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Yong Chen

Publications and source records attributed to Yong Chen.

At least 163 records · Page 9Linked to original sources
PubMed2004

Cooperative self-assembly and molecular binding behavior of cyclodextrin-crown ether conjugates mediated by alkali metal ions.

In order to quantitatively investigate their molecular binding ability, a series of cyclodextrin-crown ether conjugates containing beta-cyclodextrin (beta-CyD) and crown ether units, i.e.N-(benzoaza-15-crown-5)acylaminomethylene tethered 6-diethylenetriamino-6-deoxy-beta-CyD, N-(benzoaza-15-crown-5)acylaminomethylene tethered 6-triethylenetetraamino-6-deoxy-beta-CyD and 4',5'-dimethylene-benzo-15-crown-5 tethered 6-diethylenetriamino-6-deoxy-beta-CyD, have been prepared as ditopic molecular receptors. Their inclusion complexation behavior with four representative fluorescent dyes, i.e. ammonium 8-anilino-1-naphthalenesulfonate (ANS), sodium 6-toluidino-2-naphthalenesulfonate (TNS), acridine red (AR) and rhodamine B (RhB), has been comprehensively investigated in aqueous NaH2PO4/Na2HPO4 or KH2PO4/K2HPO4 buffer solution (pH 7.20) by means of circular dichroism, fluorescence, and 2D NMR spectra. The results indicate that the self-assembly of crown ether modified beta-CyD mediated by potassium ion exhibits a dimeric structure, which significantly enhances the original binding ability and molecular selectivity of parent beta-CyD and its derivatives towards guest molecules through the cooperative binding of two hydrophobic CyD cavities with one guest. This cooperative binding mode of K+/CyD-crown ether systems are further confirmed by Job's experiments and 2D NMR investigations. Attributed to the positive contributions from the metal-ligated crown ether cap and K+-mediated dimerization of CyDs, the binding constant (Ks) values of CyD-crown ether conjugates toward ANS are 10-83 times higher than that of beta-CyD. The increased binding ability and molecular selectivity of CyD-crown ether conjugates are discussed from the viewpoints of size/shape-fit and multiple recognition mechanism.

Journal Article↗
PubMed2004

Molecular alignment of rigid rods in nonrigid spherical pores.

We have investigated the orientation ordering of two shish-kebab chains confined by spherically harmonic potentials through Monte Carlo simulations and asymptotic analysis. The rigid rod is modeled as shish-kebab chains consisting of tangent hard spheres aligned in the same axis, and the harmonic potential is chosen to model nonrigid cavities. We first show that the interactions between a rod and the spherically harmonic potential are independent of chain orientation, indicating that the alignment of two confined rods arises from the excluded volume interactions alone. In the strong fields, the order parameter of two confined rods converges to different values, depending on the parity of chain length. From asymptotic order parameters, we find that the rods of odd-number beads rotate more freely even under the limiting strong confinement. However, the two rods of even-number beads are essentially trapped in a configuration of perpendicular alignment through intercalation of their central grooves. We attribute the dependence of the parity of chain length to the different locations of the center-of-mass in a rod for these two cases. Furthermore, we compare the shish-kebab chains with different rod models in the simulations, and utilize these models to explore the effect of the local rod smoothness on molecular alignment. Our findings suggest that increasing local rod smoothness enhances the rotational degree of freedom for confined rods, and the effect of local rod roughness emerges under strong enough applied potentials.

Journal Article↗
PubMed2004

SNARE assembly and membrane fusion, a kinetic analysis.

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) assembly may promote intracellular membrane fusion, an essential process for vesicular transport in cells. Core complex formation between vesicle-associated SNARE and target membrane SNARE perhaps drives the merging of two membranes into a single bilayer. Using spin-labeling EPR, trans-SNARE complex formation was monitored "locally" at four different core locations of recombinant yeast SNAREs, which are individually reconstituted into phospholipid vesicles. The results indicate that the time scales of core formation are virtually the same at all four locations throughout the core region, indicating the possibility of a single step core assembly, which appears to be somewhat different from what has been postulated by the "zipper" model. The EPR data were then compared with the kinetics of the lipid mixing measured with the fluorescence assay. The analysis suggests that SNARE core assembly occurs on a much faster time scale than the lipid mixing, providing a new insight into the timing of individual events in SNARE-induced membrane fusion.

Cell Membrane↗
PubMed2004

Cooperative molecular recognition of dyes by dyad and triad cyclodextrin-crown ether conjugates.

Three beta-cyclodextrin (beta-CyD) derivatives with crown ether units, that is N-(4'-benzo-15-crown-5)-6-imino-6-deoxy-beta-CyD (2), 6,6'-[N-(4,4'-dibenzo-18-crown-6)-imino]-bridged bis(beta-CyD)(3), and 2,2'-[O-(4',5'-benzo-15-crown-5)-ethyl]-bridged bis (beta-CyD)(5), were synthesized as cooperative recognition receptor models. Their molecular binding behavior with four representative fluorescent dyes, i.e., ammonium 8-anilino-1-naphthalenesulfonate (ANS), sodium-6-toluidino-2-naphthalene-sulfonate (TNS), Acridine Red (AR) and Rhodamine B (RhB), was investigated in buffer solutions (pH = 7.20) at 25 degreesC by means of circular dichroism, NMR and fluorescence spectroscopy. 2D-ROESY experiments showed that dyad host 2 and triad host 3 adopted a CyD-guest-crown ether binding mode, while triad host 5 adopted a CyD-guest-CyD binding mode, upon inclusion complexation with guest molecules. Therefore, hosts 2 and 3 showed high molecular recognition ability towards charged guests, giving an enhanced binding ability up to 115 times for ANS by 3 and fairly high molecular selectivity up to 1450 times for the ANS/AR pair by 2 as compared with native beta-CyD in an aqueous phosphate buffer solution. On the other hand, host 5 was found to be able to effectively recognize the shape of a guest molecule, showing significantly higher binding ability towards linear guests. The binding affinities and molecular recognition abilities of these CyD-crown ether conjugates towards guest molecules are discussed from the viewpoint of electrostatic and/or hydrophobic interactions, size/shape-fit concept, and multiple recognition mechanism between host and guest.

Anilino Naphthalenesulfonates↗
PubMed2004

Inhibition of accelerated graft arteriosclerosis by gene transfer of soluble fibroblast growth factor receptor-1 in rat aortic transplants.

OBJECTIVE: Because increased fibroblast growth factor-1 (FGF-1) and FGF receptor (FGFR) expression correlate with the development of accelerated graft arteriosclerosis in transplanted human hearts, this study sought to determine whether local gene transfer of soluble FGFR-1, capable of binding both FGF-1 and FGF-2, could blunt the development of accelerated graft arteriosclerosis in the rat aortic transplant model. METHODS AND RESULTS: A construct encoding the FGFR-1 ectodomain, capable of neutralizing FGF-2 action, was expressed in rat aortic allografts, using adenoviral gene transfer at the time of transplantation. Neointima formation was inhibited in aortic allografts transduced with soluble FGFR-1, compared with allografts transduced with Null virus. CONCLUSIONS: FGFs play a causal role in the development of accelerated graft arteriosclerosis in the rat aortic transplant model. Targeted interruption of FGF function could potentially reduce neointima formation in patients with heart and kidney transplants.

Adenoviridae↗
PubMed2004

[The classification and management of pancreatic duct stone].

OBJECTIVE: To set up a stand for surgical classification of pancreatic duct stone and evaluate the benefits of different management according to the classification. METHODS: Retrospectively analysis the diagnosis and prognosis of different management of 33 cases pancreatic duct stones to establish a new standard of classification and strategy of management of pancreatic duct stone. RESULTS: According to the results of imaging examination (B-US, CT, ERCP) and finding during surgery, pancreatic duct stone can be classified into four different types: Type I: The stones mainly located in the head of pancreas. Endoscopic pancreas drainage and remove of stones is the first line choice of treatment. If it fail the Whipple procedure should be applied. Type II, The stones mainly located in the body of pancreas. It can be treated by Pusetow procedure. Type III, The stones mainly located in the tail of pancreas. The resection of the tail of pancreas or combined with spleenectomy was recommended for the management of this type stones. Type IV, The stones can be found from the head to tail of the main duct of pancreas. The Pusetow-Gillesby procedure or dividing of the neck of pancreas removing stones from both ends of pancreatic duct and reconstructed by two ends pancreatic duct-ileostomy in Roux-en-Y fashion are the choice of management. CONCLUSION: The invadulaized strategy of the management based upon correct diagnosis and classification play the most important role in the treatment of pancreatic duct stone.

Adult↗
PubMed2004

Constitutive versus regulated SNARE assembly: a structural basis.

SNARE complex formation is essential for intracellular membrane fusion. Vesicle-associated (v-) SNARE intertwines with target membrane (t-) SNARE to form a coiled coil that bridges two membranes and facilitates fusion. For the SNARE family involved in neuronal communications, complex formation is tightly regulated by the v-SNARE-membrane interactions. However, it was found using EPR that complex formation is spontaneous for a different SNARE family that is involved in protein trafficking in yeast. Further, reconstituted yeast SNAREs promoted membrane fusion, different from the inhibited fusion for reconstituted neuronal SNAREs. The EPR structural analysis showed that none of the coiled-coil residues of yeast v-SNARE is buried in the hydrophobic layer of the membrane, making the entire coiled-coil motif accessible, again different from the deep insertion of the membrane-proximal region of neuronal v-SNARE into the bilayer. Importantly, yeast membrane fusion is constitutively active, while synaptic membrane fusion is regulated, consistent with the present results for two SNARE families. Thus, the v-SNARE-membrane interaction may be a major molecular determinant for regulated versus constitutive membrane fusion in cells.

Amino Acid Sequence↗
PubMed2004

Atomic force bio-analytics of polymerization and aggregation of phycoerythrin-conjugated immunoglobulin G molecules.

While bio-labeled immunoglobulin (IgG) or antibodies are extensively used in imaging studies and therapeutic modality, there have been no reports describing atomic force microscopy (AFM) micrographs of these labeled IgG molecules. Here, AFM studies of phycoerythrin (PE)-conjugated IgG were undertaken to examine whether PE conjugation induced conformational changes or molecular interaction, and subsequently resulted in an alteration in nano-structures of PE-conjugated IgG complex. Once immobilized on mica, single PE-conjugated IgG molecule exhibited globular shape with approximately 60 microns in diameter and 5 microns in height. PE-conjugated IgG were able to form monomers, spindle-like trimers, and hexamers that developed through an end-end connection of two trimers, after they were continuously immobilized on mica. Interestingly, these multimers could aggregate in different directions to form circular monolayers with a highly dense core of PE-conjugated IgG polymers. The formation of these well-organized polymers and aggregates of PE-conjugated IgG may be attributed to the PE conjugation as well as the air-liquid tension on subtract. These findings may help to understand the nano-structures of bio-labeled IgG or antibodies, and facilitate the potential use of PE-conjugated antibodies as markers or immunosensers for AFM bio-analytics of biomolecules in cells and membranes.

Affinity Labels↗
PubMed2004

Study in vitro and in vivo of nociceptin/orphanin FQ(1-13)NH2 analogues substituting N-Me-Gly for Gly2 or Gly3.

In the present study, two analogues containing N-Me-Gly (Sarcosine, Sar) were synthesized to further investigate the structural-activity relationships of orphanin FQ/nociceptin (OFQ/NC, NC). The replacement of Gly(2) or Gly(3) with Sar increased the flexibility and decreased the hydrophobicity of the N-terminal tetrapeptide. The activity of the analogues was investigated in a series of assays in vivo and in vitro. [Sar(2)]NC(1-13)NH(2) was found to (1) produce dose-dependent inhibition of the electrically induced contraction in MVD assay (pEC(50) = 6.14); (2) produce significant hyperalgesia effects in a dose-dependent manner when intracerebroventricularly (i.c.v.) injected in mice. The inhibitive effects of [Sar(2)]NC(1-13)NH(2) in MVD assay could be significantly antagonized by [Nphe(1)]NC(1-13)NH(2), and partially antagonized by naloxone; the hyperalgesic effect of [Sar(2)]NC(1-13)NH(2) could be significantly antagonized by naloxone, and partially antagonized by [Nphe(1)]NC(1-13)NH(2). On the contrary, [Sar(3)]NC(1-13)NH(2) showed no effects in these assays. All the findings suggest that the flexibility of the peptide bond between Phe(1) and Gly(2) and between Gly(2) and Gly(3) play an important role in NC-OP(4) receptor interaction, and the hydrophobicity of the N-terminal tetrapeptide showed no significant effect on this interaction. The present work also helps to provide a novel method to elucidate structural and conformational requirements of the opioid peptide-receptor interaction.

Amino Acid Substitution↗
PubMed2004

Glucosylceramide synthase activity and ceramide levels are modulated during cerebral ischemia after ischemic preconditioning.

After 24-hour middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats, brain ceramide level increased from baseline reached 595% (ischemic core) and 460% (perifocal/penumbral areas); brain glucosylceramide synthase (GCS) activities in these areas simultaneously decreased by 70% and 50%, respectively. Ten-minute MCAO preconditioning significantly attenuated 24-hour MCAO-induced ceramide accumulation by 40% to 60% in ischemic core and perifocal areas, and GCS activities improved by 60% to 70% in both areas. Thus, potentially toxic levels of brain ceramide induced by MCAO were attenuated to intermediate levels in preconditioned animals; brain GCS activity was relatively preserved. In ischemic tolerance, GCS appears to modulate otherwise high levels of brain ceramide.

Animals↗
PubMed2004

Clinical application of transarterial embolization for massive hemorrhage in the nasopharyngeal and maxillofacial regions.

OBJECTIVE: To study the effect and safety of transarterial embolization (TAE) in the management of massive hemorrhage in the nasopharyngeal and maxillofacial regions. METHODS: Forty-two cases of massive hemorrhage in the nasopharyngeal and maxillofacial regions were treated by TAE. Gelfoam particles, polyvinyl acohol particles, and metallic coil were used to for embolism of the external carotid artery, maxillary artery, facial artery, occipital artery, sphenopalatine artery and ascending pharyngeal artery respectively according to the angiographic findings and the region of hemorrhage sites. RESULTS: TAE was successfully performed in all the cases, and no recurrence or serious complications were observed in the 3 to 12-month follow-up. CONCLUSION: TAE is safe and effective in the treatment of massive hemorrhage in the nasopharyngeal and maxillofacial regions.

Adolescent↗
PubMed2004

[Role of radical vaginal trachelectomy and laparoscopic pelvic lymphadenectomy in treating early cervical carcinoma].

OBJECTIVE: To investigate the possibility and effect of radical vaginal trachelectomy and laparoscopic pelvic lymphadenectomy in treating women with early cervical cancers who desired to maintain fertility. METHODS: From August 2001 through May 2003, we performed vaginal radical trachelectomy with laparoscopic lymphadenectomy on 12 patients with biopsy-proven early stage cervical carcinomas. Subjects were selected for this treatment on the basis of favorable cervical tumors and a desire to maintain fertility. Pelvic lymphadenectomies were performed in all patients. Vaginal radical trachelectomy was performed immediately if lymph nodes were negative. RESULTS: Twelve women underwent this procedure. The median age was 27.6 years (range 24 - 31 years); 10 were nulligravid and 2 were multipara. Mean operative time was 142 min (115 - 178 min), with a mean blood loss of 180 ml (120 - 230 ml), and an average hospital stay of 6.7 days. There was no intra- or post-operative complication. With an average follow-up of 21.5 months, there have been no recurrences. One woman has become pregnant. CONCLUSIONS: Radical vaginal trachelectomy with laparoscopic pelvic lymphadenectomy permits preservation of fertility in selected patients. It is mini-invasive, and needs shorter recovery time.

Adult↗
PubMed2004

[18F-Fluorodeoxyglucose uptake in hepatocellular carcinoma on positron emission tomography correlates with alpha-fetoprotein].

OBJECTIVE: To investigate whether (18)F-fluorodexyglucose (FDG) uptake in the primary hepatocellular carcinoma (HCC) correlates with serum alpha-fetoprotein (AFP). METHODS: Forty-five patients with histologically confirmed HCC underwent whole-body (18)F-FDG PET examination. Standardized uptake value (SUV) and tumor-to-nontumor ratio of the SUV (SUVratio) were calculated, and the relationship between serum AFP and glucose metabolism in HCC was analyzed. RESULTS: Of the 45 cases, the primary tumor and metastatic lymph nodes were clearly displayed on PET images in 43 cases and the well-differentiated tumors were shown negative in the other 2 cases. A linear correlation of the AFP with SUV (r=0.426, P<0.05) and SUVratio (r=0.532, P<0.001) was noted. CONCLUSION: Serum AFP correlates significantly with both SUV and SUN ratio, indicating that AFP is involved in glucose metabolism and cell proliferation in HCC.

Carcinoma, Hepatocellular↗
PubMed2004

[Subunit of voltage-dependent calcium channels in the murine spiral ganglion cells].

OBJECTIVE: To investigate subunit type of voltage-dependent calcium channels in the spiral ganglion cells of the mouse. METHODS: The spiral ganglion cells were dissected from cochleae of neonatal mice and cultured for 24 h. Total RNA was extracted from cultured spiral ganglion cells. After reverse transcription, resulting cDNA was amplified by polymerase chain reaction (PCR) with primers targeted to nucleotide sequences corresponding to 7 different calcium channel subunits. The types of calcium channel subunits were identified by PCR analysis and nucleotide sequencing. RESULTS: Reverse transcription (RT)-PCR products representing subunit gene expression were strongly and consistently amplified for alpha1 D, alpha1 E, alpha2/delta, beta1 and beta3. Nucleotide sequencing confirmed the identity of mouse cochlear subunit cDNAs. CONCLUSIONS: alpha1D, alpha1E, alpha2/delta, beta1 and beta3 subunits are expressed in spiral ganglion cells. And the coexpression of alpha1D and alpha1 E demonstrate the presence of L-type and R-type calcium channels in mammalian spiral ganglion cells.

Animals↗