Molecular Insights into the Antistress Potentials of Brazilian Green Propolis Extract and Its Constituent Artepillin C

Propolis, also known as bee-glue, is a resinous substance produced by honeybees from materials collected from plants they visit. It contains mixtures of wax and bee enzymes and is used by bees as a building material in their hives and by humans for different purposes in traditional healthcare practices. Although the composition of propolis has been shown to depend on its geographic location, climatic zone, and local flora; two largely studied types of propolis: (i) New Zealand and (ii) Brazilian green propolis have been shown to possess Caffeic Acid Phenethyl Ester (CAPE) and Artepillin C (ARC) as the main bioactive constituents, respectively. We have earlier reported that CAPE and ARC possess anticancer activities, mediated by abrogation of mortalin-p53 complex and reactivation of p53 tumor suppressor function. Like CAPE, Artepillin C (ARC) and the supercritical extract of green propolis (GPSE) showed potent anticancer activity. In this study, we recruited low doses of GPSE and ARC (that did not affect either cancer cell proliferation or migration) to investigate their antistress potential using in vitro cell based assays. We report that both GPSE and ARC have the capability to disaggregate metal- and heat-induced aggregated proteins. Metal-induced aggregation of GFP was reduced by fourfold in GPSE- as well as ARC-treated cells. Similarly, whereas heat-induced misfolding of luciferase protein showed 80% loss of activity, the cells treated with either GPSE or ARC showed 60–80% recovery. Furthermore, we demonstrate their pro-hypoxia (marked by the upregulation of HIF-1α) and neuro-differentiation (marked by differentiation morphology and upregulation of expression of GFAP, β-tubulin III, and MAP2). Both GPSE and ARC also offered significant protection against oxidative stress and, hence, may be useful in the treatment of old age-related brain pathologies.     

柚皮素、柚皮苷与溶菌酶相互作用的荧光光谱法研究

应用荧光光谱法研究了50%甲醇/水体系中柚皮素、柚皮苷与溶菌酶分子间的结合反应. 以Lineweaver-Burk双倒数方程和能量传递原理分别计算了两者与溶菌酶反应的结合常数(K)和结合距离(r): K_柚皮素^{25 ℃}＝4.00×10⁴, K_柚皮苷^{25 ℃}＝3.48×10⁴; r_柚皮素＝3.21 nm, r_柚皮苷＝3.30 nm, 以及由热力学参数的计算判断了两种分子与溶菌酶之间的作用力类型. 结果表明: 柚皮素、柚皮苷均能与溶菌酶以疏水作用相结合形成非共价化合物, 从而导致溶菌酶内在荧光的静态猝灭; 相对柚皮素, 柚皮苷与溶菌酶的结合距离增大, 作用强度减弱, 表明黄酮分子上多糖的取代不利于黄酮分子与蛋白之间的亲和作用. 根据Haslam等提出的多酚-蛋白质反应模型, 从分子水平初步探讨了糖取代对黄酮分子与蛋白相互作用减弱的原因.     

钌联吡啶络合物与脱氧核糖核酸分子相互作用的荧光光谱研究与分析应用

合成了2苯基(4溴)咪唑[f]邻菲咯啉(简称PIP(Ⅲ)新的配体及〔Ru(bpy)_2PIP(Ⅲ)]~(2+)新的络合物,用荧光光谱研究了络合物与小牛胸腺DNA分子的结合情况,在 pH7.4,络合物与DNA作用后,在587nm(λ_(ex)=471nm)产生很强的荧光峰,其发光强度与DNA浓度呈线性关系;线性范围0～1.2mg/L;检测限(3a(?))为2.8mg/L.该方法具有较高灵敏度和准确度,对合成样品测定,结果令人满意.     

Interaction of Chlorpromazine and Trifluoperazine with Anionic Sodium Dodecyl Sulfate (SDS) Micelles: Electronic Absorption and Fluorescence Studies

The characteristics of binding of two phenothiazine antipsychothic drugs, chlorpromazine (CPZ) and trifluoperazine (TFP), to anionic sodium dodecyl sulfate (SDS) monomers and/or micelles were investigated using electronic absorption and fluorescence spectroscopies. Binding constants K(b) and pK(a) values for the drugs in SDS micelles were estimated using the red shifts of the maximum absorption and changes in absorption upon alkalization or in the presence of surfactant. The pK(a) shift of CPZ due to its interaction with SDS micelles is about 0.7 unit to higher values, as compared to the reported value of pK(a) obtained in buffer around 9.3. For TFP the pK(a) shift is 0.4 unit to higher values compared to that in buffer, reported as 4.0. The electronic absorption spectroscopic data suggest a biphasic interaction as a function of detergent concentration which is quite dependent of the protonation states of the drugs. In the case of TFP a very strong binding takes place when the drug is fully protonated (pH 2.0) and a distinct binding takes place at stoichiometric (low) surfactant concentrations (interaction via surfactant monomers) and at higher concentrations (in the presence of micelles). Static fluorescence probe analysis using pyrene was used to study the nature of the phenothiazine-surfactant premicellar and self-aggregates. The I(3)/I(1) and I(475)/I(1) ratios associated to pyrene fluorescence vibronic bands and excimer intensities ratios, respectively, were monitored for several ratios [SDS]/[drug] and significant changes, dependent of the drug presence and its protonation state, have been observed revealing a hydrophobic microenvironment provided by TFP-SDS aggregates in comparison with CPZ both at pH 7.0 and 4.0. Static anisotropy was also used to monitor the changes of the self-aggregates and micellar packing in the presence of the phenothiazine drugs. In aqueous solutions the anisotropy of the fluorescent probe dipyridamole (DIP) is quite low, being around 0.005 at pH 7.0 and 0.025 at pH 4.0, and the addition of detergent leads to an increase in the values of anisotropy to 0.030 at pH 7.0 and 0.070 at pH 4.0. In the presence of the phenothiazine drugs, and in the premicellar detergent concentration range, the anisotropy of DIP increases to 0.134 and 0.111 (dependent on drug concentration) for CPZ and TFP, respectively, at pH 4.0. These results suggest that the presence of both phenotiazine drugs makes the premicellar aggregates more rigid by decreasing the probe mobility, and are consistent with a more polar localization of the CPZ in the micelles as compared with TFP. At pH 7.0 the anisotropy changes are smaller, suggesting a slight decrease in CMC induced by the phenothiazines. Copyright 2000 Academic Press.     

金属离子对一种分子内电荷转移荧光探针与牛血清白蛋白相互作用的影响

采用荧光光谱法研究了Fe~(3+)、Cu~(2+)、Pb~(2+)三种离子对1-酮-2-(对二甲氨基苯亚甲基)-四氢萘与牛血清白蛋白相互作用的影响.三种金属离子分别存在时能增强1-酮-2-(对二甲氨基苯亚甲基)-四氢萘对牛血清白蛋白的猝灭作用及二者的结合作用,使体系的猝灭常数及结合常数增大,且影响顺序为Fe~(3+)>Cu~(2+)>Pb~(2+).实验表明金属离子对蛋白质在物质的贮存、运转、代谢等方面有重要意义.     

Novel Azobenzene-Functionalized Polyelectrolytes of Different Substituted Head Groups 1: Synthesis,Characterization and Absorption Spectroscopy Studies

A new class of a series of amphiphilic polyelectrolytes functionalized with azobenzene chromophores have been synthesized and thoroughly characterized by various techniques. A facile two stage strategy is developed, and first involved the preparation of a precursor base polymer, designated as P(APEA), by the free-radical copolymerization of the monomers of acrylic acid (AA) and 2-(phenylethylamino)ethyl acrylate (PEA). In the second step, precursor PAPEA polymers are reacted and post-polymer modified with the diazonium salts to synthesize azobenzene polyelectrolyte, PAPEA-R with different substituted R-groups present on the para position of the aromatic ring of the azo chromophores. The PAPEA-R polyelectrolytes are same in their degree of polymerization and repeat unit compositions of AA and PEA monomers, and only differ from each other by the type of R-groups. The copolymers were classified on the basis of the characteristics of their R-groups into the hydrophilic-ionizeable smaller pair of ─SO₃H and ─COOH, the hydrophobic-non-ionizeable smaller pair of ─ H and ─OC₂H₅, and the hydrophobic-non-ionizeable larger octyl pair of ─C₈H₁₇ and ─ C₈F₁₇. The prepared copolymers are also characterized by NMR spectroscopy for structure, GPC for molecular weight, and UV-Visible spectroscopy for absorption determination. In DMF solvent, approximately similar absorption maxima, (λ_max) values were observed for azo chromophore-containing monomers and after incorporating these into their corresponding polymers structures. However, for the self-assembled multilayer thin films, λ_max moved to lower wavelengths to exhibit a blue shift with hydrophobic R-group of ─C₈H₁₇, while this behaviour was not observed for hydrophilic R-group of ─COOH. The shift in λ_max is found to be highly dependent on the type of substituted R-group, and attributed to aggregation of hydrophobic azo chromophores in DMF:H₂O mixture employed for self-assembly. The presence of the ionizeable AA and light-sensitive azo-chromophore functionalized PEA monomers in the PAPEA-R polyelectrolytes impart self-assembling and photoswitchable characteristics, respectively. Through understanding and controlling the solubility and complex solution aggregation behaviour of the different substituted R-groups of azo PEL, their adsorption, thickness, morphology, wetting, molecular-control, and photoresponsiveness can be tailored to enhance the capabilities of the self-assembled multilayer film process in diversified areas of microfluidics, sensing, and controlled release.     

Interaction of L-Ascorbic Acid with Activated Carbon: Kinetic Studies and the Effect of pH

Colloid Journal - This article investigates the interaction of vitamin C with commercial activated Granucol-type carbons and newly produced AC-C coal at 25 and 35°C. L-Ascorbic acid molecules...     

Solvent Effect on the Absorption and Fluorescence Emission Spectra of Some Purine Derivatives: Spectrofluorometric Quantitative Studies

The absorption and emission spectra of six purine derivatives: adenine (I), N(9)-hydroxyethyladenine (II), N(6)-acetyladenine (III), N(6)-isobutyryladenine (IV), guanine (V), and N(2),N(9)-diacetylguanine (VI) have been investigated. The effects of solvent and pH on the positions of λ _max (absorption) and λ _max (emission) of these compounds were determined. Correlations between the absorption wavelength (λ _max) of these organic compounds and the solvent parameters (D,n,E) or (K,M,N) show that the peak position is affected mainly by specific- and non-specific types of interactions between the solvent and solute. Solvent effects on the electronic absorption band shifts are indicative of the extent of charge reorganization of the solute molecules upon electronic excitation. The Stokes shift (ν _abs−ν _em) was correlated with the orientation polarizability (Δf) and was found to depend mainly on the dielectric constant and the refractive index of the solvents. This shift reflects the influence of the equilibrium solvent arrangement around the excited solute molecule, which rearranges inertially due to the instantaneous charge redistribution upon radiative deactivation to the electronic ground state. A spectrofluorometric analysis technique was applied for the quantitative analysis of the components of a ternary mixture of compounds (I–III).     

Formation and Optical Absorption of Clusters of the p-tert-butylcalix[8]arene:C60 Complex

Depending on the initial concentrations of fullerene (C₆₀) and p-tert-butyl calix[8]arene (C[8]A) in toluene, two regimes of their interaction were distinguished. The changes in optical absorption of C₆₀:C[8]A mixed solutions observed over a period of time suggest that the following consecutive processes take place upon interaction between C₆₀ and C[8]A in toluene: (1) molecular inclusion, and (2) growth and sedimentation of the insoluble C₆₀/C[8]A clusters. At increased concentrations of the components, process (2) is suppressed and stable C₆₀/C[8]A colloids can be formed. Spectral features of these colloids in different solvents clearly indicate the difference between self-aggregated C₆₀ and small clusters of the complex. A specific influence of the C[8]A cage on the entrapped C₆₀ molecules is also confirmed by IR spectroscopy of the complex in the solid state.     

Green and Catalytic Synthesis of Dominicalure I,Major Component of the Aggregation Pheromone of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae)

A new concise and efficient catalytic synthesis of dominicalure I, the male-produced aggregation pheromone of the grain borer Rhyzopertha dominica, is herein reported. The synthetic route was designed starting from easily available propanal through an organocatalytic key step and completed with biocatalytic procedures.     

Carbon,Nitrogen, and Chalcogen Substitution Effects on 2,1,3-Benzothiadiazole Derivative: Theoretical Investigations of Electronic,Optical, and Charge Transport Properties

A series of CH₂, NH, O, and Se substituted 2,1,3-benzothiadiazole derivatives have been de-signed and investigated computationally to elucidate their potential as organic light-emitting materials for organic light-emitting diodes. Both ab initio Hartree-Fock and hybrid density functional methods are used. It is found that adjusting the central aromatic ring by replacing S by CH₂, NH, O, and Se makes it possible to fine-tune the electronic, optical, and charge transport properties of the pristine molecule.     

Investigation of the Interaction between N,N′‐Di(4‐Chlorophenyl)Thiourea and Human Serum Albumin by Fluorescence Spectroscopy: Synchronous Fluorescence Determination of Human Serum Albumin

Under physiological conditions, interaction between N,N′‐di(4‐chlorophenyl)thiourea synthesized and human serum albumin was investigated by using fluorescence spectroscopy and UV absorption spectrum. The intrinsic fluorescence of human serum albumin was quenched by N,N′‐di(4‐chlorophenyl)‐thiourea through a static quenching procedure. The binding constants (K) at 14 °C and 24 °C were obtained, and the values were 2.541 × 10⁵ M^?1 and 2.021 × 10⁵ M^?1, respectively. Thermodynamic parameter enthalpy change (ΔH) and entropy change (ΔS) were calculated to be ‐16.19 KJ/mol and 47.05 J·mol¹·K^?1, respectively, which indicated that hydrophobic force played a major role in interaction. The binding distance was evaluated on the basis of the theory of Föster energy transfer. The effects of various metal ions on the binding constants of N,N′‐di(4‐chlorophenyl)thiourea with human serum albumin were studied. A synchronous fluorescence technique for determination of human serum albumin was developed, and the method was successfully applied to the detection of HSA in human serum samples.     

Multi-spectroscopic and HPLC Studies of the Interaction Between Estradiol and Cyclophosphamide With Human Serum Albumin: Binary and Ternary Systems

Drug resistance is a phenomenon that frequently impairs a proper treatment of infections and cancer with chemotherapy. Multidrug efflux transporters extrude structurally dissimilar organic compounds often providing resistance to multiple toxic chemotherapeutic agents. The quantitative analysis of drug efflux requires measuring the affinity of ligands. In this work, the interaction between cyclophosphamide (Cyc) and estradiol (ES) with human serum albumin (HSA) was studied by fluorescence polarization, circular dichroism and high-performance liquid chromatography (HPLC) under physiological conditions (pH = 7.4). Gradual addition of HSA led to a marked increase in fluorescence polarization. Our assays indicated that the protein was bound to these drugs with different K _d. Also, the Hill coefficient showed a simple drug binding process with no cooperativity. Circular dichroism results revealed the occurrence of conformational changes in HSA molecules by the binding of Cyc and ES. The protein binding of the drug was studied by HPLC. Our results indicated that the drug was bound to the protein and that the presence of a second drug affected the interaction and resistance between the first drug and the protein.     

The Effects of pH and Ionic Strength on the Aggregation of Bacteriochlorophyll c in Aqueous Organic Media: The Possibility of Two Kinds of Aggregates

The aggregation behavior of two homologs of bacteriochlorophyll c (BChl c) in various media was investigated for the effects of pH and salt, and the corresponding structures were analyzed by Fourier transform (FT)-IR spectroscopy. R-[P, E] BChl c_F (3¹-R-form of BChl c with a propyl group at the C-8 position and an ethyl group at the C-12 position) and R-[E, E] BChl c_F (3¹-R-form of BChl c with two ethyl groups at positions C-8 and C-12) were isolated from the green sulfur bacterium Chloro-bium limicola. Aggregates of each homolog showed a pH-dependent shift of the absorption maximum; at low pH, the peak moved to the red. This tendency was also revealed by circular dichroic spectra. A similar red shift of the peak was also induced by a high concentration of salt (NaCl) or buffer for both homologs. The FT-IR spectrum indicates that at low pH, both homologs formed a rather amorphous aggregate. On the other hand, a regular structure of R-[P, E] BChl c_F was indicated in an acetone-water mixture. This structure was stabilized by a triangular interaction among three pigment molecules through the Mg-OH (3>) O = C (13¹) linkage. This structure was not found for R-[E, E] BChl c_F. These results indicate that the replacement of the side chain at the C-8 position on the macrocycle induces a change in aggregation behavior. A possible heterogeneity of the in vivo rod structure of chlorosomes in green sulfur bacteria is discussed based on the above results.     

Cobalt Complexes with Pyrazole Ligands as Catalyst Precursors for the Peroxidative Oxidation of Cyclohexane: X‐ray Absorption Spectroscopy Studies and Biological Applications

[CoCl(μ‐Cl)(Hpz^Ph)₃]₂ ( 1 ) and [CoCl₂(Hpz^Ph)₄] ( 2 ) were obtained by reaction of CoCl₂ with HC(pz^Ph)₃ and Hpz^Ph, respectively (Hpz^Ph=3‐phenylpyrazole). The compounds were isolated as air‐stable solids and fully characterized by IR and far‐IR spectroscopy, MS(ESI+/?), elemental analysis, cyclic voltammetry (CV), controlled potential electrolysis, and single‐crystal X‐ray diffraction. Electrochemical studies showed that 1 and 2 undergo single‐electron irreversible Co^II→Co^III oxidations and Co^II→Co^I reductions at potentials measured by CV, which also allowed, in the case of dinuclear complex 1 , the detection of electronic communication between the Co centers through the chloride bridging ligands. The electrochemical behavior of models of 1 and 2 were also investigated by density functional theory (DFT) methods, which indicated that the vertical oxidation of 1 and 2 (that before structural relaxation) affects mostly the chloride and pyrazolyl ligands, whereas adiabatic oxidation (that after the geometry relaxation) and reduction are mostly metal centered. Compounds 1 and 2 and, for comparative purposes, other related scorpionate and pyrazole cobalt complexes, exhibit catalytic activity for the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone under mild conditions (room temperature, aqueous H₂O₂). In situ X‐ray absorption spectroscopy studies indicated that the species derived from complexes 1 and 2 during the oxidation of cyclohexane (i.e., Ox‐ 1 and Ox‐ 2 , respectively) are analogous and contain a Co^III site. Complex 2 showed low in vitro cytotoxicity toward the HCT116 colorectal carcinoma and MCF7 breast adenocarcinoma cell lines.     

Synthesis,Characterization, and Properties of Subporphyrazines: A New Class of Nonplanar,Aromatic Macrocycles with Absorption in the Green Region

Novel subphthalocyanine analogues that display strong absorption in the green region have been synthesized by using a boron template cyclotrimerization of maleonitrile derivatives. The spectroscopic properties of these macrocycles indicate that, like subphthalocyanines, they have 14 π electrons and are aromatic compounds with a conical shape. The removal of the three fused benzene rings from the subphthalocyanine skeleton produces a 75–80 nm blue shift of the Q‐band and a slight lowering of the absorption coefficients for this band. In addition, the reduction of the π system from 18 to 14 electrons that accompanies progression from porphyrazines to subporphyrazines causes a hypsochromic shift of the Q‐band of around 100 nm. Subporphyrazines that are peripherally functionalized with six thioether chains, and in which the sulfur atoms are attached directly to the pyrrole moieties, exhibit optical features that may be explained in terms of the extension of π conjugation over the six thiolene groups, as well as strong π donation from the sulfur lone pairs to the macrocycle. These two effects are quantitatively and qualitatively very similar to those observed for porphyrazines that possess the same type of substitution. In addition, the mesomorphic behavior at low temperatures of a macrocycle that is substituted with six thiododecyl chains was demonstrated by using differential scanning calorimetry and optical polarising microscopy.     

ChemInform Abstract: Interaction of Metal Ions with Water: Ab initio Molecular Orbital Studies of Structure,Bonding Enthalpies,Vibrational Frequencies and Charge Distributions. Part 1. Monohydrates.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Selective Interaction Between Proteins and the Outermost Surface of Polyelectrolyte Multilayers: Influence of the Polyanion Type,pH and Salt

Protein adsorption was studied by in-situ ATR-FT-IR spectroscopy of consecutively deposited polyelectrolyte multilayer systems terminated either with poly(ethyleneimine) (PEI) or polyanions, such as poly-(acrylic acid) (PAC), poly(maleic acid-co-propylene) (PMA-P) or poly(vinyl sulfate) (PVS). The influence of the polyanion type, pH and ionic strength was investigated. Negatively charged human serum albumin (HSA) was strongly repelled by multilayers terminated with weak polyanions (PAC, PMA-P), whereas moderate attraction was observed for those terminated with the strong polyanion PVS. Changing the pH from 7.4 to 5 resulted in enhanced HSA adsorption onto PAC-terminated multilayers. An increase in ionic strength diminished the attractive HSA adsorption onto PEI-terminated multilayers. For the PEI/PAC system, the biomedically relevant adsorption of human fibrinogen (FGN) is determined via its isoelectric point in accordance with three other proteins.     

Studies on leaching behaviour of sodium borosilicate glasses by neutron activation: Effects of groundwater composition,pH, surface area to volume ratio,and temperature

Static leaching experiments have been conducted to evaluate the durability of sodium borosilicate glass as the host matrix for immobilized high-level radioactive wastes. Simulated granitic groundawater, synthetic Grande Ronde basaltic groundwater and distilled deionized water have been used. The results indicated a strong influence of the leachant composition through both its pH and nature as well as concentrations of the ions present on the leach rate. The roles of silicon, boron and a few other elements on leaching have been examined. Three surface area to volume ratios (SA/V) and two temperatures were investigated. Total mass loss and normalized elemental mass loss results showed that the rate of release decreased with increased SA/V ratio in the three leachants at both temperatures. The rate of leaching at 90 °C was 5–30 times higher than that at 40 °C. Activation energies for the glass at three SA/V ratios have been calculated.