接枝羧基对单壁碳纳米管弹性性质的影响

采用分子动力学方法对端口接枝不同数量羧基的扶手椅型和锯齿型单壁碳纳米管弹性模量进行了模拟研究. 结果表明, 扶手椅型(5, 5)、(10, 10)管和锯齿型(9, 0)、(18, 0)管在未接枝状态下杨氏模量分别为948、901GPa和804、860 GPa. 在接枝2-8个羧基情况下, 扶手椅型单壁碳纳米管拉伸杨氏模量基本不随接枝数量的增加而发生变化, 而锯齿型单壁碳纳米管则不同, 接枝状态下的弹性模量比未接枝状态小很多, 但随接枝数量的增加又呈略增趋势. 分别从接枝后碳纳米管变形电子密度等值线结构变化、键长变化和系统势能变化规律等方面, 对单壁碳纳米管弹性模量的接枝效应进行了分析.     

石墨烯/氧化铜纳米粒子/铜修饰电极对亚叶酸钙的电催化氧化及其分析应用

采用阳极极化的方法在铜电极表面形成氧化铜纳米粒子,然后采用循环伏安法将羧基化石墨烯电沉积到上述电极表面,成功制备了石墨烯/氧化铜纳米粒子/铜电极,用于碱性溶液中亚叶酸钙的检测.采用循环伏安法对亚叶酸钙在修饰电极上的催化氧化行为进行了研究,阳极扫描极化反向催化伏安法应用于亚叶酸钙的检测.在2.0×10^-7~2.0×10^-5 mol/L范围内,该电极显示出良好的线性关系,灵敏度为22.0 μA·μL/（μmol/cm²）,检测限达到7.6×10^-8 mol/L（S/N=3）,成功应用于实际样品的检测.     

FRET-based fluorescence probes for hydrolysis study and pig liver esterase activity

New fluorescent probes based on simple organic synthesis were designed and synthesized, and their hydrolysis catalyzed via base and pig liver esterase (PLE) was studied using FRET (fluorescence resonant energy transfer), with 1-naphthylacetic group as a donor and dansyl group as an acceptor. By simultaneous recording of changes of the donor fluorescence intensities, kinetic parameters for base-catalyzed and PLE-catalyzed hydrolysis can be determined. The presented FRET assay is a convenient and simple method and both fluorescent probes are good real-time indicators for the analysis of ester hydrolysis such as PLE activities.     

Large‐scale Enrichment of Sulfur‐containing Acid in Acetonitrile Using Triazine Analog as the Derivatizing Reagent for Desorption from Humic‐fraction‐modified Silica Gel

The analog of triazine is used as the derivatizing reagent for enriching large‐scale acid (e.g. amino acid) containing a sulfur atom on the humic‐fraction‐modified silica gel in acetonitrile and desorbing from the adsorbent in hexane, respectively. The percent yield of the chemical derivatization under alkaline conditions, ranging from about 8 to almost 100 %, is pH dependent, and varies significantly among these examined analytes, believed to be due to the structure of the analyte, not the derivatizing reagent. The percentage of enrichment, not reproducible under an aqueous environment and independent of the type of triazine analogs, reaches almost 100 % in all cases. The force leading to the adsorption is the complexation between carboxyl groups on analyte and a humic‐fraction‐modified adsorbent based on the adsorption equilibrium results. Consequently, these results are not reproducible under ethyl ether or methanol environments due to the competition for binding sites from solvent molecules.     

Determination of carboxyl content in carboxylated nitrile butadiene rubber (XNBR) after degradation via olefin cross metathesis

Carboxyl content in nitrile butadiene rubber (XNBR) has an impact on its application performance. However, its poor solubility makes it difficult to determine the carboxyl content in XNBR due to its high molecular weight. In the present work, olefin cross metathesis was used to degrade XNBR with acrylonitrile (AN) as chain transfer agent for the first time, to solve the solubility problem. After degradation under the optimized condition, with 2% AN and 0.2% catalyst at 60 °C for 30 min, the weight-average molecular weight (M_w) of the product decreased to 0.98 × 10⁴ with distribution (M_w/M_n) of 3.83. Such product was easy to be dissolved, so the carboxyl content in XNBR could be determined with the routine titrimetric analysis methods.     

人纤维蛋白溶酶原的化学修饰

分别以乙基咪唑 (NAI)、 1 ,2 -环己二酮 (CHD)、碳二亚胺 (EDC)和氯氨 -T(Ch-T)作修饰剂 ,研究人纤维蛋白溶酶原 (HPg)中的酪氨酸、精氨酸、羧基和蛋氨酸残基对 HPg活性的影响 ,发现 HPg中的酪氨酸和精氨酸残基的修饰对 HPg活性影响不大 ,而羧基和蛋氨酸残基的修饰导致 HPg酶活性丧失 .按 Keech和Farrant动力学方法分析 ,得出有以两个羧基和一个蛋氨酸残基为 HPg活性的必需基团 ,其中一个羧基为活性中心外的必需基团     

Comparison between experimental and predicted specific absorption rate of functionalized iron oxide nanoparticle suspensions

Radio-frequency heated magnetic nanoaparticle suspensions have potential applications in cancer hyperthermia. To optimize these systems for hyperthermia applications it is important to be able to predict how their heat generation or specific absorption rate (SAR) is influenced by various factors, including nanoparticle coating or functionalization and aggregation. However, at present it is unclear how well-existing models predict experimental SAR results. Direct comparisons between predicted and measured SAR are scarce, despite an abundance of works reporting on heat generation rate of various magnetic nanoparticles suspensions. The main objective of this paper is to experimentally assess the validity of current models for SAR and extract information on the effects of coating and aggregation on heat generation rate. In this context, AC susceptibility and magnetization of suspensions of uncoated particles, as well as particles with aminosilane and carboxymethyl-dextran functionalizations, were measured. These properties were then used to predict the heat generation rate in alternating magnetic field starting from first principles, which was then compared to measured SAR. It was found that experimental SAR agrees relatively well with predictions (by a factor of two) when using experimental susceptibility values for the SAR calculation. However, for uncoated and amine-functionalized particles poor agreement (more than an order of magnitude difference) was found when the experimental susceptibility was substituted with predictions based on the Debye model. This apparent discrepancy is attributed to dipolar interactions between nanoparticles within aggregates in these samples, which enhances the imaginary part of the susceptibility and, consequently, the SAR values. The results also suggest that the thermal resistance effect of the coating has little influence on the SAR.     

分散共聚合制备PSt-AA-EGDMA功能性单分散微米级交联微球的研究

以苯乙烯(St)为主单体,丙烯酸(AA)为功能单体,乙二醇二甲基双丙烯酸酯(EGDMA)为交联单体,聚乙烯吡咯烷酮(PVP)为稳定剂,偶氮二异丁腈(AIBN)为引发剂,乙醇/水混合溶剂为分散介质,用分散聚合法一步合成了功能性单分散大粒径(10～20μm)交联聚苯乙烯微球.研究了PSt-AA-EGDMA三元分散共聚合体系的动力学,由转化率-时间关联得到动力学方程;R_p=k[I]^0.13([St]^1.87+[AA]^0.13+[EGDMA]^0.2)·(1+[PVP]^0.2)exp(-E/RT).详细讨论了AA,EGDMA,PVP的浓度和溶剂极性对羧基分布的影响,阐述了AA和EGDMA对粒子形态、粒径及粒径分布的影响.     

Chemical Modification of Amino Acid Residues in Human Plasminogen

The chemical modification of human plasminogen (HPg) was studied with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), N-acetylimidazole (NAI), 1,2-cyclohexanedione (CHD), chloramine T(Ch-T)and N-bromosuccinimide (NBS) as modifying reagents at its carboxyl group, tyrosine, arginine, methionine and tryptophan residues, respectively. The results indicate that tyrosine and arginine residues are not essential for HPg activity, while carboxyl groups, methionine and tryptophan residues are important for the activi-ty of HPg. The Keech and Farrant‘s kinetic analysis reveals that one tryptophan residue, one methionine residue and two carboxyl groups are essential for HPg activity.     

Syntheses and crystal structures of two Cd(II) coordination polymers: one-dimensional chain [Cd(C4H6N2)2(C4H2O4)(H2O)2] n and two-dimensional sheet [Cd(C4H6N2)(H2O)(C4H4O4)] n · n H2O

Two new Cd(II) coordination polymers, [Cd(C₄H₆N₂)₂(C₄H₂O₄)(H₂O)₂] _n (1) (where C₄H₆N₂?=?2-methylimidazole, C₄H₂O₄?=?fumarate), and [Cd(C₄H₆N₂)(H₂O)(C₄H₄O₄)] _n ?·?nH₂O (2), (where C₄H₄O₄?=?succinates), have been prepared and structurally characterized by single crystal X-ray diffraction. Complex 1 crystallizes in the triclinic space group P 1 in a one-dimensional chain structure, in which carboxy is monodentate; a three-dimensional supermolecular network structure was formed through hydrogen bonding. In complex 2, the coordination geometry of the Cd atoms is a pentagonal bipyramid, and a two-dimensional sheet is formed though carboxyl group bridging. In 1 and 2, IR spectra indicate the presence of bridging carboxyl groups, confirmed by structure analyses.