Biomedical subjects

Guang Wu

Publications and source records attributed to Guang Wu.

At least 19 recordsLinked to original sources

PubMed2006

Gamma-aminobutyric acid secreted from islet beta-cells modulates exocrine secretion in rat pancreas.

AIM: To investigate the role of endogenous gamma-amino-butyric acid (GABA) in pancreatic exocrine secretion. METHODS: The isolated, vascularly perfused rat pancreas was employed in this study to eliminate the possible influences of extrinsic nerves and hormones. Cholecystokinin (CCK; 10 pmol/L) was intra-arterially given to stimulate exocrine secretion of the pancreas. RESULTS: Glutamine, a major precursor of GABA, which was given intra-arterially at concentrations of 1, 4 and 10 mmol/L, dose-dependently elevated the CCK-stimulated secretions of fluid and amylase in the normal pancreas. Bicuculline (10 micromol/L), a GABA(A) receptor antagonist, blocked the enhancing effect of glutamine (4 mmol/L) on the CCK-stimulated exocrine secretions. Glutamine, at concentrations of 1, 4 and 10 mmol/L, dose-dependently increased the GABA concentration in portal effluent of the normal pancreas. The effects of glutamine on the CCK-stimulated exocrine secretion as well as the GABA secretion were markedly reduced in the streptozotocin-treated pancreas. CONCLUSION: GABA could be secreted from beta-cells into the islet-acinar portal system after administration of glutainine, and could enhance the CCK-stimulated exocrine secretion through GABA(A) receptors. Thus, GABA in islet beta-cells is a hormone modulating pancreatic exocrine secretion.

Animals↗

PubMed2006

Multigate single-photon detection and timing discrimination with an InGaAs/lnP avalanche photodiode.

Multigate detection of single photons at 1550 nm is achieved by using capacitor-balanced InGaAs/InP avalanche photodiodes, with which we experimentally demonstrate the efficient discrimination of single-photon timing by counting single-photon clicks and the corresponding afterpulses within the multiple gates. Results show that the technique of multigate detection is a practical method for the single-photon timing information process.

Journal Article↗

PubMed2006

Substituent effects on nitrosyl iron corrole complexes Fe(Ar3C)(NO).

A series of nitrosyl tris(5,10,15-aryl)corrolate complexes of iron(III) Fe(Ar3C)(NO) with different substituents on the aryl groups have been prepared, and certain spectroscopic and reaction properties were compared. The cyclic voltammetric analysis of the various Fe(Ar3C)(NO) complexes demonstrated that both the one-electron oxidation and one-electron reduction potentials respond in systematic and nearly identical trends relative to the electron-donor properties of the substituents. A similar pattern was seen in the nitrosyl stretching frequency, nu(NO), which modestly decreased with the stronger donor substituents. Flash photolysis of Fe(Ar3C)(NO) solutions in toluene leads to NO dissociation followed by rapid [NO]-dependent decay of the transients formed (presumably Fe(Ar3C)) to regenerate the original spectra. As was seen in an earlier flash photolysis study of Fe(TNPC)(NO) (TNPC3- = 5,10,15-tris(4-nitro-phenyl)corrolate; Joseph, C.; Ford, P. C. J. Am. Chem. Soc. 2005, 127, 6737-6743), the second-order rate constants, k(NO), are all much faster ((1-9) x 10(8) M(-1) s(-1) at 298 K) than those for analogous iron(III) complexes of porphyrins. However, on a more microscopic level there is no obvious pattern in these rates with respect to the donor properties of the aryl ring substituents. The high reactivity of the ferric triarylcorrolates with NO data is interpreted in terms of the strongly electron-donating character of the Ar3C3- ligand and the quartet electronic configuration of the Fe(Ar3C) intermediate.

Electrochemistry↗

PubMed2006

Photochemical and time resolved spectroscopic studies of intermediates relevant to iridium-catalyzed methanol carbonylation: photoinduced CO migratory insertion.

Photoreaction, time-resolved infrared (TRIR), and DFT studies were utilized to probe transformations between iridium complexes with possible relevance to the mechanisms of the iridium/iodide-catalyzed methanol carbonylation to acetic acid. Solution-phase continuous and laser flash photolysis of the tetraphenylarsonium salt of the fac-[CH3Ir(CO)2I3]- anion (1a) under excess carbon monoxide resulted in migratory insertion to give the acyl complex ion mer,trans-[Ir(C(O)CH3)(CO)2I3]- (2a). The latter was isolated as its AsPh4+ salt, and its X-ray crystal structure was determined. TRIR spectra indicate that several transients are generated upon flash photolysis of 1a. The principal photoreaction is CO dissociation, and this is proposed to generate the isomeric complexes fac-[CH3Ir(CO)(Sol)I3]- (I(CO)(fac), Sol = solvent) and mer,trans-[CH3Ir(CO)(Sol)I3]- (I(CO)(mer)). I(CO)(fac) reacts with CO to regenerate 1a with a second-order rate constant (k(CO)) approximately 2.5 x 10(7) M(-1) s(-1) in ambient dichloroethane, while I(CO)(mer) is the apparent precursor to 2a. Kinetics studies indicate the photoinduced formation of a third intermediate (I(M)), hypothesized to be the anionic acyl complex fac-[Ir(C(O)CH3)(CO)(Sol)I3]-. In the absence of added CO, these intermediates undergo dimerization to form a mixture of isomers with the apparent formula [Ir(C(O)CH3)(CO)I3]2(2-). One of these dimers was isolated as the AsPh4+ salt, and the crystal structure was determined. Addition of excess pyridine to a solution of the dimers gave the neutral complex mer,trans-[Ir(C(O)CH3)(CO)(py)2I2], which was characterized by FTIR, NMR, and X-ray crystallography. These transformations, especially the unprecedented photoinduced CO insertion reaction, are discussed and interpreted in terms of the factors favoring migratory insertion dynamics.

Journal Article↗

PubMed2006

Mutation trend of hemagglutinin of influenza A virus: a review from a computational mutation viewpoint.

Since 1999 we have developed two computational mutation approaches to analyze the protein primary structure whose methodology and implications were reviewed in 2002. Our first approach is the calculation of predictable and unpredictable portions of amino-acid pairs in a protein, and the second is the calculation of amino-acid distribution rank in a protein. Both approaches provide quantitative measures to present a protein, which we have used to study a number of proteins with numerous mutations such as p53 proteins. More recently, we focussed our efforts on analyzing the proteins mutating frequently over time such as hemagglutinins of influenza A viruses. In this review we summarise our findings and their implications for hemagglutinin mutations in combination with some newly available data. Our approaches throw light on the true nature of genetic heterogeneity of influenza virus hemagglutinins; that is, the protein variability is highly relevant to its amino-acid construction. Using these approaches, we can monitor new mutations from influenza virus hemagglutinins and may predict their mutations in the future.

Amino Acids↗

PubMed2006

Pattern of positions sensitive to mutations in human haemoglobin alpha-chain.

In this study, we used the distribution rank, which has been developed by us over the past several years, to quantify 134 mutations in the human hemoglobin alpha-chain in order to gain an insight into the general pattern in mutations. The results suggest that the pattern presented by distribution rank can approximately estimate the positions that are sensitive to mutations in human hemoglobin alpha-chain.

Hemoglobins↗

PubMed2006

Timing of mutation in influenza A virus hemagglutinins by means of amino-acid distribution rank and fast Fourier transform.

In this study, we calculated the amino-acid distribution rank of 1201 hemagglutinins from influenza A viruses dated from 1918 to 2004 in order to compare them with respect to subtypes, species and years. After noticing fluctuations in distribution rank along the time course, we used the fast Fourier transform to determine the mutation periodicity of the hemagglutinins. Then we estimated our position at the current cycle of hemagglutinin evolutionary process to determine how many years remain before the next possible outbreak of influenza and bird flu. Finally, we used the trend channel to outlook the future of hemagglutinins for the next half a century. As our study covers almost all the full-length amino-acid sequences of hemagglutinins from various influenza A viruses, the conclusions will be valid for years until the number of hemagglutinins in Protein Databank is significantly increased.

Amino Acids↗

PubMed2006

Fate of influenza A virus proteins.

In this review we summarize the current state, history, future, mutation tendency and species susceptibility of influenza A virus proteins based on our probabilistic analyses on amino acid pairs, and compare the current state of influenza A virus proteins with that of proteins which we have studied in the past.

Amino Acids↗

PubMed2006

Determination of mutation trend in hemagglutinins by means of translation probability between RNA codons and mutated amino acids.

In this study, we used the 183 translation probabilities between RNA codons and mutated amino acids to construct the theoretical distributions of mutated amino acids in hemagglutinins of influenza A virus. We then compared the actual distributions of mutated amino acids from 953 hemagglutinins with their theoretical ones. The results demonstrated that mutated amino acids generally follow the direction of the theoretical distributions governed by RNA codons. This, in turn, highlights the mutation trend of amino acids in hemagglutinins and provides a method for estimating possible mutations in a protein according to its theoretical distributions of mutated amino acids.

Algorithms↗

PubMed2006

Prediction of mutations in H5N1 hemagglutinins from influenza A virus.

In this study, we determine the mutation relation among 333 H5N1 hemagglutinins of influenza A viruses according to their amino acid and RNA codon sequences. Then, we calculate seven probabilistic numbers, which have been developed by us since 1999, for each amino acid in these hemagglutinins. With the seven numeric numbers as independents and the probability of occurrence of mutation at each hemagglutinin position as dependent, we use the logistic regression to model 967 missense point mutations from 333 hemagglutinins to get the population estimates. Thereafter, we predict the future mutation positions in H5N1 hemagglutinin. Finally, we use the translation probabilities between RNA codons and mutated amino acids to predict the would-be-mutated amino acids in H5N1 hemagglutinin.

Hemagglutinin Glycoproteins, Influenza Virus↗

PubMed2005

Chelate bis(imino)pyridine cobalt complexes: synthesis, reduction, and evidence for the generation of ethene polymerization catalysts by Li+ cation activation.

Treatment of the bis(iminobenzyl)pyridine chelate Schiff-base ligand 8 (ligPh) with FeCl2 or CoCl2 yielded the corresponding (ligPh)MCl2 complexes 9 (Fe) and 10 (Co). The reaction of 10 with methyllithium or "butadiene-magnesium" resulted in reduction to give the corresponding (ligPh)Co(I)Cl product 11. Similarly, the bis(aryliminoethyl)pyridine ligand (ligMe) was reacted with CoCl2 to yield (ligMe)CoCl2 (12). Reduction to (ligMe)CoCl (13) was effected by treatment with "butadiene-magnesium". Complex 13 reacted with Li[B(C6F5)4] in toluene followed by treatment with pyridine to yield [(ligMe)Co+-pyridine] (15). The reaction of the Co(II) complexes 10 or 12 with ca. 3 molar equiv of methyllithium gave the cobalt(I) complexes 16 and 17, respectively. Treatment of the (ligMe)CoCH3 (17) with Li[B(C6F5)4] gave a low activity ethene polymerization catalyst. Likewise, complex 16 produced polyethylene (activity = 33 g(PE) mmol(cat)(-1) h(-1) bar(-1) at room temperature) upon treatment with a stoichiometric amount of Li[B(C6F5)4]. A third ligand (lig(OMe)) was synthesized featuring methoxy groups in the ligand backbone (22). Coordination to FeCl2 and CoCl2 yielded the desired compounds 23 and 24. Reaction with MeLi gave (ligOMe)CoMe (25/26). Treatment of 25/26 with excess B(C6F5)3 gave the eta6-arene cation complex 27, where one Co-N linkage was cleaved. Activation of 25/26 with Li[B(C6F5)4] again gave a catalytically active species.

Catalysis↗

PubMed2005

Determination of mutation trend in proteins by means of translation probability between RNA codes and mutated amino acids.

In this study, we estimate the translation probability to amino acid from RNA codon. With the determined 183 translation probabilities and amino-acid composition of eight highly mutated proteins, we construct the theoretical distributions of mutated amino acids in these proteins and then compare them with their actual distributions affected by mutations. Thereafter we trace the pattern of translation probabilities from RNA codons to mutated amino acids of 1053 point missense mutations. Finally, we statistically conclude that the natural mutation trend goes along the theoretical translation probability.

Amino Acid Sequence↗

PubMed2005

Mutation features of 215 polymerase proteins from different influenza A viruses.

BACKGROUND: The aim of the present study is to analyze 215 polymerase proteins from different influenza A viruses in order to gain insight into their mutation features. MATERIAL/METHODS: Using our computational mutation models to calculate differences between actual and predicted frequencies, the amino-acid pairs in a protein can be classified into randomly predictable or unpredictable portions. By comparing the percentages of both portions and the magnitudes of the differences among different proteins, we can determine which proteins have larger unpredictable portions and larger differences, and these proteins would be more sensitive to mutations according to our previous studies. RESULTS: There are five features regarding polymerase acidic protein (PA), polymerase basic protein 1 (PB1), and polymerase basic protein 2 (PB2): (i) the PA proteins are more sensitive to mutations; (ii) the PA and PB1 proteins have experienced more mutations in the past; (iii) the PA and PB2 proteins have a larger potential for future mutations; (iv) the impact of mutations on polymerase proteins is to minimize the difference between the actual and predicted frequencies of amino-acid pairs, and (v) the avian PA proteins are more vulnerable to mutations than the human ones. CONCLUSIONS: This study provides probabilistic evidence on the current state, history, and future of different polymerase proteins from influenza A viruses towards mutation. Our analyses also highlight the mutation tendency over time and the species susceptibility.

Influenza A virus↗

PubMed2005

Timing of mutation in hemagglutinins from influenza A virus by means of unpredictable portion of amino-acid pair and fast Fourier transform.

In this study, we calculate the unpredictable portion of amino-acid pairs, which has been developed by us over the last several years, of 1201 hemagglutinins from influenza A viruses dated from 1918 to 2004 in order to compare them with respect to subtypes, species, and years. After noticing the fluctuations of unpredictable portion along the time course, we use the fast Fourier transform to find the mutation periodicity of hemagglutinins. Then we estimate our position at the current cycle of hemagglutinin evolutionary process to determine how many years remain before the next outbreak of influenza and bird flu. Finally, we use the trend line and channel to outlook the hemagglutinins for the next half a century. As our study covers almost all the full-length amino-acid sequences of hemagglutinins from various influenza A viruses, the conclusion will be valid for years until the number of hemagglutinins in protein databank will be significantly increased.

Amino Acid Substitution↗

PubMed2005

Prediction of mutation trend in hemagglutinins and neuraminidases from influenza A viruses by means of cross-impact analysis.

In this study, we use the cross-impact analysis to define the relationship among impact, mutation, and outbreak of bird flu. Then we use the distribution rank, which is developed by us over last several years, to quantify the mutations from amino acid sequences of 134 hemagglutinins and 97 neuraminidases. With the help of Bayesian equation, we calculate the probability of occurring of mutation in H5, H6, and H9 hemagglutinins, and N1 and N2 neuraminidases. Finally, we estimate the probability of occurring of mutation with different intensities of an impact. Although we have no means to predict an impact, which is severe enough to lead to the mutations in hemagglutinins and neuraminidases resulting in the outbreak of bird flu, we can in principle monitor the changes in distribution rank along the time course, and predict the trend of mutations, even to predict the degree of outbreak of bird flu.

Amino Acids↗

PubMed2005

Amino acid pairs susceptible to variants in human protein C precursor.

In this study, we analyze the amino acid pairs in human protein C precursor to determine which amino acid pairs are more susceptible to 71 variants from missense mutant human protein C precursor. The results show 85.92% of 71 variants occur at randomly unpredictable amino acid pairs accounting for 61.96% of amino acid pairs in protein C.

Amino Acid Substitution↗

PubMed2004

Reasoning of spike glycoproteins being more vulnerable to mutations among 158 coronavirus proteins from different species.

In this study, we used the probabilistic models developed by us over the last several years to analyze 158 proteins from coronaviruses in order to determine which protein is more vulnerable to mutations. The results provide three lines of evidence suggesting that the spike glycoprotein is different from the other coronavirus proteins: (1) the spike glycoprotein is more sensitive to mutations, this is the current state of the spike glycoprotein, (2) the spike glycoprotein has undergone more mutations in the past, this is the history of spike glycoprotein, and (3) the spike glycoprotein has a bigger potential towards future mutations, this is the future of spike glycoprotein. Furthermore, this study gives a clue on the species susceptibility regarding different proteins.

Analysis of Variance↗

PubMed2004

Strategies for the structure determination of endohedral fullerenes applied to the example of Ba@C(74)xCo(octaethylporphyrin)x2C(6)H(6).

The structure determination of endohedral fullerenes is complicated because of the high degree of disorder which may affect the different structural components, e.g. the endohedral atom/molecule, the fullerene cage and solvent molecules. Even worse, the data-to-parameter ratio and, in particular, the scattering power is low. Different strategies are employed to deal with these problems. The observed fraction of the reciprocal lattice may be increased by means of synchrotron diffraction studies. The number of parameters may be reduced by applying rigid-body refinement strategies and by restricting the displacement parameters in the framework of the TLS approach. In the first section, we will give a short overview of the structure determinations of endohedral fullerenes from single-crystal data and discuss the severe problems one may encounter. Then we will give an example of a successful structure analysis of a metal-containing endohedral fullerene, i.e. Ba@C(74)xCo(OEP)x2C(6)H(6) (OEP = octaethylporphyrin). Several strategies of refinement, beyond the black box level, have been checked and compared, e.g. TLS, split-atom models, twin and single crystal models, anharmonic displacement parameters, and rigid-body models.

Journal Article↗