Ultrasensitive photoelectrochemical aptasensing of miR-155 using efficient and stable CH3NH3PbI3 quantum dots sensitized ZnO nanosheets as light harvester.

An ultrasensitive photoelectrochemical (PEC) aptasensor based on a novel signal amplification strategy was developed for the quantitative determination of microRNA (miR)-155. CH3NH3PbI3 quantum dots (QDs) functionalized ZnO nanosheets (NSs) were employed as the light harvester. Owing to the synergetic effect between CH3NH3PbI3 QDs and ZnO NSs, ZnO@CH3NH3PbI3 can provide an obviously increasing PEC signal by forming the heterojunction. Due to the larger steric hindrance, the sensitive decrease of the PEC signal can be achieved by the specific recognition between the primers and ssDNA of miR-155. In this sense, this developed aptasensor can achieve a high sensitivity (especially in the presence of the low concentrations of miR-155) and a wide detection range (0.01fmol/L to 20,000pmol/L). Under the optimal conditions, the proposed aptasensor offered an ultrasensitive and specific determination of miR-155 down to 0.005fmol/L. This aptassay method would open up a new promising platform at ultralow levels for early diagnose of different miRNA.

Binding of citreoviridin to human serum albumin: multispectroscopic and molecular docking.

Citreoviridin (CIT), a mycotoxin produced by Penicillium citreonigrum, is a common contaminant of wide range of agriproducts and detrimental to human and animal health. In this study, the interaction of CIT with human serum albumin (HSA) is researched by steady-state fluorescence, ultraviolet-visible (UV-Vis) absorption, circular dichroism (CD) methods, and molecular modeling. The association constants, binding site numbers, and corresponding thermodynamic parameters are used to investigate the quenching mechanism. The alternations of HSA secondary structure in the presence of CIT are demonstrated with UV-Vis, synchronous fluorescence, and CD spectra. The molecular modeling results reveal that CIT can bind with hydrophobic pocket of HSA with hydrophobic and hydrogen bond force. Moreover, an apparent distance of 3.25 nm between Trp214 and CIT is obtained via fluorescence resonance energy transfer method.

Prediction on the inhibition ratio of pyrrolidine derivatives on matrix metalloproteinase based on gene expression programming.

Quantitative structure-activity relationships (QSAR) were developed to predict the inhibition ratio of pyrrolidine derivatives on matrix metalloproteinase via heuristic method (HM) and gene expression programming (GEP). The descriptors of 33 pyrrolidine derivatives were calculated by the software CODESSA, which can calculate quantum chemical, topological, geometrical, constitutional, and electrostatic descriptors. HM was also used for the preselection of 5 appropriate molecular descriptors. Linear and nonlinear QSAR models were developed based on the HM and GEP separately and two prediction models lead to a good correlation coefficient (R (2)) of 0.93 and 0.94. The two QSAR models are useful in predicting the inhibition ratio of pyrrolidine derivatives on matrix metalloproteinase during the discovery of new anticancer drugs and providing theory information for studying the new drugs.

Study on the interaction of ß-cyclodextrin and berberine hydrochloride and its analytical application.

The fluorescence enhancement of berberine hydrochloride (BBH) as a result of complex with ß-cyclodextrin (ß-CD) is investigated. The mechanism of the inclusion was studied and discussed by spectrofluoremetry and infrared spectrograms. The results showed that a 1∶1 (ß-CD: BBH) complex was formed with an apparent association constant of 4.23×10(2) L/mol. Based on the enhancement of the fluorescent intensity of berberine hydrochloride, a new spectrofluorimetric method for the determination of BBH in the presence of ß-CD was developed. The linear range was 1.00∼4.00 µg/mL with the detection limit of 5.54 ng/mL. The proposed method was successfully applied to the determination of BBH in tablets.

Optimization of ultrasonic extraction of total flavonoids from Tussilago farfara L. using response surface methodology.

In this work, ultrasound technology was used for the extraction of total flavonoids from Tussilago farfara L. Response surface methodology (RSM), based on a Box-Behnken design (BBD), was used to optimize the effects of processing parameters on total flavonoids yields. The parameters were ultrasonic frequency (X1), extraction time (X2) and ratio of liquid to solid (X3). The statistical analysis indicated that the parameters of ultrasonic power and ratio of liquid to solid, and the square effects among them had significant effects on the yield of flavonoids from Tussilago farfara L. The interaction between ultrasonic power and extraction time, and ultrasonic power and ratio of liquid to solid also caused significant effects on the yields. The optimum extraction conditions were determined as follows: ultrasonic power 420 W, extraction time 30 min, ratio of liquid to solid 25 mL/g. Under these conditions, the experimental yield 6.59 +/- 0.061% agreed closely with the predicted yield (6.64%).

The interaction of 2-mercaptobenzimidazole with human serum albumin as determined by spectroscopy, atomic force microscopy and molecular modeling.

The interaction of 2-mercaptobenzimidazole (MBI) with human serum albumin (HSA) was studied in vitro by equilibrium dialysis under normal physiological conditions. This study used fluorescence, ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared (FT-IR), circular dichroism (CD) and Raman spectroscopy, atomic force microscopy (AFM) and molecular modeling techniques. Association constants, the number of binding sites and basic thermodynamic parameters were used to investigate the quenching mechanism. Based on the fluorescence resonance energy transfer, the distance between the HSA and MBI was 2.495 nm. The ΔG(0), ΔH(0), and ΔS(0) values across temperature indicated that the hydrophobic interaction was the predominant binding Force. The UV, FT-IR, CD and Raman spectra confirmed that the HSA secondary structure was altered in the presence of MBI. In addition, the molecular modeling showed that the MBI-HSA complex was stabilized by hydrophobic forces, which resulted from amino acid residues. The AFM results revealed that the individual HSA molecule dimensions were larger after interaction with MBI. Overall, this study suggested a method for characterizing the weak intermolecular interaction. In addition, this method is potentially useful for elucidating the toxigenicity of MBI when it is combined with the biomolecular function effect, transmembrane transport, toxicological testing and other experiments.

Study of the interaction of deoxynivalenol with human serum albumin by spectroscopic technique and molecular modelling.

The mechanism of interaction between deoxynivalenol (DON) and human serum albumin (HSA) was studied using spectroscopic methods including fluorescence spectra, UV-VIS, Fourier transform infrared (FT-IR) and circular dichroism (CD). The quenching mechanism was investigated in terms of the association constants, number of binding sites and basic thermodynamic parameters. The distance between the HSA donor and the acceptor DON was 2.80 nm as derived from fluorescence resonance energy transfer. The secondary structure compositions of free HSA and its DON complexes were estimated by the FT-IR spectra. Alteration of the secondary protein structure in the presence of DON was confirmed by UV-VIS and CD spectroscopy. Molecular modelling revealed that a DON-protein complex was stabilised by hydrophobic forces and hydrogen bonding. It was potentially useful for elucidating the toxigenicity of DON when combined with biomolecular function effect, transmembrane transport, toxicological testing and the other experiments.

Capillary electrophoresis with field-amplified sample stacking for rapid and sensitive determination of sulfadiazine and sulfamethoxazole.

A new capillary electrophoresis method with field-amplified sample stacking (FASS) was developed for the analysis of sulfadiazine and sulfamethoxazole. After optimization of the separation and concentration conditions, the two compounds can be separated within 7 min and quantified with high sensitivity, with detection limits of 0.48 ng/mL for sulfadiazine and 0.76 ng/mL for sulfamethoxazole. This resulted in a 300-1500-fold improvement in concentration sensitivity relative to conventional capillary electrophoresis methods. The method was useful for qualitative and quantitative analysis of sulfadiazine and sulfamethoxazole in their preparations with recovery of 99.0%-102% for sulfadiazine and 99.5% - 99.7% for sulfamethoxazole.

Ethyl 1-benzyl-3-(4-methyl-phen-yl)-1H-pyrazole-5-carboxyl-ate.

In the title compound, C(20)H(20)N(2)O(2), the pyrazole ring makes dihedral angles of 15.68 (4) and 83.40 (4)°, respectively, with the tolyl and benzyl rings, respectively.

[Capillary electrophoresis with field-enhanced stacking for determination of water-soluble active principles in Salvia miltiorrhiza var. miltiorrhiza f. alba].

A simple and sensitive capillary electrophoresis method with field-enhanced stacking concentration for the analysis of protocatechuic aldehyde, protocatechuic acid, danshensu, rosmarinic acid and salvianolic acid B in Salvia miltiorrhiza var. miltiorrhiza f. alba was developed. The separation was achieved with a fused-silica capillary (75 microm x 50.2 cm, effective length was 40 cm) and a running buffer 15 mmol x L(-1) borax (pH 10.0) containing 20% CH3 OH. The UV detection wavelength was 210 nm. The applied voltage was 28 kV, and the cartridge temperature was 25 degrees C. Water plug was introduced from the anode by 0.5 psi x 4 s before injection. Sample was injected by electrokinetic injection - 8 kV x 3 s. The linear range of protocatechuic aldehyde is 3.0-60.00 mg x L(-1) (R2 = 0.999 8); that of protocatechuic acid, danshensu, rosmarinic acid and salvianolic acid B are 1.0-20.00 mg x L(-1) (R2 are 0.999 1, 0.999 4, 0.998 9 and 0.999 8, respectively), and the limits of detection of five analyts are 0.55, 0.40, 0.25, 0.32, 0.38 microg x L(-1), respectively, Stacking factor is higher and precision is satisfactory. The recoveries ranges were from 97.3% to 99.8%. The proposed method was used to determine the protocatechuic aldehyde, protocatechuic acid, danshensu, rosmarinic acid and salvianolic acid B in S. miltiorrhiza var. miltiorrhiza f. alba. The proposed method is simple, rapid, accurate and high sensitivity, and can be used to control of the quality of S. miltiorrhiza var. miltiorrhiza f. alba.

[Determination of tetrandrine and fangchinoline in Radix Stephaniae tetrandrae and its preparation by nonaqueous capillary chromatography].

OBJECTIVE: To establish a new method for the determination of fangchinoline and tetrandrine in Stephania tetrandra and Fengtongan capsule by noanqueous capillary electrophoresis. METHOD: Separation was carried out in an uncoated fused capillary (50 cm x 75 microm i.d.) with a running buffer containing 50 mmol x L(-1) ammonium acetate, 1.0% acetic acid and 20% acetonitrile in methanol. A separation voltage of 20 kV and a UV detector wavelength at 214 nm were adopted. Sample was introduced from the anode. RESULT: The calibration ranges were 1.00, 500 mg x L(-1) for both analytes. Under the optimum conditions, the relative standard deviation (RSD, n = 6) for the migration time of each analyte were 0.09%, 1.9% (intra-day) and 0.63%, 1.9% (inter-day); The RSD for the peak area of each analyte were 0.45%, 5.9% (intra-day) and 2.3%, 5.6% (inter-day), respectively. The contents of the analytes were determined easily with average recoveries 102% for fangchinoline and 105% for tetrandrine in S. tetrandra and 94.6% for fangchinoline and 98.7% for tetrandrine in Fengtongan capsules, respectively. CONCLUSION: The proposed method is simple, rapid, accurate and higher repeatable, and can be used to control of the quality of S. tetrandra and Fengtongan capsules.

Study on the supramolecular interaction of thiabendazole and beta-cyclodextrin by spectrophotometry and its analytical application.

The beta-cyclodextrin-thiabendazole (beta-CD-TBZ) inclusion complex was synthesized and its structure characterized by (1)H NMR and IR. The mechanism of the supramolecular interaction of TBZ and beta-CD has been studied and discussed by spectrophotometry. The results showed that the phenyl ring of TBZ was included in the beta-CD cavity to form a 1:1 host-guest complex with an apparent formation constant of 1.60 x 10(3) mol(-1).L. On the basis of the enhancement of the absorbance of TBZ produced through complex formation, a spectrophotometric method for the determination of TBZ in bulk aqueous solution in the presence of beta-CD was developed. The linear relationship between the absorbance and TBZ concentration was obtained in the range of 8.86 x 10(-7)-1.45 x 10(-5) mol/L. The detection limit was 2.71 x 10(-7)mol/L, and the relative standard deviation was 0.86%. The interference of 48 coexisting substances was slight. The proposed method has been successfully applied to the determination of TBZ in fruits with recoveries of 96-103%.

Flow injection spectrofluorimetric study of the supramolecular interaction between beta-cyclodextrin and dequalinium chloride and its analytical application.

The supramolecular interaction of dequalinium chloride (DQC) and beta-cyclodextrin has been studied by flow injection spectrofluorimetry. The results showed that beta-CD reacted with DQC to form a 1:1 host:guest complex with an apparent association constant of 4.99 x 10(2) L mol(-1). Based on the enhancement of the fluorescence intensity of DQC, a flow injection spectrofluorometric method for the determination of DQC in bulk aqueous solution in the presence of beta-CD was developed. The linear range was 0.0412-30.00 microg mL(-1). The detection limit was 12.3 ng mL(-1) with a sampling rate of 80 h(-1). There was no interference from the excipients normally used in tablets and serum compositions. The proposed method was successfully applied to the determination of DQC in tablets and serum.