槲皮素的热降解机理及其分解动力学研究

利用TG-DTG技术测得槲皮素在氮气气氛中不同升温速率β下的热分解曲线,协同使用Achar法、Coats-Redfern法、Kissinger法和Ozawa法等4种方法同时进行动力学处理,根据热分解的表观活化能Eα和指前因子A计算推断槲皮素的贮存期.随着升温速率的提高,槲皮素的热分解温度逐渐升高;槲皮素热二步分解的机理依次是随机成核与随后生长控制和化学反应控制,对应的函数名称是Avrami-Erofeev方程和反应级数方程;经Gaussian模拟和热重数据结合分析,槲皮素在第一步分解时,失去两个O原子;第二步分解时失去一个苯环;根据第一步热分解的表观活化能Eα和指前因子A推断,在室温25℃下,槲皮素的贮存期为1.5 ～2年.     

雷公藤甲素和雷公藤内酯酮热稳定性与分解动力学

研究雷公藤甲素和雷公藤内酯酮的热稳定性与分解动力学。利用热重—微商热重(TG-DTG)和差热—微商差热(DTA-DDTA)分析技术测得这两种活性成分在氮气气氛中不同升温速率(β)下的热分解曲线,结合使用Kissinger法、Ozawa法、Coats-Redfern法和Achar法进行动力学处理,根据热分解的表观活化能(Ea)和指前因子(A)计算推断这两种活性成分的贮存期。结果表明,除脱水峰外,雷公藤甲素和雷公藤内酯酮热分解行为相似,失重均分为两步:第一步分别从200℃到340℃,200℃到290℃;第二步分别从340℃到440℃,290℃到490℃。雷公藤甲素和雷公藤内酯酮的两步热分解严重重叠,总失重率分别为85.5%和64.4%。DTA-DDTA曲线分别出现232℃和252℃吸热峰以及298℃和280℃放热峰。雷公藤甲素的第一步热分解的机制是Chemical reaction控制,对应的函数为Reaction order方程。测得平均表观活化能Ea为136.66 k J/mol,指前因子ln A为26.47;雷公藤内酯酮的第一步热分解的机制是Chemical reaction控制,对应的函数为二级反应方程。测得平均表观活化能Ea为127.19 k J/mol,指前因子ln A为25.23。根据第一步热分解的Ea和A推断,在室温(25℃)下,雷公藤甲素和雷公藤内酯酮的理论贮存期均为4~5年。研究结果可为含雷公藤甲素和雷公藤内酯酮药品的质量控制和制剂工艺、雷公藤的炮制减毒以及热分解产物研究提供参考。     

奎宁的热解机理、动力学及贮存期研究

利用热重-红外联用技术测得奎宁在氮气气氛中的热分解曲线,协同使用Achar法和Coats-Redfern法两种方法同时进行动力学处理,根据热分解的表观活化能(E_a)和指前因子(A)计算推断奎宁的贮存期。奎宁晶体在219.93～389.93℃发生了第一步分解,先后释放了醇类、CO、CO_2、醚类、胺类等物质,反应机理为化学反应控制,对应的函数名称是反应级数方程,反应级数n=2;第二步分解(389.93～800℃)是由于残余分子骨架中苯并吡啶环的深度裂解碳化,过程较为缓慢,形成了CO_2、H_2O、NH_3等气体。经红外光谱解析和热重数据结合分析,晶体在第一步分解时又先后分为两个阶段,首先是苯并吡啶环上与两个氧原子相连的化学键断裂,其次是支链上的其它原子化学键相继发生断裂并裂解;根据第一步热分解的表观活化能(E_a)和指前因子(A)推断,在室温25℃下,奎宁的贮存期为4～5年。     

大渡河流域黄石爬鮡的年龄与生长

2012年7月和2013年6月从大渡河支流脚木足河采集黄石爬(鱼兆)(Euchiloglanis kishinouyei)383尾,以脊椎骨作为主要年龄鉴定材料,对其年龄结构和生长特性进行了研究.黄石爬(鱼兆)体长92～190 mm,其中110 ～ 140mm个体占渔获物总量的74.41％;体重14.70 ～ 119.80 g,其中20～60 g个体占渔获物总量的84.86％;由3～ 13龄11个年龄组组成,5～8龄鱼占渔获物总量的84.07％;种群雌雄性比为1∶1.06.体长(L)与脊椎骨半径(Ro)回归方程为L=67.038+ 50.783Ro(n=325,R2=0.758,P＜ 0.01).雌雄个体体长和体重生长无显著差异,据体长(L,单位mm)与体重(W,单位g)关系式W=3×10-5L2.9279(n=383,R2=0.807 1,P＜0.01),黄石爬(鱼兆)为等速生长类型.据体长、体重生长方程Lt=208.42[1-e-0.089(t+1.20)]、Wt=184.82[1-e-0.089(t+1.20)]2.9279,体长和体重生长速度方程分别为dL/dt=18.549 4 e0089(t+ 1.20)和dW/dt=48.161 0 e-0.089(t+1.20)[1-e-0.089(t+ 1.20)] 1.9279,体长和体重生长加速度方程分别为d2L/dt2=-1.650 9 e-0.089(t+1.20)和d2W/dt2=4.286 3 e-0.089(t+1.20)[1-e-0.089(t+1.20)]0.9279[2.927 9 e-0.089(t+1.20)-1],黄石爬(鱼兆)属于生长缓慢,生命周期较长的鱼类.生长拐点年龄为10.87,落后于性成熟年龄(♀6龄,♂5龄),属于性成熟后生长仍然较快的类型.产卵群体主要以补充群体(5、6龄)和低龄剩余群体(7、8龄)为主,资源已经受到严重破坏,需加大保护力度.     

虾青素的热稳定性及分解动力学

用热重/差热分析研究了虾青素的热稳定性,其开始分解温度为250℃左右。通过动力学分析确定其活化能为EA=121.14kJ/mol,指前因子k0=3.25×108/min。对比在有氧和无氧条件下虾青素的热重/差热曲线发现,氧对于虾青素的热分解温度影响不大,但在高温下会生成耐热的降解残余物。     

连花清瘟胶囊原料药的化学成分研究北大核心CSCD

采用硅胶柱层析、Sephadex LH-20凝胶、制备液相等方法从连花清瘟胶囊原料药中分离得到17个化合物。通过IR、MS、1H NMR、13C NMR等波谱手段鉴定为(+)-松脂素(1)、连翘苷(2)、表松脂素-4'-O-β-D-葡萄糖苷(3)、罗汉松脂素-4'-O-β-D-葡萄糖苷(4)、大黄酚-1-O-β-D-葡萄糖苷(5)、芦荟大黄素-8-O-β-D-葡萄糖苷(6)、大黄酚(7)、大黄素(8)、大黄素甲醚(9)、芦荟大黄素(10)、芦荟大黄素乙酸酯(11)、槲皮素-3-O-α-L-鼠李糖苷(12)、山柰酚-3-O-α-L-鼠李糖苷(13)、五福花苷酸(14)、没食子酸(15)、苯甲酸(16)和β-谷甾醇(17)。本研究首次通过系统化学分离、鉴定手段从连花清瘟胶囊原料药中分离、鉴定17个化合物,为阐明连花清瘟胶囊的化学物质基础提供了重要的科学研究数据。     

连花清瘟胶囊原料药的化学成分研究

采用硅胶柱层析、Sephadex LH-20凝胶、制备液相等方法从连花清瘟胶囊原料药中分离得到17个化合物。通过IR、MS、1H NMR、13C NMR等波谱手段鉴定为(+)-松脂素(1)、连翘苷(2)、表松脂素-4'-O-β-D-葡萄糖苷(3)、罗汉松脂素-4'-O-β-D-葡萄糖苷(4)、大黄酚-1-O-β-D-葡萄糖苷(5)、芦荟大黄素-8-O-β-D-葡萄糖苷(6)、大黄酚(7)、大黄素(8)、大黄素甲醚(9)、芦荟大黄素(10)、芦荟大黄素乙酸酯(11)、槲皮素-3-O-α-L-鼠李糖苷(12)、山柰酚-3-O-α-L-鼠李糖苷(13)、五福花苷酸(14)、没食子酸(15)、苯甲酸(16)和β-谷甾醇(17)。本研究首次通过系统化学分离、鉴定手段从连花清瘟胶囊原料药中分离、鉴定17个化合物,为阐明连花清瘟胶囊的化学物质基础提供了重要的科学研究数据。     

给药剂量对氟苯尼考在中华绒鳌蟹体内的药物代谢动力学影响

在17℃水温下,单次肌肉注射给药,高效液相色谱法-荧光法测定中华绒螯蟹(Eriocheir sinensis)血淋巴、肌肉和肝中药物残留浓度,利用3P97药代动力学软件分析数据,研究不同剂量氟苯尼考在中华绒螯蟹血淋巴、肌肉和肝组织中的代谢规律及组织分布。结果表明,在3种(5.0、10.0、20.0mg/kg)给药剂量下,血淋巴和肌肉组织中氟苯尼考含量瞬时达到峰值,而肝中氟苯尼考含量则随给药时间,先上升后下降,各组织含量从大到小依次为:肌肉、血淋巴、肝。应用药代动力学计算软件3P97分析结果表明,血淋巴、肌肉、肝组织中氟苯尼考的代谢规律均符合二室开放模型,以3个浓度给药后,血淋巴中氟苯尼考的吸收半衰期(T1/2α)及消除半衰期(T1/2β)分别为0.04、0.21、0.87h和0.60、1.48、3.29h,整体清除率(CLs)分别是2.17、1.99和2.12ml/(kg·h),肌肉中氟苯尼考的T1/2α及T1/2β分别是1.38、0.93、0.47h和10.39、31.78、23.91h,CLs分别是0.07、0.03、0.03ml/(kg·h),肝中氟苯尼考的T1/2α及T1/2β分别是0.69、0.07、0.12h和0.73、4.90、4.49h,CLs分别是1.79、2.55、3.89ml/(kg·h)。     

大黄素对顺铂耐药卵巢癌细胞的逆转作用及其相关基因表达研究

为了研究大黄素对人卵巢癌耐药细胞株SKOV3/DDP细胞耐药逆转作用及其机制,本研究以卵巢癌SK-OV3和多药耐药细胞株SKOV3/DDP为研究对象,通过噻唑蓝(MTT)法测定SKOV3/DDP细胞的耐药指数和大黄素在无细胞毒浓度下对卵巢癌细胞耐受顺铂(DDP)的逆转作用;采用Real-time PCR技术检测耐药相关基因HIF-1α、STAT1、CK2α、GSTP1 mRNA表达情况。结果发现无细胞毒作用浓度的7.8 mg/L和3.9 mg/L大黄素能逆转SKOV3/DDP细胞对DDP的耐药性,对DDP的逆转倍数分别为1.91倍和1.30倍,与SKOV3比较,SKOV3/DDP细胞的HIF-1α、STAT1、CK2α、GSTP1 mRNA表达明显升高(P<0.01)。3.9 mg/L和7.8 mg/L大黄素作用均可下调HIF-1α、CK2α、STAT1 mRNA表达,存在剂量-效应依赖关系。7.8 mg/L大黄素作用可下调GSTP1 mR-NA表达,但3.9 mg/L大黄素作用不明显。7.8 mg/L和3.9 mg/L大黄素联合IC50浓度的DDP时,四个耐药相关基因的表达与单独化疗药组作用相比明显下调(P<0.01)。提示无细胞毒浓度的大黄素对卵巢癌细胞耐药逆转的作用可能是通过下调HIF-1α、STAT1、GSTP1、CK2α的表达起作用。     

α-氯丙酸脱卤酶发酵动力学模型

对α-氯丙酸脱卤酶发酵动力学进行了研究。基于Logistic方程和Luedeking-Piret方程,得到了描述Pseudomonas W20菌发酵过程菌体生长、α-氯丙酸脱卤酶生成及基质消耗的动力学数学模型和模型参数,对试验数据与模型进行了验证比较,模型计算值与试验结果拟合良好,平均相对误差大部分小于10%;对脱卤酶反应动力学进行了研究,结果表明脱卤酶的脱卤反应基本符合米氏方程,并求得最大反应速率V_(max)=1.11×10~(-5)mol/(g·min),表观米氏常数K_m=3.72×10~(-3)mol/L。     

Thermal Stability and Decomposition Kinetic Studies of Acyclovir and Zidovudine Drug Compounds

Investigations on thermal behavior of drug samples such as acyclovir and zidovudine are interesting not only for obtaining stability information for their processing in pharmaceutical industry but also for predicting their shelf lives and suitable storage conditions. The present work describes thermal behaviors and decomposition kinetics of acyclovir and zidovudine in solid state, studied by some thermal analysis techniques including differential scanning calorimetry (DSC) and simultaneous thermogravimetry–differential thermal analysis (TG/DTA). TG analysis revealed that thermal degradation of the acyclovir and zidovudine is started at the temperatures of 400°C and 190°C, respectively. Meanwhile, TG–DTA analysis of acyclovir indicated that this drug melts at about 256°C. However, melting of zidovudine occurred at 142°C, which is 100°C before starting its decomposition (242°C). Different heating rates were applied to study the DSC behavior of drug samples in order to compute their thermokinetic and thermodynamic parameters by non-isothermal kinetic methods. Thermokinetic data showed that both drugs at the room temperature have slow degradation reaction rates and long shelf lives. However, acyclovir is considerably more thermally stable than zidovudine.     

Four mixed-ligands lead(II) complexes based on 8-hydroxyquinolin (8-HQuin), [Pb(8-Quin)X]; X = 4-pyridinecarboxylate, acetate, thiocyanate and nitrate; structural and thermal studies

Lead(II) 8-hydroxychinolate complexes (8-Quin) containing four different anions, [Pb(8-Quin)X]; X = 4-pyridinecarboxylate (1), acetate (2), thiocyanate (3) and nitrate (4), have been synthesized and characterized by elemental analysis, IR-, ¹H NMR- and ¹³C NMR-spectroscopy. All these compounds were structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of compounds 1–4 were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The results show the influence of different counter-ions to form dimers in compound 2, one-dimensional polymer in compound 4 and two-dimensional polymer in compounds 1 and 3.     

Structural Basis for Antigen Recognition by Transglutaminase 2-specific Autoantibodies in Celiac Disease

Antibodies to the autoantigen transglutaminase 2 (TG2) are a hallmark of celiac disease. We have studied the interaction between TG2 and an anti-TG2 antibody (679-14-E06) derived from a single gut IgA plasma cell of a celiac disease patient. The antibody recognizes one of four identified epitopes targeted by antibodies of plasma cells of the disease lesion. The binding interface was identified by small angle x-ray scattering, ab initio and rigid body modeling using the known crystal structure of TG2 and the crystal structure of the antibody Fab fragment, which was solved at 2.4 Å resolution. The result was confirmed by testing binding of the antibody to TG2 mutants by ELISA and surface plasmon resonance. TG2 residues Arg-116 and His-134 were identified to be critical for binding of 679-14-E06 as well as other epitope 1 antibodies. In contrast, antibodies directed toward the two other main epitopes (epitopes 2 and 3) were not affected by these mutations. Molecular dynamics simulations suggest interactions of 679-14-E06 with the N-terminal domain of TG2 via the CDR2 and CDR3 loops of the heavy chain and the CDR2 loop of the light chain. In addition there were contacts of the framework 3 region of the heavy chain with the catalytic domain of TG2. The results provide an explanation for the biased usage of certain heavy and light chain gene segments by epitope 1-specific antibodies in celiac disease.     

Kinetics of heat- and acidification-induced aggregation of firefly luciferase

The general approach to analysis of the kinetics of protein aggregation registered by the turbidimetric method has been elaborated. The terminal part of the kinetic curves is analyzed using a theoretical equation connecting the derivative of the apparent absorbance (A) with respect to time (dA/dt) and A (t is time). This analysis allows the limiting value of A at t--> infinity (A(lim)) and the order of aggregation with respect to protein (n) to be calculated. Approach proposed was applied to analysis of thermal and acidification-induced aggregation of firefly luciferase. In both cases the A(lim) value is a linear function of the protein concentration. The terminal part of the kinetic curves of thermal aggregation follows the first-order kinetics (n=1), whereas the kinetics of acidification-induced aggregation are characterized by the value of n higher than unity (n=1.29). The mechanism of nucleation-dependent aggregation has been discussed.     

2D Holodirected lead(II) bromide coordination polymers constructed of rigid and flexible ligands

Three new 2D Pb^II coordination polymers containing 4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethane (bpa) and 1,2-bis(4-pyridyl)ethene (bpe) with bromide anions, [Pb(μ-4,4′-bipy)(μ-Br)₂]_n (1), [Pb(μ-bpa)(μ-Br)₂]_n (2) and [Pb(μ-bpe)(μ-Br)₂]_n (3) have been synthesized and characterized by elemental analysis, IR spectroscopy and their structures studied by X-ray crystallography. The thermal stability of compounds 1-3 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single-crystal X-ray data shows that the Pb²⁺-ions have coordination numbers of six and contain the rarely holodirected geometries.     

A new two-dimensional thallium(I) coordination polymer with 4-hydroxybenzylidene-4-aminobenzoate: Thermal, structural, solution and solvatochromic studies

A new one-dimensional thallium(I) coordination polymer with a Schiff base ligand, {[Tl(L)(HL)](H₂O)_0.77}_n (1) [HL = 4-hydroxybenzylidene-4-aminobenzoic acid], has been synthesized and characterized. The single-crystal X-ray data of compound 1 show the coordination number of the Tl^I ions to be seven. The thermal stability of 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The overall stoichiometry in the solid state is 1:2, but both spectrophotometric and conductometric methods did not support formation of a complex with this stoichiometry in solution. The solvatochromic behaviour of 4-hydroxybenzylidene-4-aminobenzoic acid was also investigated by studying its spectra in a selection of different organic solvents. The observed bands are assigned to electronic transitions.     

Cultures and thermal analysis of the marine microalga Tetraselmis suecica Kylin (Butch).

In this paper, the growth of the marine microalga Tetraselmis suecica was investigated using thermogravimetry (TG) and differential thermal analysis (DTA) to determine suitable diets for larval and juvenile development in aquaculture systems. Microalgae were maintained in synthetic sea water (19@1000 salinity, 18 degrees C constant temperature) and the algal growth was evaluated by cell abundance. Exponential, stationary and senescence cells were analyzed by TG and DTA. The results of thermal analysis pointed out marked differences between exponential, stationary and senescence phases and showed that exponentially growing microalgae could represent a suitable food in aquaculture systems.     

TG/DTG/DTA evaluation of flame retarded cotton fabrics and comparison to cone calorimeter data

Unbleached cotton fabrics (UCF) with 12.5% polypropylene scrim treated with two phosphate-urea based fire-retardant (FR) formulations were evaluated for FR properties using thermogravimetry/differential thermogravimetry/differential thermal analysis (TG/DTG/DTA) method. In addition to testing the two FR-treated unbleached cotton fabrics (CF-FR1 and CF-FR2), bleached cotton fabric (BCF) treated with the two FR formulations (BCF-FR1 and BCF-FR2) was evaluated. Both formulations were washable with add-on of FR chemicals at 18.7% (FR1) or 17.4% (FR2) for UCF and 22.5% (FR1) or 24.9% (FR2) for BCF. The decreasing order of sums at maximal rates of samples degradation in air environment according to DTG method was: BCF (21.40%/min)>UCF (12.91%/min)>BCF-FR2 (12.83%/min)>BCF-FR1 (11.68%/min)>CF-FR2 (10.20%/min)>CF-FR1 (9.73%/min). It indicates that both formulations cause the decrease of thermooxidation of the products at slower rates than the starting material. Several endo- and exothermic peaks observed by DTA in inert and oxidative environment gives additional information about the degradation process. The order of decreasing thermal responses of the studied samples based on sums of DTA peak values of endothermic and exothermic peaks in air environment is: UCF (0.597°C/mg)>BCF (0.120°C/mg)>CF-FR1 (0.089°C/mg)>BCF-FR1 (0.077°C/mg)>CF-FR2 (0.062°C/mg)>BCF-FR2 (0.053°C/mg). This is in agreement with the cone calorimeter results according to which the flammability properties are improving with the decreasing heat release rates or ignition time prolongation in order: UCF>CF-FR1>CF-FR2. The advantage of TG/DTG/DTA method is slower linear heating rate, which allows the more detailed evaluation of the light and flammable cotton fabric.     

Characterization of bis(isoorotato)diaquamagnesium(II) dihydrate: a potentially useful complex for magnesium supplementation.

The synthesis and crystal structure of a new Mg(II) complex of stoichiometry [Mg(isoor)2(H2O)2].2H2O, where isoor is the monoanion of 5-carboxyuracil (isoorotic acid), are reported. The structure, solved by single-crystal X-ray diffractometry, shows that it crystallizes in the triclinic space group P(-1) with Z = 1. The electronic, IR and Raman spectra of the complex are briefly discussed. Its thermal behavior was also investigated by means of thermal gravimetry (TG) and differential thermal analysis (DTA) measurements in an oxygen atmosphere. Dissolution studies support the usefulness of the compound for magnesium supplementation.     

Thermolysis preparation of zinc(II) oxide nanoparticles from a new micro-rods one-dimensional zinc(II) coordination polymer synthesized by ultrasonic method

The reaction of the zinc(II) acetate and 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) in presence of perchlorate anions produces a new one-dimensional coordination polymer, {[Zn(μ-3-bpdb)(3-bpdb)₂(H₂O)₂](ClO₄)₂·3-bpdb}_n (1). The compound 1 has been characterized by IR, ¹HNMR and ¹³CNMR spectroscopies. The single crystal X-ray data shows an infinite one-dimensional structure that grows in two- and three-dimensions by hydrogen bonding and π-π stacking. The compound 1 also has been synthesized at micro-size by sonochemical processes and characterized by IR and X-ray powder diffraction (XRD). The scanning electron microscopy (SEM) shows compound 1 has been grown as micro-rod morphology. The thermal stabilities at bulk and micro-size scale were studied by thermal gravimetric (TG) and differential thermal analysis (DTA). The ZnO nanoparticles were obtained by direct calcination at 400 °C under air atmosphere and by thermolysis in oleic acid at 200 °C. The obtained zinc(II) oxide nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).