Biomedical subjects

Feng Wang

Publications and source records attributed to Feng Wang.

At least 109 records · Page 6Linked to original sources

PubMed2005

Understanding glycine conformation through molecular orbitals.

The four most stable C(s) conformers of glycine have been investigated using a variety of quantum-mechanical methods based on Hartree-Fock theory, density-functional theory (B3LYP and statistical average of orbital potential), and electron propagation (OVGF) treatments. Information obtained from these models were analyzed in coordinate and momentum spaces using dual space analysis to provide insight based on orbitals into the bonding mechanisms of glycine conformers, which are generated by rotation of C-O(H) (II), C-C (III), and C-N (IV) bonds from the global minimum structure (I). Wave functions generated from the B3LYP/TZVP model revealed that each rotation produced a unique set of fingerprint orbitals that correspond to a specific group of outer valence orbitals, generally of a' symmetry. Orbitals 14a', 13a', 12a', and 11a' are identified as the fingerprint orbitals for the C-O(H) (II) rotation, whereas fingerprint orbitals for the C-C (III) bond rotation are located as 16a' [highest occupied molecular orbital (HOMO)], 15a' [next highest molecular occupied molecular orbital (NHOMO)], 14a', and 12a' orbitals. Fingerprint orbitals for IV generated by the combined rotations around the C-C, C-O(H), and C-N bonds are found as 16a', 15a', 14a', 13a', and 11a', as well as in orbitals 2a" and 1a". Orbital 14a' is identified as the fingerprint orbital for all three conformational processes, as it is the only orbital in the outer valence region which is significantly affected by the conformational processes regardless rotation of which bond. Binding energies, molecular geometries, and other molecular properties such as dipole moments calculated based on the specified treatments agree well with available experimental measurements and with previous theoretical calculation.

Electrons↗

PubMed2005

A strategy for single supersaturated droplet analysis: confocal Raman investigations on the complicated hygroscopic properties of individual MgSO4 droplets on the quartz substrate.

We report a new strategy for single supersaturated droplet analysis, i.e., the complicated hygroscopic properties of MgSO4 aerosols under supersaturated state were studied through the micro-Raman observation on an individual MgSO4 droplet deposited on a quartz substrate in a relative-humidity-controlled chamber. Upon reduction of the ambient relative humidity (RH), MgSO4 droplets with tiny volume lost water but did not effloresce. Thus, a detailed spectral evolution of the symmetric stretching vibration band (v1-SO4(2-)) from free ions (at approximately 983 cm(-1)) to monodentate (approximately 995 cm(-1)) and then to bidentate contact ion pairs (CIPs) or more complex chain-structural compositions (approximately 1021 cm(-1)) was observed with the high signal-to-noise (S/N) confocal Raman spectra of the droplet with a diameter of approximately 80 microns. Such a transition process could be well-described by the changes of relative intensity at 983, 995, and 1021 cm(-1). Four steps, i.e., concentrated step, monodentate CIPs step, bidentate CIPs step, and gel step, were roughly observed in the dehumidifying-humidifying cycle according to the intensity ratios of I995/I983 and I1021/I983. Even though the area ratio of the O-H stretching band of water molecules to the v1-SO4(2-) band seemed reversible in the dehumidifying and humidifying processes, the intensity ratios of I995/I983 and I1021/I983 showed a hysteresis in the decomposition of CIPs in the humidifying process with the RH < 40%. The O-H stretching envelope of the MgSO4 droplet was also observed to be sensitive to the structural changes of the hydrogen bonding of water molecules in the four steps. The intensity ratio of Raman scattering for the components with strong hydrogen bonds to those with weak ones, i.e., I3224/I3431, was used to understand the effects of CIPs on the water structures of the first hydration layer of Mg2+. Good consistency on the hysteresis in the humidifying process was also observed from the ratio of I3224/I3431 changing with RH.

Journal Article↗

PubMed2005

Effect of gemfibrozil on the pharmacokinetics of pioglitazone.

OBJECTIVE: Our objective was to study the effects of gemfibrozil on the pharmacokinetics of pioglitazone and the active compounds, which are all the substrates of CYP2C8 and CYP3A4. METHODS: In a randomized, two-phase crossover study, 10 healthy volunteers were pretreated for 2 days with either 600 mg oral gemfibrozil or placebo twice daily. On day 3, they received a single dose of 600 mg gemfibrozil or placebo, and 1 h later they received a single oral dose of 30 mg pioglitazone. Plasma concentrations of pioglitazone and both active metabolites M-III and M-IV were measured for up to 120 h. RESULTS: Gemfibrozil raised the mean total area under the concentration-time curve (AUC) of parent pioglitazone 3.4-fold (P<0.001). No statistically significant changes were seen in the total AUC of M-III or M-IV after gemfibrozil pretreatment. Gemfibrozil reduced the M-III/pioglitazone and M-IV/pioglitazone AUC(0-infinity) ratio by 71% (P<0.001) and 65%(P<0.001), strikingly prolonging their t((1/2)). CONCLUSION: Gemfibrozil greatly increased the plasma concentration of parent pioglitazone and also inhibited the further metabolism of M-III and M-IV. Careful blood glucose monitoring and dosage adjustments are suggested during coadministration of pioglitazone and gemfibrozil.

Adult↗

PubMed2005

Structural study of the self-assembled fullerene carboxylates: monoadducts versus bisadducts.

Laser light scattering and transmission electronic microscopy have been used to study the self-assembled structures of mono- and bisadducts of fullerene carboxylic acids in tetrahydrofuran (THF) and their sodium salts in aqueous solutions, respectively. In THF, the self-association of monoadducts of fullerene carboxylic acid (MFCA) produces large but narrowly distributed particles with R(h) approximately 145 nm. The self-aggregates from the bisadducts of fullerene carboxylic acid (BFCA) in THF are relatively small in size (R(h) approximately 80 nm) due to the better solubility. After the ionization of carboxylic acid groups on the C(60) cage in dilute NaOH solutions, these aggregates dissolved and reorganized. The self-assembly of the monoadducts of sodium carboxylate fullerenes (MSCF) produces small solid spherical particles with R(h) approximately 32 nm. The ratio of R(g)/R(h) approximately 0.83 indicates that the particles have a nearly uniform density. The increase in concentrations leads to strong interparticle associations to form rodlike and irregularly shaped large aggregates. In contrast, the self-assembly of bisadducts of sodium carboxylate fullerenes (BSCF) results in hollow shells with mainly two different size scales of R(h) approximately 23 nm and R(h) approximately 104 nm. At high concentrations, the hollow shells associate and melt together to generate three-dimensional networks.

Acids↗

PubMed2005

Extracting subnanometer single shells from ultralong multiwalled carbon nanotubes.

We report a simple but powerful method for engineering multi-walled carbon nanotubes (MWNTs) by using manipulation by an atomic-force microscope. The successive shell-by-shell extraction process of ultralong MWNTs allows the exposure of the innermost single-walled carbon nanotubes (SWNTs), which have diameters as small as approximately 0.4 nm. The inner-shell extraction process changes the electrical characteristics of the MWNTs. Whereas the outer hollowed-out nanotubes show either metallic or semiconducting character, the innermost SWNTs of small diameter exhibit predominantly metallic transport properties.

Journal Article↗

PubMed2005

Coexistence of 1,3-butadiene conformers in ionization energies and Dyson orbitals.

The minimum-energy structures on the torsional potential-energy surface of 1,3-butadiene have been studied quantum mechanically using a range of models including ab initio Hartree-Fock and second-order Møller-Plesset theories, outer valence Green's function, and density-functional theory with a hybrid functional and statistical average orbital potential model in order to understand the binding-energy (ionization energy) spectra and orbital cross sections observed by experiments. The unique full geometry optimization process locates the s-trans-1,3-butadiene as the global minimum structure and the s-gauche-1,3-butadiene as the local minimum structure. The latter possesses the dihedral angle of the central carbon bond of 32.81 degrees in agreement with the range of 30 degrees-41 degrees obtained by other theoretical models. Ionization energies in the outer valence space of the conformer pair have been obtained using Hartree-Fock, outer valence Green's function, and density-functional (statistical average orbital potentials) models, respectively. The Hartree-Fock results indicate that electron correlation (and orbital relaxation) effects become more significant towards the inner shell. The spectroscopic pole strengths calculated in the Green's function model are in the range of 0.85-0.91, suggesting that the independent particle picture is a good approximation in the present study. The binding energies from the density-functional (statisticaly averaged orbital potential) model are in good agreement with photoelectron spectroscopy, and the simulated Dyson orbitals in momentum space approximated by the density-functional orbitals using plane-wave impulse approximation agree well with those from experimental electron momentum spectroscopy. The coexistence of the conformer pair under the experimental conditions is supported by the approximated experimental binding-energy spectra due to the split conformer orbital energies, as well as the orbital momentum distributions of the mixed conformer pair observed in the orbital cross sections of electron momentum spectroscopy.

Butadienes↗

PubMed2005

Host range mutants of Minute Virus of Mice with a single VP2 amino acid change require additional silent mutations that regulate NS2 accumulation.

Two host range switch mutants of the immunosuppressive strain of parvovirus Minute Virus of Mice (MVMi) were isolated from plaques on A9 fibroblasts. Both carried a single coding mutation at residue D399 in VP2, to alanine and glycine in hr105 and hr107, respectively, and a second, non-coding, guanine-to-adenine change at nucleotide 1970 in hr105 and 1967 in hr107. These mutations were recreated in a wild type MVMi infectious plasmid clone, both alone and as pairs, in either the original or switched combinations. All single mutants failed to replicate productively in fibroblasts, but the two pairs of changes were functionally equivalent. Single D399 mutations allowed the viruses to initiate infection in fibroblasts, but NS2 expression was severely restricted and correlated with poor accumulation and release of progeny virus. Mutations at 1967 or 1970 enhanced NS2 accumulation, and allowed efficient progeny production and release. Conversely, the D399 mutations destroyed the viruses' ability to infect EL4 lymphocytes. In all productive EL4 infections, NS2 was expressed at high ratios even in the absence of upstream mutations, and progeny accumulation was efficient. However, EL4 cells lack a mechanism for early progeny release, potentially explaining why virus amplification in these cells is slow.

Amino Acid Sequence↗

PubMed2005

Characterization and crystallization of human DPY-30-like protein, an essential component of dosage compensation complex.

Human DPY-30-like is a homolog of C. elegans DPY-30. DPY-30 is an essential component of dosage compensation machinery and loss of dpy-30 activity results in XX-specific lethality. In XO animals, DPY-30 is required for developmental processes other than dosage compensation. In yeast, the homolog of DPY-30, Saf19p, functions as a member of histone 3 lysine 4 methylation complex, which is the key part of epigenetic developmental control. In this report, human DPY-30-like protein was overexpressed and purified with the goal of structure determination. It was crystallized at 291 K in hanging drops by the vapour diffusion technique from a precipitant solution consisting of (NH4)2SO4 (1.5-2.0 M), Tris-HCl (0.1 M, pH 8.0). The crystal diffracted to 2.7 A resolution at 100 K in-house and belongs to the space group P4(1)2(1)2 or P4(3)2(1)2 with unit-cell parameters of a=b=74.5 A, c=87.0 A, alpha=beta=gamma=90.0 degrees. The asymmetric unit contains two molecules with 49% solvent content. We also analyzed its biochemical and biophysical characterizations. Efforts are now under way to determine the molecular structure of the DPY-30-like. These studies will open a new avenue towards the structure-based functional analysis of human DPY-30-like and dosage compensation machinery.

Animals↗

PubMed2005

Acute pancreatitis as an initial symptom of systemic lupus erythematosus: a case report and review of the literature.

Acute pancreatitis as an initial symptom of systemic lupus erythematosus (SLE) is rare. We present a report of a 46-year-old female patient who had fever, abdominal pain and vomiting, elevated pancreatic enzyme levels, hypocalcemia, hypoxemia, and various other laboratory abnormalities. She was first diagnosed with acute severe pancreatitis and then with SLE after further investigations. After a 2-mo treatment with somatostatin, the patient recovered.

Acute Disease↗

PubMed2005

ICAT-MS-MS time course analysis of atrophying mouse skeletal muscle cytosolic subproteome.

Skeletal muscle atrophy is a process in which protein degradation exceeds protein synthesis, resulting in a decrease of the muscle's physiological cross-sectional area and mass, and is often a serious consequence of numerous health problems. We used the isotope-coded affinity tag (ICAT) labelling approach and MS-MS to protein profile cytosolic subcellular fractions from mouse tibialis anterior skeletal muscle undergoing 0, 4, 8, or 16 days of immobilisation-induced atrophy. For the validation of peptide and protein identifications statistical algorithms were applied to the sequence database search results in order to obtain consistent sensitivity/error rates for protein and peptide identifications at each immobilisation time point. In this study, we identified and quantified a large number of mouse skeletal muscle proteins. At a protein probability (P) of P> or = 0.9 (corresponding to a false positive error rate of less than 1%) 807 proteins were identified (231, 226, 217 for 4, 8, 16 days of immobilisation and 133 for the control sample, respectively), from which 51 displayed altered protein abundance with atrophy. Due to randomness of data acquisition, a full time course could be generated only for 62 proteins, most of which displayed unchanged protein abundance. In spite of this, useful information about dataset characteristics and underlying biological processes could be obtained through gene over-representation analysis. 20 gene categories-mainly but not exclusively encoded by the subset of overlapping proteins--were consistently found to be significantly (p < 0.05) over-represented in all 4 sub-datasets.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Crystal structure of pyridoxal kinase in complex with roscovitine and derivatives.

Pyridoxal kinase (PDXK) catalyzes the phosphorylation of pyridoxal, pyridoxamine, and pyridoxine in the presence of ATP and Zn2+. This constitutes an essential step in the synthesis of pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, a cofactor for over 140 enzymes. (R)-Roscovitine (CYC202, Seliciclib) is a relatively selective inhibitor of cyclin-dependent kinases (CDKs), currently evaluated for the treatment of cancers, neurodegenerative disorders, renal diseases, and several viral infections. Affinity chromatography investigations have shown that (R)-roscovitine also interacts with PDXK. To understand this interaction, we determined the crystal structure of PDXK in complex with (R)-roscovitine, N6-methyl-(R)-roscovitine, and O6-(R)-roscovitine, the two latter derivatives being designed to bind to PDXK but not to CDKs. Structural analysis revealed that these three roscovitines bind similarly in the pyridoxal-binding site of PDXK rather than in the anticipated ATP-binding site. The pyridoxal pocket has thus an unexpected ability to accommodate molecules different from and larger than pyridoxal. This work provides detailed structural information on the interactions between PDXK and roscovitine and analogs. It could also aid in the design of roscovitine derivatives displaying strict selectivity for either PDXK or CDKs.

Animals↗

PubMed2005

Crystal structure of earthworm fibrinolytic enzyme component B: a novel, glycosylated two-chained trypsin.

The earthworm fibrinolytic enzyme (EFE), belonging to a group of serine proteases with strong fibrinolytic activity, has been used in a mixture as an oral drug for prevention and treatment of thrombosis in East Asia. The EFE component b (EFE-b) is one of seven EFE components from Eisenia fetida, and among them it has nearly the highest fibrinolytic activity. Here, we report its crystal structure at a resolution of 2.06A. The structural analysis shows that EFE-b should be classified as a trypsin from earthworm. However, it is distinct from other trypsins. It is a two-chained protease with an N-terminal, pyroglutamated light chain and an N-glycosylated heavy chain. Furthermore, the heavy chain contains a novel structural motif, an eight-membered ring resulting from a disulfide bridge between two neighboring cysteine residues, and a cis peptide bond exists between these two cysteine residues. The crystal structure of EFE-b provides the structural basis for its high level of stability and reveals its complicated post-translational modifications in earthworm. This structure is the first reported for a glycosylated two-chained trypsin, which may provide useful clues to explain the origin and evolution of the chymotrypsin family.

Amino Acid Sequence↗

PubMed2005

The optical resonances in carbon nanotubes arise from excitons.

Optical transitions in carbon nanotubes are of central importance for nanotube characterization. They also provide insight into the nature of excited states in these one-dimensional systems. Recent work suggests that light absorption produces strongly correlated electron-hole states in the form of excitons. However, it has been difficult to rule out a simpler model in which resonances arise from the van Hove singularities associated with the one-dimensional band [corrected] structure of the nanotubes. Here, two-photon excitation spectroscopy bolsters the exciton picture. We found binding energies of approximately 400 millielectron volts for semiconducting single-walled nanotubes with 0.8-nanometer diameters. The results demonstrate the dominant role of many-body interactions in the excited-state properties of one-dimensional systems.

Journal Article↗

PubMed2005

A linear-scaling self-consistent generalization of the multistate empirical valence bond method for multiple excess protons in aqueous systems.

An extension to the multistate empirical valence bond (MS-EVB) method is presented in this paper that is capable of treating multiple excess protons within the context of molecular-dynamics simulation. The computational cost of the method scales linearly with respect to the number of excess protons. Calculations for a 0.44 M HCl systems are carried out to illustrate the multiproton extension of the MS-EVB method. A significant decrease in the Eigen-type H(9)O(4)(+) cation is observed in the contact ion-pair configuration formed between Cl(-) and hydronium ions.

Journal Article↗

PubMed2005

Biodiversity analysis of microbial community in the chem-bioflocculation treatment process.

Total DNA was directly extracted from environmental samples and amplified with polymerase chain reaction (PCR) technique. The PCR products were fingerprinted via denaturing gradient gel electrophoresis (DGGE). Significant differences were observed in the microbial community structures between traditional treatment process and chem-bioflocculation process. The microbial community structure shift at different sampling locations in chem-bioflocculation process and on two typical operational conditions was studied. 16S rDNA V3 regions of some dominant species were sequenced and the species were identified. The microbial communities were stable in both the chem-bioflocculation process and the activated sludge process under various experimental conditions presented in this work. The attached growth treatment process was less stable when operational conditions changed.

Bacteria↗

PubMed2005

Excess proton solvation and delocalization in a hydrophilic pocket of the proton conducting polymer membrane nafion.

Solvation properties of the hydrated excess proton are studied in a hydrophilic pocket of Nafion 117 through a series of molecular dynamics simulations. The multistate empirical valence bond (MS-EVB) methodology, which enables the delocalization of the excess proton through the Grotthuss hopping mechanism, was employed for one of the excess protons in the simulation cell. Simulations were performed such that "classical" nondissociable hydronium cations and a single excess proton treated with the MS-EVB methodology were at a concentration ratio of 39:1. Two degrees of hydration of the Nafion polymer electrolyte membrane were simulated, each displaying the same marked difference between the solvation structures of the classical versus MS-EVB treated (Grotthuss shuttling) excess proton species. These differences are attributed to the solvent dynamics needed to transfer the cation between the solvent separated and contact pair positions about the sulfonic acid counterion. The results demonstrate that it is generally impossible to describe the low pH conditions in the hydrophilic domains of Nafion without the explicit treatment of Grotthuss delocalization in the underlying molecular dynamics model for the excess protons.

Fluorocarbon Polymers↗

PubMed2005

Reflective-type configuration for nearly phase-matching cerenkov second-harmonic generation in a nonlinear-optical polymer waveguide.

A new technique for achieving efficient Cerenkov-type second-harmonic generation (SHG) in a nonlinear-optical (NLO) polymer waveguide is presented. The configuration, which can prevent the losses of light caused by relatively long-distance propagation and the multiple reflections that appear in the conventional Cerenkov technique, exhibits ease of fabrication and compactness. We experimentally observed a conversion efficiency of 1.6% W(-1) cm(-1), which to our knowledge is the highest value reported for Cerenkov SHG in polymer, by tuning both the thickness and the refractive index of the polymer film close to phase matching between a guided fundamental wave and a guided harmonic wave. The experimental results agreed well with the theoretical prediction.

Journal Article↗

PubMed2005

L-arginine administration ameliorates serum and pulmonary cytokine response after gut ischemia-reperfusion in immature rats.

AIM: Small intestinal ischemia-reperfusion (IR) has been demonstrated to result in both local mucosal injury and systemic injuries. The exact role of nitric oxide (NO) in intestinal IR is unclear. We propose that NO and some other cytokines change in the reperfusion period and these changes are associated with lung injury. The aim of this study was to determine the effect of supplementing NO substrate, L-arginine (L-arg), on serum and pulmonary cytokine production during small intestinal IR in immature rats. METHODS: Immature rats underwent 60 min. of superior mesenteric artery occlusion followed by 90 min of reperfusion. L-arg (250 mg/kg) was given intravenously to the experimental group (IR+L-arg) which received L-arg after 45 min of intestinal ischemia. Serum and lung endothelin-1 (ET-1), NO, malondialdehyde (MDA), and tumor necrosis factor alpha (TNFalpha) were measured. Sham operation (SHAM) and intestinal IR (IR) groups were performed as control. The lavage fluid of the lung was collected by bronchoalveolar lavage (BAL) and white blood cells and polymorphonuclear cells (PMNs) were immediately counted to identify lung damage. RESULTS: When L-arg was given during small intestinal IR, serum NO concentration increased significantly in IR+L-arg group (162.17+/-42.93 micromol/L) when compared with IR group (87.57+/-23.17 micromol/L, t = 3.190, P = 0.008<0.01). Serum MDA reduced significantly in IR+L-arg group (8.93+/-1.50 nmol/L) when compared with SHAM (23.78+/-7.81 nmol/L, t = 3.243, P = 0.007<0.01) and IR (25.54+/-9.32 nmol/L, t = 3.421, P = 0.006<0.01). ET-1 level in lung tissues was significantly lower in IR+L-arg group (13.81+/-7.84 pg/mL) than that in SHAM (35.52+/-10.82 pg/mL, t = 2.571, P = 0.03<0.05) and IR (50.83+/-22.05 pg/mL, t = 3.025, P = 0.009<0.01) groups. MDA contents in lung tissues were significantly lower in IR+L-arg group (10.73+/-1.99 nmol/L) than in SHAM (16.62+/-2.28 nmol/L, t = 3.280, P = 0.007<0.01) and IR (21.90+/-4.82 nmol/L, t = 3.322, P = 0.007<0.01) groups. Serum and lung TNFalpha concentrations were not significantly different in three groups. NO contents in lung homogenates and white blood cell counts in BAL had no significant difference in three groups; but the percentage of PMNs in BAL was 13.50+/-8.92, 33.20+/-16.59, and 22.50+/-6.09 in SHAM, IR, and IR+L-arg groups, respectively. CONCLUSION: Small intestinal IR induced increases of pulmonary neutrophil infiltration in immature rats. Neutrophil infiltration in lung tissues was reduced by L-arg administration but remained higher than in SHAM group. L-arg administration during intestinal IR enhances serum NO production, reduces serum MDA and lung ET-1 and MDA levels, resulting in the improvement of systemic endothelial function. L-arg supplementation before reperfusion may act as a useful clinical adjunct in the management of intestinal IR, thus preventing the development of adult respiratory distress syndrome, even multiple organ dysfunction syndrome (MODS).

Age Factors↗