Comparative studies on molecular induced aggregation of hepta-imidazoliumyl-β-cyclodextrin towards anionic surfactants

A β-cyclodextrin derivative bearing seven cationic arms and its singly charged analogue, i.e., per-6-deoxy-6-(1-methylimidazol-3-ium-3-yl)-β-cyclodextrin(3) and mono-6-deoxy-6-(1-methylimidazol-3-ium-3-yl)-β-cyclodextrin(4) were synthesized and fully characterized. Their induced aggregation behaviours towards two anionic surfactant, that is, sodium dodecyl sulfonate(SDS) and dioctyl sodium sulfosuccinate(Aerosol OT, AOT), were investigated by UV–vis, NMR, Zeta-potential, dynamic light scattering(DLS), and transmission electron microscopy. The results revealed that host 3 can induce the molecular aggregation of anionic surfactant at concentration far lower than its original CAC, leading to the larger diameter, the narrower size distribution and the higher thermal stability of the induced aggregate towards the anionic surfactant possessing more hydrophobic tails.     

2-萘-(OCH2CH2)n-金刚胺与6-单取代环糊精衍生物的光诱导电子转移反应

A number of naphthalene donor compounds that possess an adamantanamine binding moiety and an (OCH2CH2)n (nn1, 2, 3, 4, 6, 8) spacer were synthesized. The fluorescence quenching between these donor substrates and mono-6-O-p-nitrobenzoyl-β-cyclodextrin (pNBCD) and mono-6-O-m-nitrobenzoyl-β-cyclodextrin(mNBCD) was studied in detail. It was found that very efficient fluorescence quenching could occur in these supramolecular systems. This quenching was attributed to the photoinduced electron transfer inside the supramolecular assembly between the naphthalene donors and cyclodextrin acceptors. Detailed Stern-Volmer constants were measured and they were partitioned into dynamic Stern-Volmer quenching constants and static binding constants. It was demonstrated that the binding constants between all the naphthalene compounds and cyclodextrins are the same as they possess the same binding site, i.e., adamantanamine.     

Synthesis of a Novel Aromatic Diamino-bridged Bis（β-cyclodextrin） and its Inclusion Complexation with Dyes Molecules

Bridged bis(β-cyclodextrin)s (CDs), as a very important family of CD derivatives, have been known that they can significantly alter the molecular binding ability and selectivity toward a variety of guests in comparison with parent cyclodextrin. Their two…     

Synthesis and Properties of Novel Hemicyanine Dye-β-Cyclodextrin

A series of novel hemicyanine dye-β-cyclodextrin compounds： mono-6-deoxy-β-cyclodextrin-6-[p-（p-substituted styryl）pyridium] p-totylfulfonates were synthesized by the condensation of mono-6-deoxy-β- cyclodextrin-6-（p-methyl pyridinium） p-toluenesulfonate with （un）substituted benzaldehydes. Their structures were established by 1^H NMR, IR, UV-Vis and elemental analysis. The absorption and fluorescence properties of the novel compounds were measured in solution and the photostability of a selected hemicyanine dye-β-cyclodextrin compound was also investigated.     

Intercalation assembly of optical hybrid materials based on layered terbium hydroxide hosts and organic sensitizer anions guests

Optical hybrid materials based on inorganic hosts and organic sensitizer guests hold promise for a virtually unlimited number of applications.In particular,the interaction and the combination of the properties of a defined inorganic matrix and a specific sensitizer could lead to synergistic effects in luminescence enhancing and tuning.The current article focuses on the intercalation assembly of optical hybrid materials based on the layered terbium hydroxide(LTbH) hosts and organic divalent carboxylic sensitizer anion guests by a hydrothermal process.The studies on the interactions between hosts and guests indicate that the type and arrangement of organic guests in the layer spacing of the LTbH hosts can make a difference in the luminescence of the hybrid inorganic-organic materials.     

Synthesis of A novel Bridged Bis(β-cyclodextrin)s Possessing Phenanthroline Tether and Its Molecular Binding Ability with Dyes

A novel β-cyclodextrin dimer bearing 2,9-diformyl-1,10-phenanthroline tether 4 has been synthesized and its inclusion complexation behavior with two triangular model substrates (RhB and BG) has been investigated through fluorescence and ultraviolet spectrometry.The result obtained indicated that novel bridged bis(β-cyclodextrin)s could significantly cnhance the original molccular binding ability of native β-cyclodextrin by cooperative binding of two hydrophobic cavities.     

Comparative Study on the Inclusion Interaction between meso-Tetrakis（4-N-ethylpyridiniurmyl） porphyrin and β-Cyclodextrin Derivatives

The interaction of β-cyclodextrin (β-CD) and the modified cyclodextrins, hydroxy propyl-β-cyclodextrin (HP-β-CD), sulfobutylether-β-cyclodextrin (SBE-β-CD) and synthesized meso-tetrakis(4-N-ethylpyridiniurmyl)porphyrin (TEPyP) in aqueous solution has been studied by spectroscopic methods systematically. A significant change in fluorescence and absorption properties has been observed in the presence of β-CD, HP-β-CD and SBE-β-CD. The stoichiometry and formation constants have been determined by the steady-state fluorescence technique. The results showed that the β-CD derivatives were prior to the native β-CD and the hydrogen bonding and static electric forces played important roles in the formation of the inclusion complexes. The conformation was further confirmed by NMR spectroscopy.     

Studies on Reaction Mechanism Between Sparfloxacin and Bovine Serum Albumin

The binding of sparfloxacin and bovine serum albumin(BSA) in aqueous solution was studied by means of fluorescence and absorbance spectra, and the interactions influenced by Fe^3 and Cu^2 were explored. Based on the Scatchard‘s site binding model and fluorescence quenching, practical formulas for a small molecule ligand attaching to a bio-macromolecule are proposed. The binding parameters were measured according to the suggested models, and the binding distance, the transfer efficiency of energy between sparfloxacin and BSA were obtained in view of the F6rster theory of non-radiation energy transfer. The effect of sparfloxacin on the conformation of BSA was analyzed by means of synchronous fluorescence spectroscopy.     

Studies on the binding of vinpocetine to human serum albumin by molecular spectroscopy and modeling

The interaction between vinpocetine(VPC) and human serum albumin(HSA) in physiological buffer(pH 7.40) was investigated by fluorescence,FT-IR,UV-vis absorption and molecular modeling.VPC effectively quenched the intrinsic fluorescence of HSA via static quenching.The binding site number n and apparent binding constant K_a,corresponding thermodynamic parametersΔG,ΔH andΔS at different temperatures were calculated.The synchronous fluorescence and FT-IR spectra were used to investigate the structural change of HSA molecules with addition of VPC.Molecular modeling indicated that VPC could bind to the site I of HSA and hydrophobic interaction was the major acting force,which was in agreement with the binding mode study.     

Grafting of poly(sodium styrenesulfonate) onto gold surface from NaNO<Subscript>3</Subscript> solution

The chemical grafting of thiol terminated poly(sodium styrenesulfonate)(HS-PSSS) chains from sodium nitrate (NaNO_3) salt solution to a gold surface was investigated with a quartz crystal microbalance with dissipation monitoring (QCM-D) in different salt concentrations.It was found that at low salt concentration grafting density of HS-PSSS was low and the grafted chains adopted a mushroom conformation.With the increase of salt concentration polyelectrolyte chains underwent a transition toward coiled stat...     

Interaction of Surface-active Fluorescence Probes with Bovine Serum Albumin

The binding between three surface-active substituted 3H-indole fluorescence probes and bovine serum albumin (BSA) in aqueous solution was studied using fluorescence quenching. The binding constants of 3H-indole molecules with BSA were obtained. According to the Foerster resonance energy transfer theory, the distances between 3H-indole molecules and tryptophan of BSA were calculated. The results show that the oligoethyloxyethylene chain of 3H-indole molecules is longer, the binding between them is stronger, the energy transfer efficiency is higher, and the distance between tryptophan and 3H-indole is nearer.     

4-(4-羟基丁基－2－炔氧基)－3-（苯磺酰基）－1，2，5－噁二唑－2－氧化物与牛血清白蛋白结合作用的光谱法研究

The interaction between 4-(4-hydroxybut-2-ynyloxy)-3-(phenylsulfonyl)-1,2,5-oxadiazole-2-oxide(FB)andbovine serum albumin(BSA)was studied by spectroscopic methods including fluorescence and UV-Vis absorptionspectroscopy.The quenching mechanism of fluorescence of BSA by FB was considered to be a dynamic quenchingprocedure.The number of binding sites n and apparent binding constant K were measured by fluorescence quench-ing method.The results indicate that there is FB molecular binding with BSA,and forming 1∶1 complex.Thethermodynamic parameters such as ΔH,ΔG and ΔS,etc.,were calculated.The results indicate that the binding reac-tion is mainly entropy-driven and hydrophobic forces play major role in the binding reaction.The distance r be-tween donor(BSA)and acceptor(FB)was obtained according to Frster theory of non-radioactive energy transfer.     

Interaction of epicatechin with bovine serum albumin using fluorescence quenching combined with chemometrics

The interaction between BSA and epicatechin was studied using fluorescence quenching titrations combined with trilinear decomposition method and excitation-emission matrix(EEM)fluorescence.The resolved spectra were highly similar with the actual ones which indicated that the resolved results were reliable.The relevant parameters of the binding process were obtained by quantifying each substance in the complicated mixtures in situ.The quenching was static quenching,epicatechin had a weak interaction with BSA and the binding site was one.The total concentration and the free concentration of quenchers had different effect on the system.The results demonstrated that the method exploited in this article is a useful tool to investigate complicated interactions,avoiding complicated pretreatment and simplify experimental procedure.     

Conjugated polymer nanoparticles as fluorescence switch for selective cell imaging

Fluorescence switch plays a vital role in bioelectronics and bioimaging.Herein,we presented a new kind of facile electrostatic complex nanoparticles(ECNs)for fluorescence switching in cells and marking of individual cell.The ECNs were prepared by mixing positively charged poly(6-(2-(thiophen-3-yl)ethoxy)hexyl trimethylammonium bromide)(PT)and negatively charged diarylethene sodium salt(DAECOONa).DAE-COONa is a photoswitchable molecule which can be transformed between the ring-closed fo rm and ring-open form under the irradiation of UV or visible light.The closed-form of DAE-COONa can efficie ntly quench the fluorescence of PT through intermolecular energy transfer,while the open form of DAE-COONa does not influence the emission of PT.Thus,the fluorescence of ECNs can be modulated by light irradiation,and the ECNs with good fluorescence switching performance have been employed for fluorescence imaging and individual cell lighting up process successfully.We demonstrate that the electrostatic complex strategy provides a facile method to construct fluorescence switch fo r selective cell marking and imaging applications.     

Twisted IntramoIecular Charge Transfer in Supramolecular System——Microenvironmental Effects of β-Cyclodextrin on the TICT Process of p-N, N-Dimethylaminobenzaldehyde

The microenvironmental effects of β-cyclodextrin (β-CD) on the twisted intramolecular charge transfer (TICT) of ρ-N, N-dimethylaminobenzaldehyde (DMABA) are investigated using fluorescence spectroscopy. The typical TICT dual fluorescence of DMABA is observed in pure water and aqueous β-CD solution, and β-CD has s remarkable influence on the TICT fluorescence characteristics of DMABA. A linear dependence of the ratio of intensity of TICT fluorescence band (a band) to that of normal fluorescence band (b band) on DMABA concentration is also observed and the introduction of β-CD increases the linear slope. Combined with the results of absorption spectroscopy, fluorescence polarization, and peculiar salt effects, the properties of TICT state of DMABA, the interaction of DMABA with β-CD, and the intrinsic traits of the microenvironmental effects of β-CD are discussed in detail.     

Investigation of the Interaction between Isoflavonoids and Bovine Serum Albumin by Fluorescence Spectroscopy

The interactions of bovine serum albumin （BSA） with three structurally related isoflavonoids, genistein, puerarin and daidzein, were studied under physiological conditions by fluorescence spectroscopic technique. The quenching mechanism of these compounds with BSA was suggested as static quenching and the binding constants were determined at different temperatures based on the fluorescence quenching results. The transfer efficiency of energy and distance between the acceptor and BSA were investigated on the basis of the mechanism of the Forster energy transference. According to the thermodynamic parameters it has been suggested that the acting force be mainly hydrophobic force. The comparison of binding potency of the three isoflavonoids to BSA showed that the substitution by 5-OH and 8-Glc could enhance the binding affinity. All these obtained in the work can make us better understand the mode of the action and pharmacological activities of the isoflavonoids.     

STUDIES ON THE MECHANISM OF INDIRUBIN ACTION IN THE TREATMENT OF CHRONIC GRANULOCYTIC LEUKEMIA——V.BINDING BETWEEN INDIRUBIN AND DNA AND IDENTIFICATION OF THE TYPE OF BINDING

The binding between indirubin and calf thymus DNA in vitro has been verified by meansof the isotope labelling method, spectrophotometric method and thermal denaturation meas-urements. The λ_max 207 nm of indirubin shifted toward longer wave length with decrease ofabsorbance after the incubation of indirubin with DNA. The escalation of Tm value of DNAinduced by indirubin was about 2.4°C and it was reproducible. The binding force between themwas rather weak, as indirubin molecules were easily released during the precipitation withalcohol or the gel filtration. The binding was not affected by sodium chloride even at high con-centration but greatly decreased (to 20-30% of the control) in the presence of 8 M urea.These results showed that the binding between indirubin and DNA might be of hydrogen bondrather than ionic. The amount of bound ~3H-indirubin was directly proportional to the con-centration of indirubin. However, it increased abruptly when the concentration of indirubinreached 1.5×10~(-4) M. This     

Enzyme-responsive polysaccharide supramolecular nanoassembly for enhanced DNA encapsulation and controlled release

An enzyme-responsive polysaccharide supramolecular targeted nanoassembly was successfully constructed by the host-guest complexation of positively charged mono-(6-(tetraethylenepentamine)-6-deoxy)-β-cyclodextrin(TEPA-CD) with adamantane-grafted hyaluronic acid(HA-ADA).Possessing a series of positively charged polyamine chains, the obtained polysaccharide nanoassembly could serve as a biocompatible plasmid DNA(p DNA) container. More interestingly, the p DNA could be released from the nanoassembly through the enzymatic degradation of HA skeleton, which realized the controlled p DNA binding and release. Besides, the polysaccharide nanoassembly exhibited lower cytotoxicity than the commercial transfection reagents 25 k Da b PEI(PEI25 k), accompanied by similar gene delivery effect. We believe that this work might present a convenient method for targeted,controlled gene delivery.     

Binding of nucleosides with the cytotoxic plant alkaloid sanguinarine: Spectroscopic and thermodynamic studies

In spite of a large number of studies of the interaction of the cytotoxic plant alkaloid sanguinarine(SAN) with nucleic acids,the anticancer mechanism of SAN is still not clear.In contrast to the large number of studies of the interaction mechanism of SAN with DNA,there have been relatively few studies of the interaction of SAN with nucleosides.In this work,the interaction of SAN with three nucleosides-thymidine(T),uridine(U),and adenosine(A)-was investigated using a combination of conventional fluorescence and UV-vis spectroscopic techniques;thermodynamic calculations were also carried out at physiological pH 7.2.The binding processes of SAN with the different nucleosides were characterized by hypochromic and bathochromic effects in the absorption spectra of SAN and by the quenching of the fluorescence intensity of SAN.The measurements of fluorescence lifetime,the variations of the absorption spectra of the fluorophore,and the dependence of the quenching on the temperature indicated that the fluorescence quenching is static.The Stern-Volmer plot is nonlinear and approximately quadratic showing that,in this process,one SAN molecule can bind with two nucleoside molecules.These studies,together with our earlier studies of the binding of SAN with cytidine(C) and guanosine(G),showed that the binding constants of SAN with the five nucleosides at T = 308.15,318.15,and 328.15 K decreased in the order C > G > T > U > A and at T = 298.15 K decreased in the order G > C > T > U > A,and that the binding of SAN with the various nucleosides is not only slightly exothermic but also entropy-driven.All these results together with fluorescence quenching experiments advance good evidence concerning the interaction of SAN with various nucleosides.Such studies of the interaction mechanism of alkaloids with DNA may promote the development of new drugs.     

Synthesis,Crystal Structure and Bioactivity of a Pd(Ⅱ) Complex with Demethylcantharate and 2,2′-Bipyridine

A novel crystal with the molecular formula [Pd(DCA)(bipy)]2 [Pd(bipy)Cl2 ]·6.75H2O was formed by PdCl2 with disodium demethylcantharate (Na2 (DCA),DCA2= 7-oxa-bicyclo[2.2.1]heptane-2,3-bicarboxylate) and 2,2-bipyidine (bipy) through the hydrothermal method.The complex was characterized by elemental analysis and infrared spectroscopy.The structure of the complex was determined by single-crystal X-ray diffraction,which is of triclinic system,space group P1 with a=13.6818(7),b=14.8426(8),c=15.0043(8),α=97.319(3),β=92.521(3),γ=105.776(2)°,V=2898.4(3) 3,Dc=1.545 g·cm-3,Z=1,F(000)=1420,S=0.852,the final R=0.0525 and wR=0.1777 for 13634 observer reflections (I>2σ(I)).The binding reaction of the complex with ct-DNA and bovine serum albumin (BSA) was studied by fluorescence spectroscopy.The results indicated that the complex binds to ct-DNA via the partial intercalation.The binding constant K A of the complex interaction with BSA was 3.98×10 5 L·mol-1 and one binding site would be formed.The antiproliferative activity of the complex against human hepatoma cells (SMMC7721) in vitro is much higher than that of Na 2 (DCA).