两种荧光探针法研究三种非甾体抗炎药与DNA的相互作用

采用溴化乙锭(EB)和中性红(NR)两种荧光探针分别考察了三种非甾体抗炎药(吲哚美辛、舒林酸和托美丁)与DNA的相互作用, 采用荧光发射光谱和共振散射光谱技术得出了基本一致的结论: 吲哚美辛和舒林酸可以在一定程度上与DNA结合(舒林酸更强), 结合方式可能有嵌插作用, 也可能有药物分子在DNA双链表面的组装, 作用力来源于静电作用. 而托美丁几乎不与DNA作用, 因为其疏水性弱, 与DNA分子结合几率小.     

Competitive Binding of Tolmetin to β-Cyclodextrin and Human Serum Albumin: <Superscript>1</Superscript>H NMR and Fluorescence Spectroscopy Studies

The host–guest interaction of tolmetin (TOL) with β-cyclodextrin (β-CD) and the influence of human serum albumin (HSA) on the formation of the inclusion complex were studied by 1D and 2D NMR spectroscopy. The TOL/β-CD inclusion complex formed at a molar ratio of 1:1 with a binding constant value of 2164.5 L·mol^?1. Data analysis showed that the addition of 10 μmol·L^?1 of HSA weakened the strength of TOL binding to β-CD (K _a = 1493 L·mol^?1). The interaction of TOL with HSA in the absence and presence of β-CD was studied by analyzing the fluorescence quenching data. The Stern–Volmer quenching constants and the binding constants are found to be smaller in the presence of β-CD, suggesting that β-CD hinders the strong interaction of TOL with HSA by complex formation. Additionally, the presence of β-CD does not induce conformational and microenvironmental changes on HSA.     

Spectroscopic investigation of Rose Bengal/cyclodextrin interactions in aqueous solution: the case of the hydroxypropyl-cyclodextrins

The interaction of Rose Bengal (RB) with hydroxypropyl-α-cyclodextrin (HP-α-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and hydroxypropyl-γ-cyclodextrin (HP-γ-CD) has been studied in water and in acetate buffer at pH 4.5 by UV–Vis absorption, fluorescence spectroscopy and Induced Circular Dichroism at 298 K. Evidence of the complex formation between the RB and all HP-CDs have been obtained both in water and in buffer. Binding constants and stoichiometry of RB/HP-CD complexes in water have been determined by applying the modified Benesi-Hildebrand equation to the fluorescence measurements.     

Spectroscopic Investigation of Asphaltene Aggregation in Carbon Tetrachloride Medium Containing Microquantities of Water

By fluorescence spectroscopy it has been established that coal derived asphaltene (CDA) forms aggregates in CCl₄ medium. The new feature of this compound is that even before aggregate formation it can incorporate water molecules and the critical aggregation concentration (CAC) in nonaqueous medium increases with increase in ω (= water:CDA mole ratio). The fluorescence spectroscopic determination of the equilibrium constant (K) of the molecular complex of [60] fullerenes with CDA in carbon tetrachloride medium has revealed that K increases on addition of microquantities of water. This observation has been rationalized by assuming that the nitrogenatoms at one end of CDA molecules attach themselves to the water micropool and thus producing a different conformation with a wider distance at the other end. This pre-organization further facilitates inclusion. By utilizing fluorescence variation of [60]fullerene/CDA complex in CCl₄ as continuous medium with change in ω a critical ω (=5) has been found. The formation of CDA/[60]fullerene complex has also been established by NMR spectroscopy.     

Carboxylic acid recognition of diamidine having a fluorescent 1,8-diphenylanthracene unit and its detection of amidinium-carboxylate and amidinium formation

A diphenylanthracene-based diamidine (1a) fluorescent probe for the detection of dicarboxylic acids has been designed and synthesized, which has an extended π-conjugation rather than a simple anthracene ring, in order to observe highly different fluorescence wavelengths after complex formation with dicarboxylic acids. The fluorescence spectra of the mixed solution of the diamidine 1a and carboxylic acids showed two different fluorescence bands, which corresponded to the complex formation (amidinium-carboxylate formation, λ_em?=?450?nm, light blue color) and dissociated amidinium formation (λ_em?=?510?nm as a broad band, green color). The complexed and dissociated states were confirmed by DOSY NMR and TD-DFT calculations. These different fluorescence wavelengths may come from the differences in the dihedral angles between the phenyl rings at the 1,8-position and anthracene ring (difference in π-conjugation) of 1a under complex formation and dissociated amidinium formation. The proposed mechanism for the observation of the different fluorescence wavelengths (complex formation and amidinium formation) was also confirmed by the fluorescence study of diamidine 1b which causes restricted rotation of the phenyl rings by substitution of the steric methyl groups, and observed the same fluorescence spectra for the complex formation and amidinium formation (400, 420, 450?nm as a vibrational structure of anthracene ring). These fluorescence characteristics of the diamidine 1a are also applicable for the detection of α,ω?dicarboxylic acids.     

Electronic Spectroscopic Study of the Formation of a Molecular Complex Between Asphaltene and o-Chloranil in SDS Aqueous Micellar Medium

Ultraviolet-visible absorption and steady-state fluorescence of asphaltene in sodium dodecyl sulphate (SDS) micellar medium containing o-chloranil have been studied. Spectroscopic results indicate formation of a complex between asphaltene and o-chloranil. The absorption spectrum of the complex has been detected by difference spectral method. The position of maximum absorption of the complex in micellar medium agrees well with that of the complex in the carbon tetrachloride medium studied previously. The formation constant (K) has been determined using Benesi-Hildebrand equation utilizing absorption spectral data. Formation of ground state complex involving asphaltene and o-chloranil has also been evidenced from the study of quenching of asphaltene fluorescence by o-chloranil. The value of K, as obtained by Stern-Volmer plot, agrees well with that obtained by absorption spectrophotometric method.     

EVIDENCE FOR THE FORMATION OF A CHLOROPHYLL a/ZEAXANTHIN COMPLEX IN LECITHIN LIPOSOMES FROM FLUORESCENCE DECAY KINETICS

The interaction of Chi a with zeaxanthin (Zea), which is an analogue of lutein, has been studied in soya bean lecithin liposomes using the fluorescence of Chi as monitor. The fluorescence emission spectrum at 4.2 K of Chi a showed characteristic changes in the presence of Zea: the emission maximum shifted from 688 nm to 680 nm, and a peak at 731 nm appeared. The fluorescence decay kinetics of Chi a alone could be described by the sum of two exponential components (T₁,≅0.8 ns, T₂≅2.5 ns). In the presence of Zea a component with a long lifetime, T≅5 ns, appeared with a large relative amplitude (40%). This indicated the formation of a Chl a /Zea complex, in which Chl a /Chl a interaction is negligible, presumably because of strong interaction between Chl a and Zea. The fluorescence anisotropy decay kinetics supported the hypothesis of the formation of a large Chl a containing complex in the presence of Zea. A rotational correlation time, φ≅14 ns at 4°C and φ≅21 ns at 30°C, was found, which is distinctly larger than for samples containing Chl a only. We interpret these results as further evidence for a strong interaction between Chl a and Zea in the hydrophobic environment of the lecithin liposomes. This interaction may also occur in the Chl-proteins of the Chi alb light-harvesting complex of plant photosynthesis.     

Study on interaction between Tb(III) and poly(N-isopropylacrylamide)

A new kind of the thermo-sensitive and fluorescent complex of poly(N-isopropylacrylamide) (PNIPAM) and Tb(III) was synthesized by free radical polymerization, in which PNIPAM was used as a polymer ligand. The complex was characterized by using X-ray photoelectron spectroscopy (XPS), ultraviolet-visual (UV), Fourier transform infrared (FT-IR) and fluorescence spectroscopy. The results from the experiments indicated that there is a strong interaction between PNIPAM and Tb(III), leading to a decrease in the electron density of nitrogen and oxygen atoms and an increase in the electron density of Tb(III) in the PNIPAM containing Tb(III) by contrast with PNIPAM and Tb(III), respectively, meanwhile, exhibiting that the Tb(III) is mainly bonded to oxygen atoms in the polymer chain of PNIPAM and formed the complex of PNIPAM-Tb(III). After forming the PNIPAM-Tb(III) complex, the emission fluorescence intensity of Tb(III) in the PNIPAM-Tb(III) complex is significantly enhanced because the effective intramolecular energy transfer from PNIPAM to Tb(III). Especially, the emission intensity of the fluorescence peak at 547 nm can be increased as high as 145 times comparing with that of the pure Tb(III). The intramolecular energy transfer efficiency for fluorescence peak at 547 nm can reach as high as 68%. The fluorescence intensity is related the weight ratio of Tb(III) and PNIPAM in the PNIPAM-Tb(III) complex. When the weight ratio is 1.4%, the maximum fluorescence enhancement can be obtained. Nevertheless, the lower critical solution temperature of PNIPAM containing a low content of Tb(III) has not obviously changed after the formation of the complex of PNIPAM-Tb(III) by the interaction between PNIPAM and Tb(III). This novel thermosensitive and fluorescence characterization of the PNIPAM-Tb(III) complex may be useful in the fluorescence systems and the biomedical field.     

二维层状锌配合物[Zn(bibm)(glu)]n的合成、晶体结构及荧光性质

用水热法合成了1个新的锌配合物[Zn(bibm)(glu)]n(bibm=4,4′-二(苯并咪唑-1-甲基)联苯;glu=戊二酸),对它进行了红外光谱、元素分析、XRD、热重和荧光等表征,并用X-射线单晶衍射法测定了配合物的单晶结构。该配合物属单斜晶系,P21/n空间群,为二维层状结构。实验结果表明该配合物具有较好的荧光性质,是潜在的荧光光学材料。     

Thermodynamic parameters for the molecular inclusion reaction of dulcin with beta-cyclodextrin. spectrofluorimetric determination of dulcin

The inclusion of dulcin in alpha- and beta-cyclodextrin has been studied by fluorescence spectroscopy. To quantitatively describe complex formation between the beta-cyclodextrin and dulcin, an association constant of 290 M(-1) at 21 degrees was obtained. The thermodynamics associated with the complex formation between dulcin and beta-cyclodextrin in aqueous solution has been studied. The obtained value of DeltaG(0) = -13.7 kJ/mole at 21 degrees , together with DeltaH(0) = -33.6 +/- 2.3 kJ/mole and DeltaS(0) = -67.2 +/-8.3 Jmole(-1) K(-1) indicate that dulcin has a very marked tendency to associate with beta-cyclodextrin in water. The inclusion complex of dulcin in beta-cyclodextrin has been used to determine dulein in the range 0.13-5 mug/ml the method has been applied to determine dulcin in soft drinks.     

Preparation and characterization of the inclusion complex of baicalein with γ-cyclodextrin: an antioxidant ability study

The formation of the complex of Baicalein with γ-cyclodextrin (γ-CD) was studied by UV–Vis absorption spectroscopy, fluorescence spectra and nuclear magnetic resonance spectroscopy (NMR) in solution. The solid inclusion complex of Baicalein with γ-CD was synthesized by the co-precipitation method. The characterization of the solid inclusion complexes have been proved by infrared spectra. The formation constant (K) of complex was determined by fluorescence method. The results suggested that in different pH solutions, γ-CD has different inclusive capacity to different forms of Baicalein. γ-CD was most suitable for inclusion in neutral media. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of Baicalein with γ-CD. Kinetic studies of DPPH? with Baicalein and γ-CD complex were done. The results obtained indicated that the Baicalein/γ-CD complex was the most reactive form. Special configuration of complex has been proposed on NMR technique.     

Turn-on fluorescence sensor for mono- and di-phosphonic acid derivatives using anthracene-based diamidine and its detection of amidinium-phosphonate and amidinium formation

The fluorescence detection of di-phosphonic acid and mono-phosphonic acid derivatives using the anthracene-based diamidine 1 has been investigated. The diamidine 1 forms 1:1 and 1:2 complexes with the di-phosphonic acid and mono-phosphonic acid derivatives, respectively, and showed a blue fluorescence (λ_em = 432–442 nm) in a DMSO solution. The formation of amidinium-phosphonate (complex formation) and dissociated amidinum (λ_em = 468 nm as a broad band) were distinguished by the difference in the fluorescence wavelength, and confirmed by DOSY NMR spectroscopy and TD-DFT calculations. The formation of a 1:2 complex with diamidine 1 and methylphosphonic acid having additional intermolecular hydrogen-bonding between the methylphosphonic acids is proposed.     

CdTe/CdS半导体量子点作为农药百草枯的高灵敏传感器

用硫普罗宁(Tiopronin, TP)作为稳定剂合成了水溶性的高荧光CdTe/CdS量子点. 研究了该量子点与10种农药的相互作用. 实验发现, 当农药浓度为4.76×10^-6 mol/L时, 农药百草枯(Paraquat)能显著猝灭CdTe/CdS量子点的荧光, 使其荧光强度下降87.3%, 而分别加入乙酰甲胺磷及辛硫磷等其它9种农药, 仅能使CdTe/CdS量子点的荧光强度下降0.1%～5.1%, 显示了该CdTe/CdS量子点对百草枯的特异性传感作用. 采用吸收光谱和时间分辨荧光动力学研究了百草枯对CdTe/CdS量子点的荧光猝灭机理. 计算得出荧光强度猝灭的Stern-Volmer常数K为2.03×10⁶, 而寿命猝灭的Stern-Volmer常数K为4.25×10⁵. 结果表明, 百草枯对CdTe/CdS量子点的荧光猝灭主要为静态过程, 而动态过程的贡献较小. 利用二者的猝灭作用建立了对农药百草枯的高灵敏检测新方法, 校正曲线的线性范围为9.90×10^-9～1.50×10^-6 mol/L, 检出限为6.35×10^-9 mol/L, R=0.999. 用该方法对3种食品和3种水样中残留农药进行了检测, 加标回收率均在82.2%～98.5%之间, 其相对标准偏差为2.62%~8.35%.     

β-环糊精/萘丁美酮/直链醇体系的超分子作用机理及其分析应用的研究

利用稳态荧光法研究了β-环糊精（β-CD）与新型抗炎药物萘丁美酮（NAB） 间的超分子相互作用，探讨了直链醇（ROH）对该超分子体系的影响。研究表明无 论体系中是否含有直链醇，β-CD和萘丁美酮均形成1/1的超分子包合物其表观结合 常数K_(app)随醇碳链长度的增长而逐渐减小。将这一现象归因于醇对β-CD疏水性 空腔的竞争作用，而非β-CD/NAB/ROH三元包合物的形成所致。荧光猝灭实验表明 水相中β-CF增敏萘丁美酮荧光是源于其疏水性空腔对萘丁美酮激发单重态的屏蔽 效应。直链醇的加入抑制了该效应，从而进一步证实了醇对β-CD空腔的竞争作用 确实导致萘丁美酮被置换到水相中。利用β-CD对萘丁美酮的包结作用使其荧光显 著增大这一特性，建立了水相中高灵敏度测定萘丁美酮的荧光光度法，线性范围为 0～3.0μg·mL~(-1)，检测下限1.05 ng·mL~(-1)。常用药物赋形剂对测定不产生 干扰。应用本法测定片剂中萘丁美酮含量，结果令人满意。     

Salt effect on the complex formation between polyelectrolyte and oppositely charged surfactant in aqueous solution

The complex formation between sodium carboxymethylcellulose (NaCMC) and dodecyltrimethylammonium bromide (DTAB) at various sodium bromide concentrations (C(NaBr)) has been studied by microcalorimetry, turbidimetric titration, steady-state fluorescence measurements, and the fluorescence polarization technique. The addition of salt is found to influence the formation of NaCMC/DTAB complexes markedly. At C(NaBr) = 0.00, 0.01, 0.02, 0.10, and 0.20 M, DTAB monomers form micelle-like aggregates on NaCMC chains to form NaCMC/DTAB complexes above the critical surfactant concentration (C1). At C(NaBr) = 0.23 M, DTAB molecules first form micelles above a 2.46 mM DTAB concentration prompted by the added salt, and then, above C1 = 4.40 mM, these micelles can aggregate with NaCMC chains to form NaCMC/DTAB complexes. However, at C(NaBr) = 0.25 M, there is no NaCMC/DTAB complex formation because of the complete salt screening of the electrostatic attraction between DTAB micelles and NaCMC chains. It is also surprisingly found that the addition of NaBr can bring out a decrease in C1 at C(NaBr) < 0.20 M. Moreover, the addition of NaBr to a mixture of 0.01 g/L NaCMC and 3.6 mM DTAB can directly induce the formation of NaCMC/DTAB complexes. This salt-enhancing effect on the complex formation is explained as the result of competition between the screening of interaction of polyelectrolyte with surfactant and the increasing of polyelectrolyte/surfactant interaction owing to the growth of micelles by added salt. When the increasing of polyelectrolyte/surfactant interaction exceeds the screening of interaction, the complex formation can be enhanced.     

QUENCHING OF CHLOROPHYLL FLUORESCENCE BY NITROBENZENE

Abstract—Nitrobenzene quenching of chlorophyll fluorescence in ethanol has been investigated. Steady state relative quantum yields have been measured and fluorescence decay rates were determined using both nanosecond photon counting and picosecond pulses from a mode-locked Nd³⁺ glass laser.
The fluorescence decay is described by
1( t )= I ₀ exp (- t/τ−At^1/2 )
the form predicted for decay governed by the kinetics of the continuum model of diffusion controlled reactions. From the parameters of the fluorescence decay, the encounter distance is 5–7 A° the mutual diffusion coefficient is 0.62 × 10^--⁵ cm2s^-1± 12%.
Some of the fluorescence quenching is also attributed to static quenching by a nitrobenzene-chlorophyll, ground-state complex. The equilibrium constant for formation of this ground-state complex was determined to be 4.1 M ^-1. The combined dynamic and static quenching model allows calculation of quantum yields of fluorescence in good agreement with the experimentally determined quantum yields.     

Fluorescent Recognition of Small Organic Molecules Based on Supramolecular Aggregation/Deaggregation of Planar Cu(II) Coordination Complex

A Cu(II) coordination complex ( 1 ) with Schiff ligand derived from diaminomaleonitrile was synthesized and characterized, in which the ligand is rigid, planar and conjugated. The complex 1 displays an interesting fluorescent property relative to solvents which can be turned‐on by CH₂Cl₂ and CHCl₃ solvent molecules. The mechanism of this selective fluorescence emission has been studied based on the crystal structure and the spectrum analysis. The tuning on and off fluorescence of complex 1 can be controlled by the process of supramolecular aggregation/deaggregation in different solvents.     

Affinity of a new copper(II) complex to DNA/BSA and antioxidant/radical scavenging activities: crystal structure of [Cu(4,7-diphenyl-1,10-phenanthroline)(leucine)(NO3)(H2O)]

A new copper(II) complex, [Cu(Bphen)(Leu)(NO₃)(H₂O)] (Bphen = 4,7-diphenyl-1,10-phenanthroline, leu = L-leucine), has been synthesized and characterized by IR spectroscopy, CHN analysis, and single-crystal X-ray diffraction techniques. The CT-DNA binding properties of the complex have been investigated by both absorption and emission spectroscopy. The binding parameters for the fluorescence Scatchard plot were also determined. Further, the interaction of the complex with bovine serum albumin (BSA) has been investigated using absorption and emission spectroscopy. The thermodynamic parameters, free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS), were calculated by the van’t Hoff equation and discussed. The distance between BSA and the complex has been obtained according to fluorescence resonance energy transfer. Conformational changes of BSA have been observed from synchronous fluorescence. Antioxidant and radical scavenging activities of the complex were determined by various in vitro assays such as 1,1-diphenyl-2-picryl-hydrazyl free radicals (DPPH˙), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS˙⁺), and reducing ability determination by H₂O₂ scavenging methods.     

Effects of cyclodextrins on the complexation between Methylene Blue and tetrakis(4-sulfonatophenyl)porphyrin in aqueous solutions

In aqueous solutions buffered at pH 10.1, Methylene Blue (MB) forms a complex with tetrakis(4-sulfonatophenyl)porphyrin (TSPP). The equilibrium constant for the formation of the MB-TSPP complex has been evaluated to be 2.35 x 10(5) mol(-1) dm3 from the fluorescence quenching of MB by TSPP. Effects of alpha-, beta-, and gamma-cyclodextrin (CD), and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin on the complexation between MB and TSPP have been examined by means of absorption and fluorescence spectroscopy. The binding of CDs to TSPP and/or MB in the MB-TSPP complex causes the dissociation of the MB-TSPP complex.     

Synthesis of a fluorescein–porphyrin hybrid and its supramolecular self-assembly with amino-porphyrinatocopper(II) by hydrogen bonding

A fluorescein–porphyrin hybrid (Fl-PTPP) has been synthesized and characterized by UV/Vis, IR, ¹H NMR, ES-MS and elemental analysis. The supramolecular self-assembly of Fl-PTPP with the copper(II) complex of 5-(p-amino-phenyl)-10,15,20-triphenylporphyrin, (CuAPTPP), by hydoxyl-amino type hydrogen bonding was studied using vapor pressure osmometry (VPO) measurements, ES-MS, UV/Vis, ¹H NMR and fluorescence spectroscopic titration. The data indicate formation of a (Fl-PTPP)–CuAPTPP supramolecular complex. Fluorescence strengthening character was observed in a spectroscopic titration experiment for the Fl-PTPP/CuAPTPP system. The association constant of the supramolecular complex was calculated from the fluorescence titration data, and found to be less than that of a carboxyl–carboxyl type hydrogen-bonding system.