Self‐Assembled Poly(N‐methylaniline)–Lignosulfonate Spheres: From Silver‐Ion Adsorbent to Antimicrobial Material

Self‐assembled poly(N‐methylaniline)–lignosulfonate (PNMA–LS) composite spheres with reactive silver‐ion adsorbability were prepared from N‐methylaniline by using lignosulfonate (LS) as a dispersant. The results show that the PNMA–LS composite consisted of spheres with good size distribution and an average diameter of 1.03–1.27 μm, and the spheres were assembled by their final nanofibers with an average diameter of 19–34 nm. The PNMA–LS composite spheres exhibit excellent silver‐ion adsorption; the maximum adsorption capacity of silver ions is up to 2.16 g g^?1 at an adsorption temperature of 308 K. TEM and wide‐angle X‐ray results of the PNMA–LS composite spheres after absorption of silver ions show that silver ions are reduced to silver nanoparticles with a mean diameter of about 11.2 nm through a redox reaction between the PNMA–LS composite and the silver ions. The main adsorption mechanism between the PNMA–LS composite and the silver ions is chelation and redox adsorption. In particular, a ternary PNMA–LS–Ag composite achieved by using the reducing reaction between PNMA–LS composite spheres and silver ions can be used as an antibacterial material with high bactericidal rate of 99.95 and 99.99 % for Escherichia coli and Staphylococcus aureus cells, respectively.     

Butterfly‐Shaped Pentanuclear Dysprosium Single‐Molecule Magnets

Two new “butterfly‐shaped” pentanuclear dysprosium(III) clusters, [Dy₅(μ₃‐OH)₃(opch)₆(H₂O)₃] ? 3 MeOH ? 9 H₂O ( 1 ) and [Dy₅(μ₃‐OH)₃(Hopch)₂(opch)₄(MeOH)(H₂O)₂] ? (ClO₄)₂ ? 6 MeOH ? 4 H₂O ( 2 ), which were based on the heterodonor‐chelating ligand o‐vanillin pyrazine acylhydrazone (H₂opch), have been successfully synthesized by applying different reaction conditions. Single‐crystal X‐ray diffraction analysis revealed that the butterfly‐shaped cores in both compounds were comparable. However, their magnetic properties were drastically different. Indeed, compound 1 showed dual slow‐relaxation processes with a transition between them that corresponded to energy gaps (Δ) of 8.1 and 37.9 K and pre‐exponential factors (τ₀) of 1.7×10^?5 and 9.7×10^?8 s for the low‐ and high‐temperature domains, respectively, whilst only a single relaxation process was noted for compound 2 (Δ=197 K, τ₀=3.2×10^?9 s). These significant disparities are most likely due to the versatile coordination of the H₂opch ligands with particular keto–enol tautomerism, which alters the strength of the local crystal field and, hence, the nature or direction of the easy axes of anisotropic dysprosium ions.     

Structural and Dynamic Basis of Human Cytochrome P450 7B1: A Survey of Substrate Selectivity and Major Active Site Access Channels

Cytochrome P450 (CYP) 7B1 is a steroid cytochrome P450 7α‐hydroxylase that has been linked directly with bile salt synthesis and hereditary spastic paraplegia type 5 (SPG5). The enzyme provides the primary metabolic route for neurosteroids dehydroepiandrosterone (DHEA), cholesterol derivatives 25‐hydroxycholesterol (25‐HOChol), and other steroids such as 5α‐androstane‐3β,17β‐diol (anediol), and 5α‐androstene‐3β,17β‐diol (enediol). A series of investigations including homology modeling, molecular dynamics (MD), and automatic docking, combined with the results of previous experimental site‐directed mutagenesis studies and access channels analysis, have identified the structural features relevant to the substrate selectivity of CYP7B1. The results clearly identify the dominant access channels and critical residues responsible for ligand binding. Both binding free energy analysis and total interaction energy analysis are consistent with the experimental conclusion that 25‐HOChol is the best substrate. According to 20 ns MD simulations, the Phe cluster residues that lie above the active site, particularly Phe489, are proposed to merge the active site with the adjacent channel to the surface and accommodate substrate binding in a reasonable orientation. The investigation of CYP7B1–substrate binding modes provides detailed insights into the poorly understood structural features of human CYP7B1 at the atomic level, and will be valuable information for drug development and protein engineering.     

2-巯基苯并噻唑对铜缓蚀行为的表面增强红外光谱研究

2-巯基苯并噻唑(MBT)是Cu的高效缓蚀剂,但是缓蚀机理存在较大争议.本文通过电化学极化曲线从宏观角度对缓蚀效率进行评估,并利用原位衰减全反射-表面增强红外光谱技术结合理论计算研究了电位控制下的微观吸附构型.结果表明:在较高电位(大于0 V,相对饱和甘汞电极(SCE))下,MBT和金属Cu之间发生电子转移,MBT以硫醇式的环外S和N与金属Cu(I)离子配位在表面形成聚合物膜;在较低电位(小于0 V,vs SCE)下,MBT通过环外S原子以硫醇离子形式在金属Cu表面直立吸附.表面膜阻止了腐蚀介质的侵蚀,起到了较好的缓蚀效果.     

3D打印技术制备生物医用高分子材料的研究进展

3D打印技术能够根据不同患者需要,快速精确制备适合不同患者的个性化生物医用高分子材料,并能同时对材料的微观结构进行精确控制.因此,这种新兴的医用高分子材料制备技术在未来生物医学应用(尤其是组织工程应用)中具有独特的优势.近年来,对于3D打印技术制备生物医用高分子材料的研究开发受到了越来越多的关注.不同的生物相容高分子原料被应用于3D打印技术,而这些3D成型高分子材料被用于体外细胞培养,或动物模型的软组织或硬组织修复中.本文主要介绍了近年来3D打印技术在生物医用高分子材料制备中的研究进展,并对该领域的未来应用和挑战进行了展望.     

高耐热PLLA/PDLA共混物的热性能和结晶结构研究

通过熔融共混法制备了一系列等比例聚左旋乳酸(PLLA)/聚右旋乳酸(PDLA)共混试样,采用差示扫描量热法(DSC)、核磁共振(13C-NMR)及广角X射线衍射(WAXD)等方法对共混产物进行了表征和研究分析.结果表明,等比例PLLA和PDLA熔融共混生成了立构复合物(stereocomplex,sc),同时部分均聚物发生酯交换反应,生成了立体嵌段物(stereoblock,sb),从而在DSC升温曲线上sc晶体处出现特殊的熔融双峰现象;随着熔融共混温度升高,sc晶体的生成率和结晶度逐渐下降;聚乳酸立构复合物的加工稳定性较好,二次加工后,sc晶体熔点基本不变,生成率和结晶度提高;由于sc晶体的存在,PLLA/PDLA共混物的耐热性能提高,退火热处理后耐热性能得到进一步提高.这对于开发高耐热聚乳酸及其加工应用具有重要的应用价值.     

稀释蒸汽中Na+及积炭对甲醇制丙烯催化剂性能影响

考察了稀释蒸汽中Na⁺及积炭对甲醇制丙烯(MTP)催化剂物理化学性质和催化性能影响, 及离子交换后催化性能. 采用X射线衍射(XRD)、扫描电镜(SEM)、X射线荧光(XRF)光谱、N₂吸附-脱附、程序升温氨脱附(NH3-TPD)和热重(TG)分析等方法对失活和再生催化剂进行了表征, 并在101325 Pa、470℃ 和甲醇空速(WHSV)为1.0-3.0 h^-1的反应条件下, 采用连续流动固定床微型反应器考察其催化甲醇制丙烯性能. 结果表明: MTP反应970 h后的催化剂晶体结构和形貌没有受到明显破坏, 但稀释蒸汽中Na⁺极易扩散至催化剂表面,部分取代H质子的位置, 从而使催化剂酸性逐渐下降而中毒失活; 另外, MTP催化剂表面的积炭导致分子筛微孔堵塞是造成其失活的主要原因, 可通过烧炭再生过程消除, 而水蒸汽脱铝对催化剂性能的影响缓慢但更严重. 用再生和离子交换处理后, Na⁺中毒催化剂MTP反应性能基本完全恢复. 在470 h反应过程中, 甲醇转化率保持在99%以上, 丙烯选择性大于46%, 且随着反应时间的延长, 丙烯选择性逐渐升高、乙烯选择性逐渐下降.     

在四氯合锌离子诱导下反式六元瓜环与碱金属离子构筑的配位超分子自组装体

在盐酸介质中,通过四氯合锌离子诱导,碱金属离子能与反式六元瓜环端口羰基氧原子直接配位构筑形成超分子自组装体。单晶结构表明在HCl介质中,四氯合锌离子形成"蜂巢结构",而且在[ZnCl₄]^2-诱导作用下,碱金属离子和反式六元瓜环端口羰基氧直接配位形成一维超分子自组装体而填充在"蜂巢结构"中。     

基于FCS的海水痕量元素的通用测定平台

为了对海水痕量营养盐与重金属进行测定,基于FCS的设计思想,采用流动注射分光光度法研制了具有自适应外界设备、快速组建多种仪器及全数字化通信等特点的软硬件一体化的通用测定平台。平台以ARM(S3C2416)处理器为核心,Linux为操作系统,LCD作为人机交互显示,触摸屏或者USB鼠标完成输入控制,构成完整的嵌入式工控机系统;采用CAN总线并制定CAN应用层协议管理设备,提高了系统的可靠性及抗干扰能力。实际测试和应用证明,该平台自动化程度高,通用性、重用性及可扩展性均较强,可组建成亚硝氮、硝氮、氨氮、活性磷、铁等多种痕量元素的实验室、船载和原位分析系统,检测限为nmol/L级别。平台对样品的测试准确度与商品专用仪器无显著性差异。     

The localized longitudinal index theorem for Lie groupoids and the van Est map

We define the “localized index” of longitudinal elliptic operators on Lie groupoids associated with Lie algebroid cohomology classes. We derive a topological expression for these numbers using the algebraic index theorem for Poisson manifolds on the dual of the Lie algebroid. Underlying the definition and computation of the localized index, is an action of the Hopf algebroid of jets around the unit space, and the characteristic map it induces on Lie algebroid cohomology. This map can be globalized to differentiable groupoid cohomology, giving a definition of the “global index”, that can be computed by localization. This correspondence between the “global” and “localized” index is given by the van Est map for Lie groupoids.