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Fluorescence regional integration and differential fluorescence spectroscopy for analysis of structural characteristics and proton binding properties of fulvic acid sub-fractions 被引量:10
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作者 Fanhao Song Fengchang Wu +8 位作者 Weiying Feng Zhi Tang John P.Giesy Fei Guo Di Shi Xiaofei Liu Ning Qin Baoshan Xing Yingchen Bai 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2018年第12期116-125,共10页
Structural characteristics and proton binding properties of sub-fractions(FA3–FA13) of fulvic acid(FA), eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluores... Structural characteristics and proton binding properties of sub-fractions(FA3–FA13) of fulvic acid(FA), eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluorescence regional integration(FRI) and differential fluorescence spectroscopy(DFS). Humic-like(H-L) and fulvic-like(F-L) materials, which accounted for more than 80% of fluorescence response, were dominant in five sub-fractions of FA. Based on FRI analysis, except the response of F-L materials in FA9 and FA13, maximum changes in percent fluorescence response were less than 10% as pH was increased from 2.5 to 11.5.Contents of carboxylic and phenolic groups were compared for fluorescence peaks of FA sub-fractions based on pH-dependent fluorescence derived from DFS. Static quenching was the dominant mechanism for binding of protons by FA sub-fractions. Dissociation constants(p Ka) were calculated by use of results of DFS and the modified Stern-Volmer relationship. The p Kaof H-L, F-L, tryptophan-like and tyrosine-like materials of FA subfractions exhibited ranges of 3.17–4.06, 3.12–3.97, 4.14–4.45 and 4.25–4.76, respectively, for acidic pHs. At basic pHs, values of p Ka for corresponding materials were in ranges of 9.71–10.24, 9.62–10.99, 9.67–10.31 and 9.33–10.28, respectively. At acidic pH, protein-like(P-L)materials had greater affinities for protons than did either H-L or F-L materials. The dicarboxylic and phenolic groups were likely predominant sites of protonation for both H-L and F-L materials at both acidic and basic pHs. Amino acid groups were significant factors during proton binding to protein-like materials of FA sub-fractions at basic pH. 展开更多
关键词 Fluorescence titration PROTONATION Modified Stern-Volmer equation dissociation constant BINDING
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Investigations on spectroscopic parameters, vibrational levels, classical turning points and inertial rotation and centrifugal distortion constants for the 1 + X^1∑g^+ state of sodium dimer 被引量:4
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作者 余本海 戴启润 +1 位作者 施德恒 刘玉芳 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第10期2962-2967,共6页
The density functional theory (B3LYP, B3P86) and the quadratic configuration-interaction method including single and double substitutions (QCISD(T), QCISD) presented in Gaussian03 program package are employed to... The density functional theory (B3LYP, B3P86) and the quadratic configuration-interaction method including single and double substitutions (QCISD(T), QCISD) presented in Gaussian03 program package are employed to calculate the equilibrium internuclear distance Re, the dissociation energy De and the harmonic frequency We for the XIEg+ state of sodium dimer in a number of basis sets. The conclusion is gained that the best Re, De and We results can be attained at the QCISD/6-311G(3df,3pd) level of theory. The potential energy curve at this level of theory for this state is obtained over a wide internuclear separation range from 0.16 to 2.0 nm and is fitted to the analytic Murrell-Sorbie function. The spectroscopic parameters De, DO, Re, ωe, ωe Xe, αe and Be are calculated to be 0.7219 eV, 0.7135 eV, 0.31813 nm, 151.63 cm^-1, 0.7288 cm^-1, 0.000729 cm^-1 and 0.1449 cm^-1, respectively, which are in good agreement with the measurements. With the potential obtained at the QCISD/6-311G(3df,3pd) level of theory, a total of 63 vibrational states is found when J = 0 by solving the radial SchrSdinger equation of nuclear motion. The vibrational level, corresponding classical turning point and inertial rotation constant are computed for each vibrational state. The centrifugal distortion constants (Dr Hv, Lv, Mv, Nv and Ov) are reported for the first time for the first 31 vibrational states when J = 0. 展开更多
关键词 dissociation energy vibrational level turning point centrifugal distortion constant
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The Electrolytic Dissociation of Aryl Derivatives of Succinic Acid
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作者 Elene Kvaratskhelia Rusudan Kurtanidze 《Journal of Biomedical Science and Engineering》 2017年第4期163-171,共9页
In this work, an analysis of the regularities of the electrolytic dissociation of aryl derivatives of the succinic acid (phenylsuccinic, benzylsuccinic, dibenzylsuccinic and phenyl-2-benzylsuccinic acids) in their dil... In this work, an analysis of the regularities of the electrolytic dissociation of aryl derivatives of the succinic acid (phenylsuccinic, benzylsuccinic, dibenzylsuccinic and phenyl-2-benzylsuccinic acids) in their dilute (0.0001 - 0.01 mol.dm-3) solutions was carried out with the aid of a new method of determination of the dissociation parameters of weak multibasic organic acids with the “overlapping equilibria” effect previously described by authors. Values of the usual and “partial” degrees of dissociation, the concentrations of all anions, hydrogen ions and undissociated acid molecules, the activity coefficients of all charged dissociation products were calculated. Together with the accurate equations, the simple empirical equations for fast approximate determination of the various dissociation parameters were also suggested. 展开更多
关键词 dissociation constant dissociation Degree WEAK Organic ACIDS EQUATIONS dissociation Step
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南海沉积物中甲烷水合物定压分解特性 被引量:4
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作者 张郁 蔡晶 +3 位作者 李小森 陈朝阳 颜克凤 陈畅 《中国科学:物理学、力学、天文学》 CSCD 北大核心 2019年第3期136-143,共8页
在定压条件下,实验研究了我国南海神狐海域沉积物中甲烷水合物的分解特性,所使用的沉积物平均孔径为12.178 nm,总孔容为4.997×10^(-2)mL/g,比表面积为16.412 m^2/g.所用沉积物样品含水量为40%,实验的温度范围为274.15–281.15 K,... 在定压条件下,实验研究了我国南海神狐海域沉积物中甲烷水合物的分解特性,所使用的沉积物平均孔径为12.178 nm,总孔容为4.997×10^(-2)mL/g,比表面积为16.412 m^2/g.所用沉积物样品含水量为40%,实验的温度范围为274.15–281.15 K,分解压力范围为3.0–5.0 MPa.实验结果表明,海底沉积物中甲烷水合物在降压过程中就开始迅速分解,分解过程造成体系温度迅速下降,最低温度远低于冰点温度.水合物的分解速率随着分解压力的降低而增大,总的分解产气量以及水合物分解率也随着分解压力的降低而增大.在不同温度的实验中,产气速率随着实验温度的升高而增大,总的分解产气量与初始的水合物量有关.当分解压力低于实验温度下纯水的甲烷水合物平衡分解压力时,水合物可以完全分解. 展开更多
关键词 海洋沉积物 甲烷水合物 定压 分解
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Spectroscopic Studies of a Water-soluble Derivative of Hypocrellin A and Its One- and Two-Electron Reduction Products 被引量:2
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作者 胡义镇 安静仪 蒋丽金 《Science China Chemistry》 SCIE EI CAS 1994年第1期15-28,共14页
In this study the spectroscopic characteristics of a water-soluble derivative of hypocrellin A (HA), 14-dehydroxy-15-deacetyl-hypocrellin A-13-sulfonate(13-SO3Na-DDHA),and its one- and two-electron reduction products ... In this study the spectroscopic characteristics of a water-soluble derivative of hypocrellin A (HA), 14-dehydroxy-15-deacetyl-hypocrellin A-13-sulfonate(13-SO3Na-DDHA),and its one- and two-electron reduction products have been investigated. From the changes in absorbance with pH it was observed that the two phenolic hydroxy groups at C-3 and C-10 positions of 13-SO3Na-DDHA or HA dissociated stepwise with increase of pH values. The pKa values for 13-SO3Na-DDHA and HA were determined using an effective method established in this study. Attempts were also made to use absorption and ESR spectroscopies to study the photoreduction of 13-SO3Na-DDHA. It was found that 13-SO3Na-DDHA was directly reduced to its two-electron reduction product in buffered aqueous solution (pH 7. 7). However, in DMF-buffer (1 :1/ v : v,pH 7. 7), it proceeded with one-electron reduction to generate its semiquinone radical anions. The semiquinone radical anions decayed according to second-order kinetics. indicating that the termination went through protonation and disproportionation of the radical anions. Despite of four pheholic hydroxy groups in the molecule of the two-electron reduction product only two hydroxy groups seem to dissociate with increase of pH. This reflects that strong intramolecular hydrogen bonds are probably formed in the mono- and dian-ionic forms of the two-electron reduction product. 展开更多
关键词 WATER-SOLUBLE DERIVATIVE of HYPOCRELLIN A PHOTOREDUCTION electron transfer absorption SPECTRA dissociation constant.
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Preparation and Characterization of HLA-A*0201 Tetramer Loaded with IE-1_(316-324) Antigenic Peptide of Human Cytomegalovirus 被引量:1
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作者 Lihui Xu Qingbing Zha +3 位作者 Hong Sun Qiantao Jia Fengyao Li Xianhui He 《Cellular & Molecular Immunology》 SCIE CAS CSCD 2006年第5期367-371,共5页
Major histocompatibility complex (MHC) class I tetramer technology has become the central technique for analyzing antigen-specific CD8^+ T cell responses and it has been widely used to explore the differentiation a... Major histocompatibility complex (MHC) class I tetramer technology has become the central technique for analyzing antigen-specific CD8^+ T cell responses and it has been widely used to explore the differentiation and formation of memory CD8^+ T cells. Previously, a simplified and efficient procedure for preparing high quality HLA-A*0201 tetramers has been established in our lab and the tetramers loaded with HCMV peptide pp6549s.50a has been successfully applied to investigate HCMV-specific CD8^+ T cells in Chinese populations. Using similar procedure we reported here the construction of HLA-A*0201 tetramer loaded with another dominant epitope derived from immediate early (IE)-1 316.324 (VLEETSVML, VLE) of HCMV (A2-VLE) and characterization of this tetramer. After A2-VLE monomer was prepared and purified, its tetramer was then formed at a yield of 83%. The optimized amount of A2-VLE tetramer for staining 100 μl whole blood was 0.5 μg with incubation at 4℃ for 1 h. Furthermore, the dissociation constant of the tetramer binding to the specific CD8^+ T cells of one HLA-A2^+ donor was estimated to be 32.7 nmol/L, which is markedly higher than that of MHC monomer. The construction of A2-VLE tetramer provides an alternative choice for investigating HCMV-specific CD8^+ T cell responses and will deepen our understanding of the differentiation and formation of HCMV-specific memory CD8^+ T cells. Cellular & Molecular Immunology. 展开更多
关键词 HLA TETRAMER CYTOMEGALOVIRUS immediate early-1 dissociation constant
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The “Overlapping Equilibria” Effect in the Processes of the Electrolytic Dissociation of Weak Multibasic Organic Acids
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作者 Elene Kvaratskhelia Ramaz Kvaratskhelia Rusudan Kurtanidze 《Journal of Biomedical Science and Engineering》 2014年第8期563-572,共10页
The “overlapping equilibria” effect observed in the processes of electrolytic dissociation of many weak multibasic organic acids determines the character of these processes. In this communication, the degree of “ov... The “overlapping equilibria” effect observed in the processes of electrolytic dissociation of many weak multibasic organic acids determines the character of these processes. In this communication, the degree of “overlapping equilibria” in case of weak dibasic organic acids is quantitatively characterized by the values of “partial” degree of dissociation for second step and ratio of the concentrations of dianion and monoanion. It has been shown that these dissociation parameters are directly connected with the values of the second dissociation constant. It has been also shown that the contribution of third dissociation step in the “overlapping equilibria” effect is especially appreciable in case of penta and hexabasic weak organic acids causing the double “overlapping” phenomenon. 展开更多
关键词 dissociation constant dissociation Degree “Overlapping Equilibria” EFFECT WEAK Organic ACIDS
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Molecular Docking of Selective Binding Affinity of Sulfonamide Derivatives as Potential Antimalarial Agents Targeting the Glycolytic Enzymes: GAPDH, Aldolase and TPI 被引量:1
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作者 Neville Forlemu Porshaye Watkins Joseph Sloop 《Open Journal of Biophysics》 2017年第1期41-57,共17页
The parasite Plasmodium falciparum is responsible for the major world scourge malaria, a disease that affects 3.3 billion people worldwide. The development of new drugs is critical because of the diminished effectiven... The parasite Plasmodium falciparum is responsible for the major world scourge malaria, a disease that affects 3.3 billion people worldwide. The development of new drugs is critical because of the diminished effectiveness of current antimalarial agents mainly due to parasitic resistance, side effects and cost. Molecular docking was used to explore structural motifs responsible for the interactions between triose phosphate isomerase (TPI), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and aldolase (ALD) from human and Plasmodium cells with 8 novel sufonylamide derivatives. All the ligands modeled, interact with all three enzymes in the micromolar range. The top ligand (sulfaE) shows a 70-fold increase in selective binding to pfTPI compared to hTPI (dissociation constant-KI of 7.83 μM and 0.177 μM for hTPI and pfTPI respectively), on par with antimalarial drug chloroquine.ALD and GAPDH form complexes with similar binding sites, comprising amino acids of similar chemical properties and polarities. Human TPI and pfTPI bind sulfonamide derivatives using two distinct binding sites and residues. Key residues at the dimer interface of pfTPI (VAL44, SER45, TYR48, GLN64, ASN65, VAL78) form a tight pocket with favorable polar contacts. The affinity with TPI is the most specific, stable, and selective suggesting pfTPI is a candidate for development of antimalarial drugs. 展开更多
关键词 MALARIA Glycolytic Enzymes AutoDock4.2 dissociation constant Triosephosphate ISOMERASE Binding AFFINITY
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Determination of vanadyl sulfate ion-pair dissociation constant at 298.15 K by Fuoss method 被引量:1
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作者 Shu-Di Zhang Pei-Hua Ma +1 位作者 Yu-Chun Zhai Wei-Min Chen 《Rare Metals》 SCIE EI CAS CSCD 2015年第12期873-876,共4页
Vanadium battery has fast and large capacity charge and discharge characteristics, and the concentration and stability of the battery electrolyte are the key to the electrolyte performance. In actual, with higher acid... Vanadium battery has fast and large capacity charge and discharge characteristics, and the concentration and stability of the battery electrolyte are the key to the electrolyte performance. In actual, with higher acidity and higher concentration of the vanadium battery electrolyte, the ion-pair is dominant. The ion-pair dissociation constant is one of the important thermodynamic data related to battery performance. The vanadyl sulfate conductivity in aqueous solution was determined using the conductance method at 298.15K. Using the origin data fitting, the limiting molar conductance is obtained, and then by the improved Ostwald dilution law and the Davies equation, the activity coefficient is solved so as to obtain the ionic strength of the true solution. Using the Fuoss method, the dissociation constant of vanadyl sulfate ion-pair was calculated. At last, the vanadyl sulfate limiting molar conductance (Λ <sub> 0 </sub>) is 174.8251748 S·dm<sup>2</sup>·mol<sup>?1</sup>, and the vanadyl sulfate ion-pair dissociation constant K <sub>d</sub> is 0.002636367, and then other thermodynamic properties can be studied. 展开更多
关键词 Fuoss method Conductance method dissociation constant Vanadium battery Vanadyl sulfate Aqueous solution
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天然气水合物固定井压开采过程数值模拟 被引量:2
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作者 左林 由长福 《清华大学学报(自然科学版)》 EI CAS CSCD 北大核心 2008年第11期1957-1961,共5页
采用数值模拟方法研究天然气水合物在压降条件下的开采过程。在井压固定的前提下,建立了轴对称结构下的物理与数学模型。通过计算获得了储藏层中的天然气水合物在不同环境条件下的温度、压力、分解锋面与井间距离,以及以时间为函数的产... 采用数值模拟方法研究天然气水合物在压降条件下的开采过程。在井压固定的前提下,建立了轴对称结构下的物理与数学模型。通过计算获得了储藏层中的天然气水合物在不同环境条件下的温度、压力、分解锋面与井间距离,以及以时间为函数的产气率。计算结果表明:天然气水合物的分解程度对井压、储藏层温度的变化十分敏感;大范围的分解并不会带来产气率的大幅度提高;较高的储藏层温度、较低的井压将增大产量;产气率随时间缓慢降低。 展开更多
关键词 天然气水合物 固定井压 分解 数值模拟 轴对称模型
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二溴对甲基偶氮羧质子化及其离解 被引量:1
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作者 黄芳 潘教麦 《分析化学》 SCIE EI CAS CSCD 北大核心 1999年第5期578-581,共4页
用萃取法对二溴对甲基偶氮羧进行了纯化,并用分光光度法研究了二溴对甲基偶氮羧的质子化和五级离解作用,测定了其质子化常数和逐级离解常数,获得满意的效果。
关键词 二溴对甲基 偶氮羧 质子化常数 逐级离解常数
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A study of the interaction of drugs with liposomes with isothermal titration calorimetry
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作者 Hiroko Osanai Tastuya Ikehara +4 位作者 Seiji Miyauchi Kazumi Shimono Jun Tamogami Toshifumi Nara Naoki Kamo 《Journal of Biophysical Chemistry》 2013年第1期11-21,共11页
Isothermal titration calorimetry (ITC) was applied to investigate the interaction of drugs with liposomes. Two types of titration are possible. One type is when the liposome suspension in the cell is titrated by aliqu... Isothermal titration calorimetry (ITC) was applied to investigate the interaction of drugs with liposomes. Two types of titration are possible. One type is when the liposome suspension in the cell is titrated by aliquots of drug solution, and the other is when the drug and liposome solutions take the opposite roles. In this paper, we employed the latter type because the disturbance of liposomes may be minimal in this titration type. We derived an equation in which the accumulated heat-flow is expressed as a function of the added lipid concentration. In the derivation, the uniform binding model was used although there may be various binding sites. This equation contains a parameter n, the number of binding sites per lipid molecule. In addition, we derive the relation between the dissociation constant (Kd), partition coefficient (Pm) and n. Binding parameters such as Kd, n, the Gibbs energy change, enthalpy change and entropy change were estimated for ANS (1-anilino-8-naphtarenesulfonate), TPB (tetraphenylborate), amlodipine, nifedipine, amitriptyline, nortriptyline, imipramine, desipramine, propranolol, chlorpromazine, promethazine, miconazole, indomethacin, diclofenac and diflunisal. For some drugs, the enthalpy change was the major binding affinity instead of the classical hydrophobic interaction in which entropy takes the essential role. We proved an approximate rule that for drugs with smaller n (the number of binding sites per lipid molecule), the entropy change contributes more than the enthalpy change. 展开更多
关键词 TC DRUG BINDING LIPOSOME dissociation constant ΔH and ΔS Change
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Study on spectroscopic parameters and molecular constants of HCl(X^1Σ^+) molecule by using multireference configuration interaction approach
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作者 张小妞 施德恒 +2 位作者 张金平 朱遵略 孙金锋 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第5期224-232,共9页
Equilibrium internuclear separations, harmonic frequencies and potential energy curves (PECs) of HCI(X1∑+) molecule are investigated by using the highly accurate valence internally contracted multireference conf... Equilibrium internuclear separations, harmonic frequencies and potential energy curves (PECs) of HCI(X1∑+) molecule are investigated by using the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with a series of correlation-consistent basis sets in the valence range. The PECs are all fitted to the Murrell-Sorbie function, and they are used to accurately derive the spectroscopic parameters (De, Do, ωeXe, αe and Be) Compared with the available measurements, the PEC obtained at the basis set, aug-cc-pV5Z, is selected to investigate the vibrational manifolds. The constants Do, De, Re, We, ωeXe, Ore and Be at this basis set are 4.4006 eV, 4.5845 eV, 0.12757 rim, 2993.33 cm^-1, 52.6273 cm^-1, 0.2981 cm^-1 and 10.5841 cm^-1, respectively, which almost perfectly conform to the available experimental results. With the potential determined at the MRCI/aug-cc-pV5Z level of theory, by numerically solving the radial Schrodinger equation of nuclear motion in the adiabatic approximation, a total of 21 vibrational levels are predicted. Complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced, which are in excellent agreement with the available Rydberg-Klein-Rees data. Most of these theoretical vibrational manifolds are reported for the first time to the best of our knowledge. 展开更多
关键词 dissociation energy spectroscopic parameter vibrational level inertial rotation constant
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Thermodynamics of the Second Stage Dissociation Step (pK<sub>2</sub>) of Buffer Monosodium 1,4-Piperazinediethanesulfonate from (278.15 to 328.15) K
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作者 Rabindra N. Roy Lakshmi N. Roy +7 位作者 John J. Dinga Matthew R. Medcalf Katherine E. Hundley Eric B. Hines Ryan R. Parmar Jamie A. Veliz Clark B. Summers Lucas S. Tebbe 《Journal of Biophysical Chemistry》 2014年第3期91-98,共8页
Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range ... Values of the second thermodynamic dissociation constant pK2 of the protonated form of monosodium 1,4-piperazinediethanesulfonate (PIPES) have been determined at twelve different temperatures in the temperature range from (278.15 to 328.15) K including the body temperature 310.15 K by measurement of the electromotive-force for cells without liquid junction of the type: Pt (s), H2 (g), 101.325 kPa|Na-PIPES (m1) + Na 2-PIPES (m2) + NaCl (m3)|AgCl (s), Ag (s), where m1, m2 and m3 indicate the molalities of the corresponding species at 1 atm = 101.325 kPa in SI units. The pK2 values for the dissociation of Na-PIPES are represented by the equation: pK2 = -1303.76/T + 48.369 - 6.46889 lnT with an uncertainty of ± 0.001. The values of pK2 for Na-PIPES were found to be 7.1399 ± 0.0004 at 298.15 K and 7.0512 ± 0.0004 at 310.15 K, respectively, and indicate that this buffer would be useful as pH standard in the range of physiological application. Standard thermodynamic quantities for the acidic dissociation process of Na-PIPES have been derived from the temperature coefficients of the pK2. These values are compared with those of structurally related N-substituted PIPERAZINE and TAURINE at 298.15 K. 展开更多
关键词 dissociation constant ZWITTERION Ionic Strength pK2 BUFFER Compound e.m.f Thermodynamic QUANTITIES
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Acid Dissociation Constants and Related Thermodynamic Functions of Protonated 2,2-Bis(Hydroxymethyl)-2,2’,2”- Nitrilotriethanol (BIS-TRIS) from (278.15 to 328.15) K
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作者 Rabindra N. Roy Lakshmi N. Roy +5 位作者 Katherine E. Hundley John J. Dinga Mathew R. Medcalf Lucas S. Tebbe Ryan R. Parmar Jaime A. Veliz 《Journal of Biophysical Chemistry》 2014年第3期118-124,共7页
Thermodynamic dissociation constants pKa of 2,2-bis(hydroxymethyl)-2,2’,2”-nitrilotriethanol have been determined at 12 temperatures from (278.15 to 328.15) K including the body temperature 310.15 K by the electromo... Thermodynamic dissociation constants pKa of 2,2-bis(hydroxymethyl)-2,2’,2”-nitrilotriethanol have been determined at 12 temperatures from (278.15 to 328.15) K including the body temperature 310.15 K by the electromotive-force measurements (emf) of hydrogen-silver chloride cells without liquid junction of the type: Pt(s), H2(g), 101.325 kPa|BIS-TRIS (m) + BIS-TRIS·HCl (m)| AgCl(s), Ag(s), where m denotes molality. The pKa values for the dissociation process of BIS-TRIS·H++ H2O = H3O+ + BIS-TRIS given as a function of T in Kelvin (K) by the equation pKa = 921.66 (K/T) + 14.0007-1.86197 ln(T/K). At 298.15 and 310.15 K, the values of pKa for BIS-TRIS were found to be 6.4828 ± 0.0005 and 6.2906 ± 0.0006 respectively. Thus buffer solutions composed of BIS-TRIS and its hydrochloride would be useful as secondary pH buffer standards and for control of acidity in the pH range 6 to 8. At 298.15 K the thermodynamic functions G°, H°, S° and Cp° for the dissociation process of BIS-TRIS·H+ are G°=37,005 J·mol-1, H° = 28,273 J·mol-1, S°= 29.3 J·K-1·mol-1 and Cp° = 36 J·K-1·mol-1. These results are compared with the dissociation of protonated bases structurally related to BIS-TRIS·H+. 展开更多
关键词 dissociation constant pH Buffer EMF THERMODYNAMIC Function IONIC Strength
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Dissociation Constant of N-(2-Acetamido)-Iminodiacetic Acid Monosodium (ADA) from (278.15 to 328.15) K
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作者 Rabindra N. Roy Lakshmi N. Roy +6 位作者 John J. Dinga Mathew R. Medcalf Katherine E. Hundley Eric B. Hines Clark B. Summers Lucas S. Tebbe Jamie Veliz 《Open Journal of Physical Chemistry》 2014年第2期73-79,共7页
The acidic dissociation constant of N-(2-acetamido)-iminodiacetic acid monosodium (ADA) has been determined at 12 temperatures from 278.15 to 328.15 K by electromotive-force (emf) measurements of hydrogen-silver chlor... The acidic dissociation constant of N-(2-acetamido)-iminodiacetic acid monosodium (ADA) has been determined at 12 temperatures from 278.15 to 328.15 K by electromotive-force (emf) measurements of hydrogen-silver chloride cells without liquid junction. At 298.15 K, the value of the dissociation constant (pK2) is 6.8416 ± 0.0004. In response to the need for new physiological pH standards, buffer solutions of NaADA and its disodium salt, Na2ADA would be useful for pH control in the biological region of pH 6.5 to 7.5. The pK2 values over the experimental temperature range are given as a function of the thermodynamic temperature (T) by the equation pK2 = 2943.784/T - 47.05762 + 7.72703 ln T. At 298.15 K, standard thermodynamic quantities for the dissociation process have been derived from the temperature coefficients;ΔH° = 12,252 J·mol-1, ΔS° = -89.9 J·K-1·mol-1 and = -148 J·K-1·mol-1. The results are interpreted and compared with those of structurally related derivatives of GLYCINE. 展开更多
关键词 dissociation constant ADA EMF BUFFER THERMODYNAMIC Quantity
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Calculation of thermal physical parameters of dissociated air by the dissociation degree method
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作者 Yaopeng ZHAO Wei CAO 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第7期1045-1056,共12页
The high temperature gas occurs behind shock or near the wall surface of vehicle in the hypersonic flight. As the temperature exceeds 2 000 K, 4 000 K, respectively, O2 and N2 molecules are successively dissociated. B... The high temperature gas occurs behind shock or near the wall surface of vehicle in the hypersonic flight. As the temperature exceeds 2 000 K, 4 000 K, respectively, O2 and N2 molecules are successively dissociated. Because of variable components at dif- ferent temperatures and pressures, the dissociated air is no longer a perfect gas, In this paper, a new method is developed to calculate accurate thermal physical parameters with the dissociation degree providing the thermochemical equilibrium procedure. Based on the dissociation degree, it is concluded that few numbers of equations and the solutions are easily obtained. In addition, a set of formulas relating the parameter to the dissociation degree are set up four-species, O2 molecule The thermodynamic properties of dissociated air containing and N2 molecule, O atom and N atom, are studied with the new method, and the results are consistent with those with the traditional equilibrium constant method. It is shown that this method is reliable for solving thermal physical parameters easily and directly. 展开更多
关键词 dissociated air thermal physical parameter equilibrium constant dissociation degree
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水和水合氢离子的电离常数
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作者 王万林 《张家口师专学报》 2001年第6期54-55,共2页
对水和水合氢离子的电离常数进行了推导和讨论.
关键词 水合氢离子 电离常数 电离平衡
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5-(4-磺基-1-萘偶氮)-8-羟基喹啉离解常数及其与镱显色反应分光光度法的研究
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作者 刘二保 韩素琴 +3 位作者 梁建功 郭菊红 郑林艳 郭满栋 《山西师大学报(自然科学版)》 1999年第3期61-63,共3页
本文用分光光度法测定了显色剂5-(4-磺基-1-萘偶氮)-8-羟基喹啉离解常数,并研究了该显色剂与Yb的络合情况.结果表明:在pH为2-12之间,该显色剂共有三种存在形式:H2L(NH+)、HL-、L2-,它的离解常数为Ka1=1.61×10-5,Ka2... 本文用分光光度法测定了显色剂5-(4-磺基-1-萘偶氮)-8-羟基喹啉离解常数,并研究了该显色剂与Yb的络合情况.结果表明:在pH为2-12之间,该显色剂共有三种存在形式:H2L(NH+)、HL-、L2-,它的离解常数为Ka1=1.61×10-5,Ka2=4.10×10-9.在pH=9.60附近,该显色剂可与Yb3+形成3:1、2:1、1:1的配合物. 展开更多
关键词 5-(4-磺基-1-萘偶氮)-8羟基喹啉 离解常数
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直链小碳簇C_n(n=7~10)微正则解离速率常数的RRKM理论计算(Ⅱ)
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作者 王海燕 黄荣彬 +2 位作者 陈宏 张强 郑兰荪 《高等学校化学学报》 SCIE EI CAS CSCD 北大核心 2001年第7期1181-1184,共4页
用从头算法研究直链小碳簇 C7,C8,C9和 C10 的解离通道及其动力学 .在 MP2 /6-31 G* 精度上优化了这些碳簇及其过渡态的结构 ,并对它们进行了振动分析 .计算了各解离通道的活化能 ,并根据 RRKM理论估算了各个通道的微正则解离速率 ,计... 用从头算法研究直链小碳簇 C7,C8,C9和 C10 的解离通道及其动力学 .在 MP2 /6-31 G* 精度上优化了这些碳簇及其过渡态的结构 ,并对它们进行了振动分析 .计算了各解离通道的活化能 ,并根据 RRKM理论估算了各个通道的微正则解离速率 ,计算结果说明它们的主要解离通道为裂解 C3碎片的方式 。 展开更多
关键词 RRKM理论 速率常数 直链小碳簇 反应机理 活化能
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