Photochemical molecular imprinting of cholesterol

Cinnamoylated photocrosslinkable cyclodextrin derivatives (BCC) were synthesized by the substitution of β-cyclodextrin (β-CD) with cinnamoyl chloride (CC) and crosslinked with either hexamethylenediisocyanate (HMDI) or toluenediisocyanate (TDI). Cyclodextrin rings were substituted with one or two cinnamoyl moieties, as found from mass spectrometry. The polymeric matrix with cholesterol molecular imprint was obtained on irradiation of molecular assembly formed by the cinnamoyl-functionalized β-cyclodextrin-cholesterol with light at 275 nm, absorbed exclusively by the cinnamoyl chromophores. Irradiation induced crosslinking due to the photodimerization of the cinnamoyl moieties. To determine the adsorption properties of the produced material imprinting was performed in the presence of tritiated cholesterol and the intensity of β radiation from the material was measured. The materials obtained by the adsorption of tritiated cholesterol by nonirradiated polymer were used as controls. It was found that the polymer photocrosslinked in the presence of cholesterol have shown a considerable higher adsorption capacity for cholesterol than the control materials. This confirmed successful formation of molecularly imprinted polymer (MIP) by photochemical crosslinking. The selectivity of imprinting was also confirmed using compounds of similar structures, i.e. ergosterol, dehydroergosterol, and Vitamin D.     

Nanotemplating for two-dimensional molecular imprinting

A new 2D molecular imprinting technique based on nanotemplating and soft-lithography techniques is reported. This technique allows the creation of target-specific synthetic recognition sites on different substrates using a uniquely oriented and immobilized template and the attachment of a molecularly imprinted polymer on a substrate. The molecularly imprinted polymer was characterized by AFM, fluorescence microscopy, and ATR-FTIR. We evaluated the rebinding ability of the sites with theophylline (the target molecule). The selectivity of the molecularly imprinted polymer was determined for the theophylline-caffeine couple. The molecularly imprinted polymer exhibited selectivity for theophylline, as revealed by competitive rebinding experiments. Fluorescence microscopy experiments provided complementary proof of the selectivity of the molecularly imprinted polymer surfaces toward theophylline. These selective molecularly imprinted polymers have the potential for chemical sensor applications. Because of its 2D nature, this novel chemical sensor technology can be integrated with many existing high-sensitivity multichannel detection technologies.     

分子印迹技术研究进展

分子印迹是制备具有分子特异识别功能聚合物的一种技术。本文从分子印迹聚合物的识别机理、分子印迹聚合制备条件和制备技术三个方面综述了分子印迹的研究进展,最后展望了分子印迹发展前景。引用文献66篇。     

Thermally induced alkylation of diamond

We present an approach for the thermally activated formation of alkene-derived self-assembled monolayers on oxygen-terminated single and polycrystalline diamond surfaces. Chemical modification of the oxygen and hydrogen plasma-treated samples was achieved by heating in 1-octadecene. The resulting layers were characterized using X-ray photoelectron spectroscopy, thermal desorption spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and water contact angle measurements. This investigation reveals that alkenes selectively attach to the oxygen-terminated sites via covalent C-O-C bonds. The hydrophilic oxygen-terminated diamond is rendered strongly hydrophobic following this reaction. The nature of the process limits the organic layer growth to a single monolayer, and FTIR measurements reveal that such monolayers are dense and well ordered. In contrast, hydrogen-terminated diamond sites remain unaffected by this process. This method is thus complementary to the UV-initiated reaction of alkenes with diamond, which exhibits the opposite reactivity contrast. Thermal alkylation increases the range of available diamond functionalization strategies and provides a means of straightforwardly forming single organic layers in order to engineer the surface properties of diamond.     

分子印迹技术研究进展

分子印迹技术是制备对特定目标分子具有特异性识别能力的高分子材料的技术,所制备的高分子材料被称为分子印迹聚合物.分子印迹聚合物因具有预定性、识别性和实用性三大优点已广泛应用于分离、模拟抗体与受体、催化剂以及仿生传感器等方面和领域,显示出了广泛的应用前景.作者对分子印迹技术的发展历史、基本原理、分类、应用现状以及一些新的研究热点进行了综述.     

多羧基小分子化合物诱导阳离子囊泡聚集的研究

研究了由阳离子型肽脂质溴化N,N-二-十六烷基-Na-6-三甲胺基己酰基-L-丙氨酰胺(N+C5Ala2C16)形成的阳离子囊泡,在加入含羧基小分子化合物后形成的聚集。考察了乙二胺四乙酸(EDTA)加入到囊泡中后吸光值随时间的变化。结果表明:当EDTA增加到一定浓度时可以引起由阳离子囊泡的聚集;在加入Ca2+后,阳离子囊泡聚集体得到分散;借助电子显微镜观察到了囊泡的聚集和分散。超滤后,用高效液相色谱法确定了囊泡结合的EDTA量。考察了不同pH条件下EDTA对囊泡聚集的影响,当EDTA等含多羧基小分子化合物羧基解离数为三个或以上时能够引起囊泡的聚集,而少于三个时囊泡不能发生聚集。     

Electrochemistry of molecular imprinting of large entities

Molecularly imprinted polymer (MIP) is a well-known approach, in which cavities with specific affinity are formed. These functional materials are used mostly for the separation, sensing, and catalysis of small molecules. In the last two decades, the MIP concept has been expanded for the imprinting of large entities such as nanoparticles, viruses, and cells. In this emerging field termed surface imprinted polymers (SIPs), a thin matrix imprints only part of the entity to enable its easy removal and rebinding.In this review, we focus on the different recent imprinting strategies for nanoparticles, viruses, and cells in conjunction with electrochemistry and describe their applications in the fields of biology, analytical chemistry, and medicine.     

分子印迹技术在蛋白质识别中的应用进展

分子印迹技术是一种制备具有分子识别能力的聚合物的有效技术,已经广泛应用于制备对小分子具有选择性的分子印迹聚合物,但制备能够特异性识别生物大分子--蛋白质的分子印迹聚合物的研究仍然具有挑战性。本文讨论了制备蛋白质分子印迹聚合物的难点,评述了目前印迹蛋白质的方法及各自的优缺点,展望了蛋白质印迹技术的发展趋势。     

Fluorescent sensing of homocysteine by molecular imprinting

The feasibility of biomimetic molecular sensing of homocysteine, an independent risk factor for cardiovascular diseases, was studied. The sensing approach coupled fluorescent derivatization of dl-homocysteine by a thiol-specific fluoro-tagging agent, N-(1-pyrenyl)maleimide, with molecular recognition by a molecularly imprinted polymer (MIP) matrix. The non-covalent MIP was fabricated using the N-(1-pyrenyl)maleimide-dl-homocysteine (PM-H) adduct as template. The PM-H-MIP was found to possess outstanding analyte-specific affinity for PM-H with binding constant, K_B, of 9.28±1.6×10⁵ M⁻¹ and density of recognition sites, B_max, of 11.9±0.8 nmol/g dried MIP. Following in situ fluorescent derivatization, luminescent response of the MIP was found to correlate linearly with concentration of dl-homocysteine in the range corresponding to realistic total homocysteine concentration in blood plasma. Besides being a passive recognition matrix for the binding of the fluoro-tagged analyte, the PM-H-MIP material was found to be able to specifically enhance the rate of derivatization reaction between dl-homocysteine and N-(1-pyrenyl)maleimide. In a sense, the MIP transformed a fluoro-tagging agent, which is generally reactive towards a broad spectrum of thiol-containing species, into a dl-homocysteine-specific derivatizing agent. The mechanism of such analyte-specific enhancement of derivatization rate and its advantages to the biomimetic molecular sensing are discussed.     

Thermally induced paramagnetism of spiropyran salts

An increase in the effective magnetic moments and linewidths in ESR spectra caused by the presence of crystallization water molecules in crystals of tris(oxalato)chromium(III) complexes with spiropyran cations Sp⁺ was found. Dehydration (rehydration) of crystals causes a reversible decrease (increase) in thermally induced paramagnetism of Sp⁺. Thermally induced paramagnetism of crystals appears in the compounds synthesized in oxygen atmosphere but is not found in the compounds synthesized under argon atmosphere. The contributions of chromium oxalates and thermally excited spiropyran molecules to the magnetization were separated using ESR spectroscopy. The enthalpies of the biradical states of some types of spiropyran cations in crystals were determined.     

Thermally activated conduction in molecular junctions

We report temperature dependence measurements on the conductance of individual molecular wires. The results show for the first time in a molecular junction the theoretically predicted transition from coherent superexchange tunneling conductance to an activated hopping mechanism as temperature is increased.     

Thermally induced transformations in polyoxometalate-pillared hydrotalcites

Thermal decomposition of magnesium-aluminum hydrotalcites intercalated with four different polyoxometalate anions (V₁₀O₂₈ ⁶⁻,Cr₂O₇ ²⁻, W₇O₂₄ ⁶⁻or Mo₇O₂₄ ⁶⁻) was examined. The studied samples were prepared by the ion-exchange procedure starting from the parent carbonate-containing hydrotalcite. The successful synthesis was confirmed by powder X-ray diffraction and chemical analysis. The samples decomposed in two or three essential steps forming finally mixed metal oxides. The dichromate-containing hydrotalcite showed a thermal reduction of Cr⁶⁺ to Cr³⁺ ions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermally induced reorganization in LCP fibers

The molecular reorganization occurring in liquid crystalline polymer fiber during heat treatment is of great interest for many commercial reasons. Using thermal analysis techniques, WAXS and real time temperature dependent synchrotron SAXS, the structure and morphology of commercial LCP (liquid crystalline polymer), Vectran®, HBA/HNA (p-hydroxybenzoic acid/6-hydroxy-2-naphthoic acid), and its variant polymer fiber COTBP, HBA/HNA/BP/TA (BP-benzophenone, TA-terephthalic acid), have been examined. Both fibers have the typical liquid crystalline polymer structure, i.e., highly aligned with aperiodic sequencing along the fiber axis. There is a three-fold increase in strength in both fibers with heat treatment; however, the modulus is observed to increase significantly in COTBP but not in Vectran®. This paper reports on the changes and the differences on the structural and morphological behavior for both the as-spun and heat-treated LCP fibers. We propose an ‘oriented entanglement’ model to describe the differences between the two polymer fibers.     

Biotin-specific synthetic receptors prepared using molecular imprinting

The composition of new molecularly imprinted polymers (MIPs) specific for biotin was optimised using molecular modelling software. Three functional monomers: methacrylic acid (MAA), 2-(trifluoromethyl)acrylic acid (TFAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPSA), which demonstrated the highest binding scores with biotin, were tested on their ability to generate specific binding sites. The imprinted polymers were photografted to the surface of polystyrene microspheres in water. The affinity of the synthetic “receptor” sites was evaluated in binding experiments using horseradish peroxidase-labelled biotin. Good correlation was found between the modelling results and the performance of the materials in the template re-binding study. The dissociation constants for all MIPs were 1.4-16.8 nM, which is sufficient for most analytical applications where biotin is used as a label.     

发光ZnSalen配合物在分子荧光成像中的应用进展

荧光分子探针的设计、合成以及应用是分子荧光成像领域重要的化学问题.本文从Znsalen配合物的基本性质出发,概述了Znsalen配合物结构与功能的关系,特别是其发光性质与分子结构及分子聚集状态的相关性及应用.针对Znsalen配合物的发光性质,展示了其应用于分子荧光成像和活细胞中分子事件监测的研究进展.这些最新研究表明,Znsalen配合物探针的细胞毒性低(利于活细胞成像)、发光效率高(适用于单、双光子成像)、发光可调(通过配体的修饰和分子聚集状态的调节),有望作为一类重要的发光金属荧光探针实现在分子荧光成像中的应用.     

Thermally induced electrode protection against biofouling

This paper demonstrates that a combined thermal and electrochemical conditioning step can greatly minimize electrode blocking. We detected 50 ppm dopamine after a blocking step in 1000 ppm gelatine solution. Only a treatment of the electrode at −1.5 V and 61.5 °C can reveal the voltammetric dopamine signals to 82%. The increase of the peak separation of the cyclic voltammograms obtained in 50 ppm dopamine is limited to 14%, whereas negative polarization (−1.5 V) alone leads to a 31% increase compared to 109% upon thermal and 105% without any conditioning. The positive effects can be addressed to an enforced reductive degradation and accelerated removal of the blocking agents. Also the formation of hydrogen bubbles might play a significant role. Thermo-electrochemical treatment holds great promise for electrochemical sensors and detectors which are applied for long-term monitoring of samples that contain blocking matrices.     

绿色分子印迹技术简论

解析了绿色分子印迹技术(GMIT)的概念;结合水相和其他新型分子印迹技术、聚合物辅助设计及新型原材料的发展,简要阐述GMIT的发展动向.指出在绿色化学日益深入人心的今天,有必要深入探索和发展绿色分子印迹技术,从而拓展分子印迹技术研究领域、促进绿色化学的发展.     

Thermally induced fragmentation and cyclisation of C-azidohydrazones

C-Azidohydrazones 2 were synthesized from the corresponding C-chlorohydrazones 1 and submitted to thermal decomposition in boiling benzene. Various kinds of products were obtained due to competitive modes of evolution of first-formed nitrenes 13 , namely hydrogen abstraction to form aminohydrazones 3 and benzotriazepine 8 , and radical fragmentation to give ultimatively diaryls 4 and arylglyoxylate arylhydrazones 5 . Ring-closed products, namely 1, 2, 4-triazoles 6 and imidazolones 7 were also formed.