大环分子衍生物在人工跨膜离子通道领域中的研究进展

大环分子如环糊精、冠醚等因具备独特的空腔结构,能够通过主-客体相互作用实现对分子、离子的特异性识别,因此常被应用于人工跨膜离子传输系统的研究和开发.与天然的通道蛋白相比,大环分子具有价格低廉、性质稳定、结构易于修饰和功能化等诸多优点,因而备受科研工作者们的关注.本综述详细介绍了大环分子在人工离子通道领域中的研究进展,按...     

A proposal for a convertible stadium roof structure derived from Watt-I linkage

In this paper, a novel convertible stadium roof structure is introduced, which has been derived from a special geometric configuration of Watt-I linkage, a 1-DoF mechanism used in robot technologies as anthropomorphic fingers. The proposed structure can offer a wide range of different shape configurations according to the environmental conditions and spatial needs, thus offering several aesthetic and functional advantages over existing solutions. This paper serves as a feasibility investigation of this concept, mainly from geometric and structural point of view. To that affect, first kinematic analysis and geometric design of this linkage are introduced. Then, structural analyses of the proposed structure with realistic dimensions and loading conditions are performed in three different geometric configurations, in order to discuss strength and stiffness limitations. Finally, potential cover materials and actuators are briefly discussed.     

Structure Elucidation of Triterpenoid Saponins Found in an Immunoadjuvant Preparation of Quillaja brasiliensis Using Mass Spectrometry and 1H and 13C NMR Spectroscopy

An immunoadjuvant preparation (named Fraction B) was obtained from the aqueous extract of Quillaja brasiliensis leaves, and further fractionated by consecutive separations with silica flash MPLC and reverse phase HPLC. Two compounds were isolated, and their structures elucidated using a combination of NMR spectroscopy and mass spectrometry. One of these compounds is a previously undescribed triterpene saponin (Qb1), which is an isomer of QS-21, the unique adjuvant saponin employed in human vaccines. The other compound is a triterpene saponin previously isolated from Quillaja saponaria bark, known as S13. The structure of Qb1 consists of a quillaic acid residue substituted with a β-d-Galp-(1→2)-[β-d-Xylp-(1→3)]-β-d-GlcpA trisaccharide at C3, and a β-d-Xylp-(1→4)-α-l-Rhap-(1→2)-[α-l-Arap-(1→3)]-β-d-Fucp moiety at C28. The oligosaccharide at C28 was further substituted at O4 of the fucosyl residue with an acyl group capped with a β-d-Xylp residue.     

结构光测量中的高精度相位误差补偿算法

在模拟分析投影仪伽马非线性对相位误差影响的基础上,提出一种直接分析投影光栅特征并建立相位误差查找表的算法.对相位误差进行补偿.该算法通过分析一组投射到标准白色平板上的光栅图像,确定光栅相位值与相位误差的对应关系,并量化存储在一个查找表中,测量过程中使用查找表对相位误差进行补偿.实验结果表明.该方法可大大降低由投影仪伽马非线性引起的相位误差,系统测量精度达到0.043 mm,比误差补偿前提高了5.6倍.     

An Ultrastable Crystalline Acylhydrazone-Linked Covalent Organic Framework for Efficient Removal of Organic Micropollutants from Water

As an important member of crystalline porous polymers, acylhydrazone-linked covalent organic frameworks (COFs) have gained much attention in recent years. However, the low structural stability imparts a limit on their practical applications. To tackle this problem, we report a simple strategy to increase the chemical stability of acylhydrazone-linked COFs by incorporating azobenzene groups in the conjugated framework. Through reinforcing the π-π stacking interactions between the adjacent layers with increased π-surface, it is surprising to find that the resulting materials exhibit extreme stability in harsh environments, such as in strong acid, strong base, aqueous educing agent and boiling water, even exposed to air for one year. As a proof-of-concept, such frameworks have been used to remove various organic micropollutants such as antibiotics, plastic components, endocrine disruptors, and carcinogens from water with high capacity, fast speed and excellent reusability over a wide pH range at environmentally relevant concentrations. The results provide a new avenue to significantly enhance the stability of COFs for practical applications.     

Supramolecular Coordination Cages Based on N-Heterocyclic Carbene-Gold(I) Ligands and Their Precursors: Self-Assembly,Structural Transformation and Guest-Binding Properties

The incorporation of functional groups into the cavity of discrete supramolecular coordination cages (SCCs) will bring unique functions and applications. Here, three dicarboxylate ligands (H₂ L1 Cl, H₂ L2 Cl and H₂ L3 Cl) containing N-heterocyclic carbene (NHC) precursors as linkers were introduced to construct SCCs by combining with two C₃-symmertic (CpZr)₃(μ₃-O)(μ₂-OH)₃ clusters as three-connect vertices, resulted in a series of rugby-like V₂E₃ (V=vertex, E=edge) type homoleptic cages ( SCC-1 , SCC-2 and SCC-3 ). However, V₄E₆-type tetrahedral cages ( SCC-4 and SCC-5 ), incorporating six Au-NHC moieties, were obtained when the corresponding NHC-gold(I) functionalized ligands (H₂ L1 ^Au, H₂ L2 ^Au) were applied. For the first time, we present a trackable CpZr-involved cage to cage conversion to generate a heteroleptic V₂E₃ cage ( SCC-6 ) from two homoleptic cages ( SCC-2 and SCC-5 ) with different geometries of V₂E₃ and V₄E₆. The heteroleptic assembly SCC-6 can also be formed upon a subcomponent displacement strategy. The structural transformation and reassembly processes were detected and monitored by ¹H NMR spectroscopy and electrospray-ionization mass spectrometry. The formation of heteroleptic assembly was further supported by single crystal X-ray diffraction analysis. Moreover, homoleptic cage SCC-2 possesses a trigonal bipyramidal cationic cavity allowing the encapsulation of a series of sulfonate anionic guests.     

Synthesis and Hydrogen-Bond Patterns of Aryl-Group Substituted Silanediols and -triols from Alkoxy- and Chlorosilanes

Organosilanols typically show a high condensation tendency and only exist as stable isolable molecules under very specific steric and electronic conditions at the silicon atom. In the present work, various novel representatives of this class of compounds were synthesized by hydrolysis of alkoxy- or chlorosilanes. Phenyl, 1-naphthyl, and 9-phenanthrenyl substituents at the silicon atom were applied to systematically study the influence of the aromatic substituents on the structure and reactivity of the compounds. Chemical shifts in ²⁹Si NMR spectroscopy in solution, correlated well with the expected electronic situation induced by the substitution pattern on the Si atom. ¹H NMR studies allowed the detection of strong intermolecular hydrogen bonds. Single-crystal X-ray structures of the alkoxides and the chlorosilanes are dominated by π-π interactions of the aromatic systems, which are substituted by strong hydrogen bonding interactions representing various structural motifs in the respective silanol structures.     

Active transient elasto-acoustic response damping of a thick-walled liquid-coupled piezolaminated cylindrical vessel

The linear 3D piezoelasticity theory in conjunction with the versatile transfer matrix approach and the wave equation for the internal acoustic domain are employed for active non-stationary vibroacoustic response control of an arbitrarily thick, tri-laminate, fluid-filled, simply supported, piezocomposite cylindrical tank, excited by arbitrary (non-axisymmetric) time-dependent on-surface mechanical loads. The smart structure is composed of a supporting core layer of functionally graded orthotropic material perfectly bonded to inner and outer spatially distributed radially polarized functionally graded piezoceramic sensor and uniform force actuator (FGPM) layers. Active vibration damping is implemented by transferring the accumulated voltage on the sensor layer to the piezoelectric actuator layer in context of proportional and derivative control laws. Durbin's numerical inverse Laplace transform scheme is utilized to calculate the time response histories of the relevant interface displacement/stress components, center-point acoustic pressure, and actuator voltage, for selected loading configurations (i.e., concentrated step, impulse, and moving external loads). Numerical simulations demonstrate the effectiveness of the adopted distributed sensing/actuation configuration together with the active damping control strategy in suppressing the vibroacoustic response of a three-layered (Ba₂NaNb₅O₁₅/Al/PZT4) water-filled piezoelastic cylindrical tank. Limiting cases are considered and the validity of results is established by comparison with the available data as well as with the aid of a commercial finite element package.     

添加剂PVP和MTS对合成Beta分子筛结构与性能的影响

分别以铝酸钠和硅溶胶为铝源和硅源,四乙基氢氧化铵为模板剂,在水热条件下,考察了添加剂(聚乙烯吡咯烷酮(PVP)和甲基三乙氧基硅烷(MTS))对合成Beta分子筛结构与性能的影响,并通过XRD、TEM、BET、ICP、~(29)Si-NMR和NH_3-TPD等方法对合成样品进行了结构表征和作用机理讨论,同时以催化裂化异丙苯为模型反应评价其催化性能。结果表明,与传统Beta分子筛相比,加入PVP后所得样品具有更高结晶度和较高的硅铝物质的量比(25.68)以及较大的比表面积(772 m~2/g);而加入MTS后尽管具有较大比表面积(657 m~2/g)和较高硅铝物质的量比(25.76),但是结晶度却相对降低,且粒径减小(160-320 nm)。两种添加剂作用下所得样品均具有更多酸量,在催化裂化异丙苯的反应中表现出较高的催化活性。