Entrapment and release difference resulting from hydrogen bonding interactions in niosome.

In this study the influence of hydrogen bonding interaction between niosomal membrane and solutes on the drug loading and release was investigated. Salicylic acid (SA) and p-hydroxyl benzoic acid (p-BA) were selected as models. Niosomes were prepared with 1:1 molar ratios of various surfactants and cholesterol by film hydration technique, and the corresponding formulation variables were optimized to achieve the maximum entrapment efficiencies (EE%). The EE% of different formulations followed the trend Span 60>Span 40>Span 20>Span 80. Additionally, it was also found that the EE% of p-BA was much higher than that of SA. This difference may be due to the formation of hydrogen bond between p-BA and niosomal membrane, and the corresponding interaction diagram has been proposed and confirmed indirectly by UV spectroscopy method. The quantitative analysis of hydrogen binding interaction between solutes and niosome has been finished firstly, and the corresponding entrapment equilibrium constant K has been calculated as well. Moreover, in vitro the release of both drugs from niosomes was examined in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF), respectively. The results indicated that the release of p-BA in SIF was much slower than that in SGF, and the release rate of SA in SGF is apparently slower than that in SIF. The possible mechanism was given as well.

Gold nanoparticle based plasmon resonance light-scattering method as a new approach for glycogen-biomacromolecule interactions.

A model was developed for the interactions between glycogen and biomacromolecules by gold nanoparticle plasmon resonance light-scattering method. The interactions between glycogen and biomacromolecules can alter the aggregation status of gold nanoparticles, which produced intensity changes in plasmon resonance light-scattering. This is a sensitive method to study the interactions between glycogen and biomacromolecules from nano- to micromolar level. And it is also a simple method that measurement can be carried out with a common fluorospectrometer using label-free gold nanoparticles as the transducer.

[Research progresses of anabolic steroids analysis in doping control].

Anabolic steroids, a kind of physiological active substance, are widely abused to improve athletic performance in human sports. They have been forbidden in sports by the International Olympic Committee since 1983. Since then, many researchers have been focusing their attentions on the establishment of reliable detection methods. In this paper, we review the research progresses of different analytical methods for anabolic steroids since 2002, such as gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, immunoassay, electrochemistry analysis and mass spectrometry. The developing prospect of anabolic steroids analysis is also discussed.

[Study on determination of acetamiprid and interaction between acetamiprid and deoxyribonucleic acid by resonance light scattering].

The interaction between acetamiprid and deoxyribonucleic acid (DNA) was used to determine acetamiprid by resonance light scattering (RLS). The RLS signals of DNA were greatly enhanced by acetamiprid in the spectrum region of 300-600 nm. The spectrum peak is around 316.0 nm. The optimum conditions: pH is 1.73; the concentration of DNA is 2.0 microg x mL(-1)bration curve is 0-2. 25 pg * mLU , with the detection2limit of 0. 2 ig * mL '. The acetamiprid in river water sample was determined. The results were satisfactory, and the recovery rates were in the range of 98%-106%. The interaction mechanism of acetamiprid and DNA was discussed: the interactions between acetamiprid and nucleic acid base include electrostatic effect and Tr-r cumulate effect.

Enhanced anodic Ru(bpy)3(2+) electrogenerated chemiluminescence by polyphenols.

Anodic Ru(bpy)3(2+) electrogenerated chemiluminescence (ECL) can be enhanced by polyphenols in alkaline solution. Spin trapping-electron spin resonance (ESR) experiments verified that reactive oxygen species (ROS) were generated during the electrolysis of Ru(bpy)3(2+) in alkaline solution, and oxidation of quercetin enhanced Ru(bpy)3(2+) ECL at anodic potential by producing additional ROS. This ECL enhancement can be used to analyze real sample and evaluate antioxidant activity of polyphenols.

J-aggregates of diprotonated tetrakis(4-sulfonatophenyl)porphyrin induced by ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate.

The J-aggregation behavior of diprotonated tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4(2-)) in aqueous solution in the presence of the hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) was investigated in detail using UV-vis absorption spectroscopy, fluorescence spectroscopy, resonance light scattering (RLS) spectroscopy, Raman spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. With the addition of bmimBF4, increasing peaks appeared at a wavelength of 490 nm in the absorption spectra to account for the formation of H 2TPPS4(2-) J-aggregates. In addition, the experimental results also showed decreased fluorescence emission, enhanced RLS signals, intensified Raman scattering peaks, and the disappearance of NMR signals to further indicate that porphyrin J-aggregates exist in the studied system. NMR shifts of bmimBF 4 toward high field occurred corresponding to H2, H4, and H5 in the cationic imidazolium ring (bmim+), suggesting that bmim+ enters the magnetic shielding domain of the anionic phenyl sulfonate ion owing to the association process between the "large" cation and anion. Additionally, the fact that the absorption spectral shifts occurred in the nonprotonated porphyrin TPPS4(4-) further indicates the existence of the ion association effect of bmim+, which functions as an important factor in porphyrin aggregation.

Free-radical scavenging capacity using the fenton reaction with rhodamine B as the spectrophotometric indicator.

A spectrophotometric method was developed to measure antioxidant free-radical scavenging capacity. Rhodamine B (RhB) was oxidized by hydroxyl radical generated via the Fenton reaction to yield a photoinactive RhB product. RhB absorption at 550 nm was restored when antioxidant agents scavenged hydroxyl radical to protect RhB from oxidation. On the basis of the dose response of antioxidant recovery capacity, a model was developed to calculate the free-radical scavenging ability. This method was sensitive to a wide range of antioxidant activity with ascorbic acid reference set as one; the antioxidant recovery capacity of quercetin was 635 compared to 2 for benzoic acid.

Gastrodin interaction with human fibrinogen: anticoagulant effects and binding studies.

In an effort to identify the anticoagulant activity of gastrodin (GAS) and to investigate the possibility of its use as a novel anticoagulant drug, the binding characteristics of GAS to human fibrinogen (Fg) were studied by using a quartz crystal microbalance (QCM) biosensor, anticoagulant animal experiments, and a molecular docking simulation. Real-time kinetic analysis with the QCM biosensor revealed that the in vitro binding of GAS to Fg was strong under physiological ionic conditions as the determined equilibrium dissociation constant (KD) was 1.94 x 10(-6) M. To check whether this strong binding may influence the natural coagulation function of Fg, the in vivo effect of GAS on the coagulation system of rats was examined. The results showed that GAS can significantly prolong the coagulation time (CT) and decrease the Fg content, while it had no effect on the activated kaolin partial thromboplastin time (KPTT) or prothrombin time (PT) in rats. To clarify the mechanism of the specific interaction, a molecular docking simulation was also performed to provide reasonable binding models for the interaction of GAS with Fg at the atomic level. GAS binds strongly to the inherent polymerization sites "a" and "b" (holes) on the Fg molecule with similar binding free energies of about -34 kJ mol(-1). Altogether, these findings confirmed first that GAS possesses anticoagulant activity and that the possible anticoagulation mechanism of GAS mainly involves its interference with the knob-to-hole interactions between fibrin molecules, thereby effectively inhibiting the formation of clots and decreasing the risk of thrombosis. The study has also shown the potential usefulness of QCM biosensor technology for the rapid screening of drug-protein interactions.

[Study on the chemical reaction of DNA with Congo red].

The interaction of deoxyribonucleic acid(DNA) and Congo red (GGH) was investigated by UV-Vis spectrophotometry in Tris-HCl solution (pH 4.56). When DNA was added into GGH solution, the color of the system changed from red to purple, which indicated the formation of the DNA-GGH complex. The maximum absorption of the complex is at 600 nm. The molar absorptivity measured at this wavelength epsilon = 1.41 x 10(5) L x cm(-1) mol(-1), the maximum binding number is n = 32, and the detection limit is c = 8.04 x 10(-8) mol x L(-1). The basic reaction condition of best pH value, time, and temperature, and the interference of different materials on the system were also studied. The ionic strength could affect the absorption of the system. The interaction of small molecule and DNA, the molecule structure, and the relationship between the molecule conformation and the distribution of electron cloud were studied.

Selection of ligands for affinity chromatography using quartz crystal biosensor.

This paper described a new strategy for rapid selecting ligands for application in affinity chromatography using a quartz crystal microbalance (QCM) biosensor. An aminoglycoside antibiotic drug, kanamycin (KM), was immobilized on the gold electrodes of the QCM sensor chip. The binding interactions of the immobilized KM with various proteins in solution were monitored as the variations of the resonant frequency of the modified sensor. Such a rapid screen analysis of interactions indicated clearly that KM-immobilized sensor showed strong specific interaction only with lysozyme (LZM). The resultant sensorgrams were rapidly analyzed by using a kinetic analysis software based on a genetic algorithm to derive both the kinetic rate constants (k(ass) and k(diss)) and equilibrium dissociation constants (K(D)) for LZM-KM interactions. The immobilized KM showed higher affinity to LZM with a dissociation constant on the order of 10(-5) M, which is within the range of 10(-4)-10(-8) M and suitable for an affinity ligand. Therefore, KM was demonstrated for the first time as a novel affinity ligand for purification of LZM and immobilized onto the epoxy-activated silica in the presence of a high potassium phosphate concentration. The KM immobilized affinity column has proved useful for a very convenient purification of LZM from chicken egg white. The purity of LZM obtained was higher than 90%, as determined by densitometric scanning of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified fraction. These results confirmed that the selected KM ligand is indeed a valuable affinity ligand for purification of LZM. The new screening strategy based on a QCM biosensor is expected to be a promising way for rapid selecting specific ligands for purifying other valuable proteins.

Anion chelation-induced porphyrin protonation and its application for chloride anion sensing.

The protonation of a simple meso-tetraphenylporphyrin in an organic-aqueous system was found to be induced by the counteranions. During the process of protonation, the counteranion of the proton sources binds with the porphyrin core and thus promotes the complexation of the porphyrin and protons. The interaction of porphyrin and anion was characterized by fluorescence, UV-visible, cyclic voltammetry, (1)H NMR, and IR. Moreover, it could be exploited in selective fluorescent sensing of Cl(-). The sensing mechanism was based on extraction of protons from the aqueous phase into the organic phase by free base porphyrin and simultaneous coextraction of Cl(-), which promoted porphyrin protonation, and hence resulted in significant changes of the porphyrin fluorescence spectra. Selectivity trends turned out to be dependent upon the lipophilicity of anion and the binding affinity and structure complementarity between the protonated porphyrin and anions. The fluorescence enhancement of the porphyrin band at 684 nm showed modest selectivity for Cl(-) and NO(3)(-).

Fluorescent sensor for imidazole derivatives based on monomer-dimer equilibrium of a zinc porphyrin complex in a polymeric film.

A new zinc(II) porphyrin conjugate with an appended pyrene subunit has been synthesized and shown to exhibit significant and analytical usefulness for fluorescence sensing toward imidazole derivatives. The molecular recognition was based on the bridging interaction of the imidazole ring of analyte with the zinc(II) center of the porphyrin, while the transduction signal for the recognition process was the pyrene excimer fluorescence. The sensor was constructed and applied for fluorescence assay of histidine in aqueous solution by immobilizing the sensing material in a plasticized PVC membrane. When the membrane was bathed in an alkaline solution void of histidine, zinc(II) porphyrin was present in the monomer form, and pyrene emitted monomer fluorescence at 378 and 397 nm. With the presence of histidine in the sample solution, histidine was extracted into the membrane phase and bridged with the Zn(II) center of the porphyrin, causing the monomer porphyrin to be converted to its dimeric species. Since the formation of porphyrin dimer was accompanied by the enhancement of pyrene excimer emission at 454 nm, the chemical recognition process could be directly translated into a fluorescent signal. With the optode membrane M1 described, histidine in sample solution from 6.76 x 10(-7) to 5.01 x 10(-3) M can be determined. The limit of detection was 1.34 x 10(-7) M. The optical selectivity coefficient obtained for histidine over biologically relevant amino acids and anions met the selectivity requirements for the determination of histidine in biological samples. Serum histidine values obtained by the optode membrane fell in the normal range of the content reported in the literature and were in good agreement with those obtained by HPLC.

Characterization of hemoglobin immobilized on gamma-zirconium phosphate.

The fact that different gamma-zirconium phosphate (gamma-ZrP) preintercalation method induced varied degree and type of conformational change of the adsorption protein was confirmed by characterization techniques including circular dichroism (CD), fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) analysis. The results indicated that the association of hemoglobin with gamma-ZrP preintercalated using butylamine was correlated with conformational change in the secondary structure of the protein. gamma-ZrP which was preintercalated with tetra (n-butylammonium) hydroxide caused the conformational change of Hemoglobin in both the secondary structure and the tertiary structure. X-ray powder diffraction analysis was used to analyze the crystalline structure of the nanocomposites prepared by relamination. The adsorption isotherms of Hemoglobin on different matrices were set up and fitted with Langmuir and Freundlich equations.

Separation and determination of biphenyl nitrile compounds by microemulsion electrokinetic chromatography with mixed surfactants.

A mixture of six biphenyl nitrile compounds and three related substances with high hydrophobicity and similar structures was successfully separated by microemulsion electrokinetic chromatography (MEEKC) within 30 min. The microemulsion system contained 100 mM sodium dodecyl sulfate (SDS), 80 mM sodium cholate (SC), 0.81% v/v heptane, 7.5% v/v n-butanol, 10% v/v acetonitrile, and 10 mM borate. The addition of SC, organic modifiers, sample preparation, and temperature all showed remarkable effects on the separation. The capacity factor (k) was calculated by using dodecyl benzene as the marker for microemulsion, and the calculated partition coefficient log P(o/w) of the solutes was in the range of 3.35-7.38. The log k values matched well with the log P(o/w) with a correlation coefficient of 0.96. In addition, the linear correlation coefficients of each compound between peak area and concentration were from 0.996 to 0.998 with the repeatability RSD value < 1.2% for migration time and < 4.8% for peak area, and the highest theoretic plate number was > 586000. MEEKC was compared with micellar electrokinetic chromatography (MEKC) indicating that the former method is more suitable for this separation and can be used for the quality control of biphenyl nitrile compounds in the synthesis of liquid crystals.

Spectroscopic study on the interaction between methylene blue and chondroitin 4-sulfate and its analytical application.

The interaction of Methylene Blue (MB) with chondroitin-4-sulfate (CHS) has been investigated using spectroscopic techniques, including UV-Vis absorption, Rayleigh resonance scattering (RRS), and circular dichroism (CD). The addition of CHS caused a decrease in the absorbance of MB at 664 nm with a new absorption band appearing at 570 nm, enhanced RRS at 314 nm and 560 nm, and also resulted in an intense CD signal at 568 nm. The Scatchard model has been applied to calculating the binding constant and the number of binding sites. The calculated parameters are consistent with the experimental results. The factors affecting the interaction were investigated. Quantitative spectroscopic methods were developed for the first time. They are based on the fact that a decrease in the absorption at 664 nm and an enhancement of the RRS intensity at 314 nm are proportional to the concentration of CHS added in a certain range. Satisfactory results were obtained on the determination of synthetic samples.

[Study on the reaction of Lys-ZCN-CTMAB complex].

The interaction of lysozyme (Lys), O-{2-[alpha-(2-Hydroxy-5-Sulphophenlylazo)-benzylidene] hydrazino} benzoic acid (ZCN) and cetyltrimethy ammonicumbromide (CTMAB) was investigated by UV spectrophotometric method. The effect of temperature, time, and ion intensity in the buffer solution (pH 4.46) on reaction system was determined. Linear range of the reaction was 0-10 microg x mL(-1). The molar absorptivity was epsilon = 4.6164 x 10(5) L x cm(-1) x mol(-1). The reaction mechanism and interference of inorganic substance, biological substance and surface active agent to the reaction was investigated. Study system was established.

Determination of proteins with Alizarin Red S by Rayleigh light scattering technique.

A new protein determination method by enhanced Rayleigh light scattering (RLS) technique has been developed. In acid condition (pH=3.60), RLS of 1,2-dihydroxyanthraquinone-3-sulfonate (Alizarin Red S) can be greatly enhanced by addition of proteins, resulting in two characteristic peaks, 360 and 505nm, respectively. The new protein assay is based on the RLS enhancement and spectrum change. The optimum condition for the reaction was investigated. The linear range is 0.20-24.9mugml(-1) for BSA and 0.20-15.5mugml(-1) for HSA. The detection limits (S/N=3) are 9.59ngml(-1) for BSA and 9.51ngml(-1) for HSA. The results of determination for human serum samples were comparable to those obtained by Bradford method. The binding stoichiometry was determined.

3,3',5,5'-tetramethyl-N-(9-anthrylmethyl)benzidine: a dual-signaling fluorescent reagent for optical sensing of aliphatic aldehydes.

A new optical chemical sensor for continuous monitoring of aliphatic aldehydes has been proposed based on the reversible chemical reaction between a new sensing reagent, 3,3',5,5'-tetramethyl-N-(9-anthrylmethyl)benzidine (TMAB), and the analytes. TMAB, containing two receptors and two fluorescent reporters, can perform dual fluorescence responses corresponding to the reactions of hydrogen ion and carbonyl compound. When immobilized in a plasticized poly(vinyl chloride) membrane, TMAB extracts aliphatic aldehydes from aqueous solution into the bulk membrane phase and reacts with the analyte by forming a Schiff base. Since the extraction equilibrium and chemical reaction are accompanied by fluorescence increase of the sensing membrane, the chemical recognition process could be directly translated into an optical signal. At pH 3.20, the sensor exhibits a dynamic detection range from 0.017 to 4.2 mM n-butyraldehyde with a limit of detection of 0.003 mM. The forward response time (t95) of the sensor is 3-5 min, and the reverse response time is 5-7 min. The responses of the sensor toward different kinds of aldehydes and ketones depend on the lipophilicity and the reactivity of the analytes. Since the fluorescence enhancement of the sensing membrane at 296 nm/410 nm is only related to the formation of Schiff base, the measurement of aldehydes is independent of pH.

Capillary electrophoretic behaviors of pharmacologically active xanthones from Securidaca inappendiculata with beta-cyclodextrin as a buffer additive.

The capillary electrophoretic (CE) behaviors of ten xanthones in the presence of beta-cyclodextrin (CD) are investigated, and apparent analyte-selector binding constants between beta-CD and the xanthones in the CE running buffer are calculated to elucidate the migration order. Also, the separation selectivity with beta-CD additive is compared with that of sulfated beta-CD additive. It is indicated that beta-CD can greatly change the separation selectivity of xanthones, and the electrophoretic behaviors of xanthones are rather different when using beta-CD from that when using sulfated beta-CD as an additive.

Investigation of the effect of space environment on the contents of atropine and scopolamine in Datura metel by capillary zone electrophoresis.

The seeds of Datura metel were carried aboard a retrievable satellite and exposed to space environment. The effects of space environment (weightlessness and ionizing radiation) on the contents of atropine and scopolamine in D. metel were investigated by using an effective capillary zone electrophoresis (CZE) method, which employed 50 mmol/l phosphate buffer (pH 8) containing 10% (v/v) tetrahydrofuran as the running buffer. The results showed that the contents of atropine and scopolamine varied to some extent, and the earth-control group has the lowest content of atropine. However, the variation of atropine and scopolamine contents in three groups was not obvious based on t-test. At the same time, the optimization of the separation was discussed in detail and the two compounds were completely separated within 10 min with satisfactory repeatability and calibration linearity.