首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 531 毫秒
1.
李林尉  王冬冬  孙德志  刘敏  曲秀葵 《化学学报》2007,65(24):2853-2857
在298.15 K下,根据本结合过程的假设和Langmuir结合理论, 用等温滴定微量热和圆二色谱分析法研究了抗肿瘤药物5-氟尿嘧啶(5-FU)与人血清白蛋白(HSA)的相互作用. 研究结果表明, 蛋白质(HSA)与药物配体5-氟尿嘧啶的相互作用存在两类结合位点. 第一类结合, 结合位点数N=71±0.1, 结合常数 K=(1.46±0.016)×105 L•mol-1, 结合焓ΔH=(39.61±0.220) kJ•mol-1, 结合熵ΔS=(231.68±0.025) J•mol-1•K-1, 结合自由能ΔG=(-29.48±0.030) kJ•mol-1. 结合过程为熵驱动过程, 疏水相互作用是过程的主要推动力;第二类结合, 结合位点数N=140±0.2, 结合常数 K=(1.49±0.032)×105 L•mol-1, 结合焓ΔH=(-19.31±0.103) kJ•mol-1, 结合熵ΔS=(34.30±0.055) J•mol-1•K-1, 结合自由能ΔG=(-29.53±0.041) kJ•mol-1, 结合过程为焓-熵协同驱动过程, 氢键和静电相互作用是过程的主要推动力. 圆二色谱分析结果表明, 在两类结合过程中, 药物5-氟尿嘧啶(5-FU)的作用致使蛋白质(HSA)二级结构单元的相对含量发生了变化.  相似文献   

2.
The interaction between CdTe quantum dots (QDs) and bovine serum albumin (BSA) was systematically investigated by fluorescence, UV‐vis absorption and circular dichroism (CD) spectroscopy under physiological conditions. The experimental results showed that the fluorescence of BSA could be quenched by CdTe QDs with a static quenching mechanism, indicating that CdTe QDs could react with BSA. The quenching constants according to the modified Stern‐Volmer equation were obtained as 1.710×106, 1.291×106 and 1.010×106 L·mol?1 at 298, 304, and 310 K, respectively. ΔH, ΔS and ΔG for CdTe QDs‐BSA system were calculated to be ?33.68 kJ·mol?1, 6.254 J·mol?1·K?1 and ?35.54 kJ·mol?1 (298 K), respectively, showing that electrostatic interaction in the system played a major role. According to F?rster theory, the distance between Trp‐214 in BSA and CdTe QDs was given as 2.18 nm. The UV‐vis, synchronous fluorescence and CD spectra confirmed further that the conformations of BSA after addition of CdTe QDs have been changed.  相似文献   

3.
At different temperatures, the interactions between imidacloprid (IMI) and bovine serum albumin (BSA) were investigated with a fluorescence quenching spectrum, a synchronous fluorescence spectrum, a three-dimensional fluorescence spectrum and an ultraviolet-visible spectrum. The average values of bonding constants (KLB: 3.424 × 10^4 L,mol^-1), thermodynamic parameters (△H: 5.188 kJ,mol^-1, △G^(○—):-26.36 kJ,mol^-1, △S: 103.9 J,K^-1,mol^-1) and the numbers of bonding sites (n: 1.156) could be obtained through Stern-Volmer, Lineweaver-Burk and ther- modynamic equations. It was shown that the fluorescence of BSA could be quenched for its reactions with IMI to form a certain kind of new compound. The quenching belonged to a static fluorescence quenching, with a non-radiation energy transfer happening within a single molecule. The thermodynamic parameters agree with △H〉 0, △S〉0 and△G^(○-)〈0, suggesting that the binding power between IMI and BSA should be mainly a hydrophobic interaction.  相似文献   

4.
The interaction of ginkgolic acid (15:1, GA) with human serum albumin (HSA) was investigated by FT–IR, CD and fluorescence spectroscopic methods as well as molecular modeling. FT–IR and CD spectroscopic showed that complexation with the drug alters the protein’s conformation by a major reduction of α-helix from 54 % (free HSA) to 46–31 % (drug–complex), inducing a partial protein destabilization. Fluorescence emission spectra demonstrated that the fluorescence quenching of HSA by GA was by a static quenching process with binding constants on the order of 105 L·mol?1. The thermodynamic parameters (ΔH = ?28.26 kJ·mol?1, ΔS = 11.55 J·mol?1·K?1) indicate that hydrophobic forces play a leading role in the formation of the GA–HSA complex. The ratio of GA and HSA in the complex is 1:1 and the binding distance between them was calculated as 2.2 nm based on the Förster theory, which indicates that the energy transfer from the tryptophan residue in HSA to GA occurs with high probability. On the other hand, molecular docking studies reveal that GA binds to Site II of HSA (sub-domain IIIA), and it also shows that several amino acids participate in drug–protein complexation, which is stabilized by H-bonding.  相似文献   

5.
The oxidation of Na4Fe(CN)6 complex by S2O anion was found to follow an outer‐sphere electron transfer mechanism. We firstly carried out the reaction at pH=1. The specific rate constants of the reaction, kox, are (8.1±0.07)×10?2 and (4.3±0.1)×10?2 mol?1·L·s?1 at μ=1.0 mol·L?1 NaClO4, T=298 K for pH=1 (0.1 mol·L?1 HCl04) and 8, respectively. The activation parameters, obtained by measuring the rate constants of oxidation 283–303 K, were ΔH=(69.0±5.6) kJ·mol?1, ΔS=(?0.34±0.041)×102 J·mol?1·K?1 at pH=l and ΔH=(41.3±5.5) kJ·mol?1, ΔS=(?1.27±0.33)×102 J·mol?1·K?1 at pH=8, respectively. The cyclic voltammetry of Fe(CN) shows that the oxidation is a one‐electron reversible redox process with E1/2 values of 0.55 and 0.46 V vs. normal hydrogen electrode at μ=1.0 mol·L?1 LiClO4, for pH=1 and pH=8 (Tris). respectively. The kinetic results were discussed on the basis of Marcus theory.  相似文献   

6.
长春新碱与人血清白蛋白的相互作用研究   总被引:7,自引:1,他引:6  
陈克海  郑学仿  郭明  曹洪玉  唐乾  杨彦杰 《化学学报》2007,65(17):1887-1891
利用荧光和圆二色光谱研究了长春新碱(VCR)与人血清白蛋白(HSA)之间的相互作用. 通过荧光猝灭测得在288, 298和308 K时, VCR与HSA的结合常数K分别为2.14×104, 1.73×104 和1.35×104 L•mol-1, 表明VCR与HSA间具有较强的结合作用, 属于静态猝灭. 计算出焓变(ΔH)为 -17.38 kJ•mol-1, 熵变(ΔS)为22.62 J•mol-1•K-1, 结合分子模型理论计算的结果, 表明VCR与HSA相互作用时在色氨酸(Trp) 214残基和VCR分子中吲哚基间作用力以疏水作用力为主, 但在 VCR和HSA 分子间以静电引力为主. 圆二色光谱(CD)的数据表明相互作用后HSA的二级结构发生了改变:HSA的α-螺旋的含量从51.7%下降到32.9%, β-折叠的含量增加了9.2%.  相似文献   

7.
百草枯与牛血清白蛋白结合作用的荧光光谱   总被引:42,自引:3,他引:39  
颜承农  张华新  刘义  梅平  李克华  童金强 《化学学报》2005,63(18):1727-1732
在模拟动物体生理条件下, 用荧光光谱和紫外-可见吸收光谱法研究了在不同温度下, 百草枯(PQ)与牛血清白蛋白(BSA)结合反应的光谱行为. 试验发现, PQ对BSA有较强的荧光猝灭作用. 用Stern-Volmer和Lineweaver-Burk方程分别处理试验数据, 发现BSA与PQ发生反应生成了新的复合物, 属于静态荧光猝灭, 发生分子内的非辐射能量转移. 根据F?rster的偶极-偶极非辐射能量转移理论计算出结合位置距离212位色氨酸残基2.07 nm. 由Lineweaver-Burk方程求出了不同温度下反应时复合物的形成常数KLB (297 K: 2.035×104 L•mol-1; 304 K: 3.256×104 L•mo-1; 311 K: 2.889×104 L•mol-1)及对应温度下结合反应的热力学参数(⊿HØ=18.50 kJ•mol-1;⊿SØ=144.7 J•K-1/145.2 J•K-1/141.0 J•K-1; ⊿GØ=-24.50 kJ•mol-1/-25.66 kJ•mol-1/-25.36 kJ•mol-1), 证明二者主要靠疏水作用力结合. 同时用三维荧光光谱及同步荧光光谱法探讨了PQ对BSA构象的影响, 为预防和医治PQ中毒提供了重要依据.  相似文献   

8.
Low‐temperature heat capacities of gramine (C11H14N2) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 401 K. A polynomial equation of heat capacities as a function of temperature was fitted by least squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 5 K intervals. The constant‐volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen‐bomb combustion calorimeter as ΔcU=−(35336.7±13.9) J·g−1. The standard molar enthalpy of combustion of the compound was determined to be ΔcHm0=−(6163.2±2.4) kJ·mol−1, according to the definition of combustion enthalpy. Finally, the standard molar enthalpy of formation of the compound was calculated to be Δ;cHm0=−(166.2±2.8) kJ·mol−1 in accordance with Hess law.  相似文献   

9.
Introduction 2,4,8,10-Tetranitro-2,4,8,10-tetraazaspiro[5,5]udecane- 3,9-dione is a typical cyclourea nitramine (Figure 1). Its crystal density is 1.91 gcm-3. The detonation velocity according to =1.90 gcm-3 is about 8670 ms-1. Its sensitivity to impact is better than that of cyclotrimethy- lenetrinitramine. So it is the potential high explosive. Its preparation,1-3 properties,1-3 hydrolytic behavior4 and electronic structure3 have been reported. In the present work, we report its kinetic pa…  相似文献   

10.
The thermal behavior and kinetic parameters of the exothermic decomposition reaction of N‐N‐bis[N‐(2,2,2‐tri‐nitroethyl)‐N‐nitro]ethylenediamine in a temperature‐programmed mode have been investigated by means of differential scanning calorimetry (DSC). The results show that kinetic model function in differential form, apparent activation energy Ea and pre‐exponential factor A of this reaction are 3(1 ‐α)2/3, 203.67 kJ·mol?1 and 1020.61s?1, respectively. The critical temperature of thermal explosion of the compound is 182.2 °C. The values of ΔS ΔH and ΔG of this reaction are 143.3 J·mol?1·K?1, 199.5 kJ·mol?1 and 135.5 kJ·mol?1, respectively.  相似文献   

11.
Introduction Dinitroglycoluril (DINGU) is a typical cyclourea nitramine. Its crystal density is 1.94 gcm-3. The detonation velocity corresponding to =1.94 gcm-3 is about 8450 ms-1. Its sensitivity to impact is better than that of cyclotrimethylenetrinitramine. It has the potential for possible use as high explosive from the point of view of the above-mentioned high performance. Its preparation,1-4 properties1-4 and hydrolytic behavior4 have been reported. In the present paper, we report i…  相似文献   

12.
The kinetics for the esterification of cycloaliphatic epoxy resin with acrylic acid was investigated in the presence of two different catalysts, namely triethylamine (TEA) and triphenylphosphine (TPP). The reactions were carried out at four different temperatures in the range of 80–110°C and 60–90°C for TPP and TEA catalysts, respectively. The power law kinetics model was adopted for analyzing experimental data to determine reaction equations. Both differential and integral methods were applied to determine the reaction orders and reaction constants. The overall reaction order for the reaction systems was found to be 2 using both differential and integral methods. According to the differential method, the reaction orders with respect to epoxide and carboxylic acid groups were calculated to be 1.2 and 0.8, respectively. The reactions could be considered as first‐order reactions with respect to each group based on integral method analysis. The activation energies and frequency factors of these esterification reactions were found to be 77.2 kJ·mol−1 and 1.72E+10 L·mol−1·min−1 in the presence of TPP and 65.3 kJ·mol−1 and 1.44E+7 L·mol−1·min−1 in the presence of TEA. The thermodynamic parameters of reaction in the presence of TPP and TEA were calculated. The results confirmed that both reactions were spontaneous and irreversible. It was found that the reaction in the presence of TEA produced a highly ordered activated complex.  相似文献   

13.
L-脯氨酸独有的亚胺基使其在生物医药领域具有许多独特的功能,并广泛用作不对称有机化合物合成的有效催化剂。本文在碱性介质中研究了二(氢过碘酸)合银(III)配离子氧化 L-脯氨酸的反应。经质谱鉴定,脯氨酸氧化后的产物为脯氨酸脱羧生成的 γ-氨基丁酸盐;氧化反应对脯氨酸及Ag(III) 均为一级;二级速率常数 k′ 随 [IO4-] 浓度增加而减小,而与 [OHˉ] 的浓度几乎无关;推测反应机理应包括 [Ag(HIO6)2]5-与 [Ag(HIO6)(H2O)(OH)]2-之间的前期平衡,两种Ag(III)配离子均作为反应的活性组分,在速控步被完全去质子化的脯氨酸平行地还原,两速控步对应的活化参数为: k1 (25 oC)=1.87±0.04(mol·L-1)-1s-1,∆ H1=45±4 kJ · mol-1, ∆ S1=-90±13 J· K-1·mol-1 and k2 (25 oC) =3.2±0.5(mol·L-1)-1s-1, ∆ H2=34±2 kJ · mol-1, ∆ S2=-122 ±10 J· K-1·mol-1。本文第一次发现 [Ag(HIO6)2]5-配离子也具有氧化反应活性。  相似文献   

14.
Triplet‐triplet extinction coefficients for astaxanthin ( I ) and canthaxanthin ( II ) in different deaerated polarity solutions of MeCN and benzene were evaluated by laser flash photolysis at 298 K in the spectral region from 350 to 650 nm by energy transfer method, employing 2‐acetonaphthone as sensitizer. The triplet‐triplet extinction coefficients in MeCN and benzene were different in terms of the carotenoid present. The maximum triplet‐triplet extinction coefficient was 0.1–1.7×105 L·mol−1·cm−1 in different solvents. The rate constants of triplet decay were I : 1.25×1010 L·mol−1·s−1, II : 1.12×1010 L·mol−1·s−1 in MeCN; and I : 1.75×1010 L·mol−1·cm−1, II : 3.27×1010 L·mol−1·s−1 in benzene. The bimolecular rate constants of energy transfer from triplet excited 2‐acetonaphthone to carotenoids were determined from the linear regression of the decay rate constant of 2‐acetonaphthone triplet at varying carotenoid concentrations. The triplet lifetimes of 3AST* and 3CAN* in different solvents were also determined. The results indicated that triplet energy transfer was nearly diffusion‐controlled.  相似文献   

15.
4,4′-bipyridine bridged two Cu (II) complexes, [Cu2L12(4,4′-bipy)(H2O)2](ClO4)2 ( 1 ) and [Cu2L22(4,4′-bipy)]n·(2H2O)n ( 2 ) (where, HL1 = 2-[(3-methylamino-propylimino)-methyl]-phenol, H2L2 = 3-[(2-hydroxy-3-methoxy-benzylidene)-amino]-propionic acid, and 4,4′-bipy = 4,4′-bipyridine) have been synthesized and characterized by single crystal structure determination, mass spectrometry, FT-IR, electronic absorption, and emission spectroscopy. Complex 1 is dinuclear cationic compound and counter balanced by perchlorate anion, whereas complex 2 possesses 1D poly-nuclear structure. Both the complexes crystallize in monoclinic system with P21/c space group and the copper centers possess square pyramidal geometry. H-bonding, C-H···π, π···π interactions results the formation of two dimentional supramolecular structure for both the complexes. Interactions of complexes with bovine serum albumins (BSA) and human serum albumins (HSA) have been studied by using electronic absorption and emission spectroscopic technique. The calculated values of binding constants (Kb) are (9.22 ± 0.26) × 105 L mol−1 ( 1 -BSA), (7.19 ± 0.16) × 105 L mol−1 ( 1 -HSA), (5.05 ± 0.20) × 105 L mol−1 ( 2 -BSA) and (3.56 ± 0.25) × 105 L mol−1 ( 2 -HSA). The mechanism of serum albumins-complex interactions have been investigated by fluorescence lifetime measurement. Fluorescence spectroscopic studies indicate that both the complexes interact with calf thymas-DNA. Catecholase activity of the complexes has been studied in methanol using 3,5-di-tert-butylcatechol (3,5-DTBC) as substrate and the result show that both the complexes are active for catalytic oxidation of 3,5-DTBC to 3,5-di-tert-butylquinone (3,5-DTBQ) in presence of molecular oxygen. Calculated values of turnover numbers are 71.81 ± 1.04 h−1 and 69.45 ± 0.74 h−1 for 1 and 2 , respectively.  相似文献   

16.
The boiling point and volatility are important properties for fuels, as it is for quality control of the industry of petroleum diesel and biofuels. In addition, through the volatility is possible to predict properties, such as vapor pressure, density, latent heat, heat of vaporization, viscosity, and surface tension of biodiesel. From thermogravimetry analysis it is possible to find the kinetic parameters (activation energy, pre-exponential factor, and reaction order), of thermally simulated processes, like volatilization. With the kinetic parameters, it is possible to obtain the thermodynamic parameters by mathematical formula. For the kinetic parameters, the minor values of activation energy were found for mineral diesel (E = 49.38 kJ mol?1), followed by babassu biodiesel (E = 76.37 kJ mol?1), and palm biodiesel (E = 87.00 kJ mol?1). Between the two biofuels studied, the babassu biodiesel has the higher minor value of activation energy. The thermodynamics parameters of babassu biodiesel are, ΔS = ?129.12 J mol?1 K?1, ΔH = +80.38 kJ mol?1 and ΔG = +142.74 kJ mol?1. For palm biodiesel ΔS = ?119.26 J mol?1 K?1, ΔH = + 90.53 kJ mol?1 and ΔG = +141.21 kJ mol?1, and for diesel ΔS = ?131.3 J mol?1 K?1, ΔH = +53.29 kJ mol?1 and ΔG = +115.13 kJ mol?1. The kinetic thermal analysis shows that all E, ΔH, and ΔG values are positive and ΔS values are negative, consequently, all thermodynamic parameters indicate non-spontaneous processes of volatilization for all the fuels studied.  相似文献   

17.
The Interaction between vitamin B12 (VB12) and fish sperm DNA was investigated in physiological buffer (pH 7.4) using the methylene blue (MB) dye as a spectral probe by spetcrophotometery, viscosity measurements and cyclic voltammetry. The apparent binding constant of vitamin B12 with DNA was found to be 3.2×105 mol−1·L. The voltammetric behavior of vitamin B12 has been investigated at glassy carbon electrode using cyclic voltammetry. Thermodynamic parameters including ΔH0, ΔS0 and ΔG0 for the interaction between VB12 and DNA have determined as −2.3×104, 27.54 and −3.1×104J·mol−1·K−1 respectively. One indication of DNA binding mode with VB12 was the change in viscosity when a small molecule associates with DNA. The diffusion coefficients of VB12 in the absence (D0)f and presence of DNA (D0)b was calculated as 5.04×10−6 and 1.13×10−6 cm2·s−1 respectively. The results indicated that vitamin B12 can bind to DNA and the major binding mode was intercalative binding.  相似文献   

18.
N,N-dimethyl-3-oxa-glutaramic acid was purified and characterized by 1H-NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The thermal decomposition of the title compound was studied by means of thermogravimetry differential thermogravimetry (TG-DTG) and FT-IR. The kinetic parameters of its second-stage decomposition reaction were calculated and the decomposition mechanism was discussed. The kinetic model function in a differential form, apparent activation energy and pre-exponential constant of the reaction are 3/2 [(1?α)1/3?1]?1, 203.75 kJ·mol?1 and 1017.95s?1, respectively. The values of ΔS , ΔH and ΔG of the reaction are 94.28 J·mol?1·K?1, 203.75 kJ·mol?1 and 155.75 kJ·mol?1, respectively.  相似文献   

19.
邸友莹张剑  谭志诚 《中国化学》2007,25(10):1423-1429
A coordination compound of erbium perchlorate with L-α-glutamic acid, [Er2(Glu)2(H2O)6](ClO4)4·6H2O(s), was synthesized. By chemical analysis, elemental analysis, FTIR, TG/DTG, and comparison with relevant literatures, its chemical composition and structure were established. The mechanism of thermal decomposition of the complex was deduced on the basis of the TG/DTG analysis. Low-temperature heat capacities were measured by a precision automated adiabatic calorimeter from 78 to 318 K. An endothermic peak in the heat capacity curve was observed over the temperature region of 290-318 K, which was ascribed to a solid-to-solid phase transition. The temperature Ttrans, the enthalpy △transHm and the entropy △transSm of the phase transition for the compound were determined to be: (308.73±0.45) K, (10.49±0.05) kJ·mol^-1 and (33.9±0.2) J·K^-1·mol^-1. Polynomial equation of heat capacities as a function of the temperature in the region of 78-290 K was fitted by the least square method. Standard molar enthalpies of dissolution of the mixture [2ErCl3·6H2O(s)+2L-Glu(s)+6NaClO4·H2O(s)] and the mixture {[Er2(Glu)2(H2O)6](ClO4)4·6H2O(s)+6NaCl(s)} in 100 mL of 2 mol·dm^-3 HClO4 as calorimetric solvent, and {2HClO4(1)} in the solution A' at T=298.15 K were measured to be, △dHm,1=(31.552±0.026) kJ·mol^-1, △dHm,2 = (41.302±0.034) kJ·mol^-1, and △dHm,3 = ( 14.986 ± 0.064) kJ·mol^-1, respectively. In accordance with Hess law, the standard molar enthalpy of formation of the complex was determined as △fHm-=-(7551.0±2.4) kJ·mol^-1 by using an isoperibol solution-reaction calorimeter and designing a thermochemical cycle.  相似文献   

20.
用精密自动绝热量热计测定了4-硝基苯甲醇(4-NBA)在78 ~ 396 K温区的摩尔热容。其熔化温度、摩尔熔化焓及摩尔熔化熵分别为:(336.426 ± 0.088) K, (20.97 ± 0.13) kJ×mol-1 和 (57.24 ± 0.36) J×K-1×mol-1.根据热力学函数关系式,从热容值计算出了该物质在80 ~ 400 K温区的热力学函数值 [HT - H298.15 K] 和[ST - S298.15 K]. 用精密氧弹燃烧量热计测定了该物质在T=298.15 K的恒容燃烧能和标准摩尔燃烧焓分别为 (C7H7NO3, s)=- ( 3549.11 ± 1.47 ) kJ×mol-1 和 (C7H7NO3, s)=- ( 3548.49 ± 1.47 ) kJ×mol-1. 利用标准摩尔燃烧焓和其他辅助热力学数据通过盖斯热化学循环, 计算出了该物质标准摩尔生成焓 (C7H7NO3, s)=- (206.49 ± 2.52) kJ×mol-1 .  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号