In laboratory sandpack tests for heavy oil re-covery by alkaline flooding, it was found that wettability alteration of the sand had a significant impact on oil recovery. In this work, a heavy oil of 14? API was used t...In laboratory sandpack tests for heavy oil re-covery by alkaline flooding, it was found that wettability alteration of the sand had a significant impact on oil recovery. In this work, a heavy oil of 14? API was used to examine the effect of organic acids in the oil and water che- mistry on wettability alteration. From interfacial tension measurements and sand surface composition analysis, it was concluded that the water-wet sand became preferentially oil-wet by magnesium ion binding. The presence of Mg2+ in the heavy oil/Na2CO3 solution/sand system increased the oil/water interfacial tension. This confirmed the hypothesis that magnesium ion combined with the ionized organic acids to form magnesium soap at oil/water interface. Under alkaline condition, the ionized organic acids in the oil phase partition into the water phase and subsequently adsorb on the sand surfaces. The analysis of sand surface composition sugg- ested that more ionized organic acids adsorb- ed on the sand surface through magnesium ion binding. The attachment of more organic acids on the sand surface changed hydration forces, making the sand surface more oil-wet.展开更多
Sevelamer Carbonate is a crossolinked polymeric amine, it is the active ingredient in Renvela Tablets. Sevelamer Carbonate is indicated for the control of hyperphosphatamiea in patients with end-stage renal disease. T...Sevelamer Carbonate is a crossolinked polymeric amine, it is the active ingredient in Renvela Tablets. Sevelamer Carbonate is indicated for the control of hyperphosphatamiea in patients with end-stage renal disease. The binding parameter constants of Sevelamer Carbonate were determined using the Langmuir approximation for the dosage form at pH 4.0 and 7.0 by Ion Chromatography. An Ion Chromatogrpahy method has been developed to estimate free phosphate in in-vitro phosphate binding study of Sevelamer Carbonate Tablets. The method is selective and capable of detecting phosphate in the presence of placebo matrix. The method has been validated with a lower limit of quantitation of 0.2 mM for Phosphate. A linear response function was established in the range of concentrations 0.2 - 30.0 mM (r > 0.99) for Phosphate. The intra and inter day precision values for Phosphate met the acceptance as per Food and Drug Administrations guidelines. Phosphate was stable in the set of stability studies viz. bench-top and autosampler. The developed method was applied to in-vitro phosphate binding studies of Sevelamer Carbonate Tablets.展开更多
Cyanide ion was studied as an effector of Jack bean urease(JBU) at 300 K in 30 mmol/LTris buffer,pH 7 by isothermal titration calorimetry(ITC).The simple novel model was used for CN^- + JBU interaction over the whole ...Cyanide ion was studied as an effector of Jack bean urease(JBU) at 300 K in 30 mmol/LTris buffer,pH 7 by isothermal titration calorimetry(ITC).The simple novel model was used for CN^- + JBU interaction over the whole range of CN^- concentrations.The binding parameters recovered from the simple novel model were attributed to the cyanide ion interaction.It was found that cyanide ion acted as a noncooperative inhibitor of JBU,and there is a set of 12 identical and independent binding sites for CN^- ions.The di...展开更多
The variational method using a multiconfiguration wavefunction is carried out on the core-excited state 1s2s2p 4P0 for helium negative ion,including mass polarization and relativistic corrections.Binding energy and fi...The variational method using a multiconfiguration wavefunction is carried out on the core-excited state 1s2s2p 4P0 for helium negative ion,including mass polarization and relativistic corrections.Binding energy and fine structure are reported.The results are compared with other theoretical and experimental date in the literature.展开更多
The hemagglutinin (HA) of influenza viruses facilitates receptor binding and membrane fusion, which is the initial step of virus infection. Human influenza viruses preferentially bind to receptors with α2-6 lin- kage...The hemagglutinin (HA) of influenza viruses facilitates receptor binding and membrane fusion, which is the initial step of virus infection. Human influenza viruses preferentially bind to receptors with α2-6 lin- kages to galactose (SAα2,6Gal), whereas avian influenza viruses prefer receptors with α2-3 linkages to galactose (SAα2,3Gal). The current 2009 H1N1 pandemic is caused by a novel influenza A virus that has its genetic materials from birds, humans, and pigs. Its pandemic nature is characterized clearly by its dual binding to the α2-3 as well as α2-6 receptors, because the seasonal human H1N1 virus only binds to the α2-6 receptor. In a previous study, the informational spectrum method (ISM), a bioinformatics technique, was applied to uncover one highly conserved region in the HA protein associated with receptor binding preference in each of various influenza subtypes. In the present study, we extended the previous work by discovering multiple such domains in HA of 2009 H1N1 and avian H5N1 to expand our repertoire of known key regions in HA responsible for receptor binding affinity. Three such domains in HA of 2009 H1N1 were found at residue positions 106 to 130, 150 to 174, and 191 to 221, and another three domains in HA of avian H5N1 were located at residue positions 46 to 65, 136 to 153, and 269 to 286. These identified domains could be utilized as therapeutic and diagnostic targets for the prevention and treatment of influenza infection.展开更多
The binding mechanism of the interactions of halide ions (F–, Br– and I–) with bovine serum albumin (BSA) and hemoglobin (Hb) were studied at different temperatures, by using ion-selective electrodes. The experimen...The binding mechanism of the interactions of halide ions (F–, Br– and I–) with bovine serum albumin (BSA) and hemoglobin (Hb) were studied at different temperatures, by using ion-selective electrodes. The experimental data were treated according to Klotz equation, and the number of binding sites and the binding constants were determined. The results show that the binding sites of F– on protein molecules are more than those of Br– and I–. Additionally, the number of the binding sites for halide ions on protein molecules increases with increasing temperature. This study also indicates that the binding constants for the interactions of halide ions with proteins gradually decrease as the size of halide ions and temperature increases. These behaviors were reasonably interpreted with the structural and thermodynamic factors. The thermodynamic functions at different temperatures were calculated with thermodynamic equations, and the enthalpy change for the interactions were also determined by isothermal titration calorimetry (ITC) at 298.15 K, which indicate that the interactions of halide ions with proteins are mainly electrostatic interaction.展开更多
Hemagglutinin (HA) of influenza viruses is a cylindrically shaped homotrimer, where each monomer comprises two disulfide-linked subdomains HA1 and HA2. Influenza infection is initiated by binding of HA1 to its host ce...Hemagglutinin (HA) of influenza viruses is a cylindrically shaped homotrimer, where each monomer comprises two disulfide-linked subdomains HA1 and HA2. Influenza infection is initiated by binding of HA1 to its host cell receptors and followed by the fusion between viral and host endosomal membranes mediated by HA2. Human influenza viruses preferentially bind to sialic acid that is linked to galactose by an α2,6-linkage (α2,6), whereas avian and swine influenza viruses preferentially recognize α2,3 or α 2,3/α2,6. For animal influenza viruses to cross host species barriers, their HA proteins must acquire mutations to gain the capacity to allow human-to-human transmission. In this study, the informational spectrum method (ISM), a bioinformatics approach, was applied to identify mutations and to elucidate the contribution to the receptor binding specificity from each mutation in HA1 in various subtypes within or between hosts, including 2009 human H1N1, avian H5N1, human H5N1, avian H1N1, and swine H1N2. Among others, our quantitative analysis indicated that the mutations in HA1 of 2009 human H1N1 collectively tended to reduce the swine binding affinity in the seasonal H1N1 strains and to increase that in the pandemic H1N1 strains. At the same time, they increased the human binding affinity in the pandemic H1N1 strains and had little impact on that in the seasonal H1N1 strains. The mutations between the consensus HA1 sequences of human H5N1 and avian H5N1 increased the avian binding affinity and decreased the human binding affinity in avian H5N1 while produced the opposite effects on those in human H5N1. Finally, the ISM was employed to analyze and verify several mutations in HA1 well known for their critical roles in binding specificity switch, including E190D/G225D in H1N1 and Q192R/ S223L/ Q226L/ G228S in H5N1.展开更多
Nucleic acids are negatively charged biomolecules, and metal ions in solutions are important to their folding structures and thermodynamics, especially multivalent ions. However, it has been suggested that the binding...Nucleic acids are negatively charged biomolecules, and metal ions in solutions are important to their folding structures and thermodynamics, especially multivalent ions. However, it has been suggested that the binding of multivalent ions to nucleic acids cannot be quantitatively described by the well-established Poisson-Boltzmann （PB） theory. In this work, we made extensive calculations of ion distributions around various RNA-like macroions in divalent and trivalent salt solutions by PB theory and Monte Carlo （MC） simulations. Our calculations show that PB theory appears to underestimate multi- valent ion distributions around RNA-like macroions while can reliably predict monovalent ion distributions. Our extensive comparisons between PB theory and MC simulations indicate that when an RNA-like macroion gets ion neutralization be- yond a ＂critical＂ value, the multivalent ion distribution around that macroion can be approximately described by PB theory. Furthermore, an empirical formula was obtained to approximately quantify the critical ion neutralization for various RNA- like macroions in multivalent salt solutions, and this empirical formula was shown to work well for various real nucleic acids including RNAs and DNAs.展开更多
It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titra...It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titration of ACF I with rare earth ions demonstrate that ACF I has two RE 3+-binding sites, and the rare earth ions and Ca 2+ bind to ACF I competitively in the two similar sites. The association constants K 1 and K 2 of ACF I with each rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) are close to each other, which indicates the structural similarity of the two binding sites in ACF I. Although the ionic radii of Nd 3+, Sm 3+, Eu 3+, Gd 3+ and Tb 3+ are different, both their K 1 and K 2 are similar, respectively. This reveals the conformational flexibility of the two binding sites in ACF I, which offers a possibility for Ca 2+ to take play in the inducing conformational changes of ACF I and the promoting the binding of ACF I with activated coagulation factor X.展开更多
The oxidation behavior of Co 40Cr alloy with and without yttrium implantation was studied at 900 ℃ in the air. Scanning electron microscopy(SEM), secondary ion massive spectroscopy(SIMS), transmission electron micr...The oxidation behavior of Co 40Cr alloy with and without yttrium implantation was studied at 900 ℃ in the air. Scanning electron microscopy(SEM), secondary ion massive spectroscopy(SIMS), transmission electron microscopy(TEM) and high resolution electron microscopy(HREM) were used to study the forming mechanism of oxide film on the alloy. It is found that the binding energy of Cr on the alloy surface is decreased by yttrium implantation, thus the formation of protective Cr 2O 3 film on the substrate is accelerated. In the mean time, the binding energy of Cr inside the oxide scale is increased by yttrium implantation, and this would reduce the Cr 3+ cation diffusion through the film. Yttrium implantation decreases the grain size and the growing speed of oxide film. SIMS and TEM/HREM results show that some yttrium exists as small YCrO 3 particles at Cr 2O 3 grain boundary near the oxide/gas interface, and a few small Y 2O 3 particles exist near the substrate/oxide interface. Besides, yttrium may also segregate to Cr 2O 3 grain boundary as Y 3+ , reduce Cr 3+ cation diffusion and change the mechanical properties of the oxide film. The ability of anti oxidation of Co 40Cr alloy is greatly improved by yttrium implantation.展开更多
p-tert-Butylcalix[4]diazacrown-4 telomer, which contains hard and soft ion binding sites, was synthesized. It exhibited high selectivity toward cesium ions. The binding sites may complex alkali metal ions selectively.
文摘In laboratory sandpack tests for heavy oil re-covery by alkaline flooding, it was found that wettability alteration of the sand had a significant impact on oil recovery. In this work, a heavy oil of 14? API was used to examine the effect of organic acids in the oil and water che- mistry on wettability alteration. From interfacial tension measurements and sand surface composition analysis, it was concluded that the water-wet sand became preferentially oil-wet by magnesium ion binding. The presence of Mg2+ in the heavy oil/Na2CO3 solution/sand system increased the oil/water interfacial tension. This confirmed the hypothesis that magnesium ion combined with the ionized organic acids to form magnesium soap at oil/water interface. Under alkaline condition, the ionized organic acids in the oil phase partition into the water phase and subsequently adsorb on the sand surfaces. The analysis of sand surface composition sugg- ested that more ionized organic acids adsorb- ed on the sand surface through magnesium ion binding. The attachment of more organic acids on the sand surface changed hydration forces, making the sand surface more oil-wet.
文摘Sevelamer Carbonate is a crossolinked polymeric amine, it is the active ingredient in Renvela Tablets. Sevelamer Carbonate is indicated for the control of hyperphosphatamiea in patients with end-stage renal disease. The binding parameter constants of Sevelamer Carbonate were determined using the Langmuir approximation for the dosage form at pH 4.0 and 7.0 by Ion Chromatography. An Ion Chromatogrpahy method has been developed to estimate free phosphate in in-vitro phosphate binding study of Sevelamer Carbonate Tablets. The method is selective and capable of detecting phosphate in the presence of placebo matrix. The method has been validated with a lower limit of quantitation of 0.2 mM for Phosphate. A linear response function was established in the range of concentrations 0.2 - 30.0 mM (r > 0.99) for Phosphate. The intra and inter day precision values for Phosphate met the acceptance as per Food and Drug Administrations guidelines. Phosphate was stable in the set of stability studies viz. bench-top and autosampler. The developed method was applied to in-vitro phosphate binding studies of Sevelamer Carbonate Tablets.
文摘Cyanide ion was studied as an effector of Jack bean urease(JBU) at 300 K in 30 mmol/LTris buffer,pH 7 by isothermal titration calorimetry(ITC).The simple novel model was used for CN^- + JBU interaction over the whole range of CN^- concentrations.The binding parameters recovered from the simple novel model were attributed to the cyanide ion interaction.It was found that cyanide ion acted as a noncooperative inhibitor of JBU,and there is a set of 12 identical and independent binding sites for CN^- ions.The di...
文摘The variational method using a multiconfiguration wavefunction is carried out on the core-excited state 1s2s2p 4P0 for helium negative ion,including mass polarization and relativistic corrections.Binding energy and fine structure are reported.The results are compared with other theoretical and experimental date in the literature.
文摘The hemagglutinin (HA) of influenza viruses facilitates receptor binding and membrane fusion, which is the initial step of virus infection. Human influenza viruses preferentially bind to receptors with α2-6 lin- kages to galactose (SAα2,6Gal), whereas avian influenza viruses prefer receptors with α2-3 linkages to galactose (SAα2,3Gal). The current 2009 H1N1 pandemic is caused by a novel influenza A virus that has its genetic materials from birds, humans, and pigs. Its pandemic nature is characterized clearly by its dual binding to the α2-3 as well as α2-6 receptors, because the seasonal human H1N1 virus only binds to the α2-6 receptor. In a previous study, the informational spectrum method (ISM), a bioinformatics technique, was applied to uncover one highly conserved region in the HA protein associated with receptor binding preference in each of various influenza subtypes. In the present study, we extended the previous work by discovering multiple such domains in HA of 2009 H1N1 and avian H5N1 to expand our repertoire of known key regions in HA responsible for receptor binding affinity. Three such domains in HA of 2009 H1N1 were found at residue positions 106 to 130, 150 to 174, and 191 to 221, and another three domains in HA of avian H5N1 were located at residue positions 46 to 65, 136 to 153, and 269 to 286. These identified domains could be utilized as therapeutic and diagnostic targets for the prevention and treatment of influenza infection.
文摘The binding mechanism of the interactions of halide ions (F–, Br– and I–) with bovine serum albumin (BSA) and hemoglobin (Hb) were studied at different temperatures, by using ion-selective electrodes. The experimental data were treated according to Klotz equation, and the number of binding sites and the binding constants were determined. The results show that the binding sites of F– on protein molecules are more than those of Br– and I–. Additionally, the number of the binding sites for halide ions on protein molecules increases with increasing temperature. This study also indicates that the binding constants for the interactions of halide ions with proteins gradually decrease as the size of halide ions and temperature increases. These behaviors were reasonably interpreted with the structural and thermodynamic factors. The thermodynamic functions at different temperatures were calculated with thermodynamic equations, and the enthalpy change for the interactions were also determined by isothermal titration calorimetry (ITC) at 298.15 K, which indicate that the interactions of halide ions with proteins are mainly electrostatic interaction.
文摘Hemagglutinin (HA) of influenza viruses is a cylindrically shaped homotrimer, where each monomer comprises two disulfide-linked subdomains HA1 and HA2. Influenza infection is initiated by binding of HA1 to its host cell receptors and followed by the fusion between viral and host endosomal membranes mediated by HA2. Human influenza viruses preferentially bind to sialic acid that is linked to galactose by an α2,6-linkage (α2,6), whereas avian and swine influenza viruses preferentially recognize α2,3 or α 2,3/α2,6. For animal influenza viruses to cross host species barriers, their HA proteins must acquire mutations to gain the capacity to allow human-to-human transmission. In this study, the informational spectrum method (ISM), a bioinformatics approach, was applied to identify mutations and to elucidate the contribution to the receptor binding specificity from each mutation in HA1 in various subtypes within or between hosts, including 2009 human H1N1, avian H5N1, human H5N1, avian H1N1, and swine H1N2. Among others, our quantitative analysis indicated that the mutations in HA1 of 2009 human H1N1 collectively tended to reduce the swine binding affinity in the seasonal H1N1 strains and to increase that in the pandemic H1N1 strains. At the same time, they increased the human binding affinity in the pandemic H1N1 strains and had little impact on that in the seasonal H1N1 strains. The mutations between the consensus HA1 sequences of human H5N1 and avian H5N1 increased the avian binding affinity and decreased the human binding affinity in avian H5N1 while produced the opposite effects on those in human H5N1. Finally, the ISM was employed to analyze and verify several mutations in HA1 well known for their critical roles in binding specificity switch, including E190D/G225D in H1N1 and Q192R/ S223L/ Q226L/ G228S in H5N1.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374234,11575128,11774272,and 11647312)
文摘Nucleic acids are negatively charged biomolecules, and metal ions in solutions are important to their folding structures and thermodynamics, especially multivalent ions. However, it has been suggested that the binding of multivalent ions to nucleic acids cannot be quantitatively described by the well-established Poisson-Boltzmann （PB） theory. In this work, we made extensive calculations of ion distributions around various RNA-like macroions in divalent and trivalent salt solutions by PB theory and Monte Carlo （MC） simulations. Our calculations show that PB theory appears to underestimate multi- valent ion distributions around RNA-like macroions while can reliably predict monovalent ion distributions. Our extensive comparisons between PB theory and MC simulations indicate that when an RNA-like macroion gets ion neutralization be- yond a ＂critical＂ value, the multivalent ion distribution around that macroion can be approximately described by PB theory. Furthermore, an empirical formula was obtained to approximately quantify the critical ion neutralization for various RNA- like macroions in multivalent salt solutions, and this empirical formula was shown to work well for various real nucleic acids including RNAs and DNAs.
文摘It was observed that rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) have significant quenching effects on the fluorescence of anticoagulation factor I (ACF I). The results of the fluorescence titration of ACF I with rare earth ions demonstrate that ACF I has two RE 3+-binding sites, and the rare earth ions and Ca 2+ bind to ACF I competitively in the two similar sites. The association constants K 1 and K 2 of ACF I with each rare earth ions (Nd 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+) are close to each other, which indicates the structural similarity of the two binding sites in ACF I. Although the ionic radii of Nd 3+, Sm 3+, Eu 3+, Gd 3+ and Tb 3+ are different, both their K 1 and K 2 are similar, respectively. This reveals the conformational flexibility of the two binding sites in ACF I, which offers a possibility for Ca 2+ to take play in the inducing conformational changes of ACF I and the promoting the binding of ACF I with activated coagulation factor X.
文摘The oxidation behavior of Co 40Cr alloy with and without yttrium implantation was studied at 900 ℃ in the air. Scanning electron microscopy(SEM), secondary ion massive spectroscopy(SIMS), transmission electron microscopy(TEM) and high resolution electron microscopy(HREM) were used to study the forming mechanism of oxide film on the alloy. It is found that the binding energy of Cr on the alloy surface is decreased by yttrium implantation, thus the formation of protective Cr 2O 3 film on the substrate is accelerated. In the mean time, the binding energy of Cr inside the oxide scale is increased by yttrium implantation, and this would reduce the Cr 3+ cation diffusion through the film. Yttrium implantation decreases the grain size and the growing speed of oxide film. SIMS and TEM/HREM results show that some yttrium exists as small YCrO 3 particles at Cr 2O 3 grain boundary near the oxide/gas interface, and a few small Y 2O 3 particles exist near the substrate/oxide interface. Besides, yttrium may also segregate to Cr 2O 3 grain boundary as Y 3+ , reduce Cr 3+ cation diffusion and change the mechanical properties of the oxide film. The ability of anti oxidation of Co 40Cr alloy is greatly improved by yttrium implantation.
基金Financial supports from the National Natural Science Foundation of China(No.20602015)are gratefully acknowledged.
文摘p-tert-Butylcalix[4]diazacrown-4 telomer, which contains hard and soft ion binding sites, was synthesized. It exhibited high selectivity toward cesium ions. The binding sites may complex alkali metal ions selectively.
