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2001 Volume 17 Issue 10
2001, 17(10): 865-867
doi: 10.3866/PKU.WHXB20011001
Abstract:
RNase H,a ribonuclease specifically degrades the RNA chain in RNA:DNA hybrid,exists vastly in organisms from procaryotic to humanic.We use isothermal titration calorimetry to study the binding thermodynamics of Mg2＋,Mn2＋,Ca2＋ to a type II RNase H from an archaeon:Methanococcus jannaschii.For the first time we obtain the thermodynamic parameters of this binding reaction and verify that these metal ions bind with RNase HII with a ratio of 1:1.This will give an important information for studying RNase HII reaction mechanism and folding properties.
RNase H,a ribonuclease specifically degrades the RNA chain in RNA:DNA hybrid,exists vastly in organisms from procaryotic to humanic.We use isothermal titration calorimetry to study the binding thermodynamics of Mg2＋,Mn2＋,Ca2＋ to a type II RNase H from an archaeon:Methanococcus jannaschii.For the first time we obtain the thermodynamic parameters of this binding reaction and verify that these metal ions bind with RNase HII with a ratio of 1:1.This will give an important information for studying RNase HII reaction mechanism and folding properties.
2001, 17(10): 868-872
doi: 10.3866/PKU.WHXB20011002
Abstract:
Using ld nanoparticle as nanooxidation mask,tapping mode atomic force microscope (TMAFM) nanolithography and wet chemical etching techniques were combined to build nanostructure on Si surface. The nanoparticles were immobilized on mercaptopropyltrimethoxysilane (MPTS)modified silicon surface via Au－S bonding and were exploited as the lithography mask to prevent the AFM tipinduced nanooxidation of MPTS and silicon substrate. It was found that the nanostructures formed on Si surface were dependent on the tipsample separation. With a certain bias voltage,scanning rate and relative humidity,adjusting the separation to 7.5 nm,nanopillar structures were obtained;while decreasing the separation to 5 nm,nanoring structures appeared . To explain the formation mechanism of these nanostructures,a hard ball model based on nanoparticle physical shielding effect was proposed.
Using ld nanoparticle as nanooxidation mask,tapping mode atomic force microscope (TMAFM) nanolithography and wet chemical etching techniques were combined to build nanostructure on Si surface. The nanoparticles were immobilized on mercaptopropyltrimethoxysilane (MPTS)modified silicon surface via Au－S bonding and were exploited as the lithography mask to prevent the AFM tipinduced nanooxidation of MPTS and silicon substrate. It was found that the nanostructures formed on Si surface were dependent on the tipsample separation. With a certain bias voltage,scanning rate and relative humidity,adjusting the separation to 7.5 nm,nanopillar structures were obtained;while decreasing the separation to 5 nm,nanoring structures appeared . To explain the formation mechanism of these nanostructures,a hard ball model based on nanoparticle physical shielding effect was proposed.
2001, 17(10): 873-878
doi: 10.3866/PKU.WHXB20011003
Abstract:
Interaction of the gelatin with Cu2＋ and Fe3＋ are investiged at different pH and temperatures by fluorescence quenching method. The mechanisms of fluorescence quenching of Cu2＋ and Fe3＋ to gelatin are studied at different pH. The quenching constants, binding constants, and the thermodynamic functions are calculated. The results of microIR and UV show that Cu2＋ and Fe3＋ interacte with the amido bond in the gelatin molecule. The entropy change is a main factor in the interaction process of the gelatin with Cu2＋ and Fe3＋.
Interaction of the gelatin with Cu2＋ and Fe3＋ are investiged at different pH and temperatures by fluorescence quenching method. The mechanisms of fluorescence quenching of Cu2＋ and Fe3＋ to gelatin are studied at different pH. The quenching constants, binding constants, and the thermodynamic functions are calculated. The results of microIR and UV show that Cu2＋ and Fe3＋ interacte with the amido bond in the gelatin molecule. The entropy change is a main factor in the interaction process of the gelatin with Cu2＋ and Fe3＋.
2001, 17(10): 879-886
doi: 10.3866/PKU.WHXB20011004
Abstract:
5fluorouracil porphyrin compounds are a new type of potential antitumor drugs. Six new 5fluorouracil porphyrin compounds were synthesized first and characterized by means of elemental analysis, IR, 1HNMR and MS. The six 5fluorouracil porphyrin compounds were studied by absorption spectra, steadystate fluorescence spectroscopy and timeresolved single photon measurement, comparing with their primary porphyrin compounds. The 5fluorouracil porphyrin compounds with plentiful excited states and fluorescence lifetime of 7 ns are little influenced by substituents and solvents, which may be advantageously used to make singlet oxygen radical.
5fluorouracil porphyrin compounds are a new type of potential antitumor drugs. Six new 5fluorouracil porphyrin compounds were synthesized first and characterized by means of elemental analysis, IR, 1HNMR and MS. The six 5fluorouracil porphyrin compounds were studied by absorption spectra, steadystate fluorescence spectroscopy and timeresolved single photon measurement, comparing with their primary porphyrin compounds. The 5fluorouracil porphyrin compounds with plentiful excited states and fluorescence lifetime of 7 ns are little influenced by substituents and solvents, which may be advantageously used to make singlet oxygen radical.
2001, 17(10): 887-891
doi: 10.3866/PKU.WHXB20011005
Abstract:
Nanocrystalline powder of In2O3 mixed with αFe2O3 is prepared by chemical coprecipitation, effects of αFe2O3 on the conductance and gassensing properties of In2O3 are investigated. The results demonstrate that partial solid solution In2－xFexO3（0≤x≤0.40）can be formed between αFe2O3 and In2O3; Partial lattice substituting of Fe3＋ to In3＋ can notably enhance the combining force between anion and cation, it causes oxygen vacancy to decrease, free electron density to be reduced and the conductance to be poorer(to see Fig.2). The sensitivity of sensor, which is prepared with 5:5 n(Fe3＋) andn(In3＋) calcined at 800 ℃ for 4 h, to 45 μmol•L－1 C2H5OH can reach the value of 54.0. This is eight times more than that of petrol with the same concentration .
Nanocrystalline powder of In2O3 mixed with αFe2O3 is prepared by chemical coprecipitation, effects of αFe2O3 on the conductance and gassensing properties of In2O3 are investigated. The results demonstrate that partial solid solution In2－xFexO3（0≤x≤0.40）can be formed between αFe2O3 and In2O3; Partial lattice substituting of Fe3＋ to In3＋ can notably enhance the combining force between anion and cation, it causes oxygen vacancy to decrease, free electron density to be reduced and the conductance to be poorer(to see Fig.2). The sensitivity of sensor, which is prepared with 5:5 n(Fe3＋) andn(In3＋) calcined at 800 ℃ for 4 h, to 45 μmol•L－1 C2H5OH can reach the value of 54.0. This is eight times more than that of petrol with the same concentration .
2001, 17(10): 892-897
doi: 10.3866/PKU.WHXB20011006
Abstract:
A mathematical model of the air electrode used in the phosphoric acid fuel cells(PAFC) was developed. This model accounts for the diffusion of oxygen and the distribution of electrode potential across the air electrode. The model was applied to simulate the cathode performance under a variety of conditions. Two parameters AB and AI were introduced into the model. They respectively reflect the effects of the interfacial surface area between the gas and liquid phases and those of the interfacial surface area between the liquid and solid phases, on the air electrode performance. AB and AI can be determined with the aid of the operating conditions and potentialcurrent density curves of the air electrode. The main interface parameters of the air electrode can be predicted after the determination of AB and AI. It is found that there is a linear relationship between the parameter AB and the current density but that parameter AI only oscillates in a very narrow range for all current densities. The reaction rate throughout the catalyst layer was calculated by means of the model, and the results show that the reduction of oxygen does not occur uniformly in the catalyst layer. The degree to which the reduction of oxygen takes place in the catalyst layer varies with current densities. The higher the operation current density, the more probability with which the reduction of oxygen takes place in the section of catalyst layer close to the diffusion layer.
A mathematical model of the air electrode used in the phosphoric acid fuel cells(PAFC) was developed. This model accounts for the diffusion of oxygen and the distribution of electrode potential across the air electrode. The model was applied to simulate the cathode performance under a variety of conditions. Two parameters AB and AI were introduced into the model. They respectively reflect the effects of the interfacial surface area between the gas and liquid phases and those of the interfacial surface area between the liquid and solid phases, on the air electrode performance. AB and AI can be determined with the aid of the operating conditions and potentialcurrent density curves of the air electrode. The main interface parameters of the air electrode can be predicted after the determination of AB and AI. It is found that there is a linear relationship between the parameter AB and the current density but that parameter AI only oscillates in a very narrow range for all current densities. The reaction rate throughout the catalyst layer was calculated by means of the model, and the results show that the reduction of oxygen does not occur uniformly in the catalyst layer. The degree to which the reduction of oxygen takes place in the catalyst layer varies with current densities. The higher the operation current density, the more probability with which the reduction of oxygen takes place in the section of catalyst layer close to the diffusion layer.
2001, 17(10): 898-903
doi: 10.3866/PKU.WHXB20011007
Abstract:
The fluorescence emission and Xray diffraction of two metal (Ca2＋ and Zn2＋) 8hydroxyquinoline complexes (Caq2 and Znq2) have been measured at high pressure. It has been found that pressure can influence the emission dramatically. With increase of pressure Caq2 gives increasing of its emission within 3 GPa and drops quickly when the pressure gets higher. At about 7 GPa it shows almost no emission at all. The emission of Znq2 decreases gradually with increase of the pressure. The emission intensity is about 10％ of its original when the pressure gets 7 GPa. The result of in situ Xray diffraction of Caq2 indicates that at about 3～4 GPa it starts a phase transition to amorphous and this transition completes at 7 GPa. All of the diffraction peaks has disappeared at this pressure. Znq2,however,gives no significant phase transition up to 16 GPa according to its in situ Xray diffraction result at pressure.
The fluorescence emission and Xray diffraction of two metal (Ca2＋ and Zn2＋) 8hydroxyquinoline complexes (Caq2 and Znq2) have been measured at high pressure. It has been found that pressure can influence the emission dramatically. With increase of pressure Caq2 gives increasing of its emission within 3 GPa and drops quickly when the pressure gets higher. At about 7 GPa it shows almost no emission at all. The emission of Znq2 decreases gradually with increase of the pressure. The emission intensity is about 10％ of its original when the pressure gets 7 GPa. The result of in situ Xray diffraction of Caq2 indicates that at about 3～4 GPa it starts a phase transition to amorphous and this transition completes at 7 GPa. All of the diffraction peaks has disappeared at this pressure. Znq2,however,gives no significant phase transition up to 16 GPa according to its in situ Xray diffraction result at pressure.
2001, 17(10): 904-907
doi: 10.3866/PKU.WHXB20011008
Abstract:
Mixedpotential theory is introduced to discuss the experimental results of open circuit potential for the autocatalytic polymerization of aniline. The open circuit potentials of Pt, Pd and polyaniline film in acidic aniline solution are much more positive than those of other metals. Owing to the electrochemical mechanism of the autocatalytic polymerization of aniline, the metal plate as substrate is endowed with a common electrode potential as for both the anodic and the cathodic half reactions. This common potential is called mixed potential. The value of the mixed potential is experimentally equal to that of the open circuit potential, and can be regarded as a criterion for the feasibility of the autocatalytic polymerization of aniline. A much positive value of the open circuit potential corresponds to an observable autocatalytic polymerization of aniline. The experimental results of the open circuit potential of various metal plates in acidic aniline solution support the electrochemical mechanism of the autocatalytic polymerization of aniline in return.
Mixedpotential theory is introduced to discuss the experimental results of open circuit potential for the autocatalytic polymerization of aniline. The open circuit potentials of Pt, Pd and polyaniline film in acidic aniline solution are much more positive than those of other metals. Owing to the electrochemical mechanism of the autocatalytic polymerization of aniline, the metal plate as substrate is endowed with a common electrode potential as for both the anodic and the cathodic half reactions. This common potential is called mixed potential. The value of the mixed potential is experimentally equal to that of the open circuit potential, and can be regarded as a criterion for the feasibility of the autocatalytic polymerization of aniline. A much positive value of the open circuit potential corresponds to an observable autocatalytic polymerization of aniline. The experimental results of the open circuit potential of various metal plates in acidic aniline solution support the electrochemical mechanism of the autocatalytic polymerization of aniline in return.
2001, 17(10): 908-912
doi: 10.3866/PKU.WHXB20011009
Abstract:
Cyclic voltammetry (CV) and insitu Raman spectroscopy were used to study the electrochemical properties of the narrow bandgap conjugated polymer poly {(pyrrole2,5diyl)[(pN,Ndimethylamino) benzylidene]}(PPDMABE).The results reveal that the pyrrole rings in oxidized state of PPDMABE exist in oxidized state,while in reduced state aromatic and quinonoid structure pyrrole rings coexist.The electrochemical reduction of PPDMABE is easier in acid solutions than in base solutions.In acidic and neutral media,the oxidized pyrrole rings exit in the form of protonized state,while in basic media they exit both in the form of protonized and deprotonized states.
Cyclic voltammetry (CV) and insitu Raman spectroscopy were used to study the electrochemical properties of the narrow bandgap conjugated polymer poly {(pyrrole2,5diyl)[(pN,Ndimethylamino) benzylidene]}(PPDMABE).The results reveal that the pyrrole rings in oxidized state of PPDMABE exist in oxidized state,while in reduced state aromatic and quinonoid structure pyrrole rings coexist.The electrochemical reduction of PPDMABE is easier in acid solutions than in base solutions.In acidic and neutral media,the oxidized pyrrole rings exit in the form of protonized state,while in basic media they exit both in the form of protonized and deprotonized states.
2001, 17(10): 913-917
doi: 10.3866/PKU.WHXB20011010
Abstract:
Density functional (B3LYP/SDD) method with relativistic effective core potential (RECP) have been used to optimize the structure of ZrCo and ZrCoH,and to calculate energy E,entropy S and enthalpy H of ZrCoH(D,T).Considering the characteristics of different motion types,the vibration energy or electronic and vibration entropy of the molecules is assumed to be the corresponding values of their solid states.ΔH,ΔS,ΔG and hydrogen isotope equilibrium pressures of the hydrogenating reactions have been calculated based on this approximation.The formation enthalpies for ZrCoH,ZrCoD and ZrCoT at temperature from 398 to 598 K are 82.81 ,81.54 and 80.49 kJ•mol－1 respectively.The results cohere with the experimental results.It means that the present method is somehow reasonable to theoretical study on thermodynamic functions of hydrogen storage materials.
Density functional (B3LYP/SDD) method with relativistic effective core potential (RECP) have been used to optimize the structure of ZrCo and ZrCoH,and to calculate energy E,entropy S and enthalpy H of ZrCoH(D,T).Considering the characteristics of different motion types,the vibration energy or electronic and vibration entropy of the molecules is assumed to be the corresponding values of their solid states.ΔH,ΔS,ΔG and hydrogen isotope equilibrium pressures of the hydrogenating reactions have been calculated based on this approximation.The formation enthalpies for ZrCoH,ZrCoD and ZrCoT at temperature from 398 to 598 K are 82.81 ,81.54 and 80.49 kJ•mol－1 respectively.The results cohere with the experimental results.It means that the present method is somehow reasonable to theoretical study on thermodynamic functions of hydrogen storage materials.
2001, 17(10): 918-923
doi: 10.3866/PKU.WHXB20011011
Abstract:
Photogenerated charge carriers transfer and transport kinetics of nanocrystalline semiconductor thin film electrodes were studied by Intensity Modulated Photocurrent Spectroscopy(IMPS). Measuring the applied potential and sodium polysulfide solution concentration dependence of IMPS response of nanocrystalline CdSe electrodes, the interfacial holes transfer including direct process and indirect process via surface states were analyzed in terms of the parameters: normalized steady state photocurrents and surface states lifetimes. The transport processes of electrons were examined by determining the electron diffusion coefficient of nanocrystalline TiO2 electrodes obtained at different intensities of background light. HCl chemical treatment led to the increase of electron transport coefficient effectively indicating the improvement of electrons transport behavior in the nanocrystalline TiO2 electrodes.
Photogenerated charge carriers transfer and transport kinetics of nanocrystalline semiconductor thin film electrodes were studied by Intensity Modulated Photocurrent Spectroscopy(IMPS). Measuring the applied potential and sodium polysulfide solution concentration dependence of IMPS response of nanocrystalline CdSe electrodes, the interfacial holes transfer including direct process and indirect process via surface states were analyzed in terms of the parameters: normalized steady state photocurrents and surface states lifetimes. The transport processes of electrons were examined by determining the electron diffusion coefficient of nanocrystalline TiO2 electrodes obtained at different intensities of background light. HCl chemical treatment led to the increase of electron transport coefficient effectively indicating the improvement of electrons transport behavior in the nanocrystalline TiO2 electrodes.
2001, 17(10): 924-930
doi: 10.3866/PKU.WHXB20011012
Abstract:
In the calculation of solvent reorganization energy by Marcus′s twosphere model,we presented a flat sphere model based on benzenesolvent system′s exact geometry structure to describe the electron cloud of conjugated systems.We figured out the radii of electron donors and acceptors by using statistics method,after AM1 geometry optimization,and then calculated λs.Besides,according to Miller′s experiment and consulting McHale and other researchers′ Raman Spectrometry results,we supposed that the solute molecular low frequency torsion gave no contribution to λv when the frequency was too small and the λs obtained from flat sphere model had contained low frequency contribution.This revised λs was in agreement with the value figured out by subtracting revised λv from experimental λ value.By comparing them,we found that the distance between donor and acceptor,the alteration of acceptor and solvent affected the deviation of calculated λs from experiment values.Finally,we confirmed that the DA coupling,super exchange mediated by solvent molecule,surface interaction of solventsolute molecules and other similar quantum effects would reduce the classical value of λs,thus contribute to ET reaction.Our results proved the deviation of practical reaction systems to the continuum dielectric theory and reflected the necessity of describing the behaviors of solvent and solute molecules using molecular model.
In the calculation of solvent reorganization energy by Marcus′s twosphere model,we presented a flat sphere model based on benzenesolvent system′s exact geometry structure to describe the electron cloud of conjugated systems.We figured out the radii of electron donors and acceptors by using statistics method,after AM1 geometry optimization,and then calculated λs.Besides,according to Miller′s experiment and consulting McHale and other researchers′ Raman Spectrometry results,we supposed that the solute molecular low frequency torsion gave no contribution to λv when the frequency was too small and the λs obtained from flat sphere model had contained low frequency contribution.This revised λs was in agreement with the value figured out by subtracting revised λv from experimental λ value.By comparing them,we found that the distance between donor and acceptor,the alteration of acceptor and solvent affected the deviation of calculated λs from experiment values.Finally,we confirmed that the DA coupling,super exchange mediated by solvent molecule,surface interaction of solventsolute molecules and other similar quantum effects would reduce the classical value of λs,thus contribute to ET reaction.Our results proved the deviation of practical reaction systems to the continuum dielectric theory and reflected the necessity of describing the behaviors of solvent and solute molecules using molecular model.
2001, 17(10): 931-935
doi: 10.3866/PKU.WHXB20011013
Abstract:
Hydrogenterminated silicon surface was found to react with 1alkenes to produce stable monolayers. To pattern such monolayers and create surfaces with regions of different chemical functionalities, we used the combination of the photolithography and the light induced alkylation. The surfaces had been characterized by XPS, AFM, and contact angel measurement. It is shown that this procedure can be used to prepare micropatterns of chemical functional groups on silicon substrate.
Hydrogenterminated silicon surface was found to react with 1alkenes to produce stable monolayers. To pattern such monolayers and create surfaces with regions of different chemical functionalities, we used the combination of the photolithography and the light induced alkylation. The surfaces had been characterized by XPS, AFM, and contact angel measurement. It is shown that this procedure can be used to prepare micropatterns of chemical functional groups on silicon substrate.
2001, 17(10): 936-939
doi: 10.3866/PKU.WHXB20011014
Abstract:
Solid material NiSO4 was prepared. A TEACO2 laser generator was adopted as the light source to carry on laser stimulated surface coupling reaction of ethylene. The infrared vibration structure and adsorption state of C2H4adNiSO4 system were discussed based on infrared and temperature programmed desorption tests. It was showed that C2H4 is adsorbed as molecular state, bonding with NiSO4 surface through H atom at terminal O of S=O. The 1 079 cm－1 laser was selected to activate solid surfacial bond S=O, which absorbs the photon energy efficiently. At normal pressure and a temperature below 100 ℃, C2H4 conversed to butadiene with a high selectivity of 100％. Increasing laser pulse can improve conversion of C2H4 without change of selectivity. After 200 pulses, C2H4 in the system had been consumed to a large extent, and the product occupied most of the surface active sites, therefore conversion of C2H4 increased at a low speed. Temperature can also affect the laser stimulated surface reaction of C2H4adNiSO4. At 100 ℃, 15.1％ of C2H4 convert to butadiene, while keeping high selectivity of 100％. Based on the above experimental results, a mechanism of LSSR was proposed for the conversion of C2H4 to C4H6.
Solid material NiSO4 was prepared. A TEACO2 laser generator was adopted as the light source to carry on laser stimulated surface coupling reaction of ethylene. The infrared vibration structure and adsorption state of C2H4adNiSO4 system were discussed based on infrared and temperature programmed desorption tests. It was showed that C2H4 is adsorbed as molecular state, bonding with NiSO4 surface through H atom at terminal O of S=O. The 1 079 cm－1 laser was selected to activate solid surfacial bond S=O, which absorbs the photon energy efficiently. At normal pressure and a temperature below 100 ℃, C2H4 conversed to butadiene with a high selectivity of 100％. Increasing laser pulse can improve conversion of C2H4 without change of selectivity. After 200 pulses, C2H4 in the system had been consumed to a large extent, and the product occupied most of the surface active sites, therefore conversion of C2H4 increased at a low speed. Temperature can also affect the laser stimulated surface reaction of C2H4adNiSO4. At 100 ℃, 15.1％ of C2H4 convert to butadiene, while keeping high selectivity of 100％. Based on the above experimental results, a mechanism of LSSR was proposed for the conversion of C2H4 to C4H6.
2001, 17(10): 940-943
doi: 10.3866/PKU.WHXB20011015
Abstract:
A grand canonical Monte Carlo(GCMC) method is carried out to investigate adsorption of supercritical methane in layered pillared nanomaterial. In the simulation, layered pillared nanomaterial is modeled by the approach of Yi et al[6,7]with a uniform distribution of pillars. Steele′s 1043 potential is used for representing the interaction between a LennardJones(LJ) methane molecule and a layered wall in the GCMC simulation. The sitesite interaction is also used for calculating the interaction between methane of LJ fluid and pillars. The classical excess adsorption isotherms of methane with three different pore widths, are obtained at two supercritical temperatures T=207.3 and 237.0 K. The optimum adsorption pressures,corresponding to the greatest excess adsorption, are 2.4, 3.1 and 3.7 MPa in the pore widths 1.02, 1.70 and 2.38 nm at temperature 207.3 K, respectively. It can be found that the optimum adsorption pressures increase with the increase of temperature under otherwise identical conditions,which are 2.9, 3.6 and 4.9 MPa, respectively,corresponding to pore widths of 1.02, 1.70 and 2.38 nm at T=237.0 K. Simulation indicates that the GCMC method is a useful tool for providing the optimum adsorption pressure of supercritical methane in layered pillared nanomaterials.
A grand canonical Monte Carlo(GCMC) method is carried out to investigate adsorption of supercritical methane in layered pillared nanomaterial. In the simulation, layered pillared nanomaterial is modeled by the approach of Yi et al[6,7]with a uniform distribution of pillars. Steele′s 1043 potential is used for representing the interaction between a LennardJones(LJ) methane molecule and a layered wall in the GCMC simulation. The sitesite interaction is also used for calculating the interaction between methane of LJ fluid and pillars. The classical excess adsorption isotherms of methane with three different pore widths, are obtained at two supercritical temperatures T=207.3 and 237.0 K. The optimum adsorption pressures,corresponding to the greatest excess adsorption, are 2.4, 3.1 and 3.7 MPa in the pore widths 1.02, 1.70 and 2.38 nm at temperature 207.3 K, respectively. It can be found that the optimum adsorption pressures increase with the increase of temperature under otherwise identical conditions,which are 2.9, 3.6 and 4.9 MPa, respectively,corresponding to pore widths of 1.02, 1.70 and 2.38 nm at T=237.0 K. Simulation indicates that the GCMC method is a useful tool for providing the optimum adsorption pressure of supercritical methane in layered pillared nanomaterials.
2001, 17(10): 944-947
doi: 10.3866/PKU.WHXB20011016
Abstract:
CCl2 free radicals were produced by dc discharge of CCl4(in Ar). Ground electronic state CCl2 radical was electronically excited to A 1B1 (0,4,0) state with Nd:YAG laser pumped dye laser at 541.52 nm. Experimental quenching data of CCl2 (A 1B1 and a 3B1) by O2,N2,NO,CO2,CS2,H2O,SO2 and SF6 were obtained by observing time resolved fluorescence from the excited CCl2 radicals,which showed a superposition of two exponential decay components. The stateresolved rate constants kA and ka were first time acquired by analyzing and dealing with these data by using a threelevelmodel proposed by us.
CCl2 free radicals were produced by dc discharge of CCl4(in Ar). Ground electronic state CCl2 radical was electronically excited to A 1B1 (0,4,0) state with Nd:YAG laser pumped dye laser at 541.52 nm. Experimental quenching data of CCl2 (A 1B1 and a 3B1) by O2,N2,NO,CO2,CS2,H2O,SO2 and SF6 were obtained by observing time resolved fluorescence from the excited CCl2 radicals,which showed a superposition of two exponential decay components. The stateresolved rate constants kA and ka were first time acquired by analyzing and dealing with these data by using a threelevelmodel proposed by us.
2001, 17(10): 948-951
doi: 10.3866/PKU.WHXB20011017
Abstract:
Pigment gallstone is one kind of cholelithiasis.Up to now,the mechanism of the formation of pigment gallstones is not clear,and it can not be cured completely.The pigment gallstone is composed of calcium bilirubinate,with a small amount of insoluble inorganic salts such as calcium carbonate.The aim of this paper was to examine the association of calcium carbonate with unconjugated bilirubin using FTIR spectroscopy.The results indicated that solid calcium carbonate can associate with unconjugated bilirubin in aqueous solution to form calcium bilirubinate complex.Addition of bile salts can prevent the association of calcium carbonate with unconjugated bilirubin.A possible formation mechanism of pigment gallstones was discussed.
Pigment gallstone is one kind of cholelithiasis.Up to now,the mechanism of the formation of pigment gallstones is not clear,and it can not be cured completely.The pigment gallstone is composed of calcium bilirubinate,with a small amount of insoluble inorganic salts such as calcium carbonate.The aim of this paper was to examine the association of calcium carbonate with unconjugated bilirubin using FTIR spectroscopy.The results indicated that solid calcium carbonate can associate with unconjugated bilirubin in aqueous solution to form calcium bilirubinate complex.Addition of bile salts can prevent the association of calcium carbonate with unconjugated bilirubin.A possible formation mechanism of pigment gallstones was discussed.
2001, 17(10): 952-955
doi: 10.3866/PKU.WHXB20011018
Abstract:
The primary thermodynamic dissociation constants of glycine were studied by means of EMF measurements of the cell without liquid junction at different temperatures from 278.15 to 318.15 K in the 0.2 mass fraction of ethanolwater mixed solvent. The first dissociation constants of glycine were calculated by using the polynomial approach proposed on the basis of Pitzer′s electrolytic solution theory and traditional extrapolation on the basis of extended DebyeHückel equation.The results show that both methods are in agreement with each other.The thermodynamic quantities of the first dissociation process of glycine in the mixed solvent were calculated and the results were discussed.
The primary thermodynamic dissociation constants of glycine were studied by means of EMF measurements of the cell without liquid junction at different temperatures from 278.15 to 318.15 K in the 0.2 mass fraction of ethanolwater mixed solvent. The first dissociation constants of glycine were calculated by using the polynomial approach proposed on the basis of Pitzer′s electrolytic solution theory and traditional extrapolation on the basis of extended DebyeHückel equation.The results show that both methods are in agreement with each other.The thermodynamic quantities of the first dissociation process of glycine in the mixed solvent were calculated and the results were discussed.
2001, 17(10): 956-960
doi: 10.3866/PKU.WHXB20011019
Abstract:
Crystals of two complex compounds of rareearth perchlorate with Lproline,[RE2(LPro)6(H2O)4](ClO4)6(RE=Pr,Er),were synthesized.Their structures were characterized using TG,DTA,chemical analytic method and comparing with literatures,and the purity is determined as 99.24％ and 98.20％,respectively.For the calculation of chemical reaction heat,solution heat of the [2RE(NO3)3•6H2O＋6LPro＋6NaClO4•H2O] and the {[RE2(LPro)6(H2O)4](ClO4)6＋6NaNO3} were firstly measured in 2 mol•L1 HCl solvent with an isoperibel reaction calorimeter,respectively.The standard enthalpy of formation of the two crystals were calculated by chemical reaction heat and a designed thermochemical cycle at 298.15 K.The following reaction enthalpy and standard enthalpy of formation were obtained: RE=Pr:ΔrHm=－63.904 kJ•mol－1;RE=Er:ΔrHm=－ 91.017 kJ•mol－1; ΔfHm([Pr2(LPro)6(H2O)4](ClO4)6,s,298.15 K)=－6 594.78 kJ•mol－1; ΔfHm([Er2(LPro)6(H2O)4](ClO4)6,s,298.15 K)=－6 532.87 kJ•mol－1.
Crystals of two complex compounds of rareearth perchlorate with Lproline,[RE2(LPro)6(H2O)4](ClO4)6(RE=Pr,Er),were synthesized.Their structures were characterized using TG,DTA,chemical analytic method and comparing with literatures,and the purity is determined as 99.24％ and 98.20％,respectively.For the calculation of chemical reaction heat,solution heat of the [2RE(NO3)3•6H2O＋6LPro＋6NaClO4•H2O] and the {[RE2(LPro)6(H2O)4](ClO4)6＋6NaNO3} were firstly measured in 2 mol•L1 HCl solvent with an isoperibel reaction calorimeter,respectively.The standard enthalpy of formation of the two crystals were calculated by chemical reaction heat and a designed thermochemical cycle at 298.15 K.The following reaction enthalpy and standard enthalpy of formation were obtained: RE=Pr:ΔrHm=－63.904 kJ•mol－1;RE=Er:ΔrHm=－ 91.017 kJ•mol－1; ΔfHm([Pr2(LPro)6(H2O)4](ClO4)6,s,298.15 K)=－6 594.78 kJ•mol－1; ΔfHm([Er2(LPro)6(H2O)4](ClO4)6,s,298.15 K)=－6 532.87 kJ•mol－1.
