Ni(Ⅱ)-EDTA配合物与DNA相互作用机制的光谱学研究

应用光谱学方法以吖啶橙(AO)作探针研究了Ni(Ⅱ)-EDTA与DNA的作用机制.研究表明,Ni(Ⅱ)与EDTA形成配离子的摩尔结合比nNi(Ⅱ)∶nEDTA=1∶1,配合物Ni(Ⅱ)-EDTA与DNA的摩尔结合比为nNi(Ⅱ)-EDTA∶nDNA=2∶1,其结合常数K■B25℃=2.77×105 L.mol-1,K■B37℃=2.01×105 L.mol-1.该过程为熵和焓共同驱动,其ΔrS■m=171.39J.(mol.K)-1,ΔrH■m=-2.05×104 J.mol-1,25℃时ΔrG■m=-3.06×104 J.mol-1.Scatchard法和探针法等均表明Ni(Ⅱ)-EDTA与DNA之间的结合方式以沟区作用为主.     

Photodynamic Effect of Riboflavin on Chitosan Coatings and the Application in Pork Preservation

Riboflavin (RF) was considered to be possessed of photoactivity to generate reactive oxygen species (ROS) under ultraviolet (UV) light, which is thought to be a favorable antibacterial candidate. Herein, RF was incorporated into chitosan (CS) coatings and treated under UV with different exposure times (2, 4, and 6 h) to improve the physicochemical and antibacterial properties. The results showed that the light transmittance and antibacterial performance of chitosan coatings gradually increased with the extension of the UV irradiation time. The antibacterial ability of chitosan coatings correlated with the generation of ROS: ∙OH and H₂O₂, which achieved 1549.08 and 95.48 μg/g, respectively, after 6 h irradiation. Furthermore, the chitosan coatings with UV irradiation also reduced the pH value, total volatile basic nitrogen (TVB-N), ΔE, and total viable counts (TVC) and improved sensory attributes of pork. In conclusion, the UV irradiated chitosan coatings could be used as an environmentally friendly antimicrobial packaging material to effectively delay the spoilage of pork, maintain its sensory quality and prolong its shelf life.     

Mechanism for the addition of carbenoid CH2ClLi to formaldehyde

Ab initlo HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2CILi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2CILi is first formed with quite exothermic effect. Only a little activation energy of 14.6 kJ/mol is needed for the complex developing into the product through a transition state with coplanar bicyclic structure. In this process, the eletrophilic attack of carbonyl carbon of formaldehyde is more active than the nucleophilic attack of carbon of carbenoid. The exothermal effect of this addition process is up to 216.5 kJ/mol.     

Theoretical studies on the structures and isomerization of the LiSiF_3 system

Various possible isomers of LiSiF_3 system and isomerization between them have been studied at G2(MP2) level using ab initio calculations. The relative energies of four minimum points on the potential energy surface are -128.6, -194.3, -12.7 and -122.8 kJ/mol (taking the sum of the energies of LiF and SiF_2 as zero) . The structural energy of the four-membered ring that contains three F-Si-F-Li four-membered rings with C_(3v) symmetry is the lowest. The highest potential barrier for the isomerization of the remaining three-or four-membered structure is 12.5 kJ/mol.     

碳硅烷树枝状化合物的功能化研究

本文根据碳硅烷树枝状化合物功能基的种类及反应特性,介绍了有关含硅树枝状化合物的功能化的方法,并对功能化含硅树枝状化合物的用途做了相应评述.     

毛细管气相色谱法测定南美白对虾中硫丹的残留量

建立了运用毛细管气相色谱检测南美白对虾中硫丹残留的快速测定方法。用乙酸乙酯提取样品中的硫丹,提取液浓缩后以中性氧化铝和活性炭小柱进行双级柱色谱净化,用正己烷-乙酸乙酯(体积比为1∶1)洗脱,洗脱液用气相色谱-电子捕获检测器检测,以保留时间定性,外标法定量。在南美白对虾样品中分别添加0.20,0.10,0.04和0.02 mg/kg硫丹标准品,测得添加回收率为80.5%～109.5%,相对标准偏差为3.6%～8.4%。该方法在不具备凝胶渗透色谱条件下也能进行硫丹残留的检测,具有简便、准确的特点,能满足常规检测及食品安全监控的需要。     

Insertion reactions of silylenoid Ph2SiLi(OBu-t) into X-H bonds (X = F, OH, and NH2)

The insertion reactions of silylenoid [(tert-butoxy)diphenylsilyl]lithium Ph(2)SiLi(OBu-t) into HF, H(2)O, and NH(3) molecules have been studied by using density functional theory at the B3LYP/6-31G(d) level. To better understand the reactivity of silylenoid Ph(2)SiLi(OBu-t), its two most stable isomers, the p-complex (1) and the three-membered ring (2), were selected for reactants. Natural bond orbital (NBO) analysis has been performed to study the effects of charge transfer and to understand the nature of different interactions between atoms or groups. The results indicate that (i) the insertion of Ph(2)SiLi(OBu-t) into X-H bond proceeds in a concerted manner via a three-membered-ring transition state to form substituted silane Ph(2)SiHX with dissociation of LiOBu-t; (ii) the activation barrier increases in the order of HF < H(2)O < NH(3), and the barrier heights of the 1 insertions are higher than those of the 2 insertions, respectively; (iii) both 1 and 2 display ambiphilic character in their insertion reactions.     

多孔碳球封装纳米碳化钼催化剂无溶剂催化苄胺偶联反应

以盐酸多巴胺，磷钼酸（PMo）为原料，通过离子交换和聚合作用形成一种有机-杂多酸杂化材料，在N₂条件下高温碳化制备出一种新型多孔碳球封装纳米碳化钼催化剂PDA-PMo-800.利用傅里叶变换红外（FT-IR），N₂吸脱附等温仪（BET），扫描电子显微镜（SEM），透射电子显微镜（TEM），X射线粉末衍射（XRD），拉曼光谱仪（Raman），热重分析仪（TG），能谱仪（EDS）对催化剂进行表征与分析.结果显示：催化剂PDA-PMo-800具有规整的花状球体形貌以及较高的比表面积（102 m²/g），纳米碳化钼颗粒（3~4 nm）均匀地分布在多孔碳球骨架内.在无溶剂以氧气为氧化剂的条件下，将该催化剂应用于苄胺的氧化偶联反应合成亚胺，实现较高的转化率及选择性，且催化剂可以多次重复使用并保持较高的催化活性.     

Morphology and gas-sensing behavior of in situ polymerized nanostructured polyaniline films

Nanostructured polyaniline films could be easily in situ polymerized on microslides via rapidly mixing aniline with ammonium persulfate in acid solution. The influence of different conditions including aniline, acid concentration, reaction time and acid kinds on the morphology and thickness of the resulting films was studied. The gas-sensing behavior of the nanostructured films to 100 ppm of NH₃ was investigated through monitoring the change of the resistance.     

Theoretical study of solvent effects on the structures and isomerization of silylenoid H<Subscript>2</Subscript>SiLiF

The structures and isomerization of silylenoid H₂SiLiF are investigated by density functional theory (DFT) at B3LYP/6-311+G(d,p) level. The solvent effects are modeled using the self-consistent reaction field (SCRF) method with Tomasi’s polarized continuum model (PCM). Five representative solvents, i.e. benzene, ether, THF, acetone, and DMSO, are chosen for this work. Special attention is paid to THF solvent. The results indicate that the polarity of solvents has played an important role on the structures and relative stabilities of different isomers. Contrary to the three-membered ring structure 1, the relative stability of the “classical” tetrahedron structure 4 increases with increasing dielectric constants (ε) of solvents. The σ-complex isomer 3 is most unstable structure. Although the relative energies are reduced with increasing dielectric constants (ε) of solvents, the p-complex structure 2 still has the lowest energy. The effects of solvents on the dipole moments and charge distributions are also discussed.