Rapid separation and binding configuration prediction of the components in Danshen decoction to endothelin A receptor using affinity chromatography and molecular dynamics simulation.

As a famous traditional Chinese formula, Danshen Decoction has the potential to relieve the pain of pulmonary arterial hypertension patients, however, the functional components remain unknown. Herein, we reported a method to screen the functional components in Danshen Decoction targeting endothelin receptor A, an accepted target for the treatment of the disease. The receptor was functionalized on the macroporous silica gel through an epidermal growth factor receptor fusion tag and its covalent inhibitor. Using the affinity gel as the stationary phase, the bioactive compound was identified as salvianolic acid B by mass spectrometry. The binding kinetic parameter (dissociation rate constants kd ) of salvianolic acid B with the receptor was determined via peak profiling. Using the specific ligands of the receptor as probes, the binding configuration prediction of salvianolic acid B with the receptor was performed by molecular dynamics simulation. Our results indicated that salvianolic acid B is a potential bioactive compound in Danshen Decoction targeting the receptor. This work showed that receptor chromatography in combination with molecular dynamics simulation is applicable to predicting the binding kinetics and configuration of a ligand to a receptor, providing crucial insight for the rational design of drugs that recognize functional proteins.

Synthesis of nano-crystallite hydroxyapatites in different media and a comparative study for estimation of crystallite size using Scherrer method, Halder-Wagner method size-strain plot, and Williamson-Hall model.

Hydroxyapatite (HAp) [Ca10(PO4)6(OH)2] is remarkably similar to the hard tissue of the human body and the uses of this material in various fields in addition to the medical sector are increasing day by day. In this research, mustered oil, soybean oil, as well as coconut oil were employed as liquid media for synthesizing nanocrystalline HAp using a wet chemical precipitation approach. The X-ray diffraction (XRD) study verified the crystalline phase of the HAp in all the indicated media and discovered similarities with the standard database. Several prominent models such as the Scherrer's Method (SM), Halder-Wagner Method (HWM), linear straight-line method (LSLM), Williamson-Hall Method (W-M), Monshi Scherrer Method (MSM), Size-Strain Plot Method (SSPM), Sahadat-Scherrer Method (S-S) were applied for the determination of crystallite size. The stress, strain, and energy density were also computed from the above models. All the models, without the Linear straight-line technique of Scherrer's equation, resulted in an appropriate value of crystallite size for synthesized products. The calculated crystallite sizes were 6.5 nm for HAp in master oil using Halder-Wagner Method, and 143 nm for HAp in coconut oil using the Scherrer equation which were the lowest and the largest, respectively.

Elucidation of structural, electromagnetic, and optical properties of Cu-Mg ferrite nanoparticles.

Copper doped magnesium ferrite, Mg1-xCuxFe2O4(x = 0.0-1.0) nanomaterials were synthesized via. sol-gel method sintered at 600 °C for 2 h. The synthesized materials were characterized using modern sophisticated techniques viz. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy, Energy dispersive x-ray spectroscopy (EDS), Vibrating sample magnetometer, UV-visible diffuse reflectance spectra and Impedance analyzer. XRD analysis revealed that all the samples were single phase cubic spinel structure with Fd3m space group and investigated the change in structural parameters with copper concentration. The average crystallite size in the range of 11-23 nm and lattice parameters decrease with increasing Cu doping, due to the cationic distribution and ionic radius. The SEM images show the agglomeration of the particles with spherical like shape and elemental percentage were obtained from EDX. The saturation magnetization showed an increasing trend with increasing Cu concentration at a certain level and then decreases due to the rearrangement of cations at tetrahedral and octahedral sites. The Coercivity, Retentivity and magnetic crystalline anisotropy increase with changing dopant concentration. The magnetic measurements showed enhanced saturation magnetization at certain level (28.96emu/gm) and increase in coercivity up to 1102 Oe with changing dopant concentration. The estimated band gap energy is found to increase with Cu content. The dielectric constant, dielectric loss and impedance show normal behavior of ferrite. The frequency dependent dielectric constant decrease and tan delta shows a relaxation behavior at low frequencies. The synthesized nano Mg-Cu nanoparticles will be applied as humidity sensor, gas sensor, microwave devices and photocatalyst.

Extraction of gamma iron oxide (γ-Fe2O3) nanoparticles from waste can: Structure, morphology and magnetic properties.

In this work, the transformation of waste iron cans to gamma iron oxide (γ-Fe2O3) nanoparticles following acid leaching precipitation method along with their structural, surface chemistry, and magnetic properties was studied. Highly magnetic iron-based nanomaterials, maghemite with high saturation magnetization have been synthesized through an acid leaching technique by carefully tuning of pH and calcination temperature. The phase composition and crystal structure, surface morphology, surface chemistry, and surface composition of the synthesized γ-Fe2O3 nanoparticles were explored by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDS). The XRD results confirm the cubic spinel structure having crystallite size 26.90-52.15 nm. The XPS study reveals the presence of Fe, O element and the binding energy of Fe (710.31 and 724.48 eV) confirms the formation of γ-Fe2O3 as well. By dynamic light scattering (DLS) method and zeta potential analyzer, the particle size distribution and stability of the systems were investigated. The magnetic behavior of the synthesized γ-Fe2O3 nanoparticles were studied using a vibrating sample magnetometer (VSM) which confirmed the ferrimagnetic particles with saturation magnetization of 54.94 emu/g. The resultant maghemite nanoparticles will be used in photocatalysts and humidity sensing. The net impact of the work stated here is based on the principle of converting waste into useful nanomaterials. Finally, it was concluded that our results can give insights into the design of the synthesis procedure from the precursor to the high-quality gamma iron oxide nanoparticles with high saturation magnetization for different potential applications which are inexpensive and very simple.

Kinetic Analysis by Affinity Chromatography.

Important information on chemical processes in living systems can be obtained by the rates at which these biological interactions occur. This review will discuss several techniques based on traditional and high-performance affinity chromatography that may be used to examine the kinetics of biological reactions. These methods include band-broadening measurements, techniques for peak fitting, split-peak analysis, peak decay studies, and ultrafast affinity extraction. The general principles and theory of each method, as applied to the determination of rate constants, will be discussed. The applications of each approach, along with its advantages and limitations, will also be considered.

Binding kinetics of five drugs to beta2-adrenoceptor using peak profiling method and nonlinear chromatography.

Investigations of drug-protein interactions have advanced our knowledge of ways to design more rational drugs. In addition to extensive thermodynamic studies, ongoing works are needed to enhance the exploration of drug-protein binding kinetics. In this work, the beta2-adrenoceptor (ß2-AR) was immobilized on N, N'-carbonyldiimidazole activated amino polystyrene microspheres to prepare an affinity column (4.6 mm × 5.0 cm, 8 µm). The ß2-AR column was utilized to determine the binding kinetics of five drugs to the receptor. Introducing peak profiling method into this receptor chromatographic analysis, we determined the dissociation rate constants (kd) of salbutamol, terbutaline, methoxyphenamine, isoprenaline hydrochloride and ephedrine hydrochloride to ß2-AR to be 15 (±1), 22 (±1), 3.3 (±0.2), 2.3 (±0.2) and 2.1 (±0.1) s-1, respectively. The employment of nonlinear chromatography (NLC) in this case exhibited the same rank order of kd values for the five drugs bound to ß2-AR. We confirmed that both the peak profiling method and NLC were capable of routine measurement of receptor-drug binding kinetics. Compared with the peak profiling method, NLC was advantageous in the simultaneous assessment of the kinetic and apparent thermodynamic parameters. It will become a powerful method for high throughput drug-receptor interaction analysis.

Chromatographic studies of drug interactions with alpha1-acid glycoprotein by ultrafast affinity extraction and peak profiling.

Interactions with serum proteins such as alpha1-acid glycoprotein (AGP) can have a significant effect on the behavior and pharmacokinetics of drugs. Ultrafast affinity extraction and peak profiling were used with AGP microcolumns to examine these processes for several model drugs (i.e., chlorpromazine, disopyramide, imipramine, lidocaine, propranolol and verapamil). The association equilibrium constants measured for these drugs with soluble AGP by ultrafast affinity extraction were in the general range of 104-106M-1 at pH 7.4 and 37°C and gave good agreement with literature values. Some of these values were dependent on the relative drug and protein concentrations that were present when using a single-site binding model; these results suggested a more complex mixed-mode interaction was actually present, which was also then used to analyze the data. The apparent dissociation rate constants that were obtained by ultrafast affinity extraction when using a single-site model varied from 0.14 to 7.0s-1 and were dependent on the relative drug and protein concentrations. Lower apparent dissociation rate constants were obtained by this approach as the relative amount of drug versus protein was decreased, with the results approaching those measured by peak profiling at low drug concentrations. This information should be useful in better understanding how these and other drugs interact with AGP in the circulation. In addition, the chromatographic approaches that were optimized and used in this report to examine these systems can be adapted for the analysis of other solute-protein interactions of biomedical interest.

Multianalyte determination of the kinetic rate constants of drug-cyclodextrin supermolecules by high performance affinity chromatography.

The kinetics of the dissociation is fundamental to the formation and the in vivo performance of cyclodextrin supramolecules. The individual determination of the apparent dissociation rate constant (kd,app) using high performance affinity chromatography (HPAC) is a tedious process requiring numerous separate studies and massive data fitting. In this study, the multianalyte approach was employed to simultaneously measure the kd,app values of three drugs through one injection based on the investigation of the dependence of drug-cyclodextrin interaction kinetics on the mobile phase composition. As a result, the kd,app values increased when decreasing the ion strength, increasing the ionization of drugs and adding extra organic solvents. The values of kd,app for acetaminophen, phenacetin and S-flurbiprofen estimated by the multianalyte approach were 8.54±1.81, 5.36±0.94 and 0.17±0.02s(-1), respectively, which were in good agreement with those determined separately (8.31±0.58, 5.01±0.42 and 0.15±0.01s(-1)). For both of the single and multiple flow rate peak profiling methods, the results of the multianalyte approach were statistically equivalent with that of the single compound analysis for all of the three drugs (p>0.05). The multianalyte approach can be employed for the efficient evaluation of the drug-cyclodextrin kinetics with less variance caused by cyclodextrin column bleeding.

Determination of the kinetic rate constant of cyclodextrin supramolecular systems by high performance affinity chromatography.

It is challenging and extremely difficult to measure the kinetics of supramolecular systems with extensive, weak binding (Ka<10(5)M(-1)), and fast dissociation, such as those composed of cyclodextrins and drugs. In this study, a modified peak profiling method based on high performance affinity chromatography (HPAC) was established to determine the dissociation rate constant of cyclodextrin supramolecular systems. The interactions of ß-cyclodextrin with acetaminophen and sertraline were used to exemplify the method. The retention times, variances and the plate heights of the peaks for acetaminophen or sertraline, conventional non-retained substance (H2O) on the ß-cyclodextrin bonded column and a control column were determined at four flow rates under linear elution conditions. Then, plate heights for the theoretical non-retained substance were estimated by the modified HPAC method, in consideration of the diffusion and stagnant mobile phase mass transfer. As a result, apparent dissociation rate constants of 1.82 (±0.01)s(-1) and 3.55 (±0.37)s(-1) were estimated for acetaminophen and sertraline respectively at pH 6.8 and 25°C with multiple flow rates. Following subtraction of the non-specific binding with the support, dissociation rate constants were estimated as 1.78 (±0.00) and 1.91 (±0.02)s(-1) for acetaminophen and sertraline, respectively. These results for acetaminophen and sertraline were in good agreement with the magnitude of the rate constants for other drugs determined by capillary electrophoresis reported in the literature and the peak fitting method we performed. The method described in this work is thought to be suitable for other supramolecules, with relatively weak, fast and extensive interactions.