芳香噻嗪类衍生物作为选择性醛糖还原酶抑制剂的分子对接和基于受体的三维定量构效关系研究

芳香噻嗪类衍生物被证明是一类选择性较好的高活性醛糖还原酶抑制剂(ARIs).本文对44个芳香噻嗪类化合物进行了分子对接(docking)和三维定量构效关系(3D-QSAR)研究,并探索了此类化合物与醛糖还原酶(ALr²)的作用机理.醛糖还原酶与醛还原酶(ALR1)活性位点的叠加结果显示, ALr²中残基Leu 300和Cys298的存在是化合物1m具有高选择性的原因.分别建立了比较分子场分析方法(CoMFA, q² = 0.649, r² =0.934; q²:交叉验证相关系数, r²:非交叉验证相关系数)和比较分子相似性指数分析方法(CoMSIA, q² = 0.746, r² = 0.971)模型,并对影响此类化合物生物活性的结构进行了鉴定.结果显示,两个模型均具有较高预测能力,并通过测试集中的7个化合物进行了验证,其中CoMFA模型和CoMSIA模型的预测相关系数(r_Pred²)分别为0.748和0.828. 3D-QSAR模型中的三维等值线图表明,在化合物1m的苄基环上C3和C4位置以及苯并噻嗪母核上C5和C7位置进行改进可能对生物活性的提高有利,此预测与我们前期报道的苯并噻嗪母核C7位改进结果一致.本文所建3D-QSAR模型能够在理性设计具有更高生物活性的新型ARIs中发挥重要作用.     

基于分子对接和QSAR方法预测B-Raf II型抑制剂活性

B-Raf激酶在促分裂素原活化蛋白激酶(MAPK)信号转导通路中起着重要作用,已被确定为癌症治疗非常有吸引力的靶标.新型高效B-Raf抑制剂的开发成为癌症治疗的一个热门研究领域.本文以结构多样的B-Raf II型抑制剂为研究对象,联合应用分子对接和定量构效关系(QSAR)模型研究其定量构效关系去探讨抑制活性的起源.两个主题作为研究重点:生物活性构象和描述符.首先对分子对接方法(Glide、Gold、LigandFit、Cdocker和Libdock)进行准确性评价,后将研究的对象分子对接到B-Raf活性位点并获得生物活性构象.基于准确的对接结果,计算得到16个打分评价函数和21个能量描述符,以此构建定量构效关系模型. QSAR结果表明模型具有高度精确的拟合和强的预测能力(模型M1: r² = 0.852, r_(CV)² = 0.790, r_pre² = 0.864;模型M2: r² = 0.738, r_(CV)² = 0.812, r_pre² = 0.8605).同时探讨了对抑制活性有重要影响的描述符,结果表明打分评价函数(G_Score, -ECD, Dock_Score, PMF)与能量描述符(S(hb_ext), DE(int), Emodel)对抑制活性影响非常大.通过虚拟筛选和QSAR模型理论预测,一些新的具有潜在抑制活性的化合物作为B-Raf II型抑制剂被获得.上述信息对于进一步设计新颖高效的B-Raf II型抑制剂提供了有用的指导.     

溴代烷烃与活性氮的反应发光研究

在流动余辉装置上, 利用N₂空心阴极放电制备活性氮, 研究了活性氮与溴代烷烃(CHBr₃、CH₂Br₂、C₂H₅Br、C₄H₉Br) 反应的化学发光.上述所有反应中, 在550～750 nm波段均观察到了较强的NBr (b¹Σ+→X³Σ^-)跃迁发射谱. 同时在活性氮与CHBr₃和CH₂Br₂的反应中, 在流动管下游还观察到了CN (A²π, B²π→X²Σ⁺)的发射谱. 验证性的实验表明, 激发态NBr (b¹Σ⁺)是由二步过程形成: N(⁴S)与溴代烷烃反应生成NBr (X³Σ^-), 再通过N₂ (A ³Σ_u⁺)分子能量转移到激发态NBr (b¹Σ⁺); 而激发态的CN是通过N(⁴S) + CBr→CN(A, B) + Br过程形成的.     

3C-like蛋白酶抑制剂的构效关系、分子对接和分子动力学

3C-like蛋白酶是中东呼吸综合征冠状病毒（MERS-CoV）等其它冠状病毒的繁殖过程中极为重要的蛋白酶。它已成为人类在抗冠状病毒领域中的研究热点。本文基于计算生物学方法对与MERS-CoV同属的蝙蝠冠状病毒HKU4（HKU4-CoV）的43个肽类3C-like蛋白酶抑制剂分子,建立三维定量构效关系（3D-QSAR）模型。在基于配体叠合的基础上,发现比较分子相似性指数分析法（CoMSIA）中的四个场组合（位阻场、静电场、氢键供体场与氢键受体场）为最优的模型（Q²=0.522,R_ncv²=0.996,R_pre²=0.904;Q²：交叉验证相关系数,R_ncv²：非交叉验证相关系数,R_pre²：验证集分子的预测值相关系数）,并借助该模型通过分子对接（docking）与分子动力学（MD）方法阐明了配受体结合作用。实验结果表明：（1）基于最优的CoMSIA模型基础上的三维等势图形象地说明了分子基团的位阻作用、静电作用、氢键供体与氢键受体作用对分子生物活性的影响;（2）分子对接研究结果显示了疏水性以及结晶水、氨基酸His166和Glu169在配体和受体结合过程中产生重要作用;（3）分子动力学模拟进一步验证了分子对接模型的可靠性,并发现了两个新的关键氨基酸Ser24与Gln192,它们与配体产生了两个较强的氢键。此外,根据这些结果,一些新的具有潜在抑制活性的肽类化合物作为3C-like蛋白酶抑制剂被获得。以上结果能够帮助深入了解3C-like蛋白酶与肽类抑制剂的作用机理,并且能够为今后的抗MERS-CoV药物设计提供有价值的参考。     

Study of the effect of Cal-Red on the secondary structure of human serum albumin by spectroscopic techniques

The effect of Cal-Red on the structure of human serum albumin (HSA) was studied using Resonance light scattering (RLS), Fourier transformed Infrared (FT-IR) and Circular dichroism (CD) spectroscopic methods. The RLS spectroscopic results show that the RLS intensity of HSA was significantly increased in the presence of Cal-Red. The binding parameters of HSA with Cal-Red were studied at different temperatures of 289, 299, 309 and 319 K at pH 4.1. It is indicated by the Scatchard plots that the binding constant K decreased from 4.03 × 10⁸ to 7.59 × 10⁷ l/mol and the maximum binding number N decreased from 215 to 152 with increasing the temperature, respectively. The binding process was exothermic and spontaneous, as indicated by the thermodynamic analyses, and the major part of the binding energy is hydrophobic interaction. The enthalpy change ΔH⁰, the free energy change ΔG⁰ and the entropy change ΔS⁰ of 289 K were calculated to be −42.75 kJ/mol, −47.56 kJ/mol and 16.66 J/mol K, respectively. The alterations of protein secondary structure in the presence of Cal-Red in aqueous solution were quantitatively calculated from FT-IR and CD spectroscopy with reductions of -helices content about 5%, β-turn from 10% to 2% and with increases of β-sheet from 38% to 51%.     

苯在Au(100)表面化学吸附的周期性密度泛函理论研究

采用局域密度泛函理论(LDA)的VWN方法, 结合周期平板模型, 在DNP基组下, 研究了苯分子在Au(100)面的吸附情况. 构型优化的结果表明, 苯分子在穴位吸附活性最高, 吸附能为－184.8～－184.3 kJ•mol^-1, 苯环发生扭曲, C—C键明显拉长, 出现了介于苯和1,4-环己二烯之间的船状构型, 船头的2个C原子从sp²杂化重新进行sp³杂化. 苯分子在桥位和顶位的吸附活性较低, 吸附能分别为－156.7～－145.3 kJ•mol^-1、－116.5～－117.0 kJ•mol^-1, 苯分子构型有稍微的改变. 轨道分析的结果还表明, 吸附之后苯分子的轨道简并度降低, 苯分子的LUMO轨道和邻近Au原子的d_z²轨道叠加比较好, 两个对位的C原子以双σ形式连接到表面邻近的Au原子上.     

氧硫化碳在230 nm光激发下的S(~3P)解离通道

在230nm激光激发下,氧硫化碳(OCS)分子迅速解离生成振动基态但高转动激发的CO(X~1∑_g~+,v=0,J=42-69)碎片,并通过共振增强多光子电离技术实现其离子化。通过检测处于J=56-69转动激发态CO碎片的离子速度聚焦影像,我们获得了各转动态CO碎片的速度分布和空间角度分布,其中包含了S(1D)+CO的单重态和S(~3P_J)+CO三重态解离通道的贡献。不同的转动态CO碎片对应三重态产物通道的量子产率略有不同,经加权平均我们得到230 nm附近光解OCS分子中S(3P)解离通道的量子产率为4.16%。结合高精度量化计算的OCS分子势能面和吸收截面的信息,我们获得了OCS光解的三重态解离机理,即基态OCS(X~1A')分子吸收一个光子激发到弯曲的A~1A'态之后,通过内转换跃迁回弯曲构型的基电子态,随后在C-S键断裂过程中与2~3A"(c~3A")态强烈耦合并沿后者势能面绝热解离。     

Computational study of hydrogen bonding interaction between formamide and nitrosyl hydride

The hydrogen bonding interaction of formamide–nitrosyl hydride complex has been investigated using density functional theory (DFT) and ab initio method. The natural bond orbital (NBO) analysis and atom in molecules (AIM) theory were applied to understand the nature of the interaction. Two stable geometries are found on the potential energy surface, a six-membered cyclic structure of complex A and a seven-membered cyclic structure of complex B, characterized by AIM analysis. Complex A is less stable than complex B. It is confirmed that there are contractions of CH (compared with the monomer HCONH₂), NH bonds (compared with the monomer HNO) and the corresponding stretching vibrational frequencies are blue-shifted, while there is an elongation of the NH bond and the corresponding stretching vibrational frequency is red-shifted, relative to those of the monomer HCONH₂. From NBO analysis, it is evident that the electron densities in the σ^* (CH) and σ^*(NH) of the complex A are less than those of the monomers HCONH₂ and HNO, which strengthen CH and NH bonds. Furthermore, the increases in s-characters of X also strengthen XH bonds.     

Supramolecular architecture of cadmium(II)–terephthalate complexes having a tridentate or tetradentate Schiff base as blocking coligand

Two new cadmium(II)–terephthalate complexes, _∞¹{[Cd₂(μ-terephthalate)₂(L¹)₂]·9H₂O} (1) and [{Cd(H₂O)(L²)}₂(μ-terephthalate)](terephthalate) · 10H₂O (2), where L¹ = (E)-N¹,N¹-diethyl-N²-(1-(pyridin-2-yl)ethylidene)ethane-1,2-diamine; L² = N,N′-bis-(1-pyridin-2-yl-ethylidene)-ethane-1,2-diamine; have been synthesized by a conventional solution method. Characterization by single crystal X-ray crystallography shows that compound 1 is composed of 1-D polymeric zig-zag chains with distorted pentagonal-bipyramidal cadmium centers. Compound 2 consists of centrosymmetric dinuclear complexes with a distorted pentagonal-bipyramidal cadmium center in which one terephthalate ligand bridges the metal centres and another terephthalate anion with water of crystallization forms a H-bonding network.     

芘基查尔酮的合成及三阶非线性光学性质

合成了一种新的具有潜在应用价值的非线性光学(NLO)有机材料1-(芘-1-基)-3-(4-二甲氨基苯基)丙烯酮(PMAK),并通过 NMR、IR、MS和元素分析等技术手段进行了表征。 采用溶液Nd:YAG激光技术测定了PMAK的三阶非线性光学性质并确定了相关参数。 纳秒实验结果:折射率n₂=-3.5×10^-17 m²/W,吸收系数β=7.0×10^-10 m/W,极化率χ⁽³⁾=2.54×10^-11 esu,分子超极化率γ=3.44×10^-30 esu;皮秒实验结果:n₂=-2.8×10^-18 m²/W,β=8.3×10^-11 m/W,χ⁽³⁾=2.49×10^-12 esu,γ=3.33×10^-31 esu。     

Flow injection analysis methods for determination of diffusion coefficients

Two flow injection analyses (FIA) methods for the determination of diffusion coefficients in a straight single tube FIA system were developed. Based on the analytical solution of the convection-diffusion equation, linear relationships of the logarithmic values of the dispersion coefficient (D) and the half-peak width (W_1/2) with the diffusion coefficient (D_m) were obtained. Experiments were designed to verify these methods. For example, for potassium hexacyanoferrate (III) a D_m value of 0.72 × 10⁵ cm² s⁻¹ was found versus a literature value of 0.76 × 10⁵ cm² s⁻¹ (error, 5%). For potassium hexacyanoferrate (II) a D_m value of 0.67 × 10⁵ cm² s⁻¹ was obtained versus a literature value of 0.63 × 10⁵ cm² s⁻¹ (error, 6%). The diffusion coefficients of some important biomedical compounds, such as dopamine, epinephrine, norepinephrine and ascorbic acid, were then determined. The values of 10⁵ D_m/cm² s⁻¹ are 0.60 ± 0.03, 0.44 ± 0.02, 0.60 ± 0.01 and 0.68 ± 0.06, respectively.     

Thermodynamic studies of the solvation of Ph4AsPh4B in mixed solvents (MeOH—DMF)

The thermodynamic data (ΔG⁰, ΔH⁰ and TΔS⁰) of the solvation of tetraphenylarsonium-tetraphenylborate (Ph₄AsPh₄B) and its neutral parts, tetraphenylgermanium (Ph₄Ge) and tetraphenylmethane (Ph₄C) in methanol—N,N-dimethylformamide mixed solvents are discussed.

The values of the free energy of transfer, Δ^s_MG⁰, are calculated from measurements of the solubilities of Ph₄AsPh₄B, Ph₄Ge and Ph₄C in the successive fractions of MeOH in DMF at three different temperatures (15, 25, 35°C). The values of Δ^s_MH⁰ and TΔ^s_MS⁰ for the derivatives are calculated from Δ^s_MG⁰ values.

The values of Δ^s_MG⁰, Δ^s_MH⁰ and TΔ^s_MS⁰ of tetraphenylarsonium and tetraphenylborate ions have also been carefully calculated. The ratios of Δ^s_MG⁰ values (Δ^s_MG⁰ = ΔG⁰(+)/ΔG⁰(−)) were found to be greater than unity. Similarly, the ratios of Δ^s_MH⁰ and TΔ^s_MS⁰ for the positive and negative ions were found to be greater than unity.     

Effect of dose rate of gamma irradiation on biochemical quality and browning of mushrooms Agaricus bisporus

In order to enhance the shelf-life of edible mature mushrooms Agaricus bisporus, 2 kGy ionising treatments were applied at two different dose rates: 4.5 kGy/h (I⁻) and 32 kGy/h (I⁺). Both I⁺ and I⁻ showed 2 and 4 days shelf-life enhancement compared to the control (C). Before day 9, no significant difference (p>0.05) in L^* value was detected in irradiated mushrooms. However, after day 9, the highest observed L^* value (whiteness) was obtained for the mushrooms irradiated in I⁻. Analyses of phenolic compounds revealed that mushrooms in I⁻ contained more phenols than I⁺ and C, the latter containing the lower level of phenols. The polyphenol oxidase (PPO) activities of irradiated mushrooms, analysed via catechol oxidase and dopa oxidase substrates, resulted in being significantly lowered (p0.05) compared to C, with a further decrease in I⁺. Analyses of the enzymes indicated that PPO activity was lower in I⁺, contrasting with its lower phenol concentration. Ionising treatments also increased significantly (p0.05) the phenylalanine ammonia-lyase (PAL) activity. The observation of mushrooms cellular membranes, by electronic microscopy, revealed a better preserved integrity in I⁻ than in I⁺. It is thus assumed that the browning effect observed in I⁺ was caused by both the decompartimentation of vacuolar phenol and by the entry of molecular oxygen into the cell cytoplasm. The synergetic effect of the residual active PPO and the molecular oxygen, in contact with the phenols, allowed an increased oxidation rate and, therefore, a more pronounced browning in I⁺ than in I⁻.     

超高效液相色谱-串联质谱法测定鸡肉中4种蛋白酶抑制剂

建立了鸡肉中4种蛋白酶抑制剂（沙奎那韦、利托那韦、奈非那韦、茚地那韦）的超高效液相色谱-串联质谱（UPLC-MS/MS）检测方法。样品经30%（v/v）乙腈水溶液（含1%（v/v）三氯乙酸）振荡提取、混合型阳离子交换MCX柱净化,采用Luna^® C8色谱柱（150 mm×2 mm,3 μm）,以0.2%（v/v）甲酸水溶液（含5 mmol/L乙酸铵）和乙腈为流动相进行梯度洗脱,采用电喷雾电离（ESI⁺）源和多反应监测（MRM）模式检测。结果表明,在0.1~20.0 μg/L范围内,4种目标化合物呈良好的线性关系,相关系数（r²）大于0.99,方法的定量限（S/N=10）为0.20~0.90 μg/kg;鸡肉组织中4种目标化合物在1.0、2.0和10.0 μg/kg 3个水平下的平均加标回收率为69.0%~106.0%,日内和日间相对标准偏差（RSD）为2.2%~13.8%（n=6）和3.6%~14.6%（n=3）。该法简单、高效、灵敏、准确,可用于鸡肉中沙奎那韦、利托那韦、奈非那韦、茚地那韦残留量的测定。     

Flow-injection determination of iodide ion in nuclear emergency tablets, using boron-doped diamond thin film electrode

The electrochemical determination of iodide was studied at boron-doped diamond thin film electrodes (BDD) using cyclic voltammetry (CV) and flow-injection (FI) analysis, with amperometric detection. Cyclic voltammetry of iodide was conducted in a phosphate buffer pH 5. Experiments were performed using glassy carbon (GC) electrode as a comparison. Well-defined oxidation waves of the quasi-reversible cyclic voltammograms were observed at both electrodes. Voltammetric signal-to-background ratios (S/B) were comparable. However, the GC electrode gives much greater in the background current as usual. The potential sweep rate dependence exhibited that the peak current of iodide oxidation at 1 mM varied linearly (r² = 0.998) with the square root of the scan rate, from 0.01 to 0.30 V s⁻¹. This result indicates that the reaction is a diffusion-controlled process with negligible adsorption on BDD surface, at this iodide concentration. Results of the flow-injection analysis show a highly reproducible amperometric response. The linear working range was observed up to 200 μM (r² = 0.999). The detection limit, as low as 0.01 μM (3σ of blank), was obtained. This method was successfully applied for quantification of iodide contents in nuclear emergency tablets.     

Heat capacities of NaNO3 and KNO3 from 350 to 800 K

The heat capacities of NaNO₃ and KNO₃ were determined from 350 to 800 K by differential scanning calorimetry. Solid-solid transitions and melting were observed at 550 and 583 K for NaNO₃ and 406 and 612 K for KNO₃, respectively. The entropies associated with the solid-solid transitions were measured to be (8.43± 0.25) J K⁻¹ mole⁻¹ for NaNO₃ and (13.8±0.4) J K⁻¹ mole⁻¹ for KNO₃. At 298.15 K the values of C⁰_P S⁰_P, {H⁰(T)-H⁰(0)}/T and -{G⁰(T)-H⁰(0)}/T, respectively, are 91.94, 116.3, 57.73, and 58.55 J K⁻¹ mole⁻¹ for NaNO₃ and 95.39, 133.0, 62.93, and 70.02 J K⁻¹ mole⁻¹ for KNO₃. Values for S⁰_T, {H⁰(T)-H⁰(0)}/T, and -{G⁰(T)-H⁰(0)}/T were calculated and tabulated from 15 to 800 K for NaNO₃ and KNO₃.     

Second sphere interaction in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate

Trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate was synthesised and detailed packing analysis was undertaken to delineate the topological complimentarity of [trans-Co(en)₂Cl₂]⁺ and BF₄⁻ ions by second sphere coordination. The complex was completely characterised by elemental analyses, solubility product measurement and spectroscopic studies (IR, UV–Vis, multinuclear NMR). In the crystal lattice, discrete ions [trans-Co(en)₂Cl₂]⁺ and BF₄⁻ are arranged in A–B–A–B pattern (in both a and c directions of the lattice) forming columns of anions and cations. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. N–HF⁻ and N–HCl involving second sphere coordination. It appears that the topological features of [trans-Co(en)₂Cl₂]⁺ are conducive for generating second sphere interactions. This strategy may be used as a viable method for the capture of other fluoroanions.