金属卟啉对杂环及DNA分子识别研究进展

介绍了近几年国内外关于组装金属卟啉对杂环分子、DNA碱基以及RNA的分子识别的研究进展, 并简述了本课题组对金属卟啉与杂环及药物分子复合物的理论研究工作. 金属卟啉广泛存在于自然界和生物体中, 此识别过程对研究和模拟生命体中各种细胞之间的相互作用具有重要意义. 组装后的金属卟啉可通过轴向配位、氢键及π-π堆积作用等识别杂环分子. 金属卟啉对DNA的识别主要有四种作用方式, 而金属卟啉对DNA以及RNA分子的识别主要靠疏水作用力、静电力以及自堆叠作用. 卟啉阳离子与DNA的结合位点受主体侧链取代基的空间结构影响. 金属卟啉对药物分子的识别靠配位键和氢键进行, 以配位键结合的复合物通常具有更高的结合能.     

发光性分子印迹聚合物的合成及其对组胺的识别性能研究

以组胺为模板分子,α-甲基丙烯酸为共功能单体,锌原卟啉为荧光功能单体,乙二醇二甲基丙烯酸酯为交联剂,合成了一种新的发光性分子印迹聚合物.通过振荡吸附后检测悬浊液荧光和柱吸附后检测流出液中组胺紫外光谱的变化,对印迹和非印迹聚合物与组胺的结合特性进行了对比.两种方法的结果一致,表明印迹聚合物对模板分子的识别选择性优于非印迹聚合物.     

芳酰胺分子钳对阴离子的识别研究

利用差紫外光谱法考察了新的分子钳1～4对阴离子的识别性能,测定了25 ℃下,在CHCl3中主客体间的结合常数(Ka)和自由能变化(ΔG°). 结果表明,所有分子钳主体对所考察的客体分子显示良好的识别作用,主客体间形成1∶ 1型超分子配合物.识别作用的主要推动力为多重氢键作用.并利用核磁共振氢谱与计算机模拟作为辅助手段对实验结果进行了解释.     

新型手性酪氨酸卟啉锌对咪唑类客体的分子识别研究

合成了两种新型手性锌卟啉Zn(o-BocTyr)TAPP和Zn(p-BocTyr)TAPP.通过元素分析、紫外可见光谱及核磁共振谱对其性质进行了表征.研究了这两种锌卟啉对咪唑类的分子识别行为,识别的缔合常数顺序均为K(2-MeIm)>K(Im)>K(N-MeIm)>K(2-Et-4-MeIm).同时,采用理论计算和圆二色谱研究了咪唑类小分子在与锌卟啉分子识别时进攻主体位置的变化,这对于研究卟啉分子识别起到一定的作用.     

氨基酸卟啉锌配合物对氨基酸酯的分子识别研究(英文)

用紫外可见吸收光谱滴定方法研究了一种新型的苏氨酸卟啉锌配合物(主体)对氨基酸酯(客体)的分子识别.这种锌卟啉可以与氨基酸酯形成 1:1和 1:2的两种加合物.氨基酸酯的氨基首先与氨基酸残基的羧基作用形成 1:1的加合物,然后与锌卟啉的中央锌原子配位形成 1:2的加合物,客体分子与主体分子上的氨基酸残基之间的排斥作用以及主客体之间的色散力作用是主体分子能识别客体分子的另外两种作用。     

含有氢键供体大环化合物的构筑及其功能研究进展

含有氢键供体基团构筑的大环化合物因其结构中具有可以提供氢键供体的N—H基团,可以为大环化合物的主客体化学提供额外的分子间作用力,在分子识别、自组装以及超分子催化等领域被广泛应用.综述了近十年基于(硫)脲键、酰胺键构筑的大环化合物的合成方法及其在分子识别中的最新研究进展.为今后此类大环化合物的合成及应用提供参考.     

双-锌卟啉对DABCO分子识别的立体构象及其热力学研究

合成了系列不同长度以柔性侧链相连的p/p型双-锌卟啉配合物,用¹H NMR和UV-Vis研究了不同温度下该系列配合物与刚性双齿配体DABCO(1,4-二氮杂双环)的轴向配位反应,考察了侧链长度对双-锌卟啉与配体的分子识别能力影响。结果表明,主体分子双-锌卟啉可以对客体分子BABCO进行分子识别,合适长度的柔韧烷氧链可以调节主体分子的构象,使DABCO嵌入双卟啉两个卟啉环间空位中,形成锌卟啉-DABCO-锌卟啉三元夹心式配合物构象。探讨了配位反应中立体构象的变化过程,并测定了热力学参数。     

不对称卟啉化合物的合成及其与氨基酸甲酯的作用

本文合成了含有单取代酰胺基的不对称卟啉及其锌(Ⅱ)络合物Zn(m,2-CNTPP)及Zn(m,3-CNTPP).对三氯甲烷溶液中它们与谷氨酸二甲酯、亮氨酸甲酯以及苯丙氨酸甲酯的作用进行了系统的研究,讨论了卟啉化合物对氨基酸甲酯分子的结合能力、结合方式,以及二者之间的多种存在形式。结果表明,锌卟啉与氨基酸甲酯以1:1的化学计量结合,中心金属锌(Ⅱ)离子和氨基酸甲酯中的氨基配位,卟啉环上的取代基与氨基酸甲酯中的残基可形成氢键、范德华力等弱相互作用。在卟啉和氨基酸甲酯的作用中,氨基与金属离子直接配位,α-碳上的质子靠近卟啉环平面,而酯基中的甲氧基处于远离卟啉环平面的位置。     

氨基硫脲分子钳的合成及对阴离子的识别作用

合成了2个新型氨基硫脲分子钳主体3a(1,3-二（o-甲苯氧乙酰氨基硫脲甲酰基）苯)和3b(1,3-二（p-甲苯氧乙酰氨基硫脲甲酰基）苯),利用UV-Vis和1H NMR测试其对F-、AcO-、Cl-、Br-和I-的阴离子识别性质。 结果表明,主体分子在DMSO溶液中对F-和AcO-表现出明显的选择性识别。 1H NMR光谱证明,主体分子与阴离子之间以氢键相结合,结合Job曲线得出主体分子与阴离子之间形成1∶1型氢键缔合物。 讨论了NH识别位点数及空间结构对识别性质的影响。 与硫脲对比,主体3a具有多个NH结合位点,可形成多个氢键,结合常数（Ks）更大。 与化合物3b相比,主体3a较大的空间位阻阻碍了其与阴离子的结合,因此两种主体分子与F-和AcO-结合常数均体现为Ks(F-)＞Ks(AcO-)。     

咪唑修饰的卟啉化合物的合成及其对卤素离子的选择性识别

设计合成了以卟啉为分子“探针”的咪唑修饰的卟啉类化合物4和5. 通过对核磁共振氢谱、紫外-可见光谱及荧光发射光谱的研究显示, 化合物5通过卟啉环中心的锌及2个咪唑环上的活性氢与卤素离子形成三点键合超分子络合物, 并能选择性识别氟离子和氯离子(键合常数分别为5.95×10⁴和7.17×10⁴ mol^-1·L).     

Study on the binding mode of zinc(II) protoporphyrin and ctDNA in water

Spectroscopic property of a commercially available luminescent reagent Zinc(II) protoporphyrin (ZnPP) was studied. Dissociation constants of the two protons on the peripheral groups of porphyrin ring of ZnPP were determined as pK(a1)=6.31, pK(a2)=9.37. Binding evidence of ZnPP with ctDNA was found by the phosphorescence intensity change on a filter paper around pH 6.5-9.3 with the association constant being 9.1x10(3) dm(3)/mol. A novel binding mode for ZnPP and calf thymus DNA (ctDNA) suggested that the monomer ZnPP which has no axial coordination, slips into the groove of DNA and interacts with the bases of polynucleotide by zinc coordination and hydrogen bonding between H atom on carboxyl group of ZnPP and O atom on the bases.     

Solid-substrate room-temperature phosphorescence study on zinc(II) and tin(IV) protoporphyrins and their interaction with DNA

The solid-substrate room-temperature phosphorescence (SS-RTP) of two commercially available metalloporphyrin compounds, zinc(II) protoporphyrin (ZnPP) and tin(IV) protoporphyrin (SnPP) has been studied. Strong and stable RTP signals of the two metalloporphyrins in neutral to weakly basic solutions can be simply induced on filter paper without addition of external heavy atom perturbers. Their emission bands appeared at 723 nm for ZnPP and 718 nm for SnPP at an excitation wavelength of 417 nm. Compared with SnPP, ZnPP is a better RTP probe for DNA because its RTP enhancement effect is much higher under the same experimental conditions. The interaction of ZnPP with DNA at pH 8.5 gives an apparent binding constant of 9.1 x 10(3) which is similar to that of the cationic porphyrin absorption probe CuTMPyP (copper (II)- tetrakis(4-N-methylpyridyl)porphine complex). Hydrogen bonding between the monocarboxylic acid substituent of ZnPP and the base pairs of DNA plays a crucial role in the binding.     

Solid-substrate room-temperature phosphorescence study on zinc(II) and tin(IV) protoporphyrins and their interaction with DNA

The solid-substrate room-temperature phosphorescence (SS-RTP) of two commercially available metalloporphyrin compounds, zinc(II) protoporphyrin (ZnPP) and tin(IV) protoporphyrin (SnPP) has been studied. Strong and stable RTP signals of the two metalloporphyrins in neutral to weakly basic solutions can be simply induced on filter paper without addition of external heavy atom perturbers. Their emission bands appeared at 723 nm for ZnPP and 718 nm for SnPP at an excitation wavelength of 417 nm. Compared with SnPP, ZnPP is a better RTP probe for DNA because its RTP enhancement effect is much higher under the same experimental conditions. The interaction of ZnPP with DNA at pH 8.5 gives an apparent binding constant of 9.1 × 10³ which is similar to that of the cationic porphyrin absorption probe CuTMPyP (copper (II)- tetrakis(4-N-methylpyridyl)porphine complex). Hydrogen bonding between the monocarboxylic acid substituent of ZnPP and the base pairs of DNA plays a crucial role in the binding. Received: 21 December 2000 / Revised: 9 April 2001 / Accepted: 20 April 2001     

Core-shell nanostructured molecular imprinting fluorescent chemosensor for selective detection of atrazine herbicide

To convert the binding events on molecularly imprinted polymers (MIPs) into physically detectable signals and to extract the templates completely are the great challenges in developing MIP-based sensors. In this paper, a core-shell nanostructure was employed in constructing the MIP chemosensor for the improvements of template extraction efficiency and imprinted sites accessibility. Vinyl-substituted zinc(II) protoporphyrin (ZnPP) was used as both fluorescent reporter and functional monomer to synthesize atrazine-imprinted polymer shell at silica nanoparticle cores. The template atrazine coordinates with the Lewis acid binding site Zn of ZnPP to form a complex for the molecular imprinting polymerization. These imprinted sites are located in polymer matrix of the thin shells (~8 nm), possessing better accessibility and lower mass-transfer resistance for the target molecules. The fluorescence properties of ZnPP around the imprinted sites will vary upon rebinding of atrazine to these imprinted sites, realizing the conversion of rebinding events into detectable signals by monitoring fluorescence spectra. This MIP probe showed a limit of detection (LOD) of about 1.8 μM for atrazine detection. The core-shell nanostructured MIP method not only improves the sensitivity, but also shows high selectivity for atrazine detection when compared with the non-molecular imprinted counterparts.     

Electrochemical properties of protoporphyrin IX zinc(II) films

The electrochemical properties of protoporphyrin IX zinc(II) (ZnPP) films on indium-tin oxide (ITO) substrate have been studied for three types of films with different arrangements, which were an adsorbed film of ZnPP and LB films of ZnPP and its hybrid with hexadecyltrimethylammonium bromide. Cyclic voltammetry (CV) measurement showed that, as the adsorbed amount of ZnPP increases, an irreversible oxidation peak of ZnPP film is intensified. This reveals that electrochemical properties depend on the adsorbed amount rather than the orientation of porphyrin molecules. It was also supported from CV measurement and ultraviolet-visible absorption spectroscopy that porphyrins adsorbed on ITO substrate were desorbed after the single scan of potential. Additionally, photoresponse of these ZnPP films was investigated by photocurrent measurement. The photocurrent generation is due to carboxylic acid moieties but not ZnPP macrocycles.     

Direct comparison of electron transfer properties of two distinct semisynthetic triads with non-protein based triad: unambiguous experimental evidences on protein matrix effects

In order to understand the roles of protein matrix in electron transfer processes (ET) within biological systems, a heme-based donor (Zn-heme: ZnPP)-sensitizer (Ru2+(bpy)3)-acceptor (cyclic viologen: BXV4+) triad 1 was used as a probe molecule. Two semi-synthetic systems, Cyt-b562(1) and Mb(1), in which the triad is incorporated into cytochrome b562 (Cyt-b562) or into myoglobin (Mb), were constructed by cofactor reconstitution. These two semi-synthetic proteins were compared with the triad itself (i.e., without the protein matrix) using absorption spectroscopy, steady state emission and excitation studies, laser flash photolysis experiments, and molecular modeling. Photoexcitation of the ZnPP moiety of Cyt-b562(1) or Mb(1) leads to a direct ET from the triplet state of ZnPP state (3ZnPP) to BXV4+ to generate a final charge-separated (CS) state, Cyt-b562(Zn+)-Ru2+-BXV3+* or Mb(Zn+)-Ru2+-BXV3+*. On the other hand, direct ET from the excited ZnPP moiety to the BXV4+ moiety is also involved in 1 in the absence of the protein matrix, but the excited state of ZnPP involved is not 3ZnPP, but the singlet excited state (1ZnPP) in this pathway. When the Ru2+(bpy)3 moiety of Cyt-b562(1) or Mb(1) is excited, a stepwise ET relay occurs with the ion-pair, Cyt-b562(Zn)-Ru3+-BXV3+* or Mb(Zn)-Ru3*-BXV3+*, as an intermediate, leading to the same final CS state as that generated in the direct ET pathway. The lifetimes of the corresponding final CS states were determined to be 300 ns for 1 in the absence of the protein matrix, 600-900 ns for Cyt-b562(1) and 1.1-18 micros for Mb(1), the values of which are greatly affected by the protein matrix. Molecular modeling study of the three systems consistently explained the differences of their photophysical behavior.     

Ultrafast relaxation of zinc protoporphyrin encapsulated within apomyoglobin in buffer solutions

The relaxation dynamics of a zinc protoporphyrin (ZnPP) in THF, KPi buffer, and encapsulated within apomyoglobin (apoMb) was investigated in its excited state using femtosecond fluorescence up-conversion spectroscopy with S2 excitation (lambda(ex) = 430 nm). The S2 --> S1 internal conversion of ZnPP is ultrafast (tau < 100 fs), and the hot S1 ZnPP species are produced promptly after excitation. The relaxation dynamics of ZnPP in THF solution showed a dominant offset component (tau = 2.0 ns), but it disappeared completely when ZnPP formed aggregates in KPi buffer solution. When ZnPP was reconstituted into the heme pocket of apoMb to form a complex in KPi buffer solution, the fluorescence transients exhibited a biphasic decay feature with the signal approaching an asymptotic offset: at lambda(em) = 600 nm, the rapid component decayed in 710 fs and the slow one in 27 ps; at lambda(em) = 680 nm, the two time constants were 950 fs and 40 ps. We conclude that (1) the fast-decay component pertains to an efficient transfer of energy from the hot S1 ZnPP species to apoMb through a dative bond between zinc and proximal histidine of the protein; (2) the slow-decay component arises from the water-induced vibrational relaxation of the hot S1 ZnPP species; and (3) the offset component is due to S1 --> T1 intersystem crossing of the surviving cold S1 ZnPP species. The transfer of energy through bonds might lead the dative bond to break, which explains our observation of the degradation of ZnPP-Mb samples in UV-vis and CD spectra upon protracted excitation.     

Delineation of agonist binding to the human histamine H4 receptor using mutational analysis, homology modeling, and ab initio calculations

A three-dimensional homology model of the human histamine H 4 receptor was developed to investigate the binding mode of a series of structurally diverse H 4-agonists, i.e. histamine, clozapine, and the recently described selective, nonimidazole agonist VUF 8430. Mutagenesis studies and docking of these ligands in a rhodopsin-based homology model revealed two essential points of interactions in the binding pocket, i.e. Asp3.32 and Glu5.46 (Ballesteros-Weinstein numbering system). It is postulated that Asp3.32 interacts in its anionic state, whereas Glu5.46 interacts in its neutral form. The hypothesis was tested with the point mutations D3.32N and E5.46Q. For the D3.32N no binding affinity toward any of the ligands could be detected. This is in sharp contrast to the E5.46Q mutant, which discriminates between various ligands. The affinity of histamine-like ligands was decreased approximately a 1000-fold, whereas the affinity of all other ligands remained virtually unchanged. The proposed model for agonist binding as well as ab initio calculations for histamine and VUF 8430 explain the observed differences in binding to the H 4R mutants. These studies provide a molecular understanding for the action of a variety of H 4 receptor-ligands. The resulting H 4 receptor model will be the basis for the development of new H 4 receptor-ligands.     

The affinity of histamine to serum albumin: Capillary electrophoresis-frontal analysis and in-silico molecular docking approaches

Histamine is a biogenic amine found in various body tissues and responsible for many critical vital activities. It is also responsible for allergic reactions in the body. Ingestion of foods containing high amounts of histamine can cause fatal allergic reactions. Albumin in plasma controls drugs and free concentrations of bioactive constituents taken to the body with food. Hence, this study aimed to characterise the interactions of histamine with bovine serum albumin. Capillary electrophoresis in the frontal analysis mode was employed in this study as a practical approach for assessing histamine-bovine serum albumin affinity. The plateau-shaped free histamine peak was well separated from the bovine serum albumin (BSA)-histamine complex peak. The free histamine concentration was obtained by following the height of the free histamine peak. Whereas the bound histamine concentrations were obtained by calculating the difference between the height of total and free histamine peaks. Histamine bound to BSA at one independent site with a K_b value of 2.50 × 10³ L/mol. Moreover, an in-silico molecular docking method was performed, and it was revealed that the binding site of histamine was located closer to Lysine-131 in subdomain IIA of bovine serum albumin.     

Interaction of ZnII Porphyrin with TiO2 Nanoparticles: From Mechanism to Synthesis of Hybrid Nanomaterials

The mechanism of interaction of Zn porphyrin (ZnPP) with TiO₂ surfaces is investigated with a view to optimizing the synthesis of hybrid nanomaterials. The strategy consists of studying the adsorption of ZnPP on TiO₂ flat surfaces by taking advantage of complementary surface characterization techniques. Combining a detailed X‐ray photoelectron spectroscopic analysis with AFM imaging allows ZnPP–surface and ZnPP intermolecular interactions to be discriminated. Probing the adsorption of ZnPP on TiO₂ nanoparticles (NPs) reveals the dominant role of ZnPP‐mediated interactions, which are associated with the formation of ZnPP multilayers and/or with the state of aggregation of NPs. These preliminary investigations provide a guideline to synthesizing a novel ZnPP–TiO₂ hybrid nanomaterial in a one‐step protocol. In this material, ZnPP molecules are presumably involved in the TiO₂ lattice rather than on the NP surface. Furthermore, ZnPP molecules preserve their electronic properties within the TiO₂ NPs, and this makes the ZnPP–TiO₂ hybrid nanomaterial an excellent candidate for nanomedicine and related applications, such as localization of nanoparticles in cells and tissues or in photodynamic therapy.