients.

Amino Acid Sequence↗

PubMed2005

Effects of stable suppression of Group VIA phospholipase A2 expression on phospholipid content and composition, insulin secretion, and proliferation of INS-1 insulinoma cells.

Studies involving pharmacologic inhibition or transient reduction of Group VIA phospholipase A2 (iPLA2beta) expression have suggested that it is a housekeeping enzyme that regulates cell 2-lysophosphatidylcholine (LPC) levels, rates of arachidonate incorporation into phospholipids, and degradation of excess phosphatidylcholine (PC). In insulin-secreting islet beta-cells and some other cells, in contrast, iPLA2beta signaling functions have been proposed. Using retroviral vectors, we prepared clonal INS-1 beta-cell lines in which iPLA2beta expression is stably suppressed by small interfering RNA. Two such iPLA2beta knockdown (iPLA2beta-KD) cell lines express less than 20% of the iPLA2beta of control INS-1 cell lines. The iPLA2beta-KD INS-1 cells exhibit impaired insulin secretory responses and reduced proliferation rates. Electrospray ionization mass spectrometric analyses of PC and LPC species that accumulate in INS-1 cells cultured with arachidonic acid suggest that 18:0/20:4-glycerophosphocholine (GPC) synthesis involves sn-2 remodeling to yield 16:0/20:4-GPC and then sn-1 remodeling via a 1-lyso/20:4-GPC intermediate. Electrospray ionization mass spectrometric analyses also indicate that the PC and LPC content and composition of iPLA2beta-KD and control INS-1 cells are nearly identical, as are the rates of arachidonate incorporation into PC and the composition and remodeling of other phospholipid classes. These findings indicate that iPLA2beta plays signaling or effector roles in beta-cell secretion and proliferation but that stable suppression of its expression does not affect beta-cell GPC lipid content or composition even under conditions in which LPC is being actively consumed by conversion to PC. This calls into question the generality of proposed housekeeping functions for iPLA2beta in PC homeostasis and remodeling.

Animals↗

PubMed2005

Self-assembly of [60]fullerene-thiol derivatives on mercury surfaces.

Herein we report the first self-assembly of fullerene-thiol conjugates (1 and 2) on thin mercury films (TMF) deposited on a glassy carbon electrode (GCE). The fullerene-containing SAMs were investigated by cyclic voltammetry and water contact angle measurements. Two reversible, surface-confined redox couples were obtained for the fullerene-containing SAMs on TMF/GCE in CH(2)Cl(2) solution. The surface coverage of both fullerene derivatives 1 and 2 on TMF/GCE was measured to be in the range of (1.7-1.8) x 10(-10) mol cm(-2). Both SAMs of 1 and 2 partially blocked the electron transfer across the electrode in aqueous solution. The contact angle measurements performed on TMFs clearly showed an enhancement of the surface hydrophobicity upon formation of the fullerene-containing monolayer.

Journal Article↗