Synthesis of glycyrrhetinic acid by hydrolysis of licorice root extract in subcritical water

A procedure for the synthesis of glycyrrhetinic acid (glycyrrhyzic acid aglicone) by hydrolysis of licorice root extract in subcritical water was developed. The procedure was shown to be more effective than conventional hydrolysis. Glycyrrhetinic acid was identified and its concentration in the product determined by high-performance liquid chromatography. A ¹³C NMR spectroscopic study confirmed that glycyrrhetinic acid obtained in subcritical water had a β configuration at the C₁₈ atom.     

Toxic effects of copper (II) ions on bovine hemoglobin

In this paper, the toxic influence of copper ions (II) on bovine hemoglobin was investigated by the combination of ultraviolet-visible absorption, fluorescence, time-resolved fluorescence, synchronous fluorescence, and circular dichroism spectra. Driven by hydrophobic and electrostatic forces, copper ions (II) could interact with bovine hemoglobin to form bovine hemoglobin-copper ions (II) complex with one binding site. The binding constant (K) was 1.57?×?10⁴, 1.89?×?10⁴ and 2.11?×?10⁴?L/mol at 298, 304, and 310?K, respectively. The binding distance (r) was 4.24?nm. Fluorescence and time-resolved fluorescence spectra showed that bovine hemoglobin quenched by copper ions (II) was a static quenching process. Results of synchronous fluorescence spectra revealed that the microenvironment and the conformation of bovine hemoglobin were changed during the binding reaction. Data of circular dichroism spectra suggested that with the increasing concentration of copper ions (II), the secondary structure of bovine hemoglobin underwent a decrease in α-helix and alteration in backbone microenvironment. Copper ions (II) was thus evidenced to have a certain toxic effect on physical bodies.     

Rapid and quantitative determination of 10 major active components in Lonicera japonica Thunb. by ultrahigh pressure extraction-HPLC/DAD

An ultrahigh pressure extraction (UPE)-high performance liquid chromatography (HPLC)/diode array detector (DAD) method was established to evaluate the quality of Lonicera japonica Thunb. Ten active components, including neochlorogenic acid, chlorogenic acid, 4-dicaffeoylquinic acid, caffeic acid, rutin, luteoloside, isochlorogenic acid B, isochlorogenic acid A, isochlorogenic acid C, and quercetin, were qualitatively evaluated and quantitatively determined. Scanning electron microscope images elucidated the bud surface microstructure and extraction mechanism. The optimal extraction conditions of the UPE were 60% methanol solution, 400?MPa of extraction pressure, 3?min of extraction time, and 1:30 (g/mL) solid:liquid ratio. Under the optimized conditions, the total extraction yield of 10 active components was 57.62?mg/g. All the components showed good linearity (r² ≥ 0.9994) and recoveries. This method was successfully applied to quantify 10 components in 22 batches of L. japonica samples from different areas. Compared with heat reflux extraction and ultrasonic-assisted extraction, UPE can be considered as an alternative extraction technique for fast extraction of active ingredient from L. japonica.     

Photophysics and Fluorimetric Titrations of Fluorescent Ion Indicators

A test based on time-resolved fluorescence experiments (Anal. Biochem. 245, 28–37, 1997) allows one to assess the interference of the excited-state association with the fluorimetric determination of the ground-state dissociation constant K _d of fluorescent ion:indicator complexes. If an inflection point occurs in the plot of the fluorescence signal vs – log[ion] in the ion concentration range where both decay times are invariant, this inflection point can be associated with the correct K _d. Here we apply this test to the fluorescent ion indicators SBFO (for Na⁺), Mag-fura-2 (for Mg²⁺), and APTRA-BTC (for Ca²⁺). In all three cases the decay times are invariant in the concentration ranges of the respective ions where the fluorescence titrations show unique inflection points, indicating that the fluorimetrically determined K _d values are the true K _d values.     

Voltammetric determination of uric acid in the presence of ascorbic acid and dopamine using chitosan/ionic liquid composite electrode

A chitosan/ionic liquid composite electrode was prepared and used to determine uric acid (UA) in the presence of a large excess of ascorbic acid (AA) and dopamine (DA) by linear sweep voltammetry (LSV). The modified electrode shows large peak separations between DA, AA, and UA. Due to the existence of chitosan and ionic liquid in the composite, the modified electrode exhibits strong electrochemical catalytic activity toward the oxidation of UA. Under optimal conditions, the peak current is linearly dependent on the UA concentration in the range of 5?×?10^?7–2?×?10^?4 M in the presence of 5?×?10^?4 M AA and 5?×?10^?5 M DA with a correlation coefficient of 0.9978, and the detection limit is 5?×?10^?8 M at a signal-to-noise ratio of 3. With good sensitivity and stability, the constructed sensor was applied in the determination of UA in human serum samples and satisfactory results were obtained.     

Measurement of the K α to L α and K β to L β intensity ratios of seven elements in the atomic number range 52≤ Z ≤62 using photoionization at 59.5 keV1

The Kα to Lα and Kβ to Lβ intensity ratios of seven elements have been measured following photoionization at 59.5 keV by using a Si (Li) detector (FWHM=155 eV at 5.96 keV). The intensity ratios were determined by measuring K and L x-rays emitted from a standard target of a given element. The theoretical values of the Kα to Lα and Kβ to Lβ intensity ratios were calculated using theoretically tabulated values of shell/subshell photoionization cross sections, fluorescence yields, Coster-Kronig transition probabilities, and radiative decay rates for ηKLi≠ and ηKLi=0. The measured values are in good agreement with theoretical results. From Optika i Spektroskopiya, Vol. 97, No. 2, 2004, pp. 186–189. Original English Text Copyright ? 2004 by A. Kü?ük?nder, S?ğüt, E. Kü?ük?nder, Büyükkasap. This article was submitted by the authors in English.     

Defined-sector explicit solvent in the continuum model approach for computational prediction of pK a

Accurate prediction of the acidity dissociation constant (K _a) is a challenge for the theory of proton-transfer reactions, making first-principles prediction of pK _a within 0.5?pK units of experimental values a benchmark of broad interest. In the present contribution, the defined-sector explicit solvent in continuum cluster model, which considers the structure-to-chemical affinity relationship of the carboxyl functional group, is presented. The model demonstrates predictable solvent networks based on established ‘preferred’ conformations found in a training set. Predictability within 1?kcal?mol^–1 accuracy is shown for a full set of carboxylic acid systems with varying functionality.     

Analysis of Cation-Dependent DNA (G<Subscript>3</Subscript>T<Subscript>1</Subscript>)<Subscript>4</Subscript> Shape Change Using Fluorescence Correlation Spectroscopy

In G-rich DNA, it is well known that the form changes from single-strand DNA to G-quadruplex due to cations. In this study, we analyze the diffusion coefficient and fluorescence intensity obtained by fluorescence correlation spectroscopy for short G-rich DNA of the (G₃T₁)₄ sequence labeled as 5-Carboxytetramethylrhodamine (TAMRA) with variation of the K⁺ ion concentration. At a K⁺ ion concentration of more than 200 mM, the single-strand DNA was changed to the G-quadruplex. The size of the G-quadruplex decreased to 86% than the size of the single strand DNA at K⁺ ion concentration of 0 M. The size of the G-quadruplex and the fluorescence intensity of TAMRA attached to the DNA were constant with an increase in the K⁺ ion concentration between 200 and 800 mM. This means that the size of the DNA and the fluorescence intensity of the TAMRA are not affected by the K⁺ ion concentration at the G-quadruplex structure because the binding structure of DNA and TAMRA dye leads to stability at a concentration of less than 100 mM K⁺. Based on our short G-rich DNA results, longer G-rich DNA is analyzed for the diffusion coefficient of the DNA and the fluorescence intensity variation of fluorescence dye attached to the DNA.     

Optically stimulated luminescence dating of Holocene alluvial fans,East Anatolian Fault System,Turkey

In this study, the optically stimulated luminescence dating technique was used to determine the time of deposition of alluvial sediment samples from the Türko?lu-Antakya segment of the East Anatolian Fault System (EAFS) in Turkey. The double-single aliquot regenerative dose protocol on fine grain samples was used to estimate equivalent doses (D_e). Annual dose rate was computed using elemental concentration of uranium (U) and thorium (Th) determined by using thick-source alpha counting and potassium (K) concentrations using X-ray fluorescence and/or atomic absorption spectroscopy. The environmental dose was measured in situ using α-Al₂O₃:C chips inside plastic tubes for a year. The two different bulk sediment samples collected from the Islahiye trench yielded ages of 4.54?±?0.28 and 2.91?±?0.23?ka. We also obtained a 2.60?±?0.18?ka age for the alluvial deposit in the K?ranyurdu trench and 2.31?±?0.14?ka age for an excavation area called Malzeme Oca??. These ages were consistent with the corresponding calibrated Carbon-14 (¹⁴C) ages of the region. The differences between the determined ages were insufficient to clearly distinguish the disturbance event from the effects of bioturbation, biological mixing, or other sources of D_e variation in the region. They provide a record of alluvial aggradation in the region and may determine undocumented historical earthquake events.     

Self diffusion in liquid Na-K alloy

Self diffusion coefficients,D _i, in liquid Na-K alloy at 373 K have been computed in the linear trajectory approximation of Helfand, with square well as an attractive tail. From the computedD _Na andD _K, the mutual diffusion coefficient,D _NaK has also been determined.D _Na,D _K andD _NaK all increase with increase of concentration of potassium, while the ratio,D _Na/D _K remains constant (1.45 ± 0.01) over the entire concentration range.     

Experimental and computer simulation determination of the structural changes occurring through the liquid–glass transition in Cu–Zr alloys

Molecular dynamics (MD) simulations were performed of the structural changes occurring through the liquid–glass transition in Cu–Zr alloys. The total scattering functions (TSF), and their associated primary diffuse scattering peak positions (K _p), heights (K _h) and full-widths at half maximum (K _FWHM) were used as metrics to compare the simulations to high-energy X-ray scattering data. The residuals of difference between the model and experimental TSFs are ～0.03 for the liquids and about 0.07 for the glasses. Over the compositional range studied, Zr_{1? x} Cu _x (0.1 ≤ x ≤ 0.9), K _p, K _h and K _FWHM show a strong dependence on composition and temperature. The simulation and experimental data correlate well between each other. MD simulation revealed that the Cu–Zr bonds undergo the largest changes during cooling of the liquid, whereas the Cu–Cu bonds change the least. Changes in the partial-pair correlations are more readily seen in the second and third shells. The Voronoi polyhedra (VP) in glasses are dominated by only a few select types that are compositionally dependent. The relative concentrations of the dominant VPs rapidly change in their relative proportion in the deeply undercooled liquid. The experimentally determined region of best glass formability, x _Cu ～ 65%, shows the largest temperature dependent changes for the deeply undercooled liquid in the MD simulation. This region also exhibits very strong temperature dependence for the diffusivity and the total energy of the system. These data point to a strong topological change in the best glass-forming alloys and a concurrent change in the VP chemistry in the deeply undercooled liquid.     

Reaction mechanism of tylosin tartrate with lysozyme

Under simulated physiological conditions, the interaction between tylosin tartrate and lysozyme was investigated at pH?=?7.40 by fluorescence spectroscopy. The results indicated that tylosin tartrate could strongly quench the intrinsic fluorescence of lysozyme. By determining the quenching constants of the reaction between tylosin tartrate and lysozyme at different temperatures, the quenching mechanism was proven to be a static quenching process. The thermodynamic parameters (ΔH°, ΔS°) of the reaction between tylosin tartrate and lysozyme were obtained by the Van’t Hoff equation, and were 27.80?kJ mol^?1 and 166.28?J mol^?1 K^?1, respectively. The results showed that hydrophobic interaction between tylosin tartrate and lysozyme was dominant. Synchronous fluorescence spectra revealed that the conformation of lysozyme was changed. This method could be applied to measure the content of tylosin tartrate.     

Fluorescence Study on Translational Mobility in Polystyrene–Polyethyleneglycol Microbeads

Polyethyleneglycol (PEG) chain mobility in gelatineous microbeads is investigated by means of dynamic excimer formation. Pyrenebutyric acid (PYB) is covalently linked to the chain ends as probe molecule. Excimer formation is monitored by steady-state and time-resolved fluorescence spectroscopy in the presence of a series of liquid phases and in the dry state. PYB concentration in the beads is varied over three orders of magnitude up to c = 6·10^–2 M. The concentration is derived from absorption measurements in stirred bead suspensions, considering the deviations from Lambert–Beer's law in heterogeneous systems. Excimer formation is found to be a dynamic process in the presence of liquid phases which solvate both the polymer and the fluorophore. The collisional rate constant, k _DM, is of the order of k _DM-values of PYB in homogeneous solutions, indicating a high translational mobility. Excimer-to-monomer intensity ratios are in general accordance with the solvation capacity of the liquid phase. In the dry state excimer formation is found only at high PYB concentrations, c 3·10^–2 M. It is concluded that this excimer emission arises from aggregated PYB, since corresponding fluorescence response curves show no rise time.     

Fabrication of the Components for a Sustained-Release Injectable Dosage Form of Acetylsalicylic Acid Using Supercritical Carbon Dioxide

Fabrication of fine-grained (10–100 μm) bioresorbable powders of aliphatic polyesters containing therapeutically significant (up to 10 wt %) concentrations of acetylsalicylic acid using supercritical CO₂ is studied. The process for fabricating the components of sustained-release injectable dosage forms of acetylsalicylic acid is elaborated. The kinetics of release of acetylsalicylic acid from polylactide microparticles into the normal saline solution in vitro is studied by high-performance liquid chromatography.     

Quantitative and multicomponent analysis of prevalent urinary calculi using Raman spectroscopy

This study established a quantitative micro‐Raman spectroscopic (MRS) method for measuring multicomponents (binary and ternary compositions) of prevalent urine calculi extracted from the ureter after the ureteroscopic lithotripsy (URSL) procedure. The analysis used calibration curves of known mixtures of synthetically prepared calcium oxalate monohydrate (COM), hydroxyapatite (HAP), calcium oxalate dehydrate (COD), dicalcium phosphate dehydrate (DCPD), and uric acid. A variety of samples of binary and ternary mixtures including COM/HAP, COM/COD, COD/HAP, COM/uric acid, COD/uric acid, HAP/uric acid, HAP/DCPD, and COM/COD/HAP were prepared in various concentration ratios for use as the basis of the quantitative analysis. Intensities of the characteristic bands at 961 cm⁻¹ (I_HAP), 986 cm⁻¹ (I_DCPD), 1402 cm⁻¹ (I_UricAcid), 1462 cm⁻¹ (I_COM), and 1477 cm⁻¹ (I_COD) were used for the calculation. We derived a set of quantitative analysis equations for the ternary composition COD/COM/HAP group by combining two binary equations from the groups COM/COD and the HAP/COM. This study quantitatively measured 18 urine samples extracted from the 18 patients' ureters after the URSL procedure. Fifteen samples were binary mixtures, whereas three samples were ternary mixtures. This research successfully applied the quantitative MRS‐based analysis technique from bench to bedside. Copyright © 2012 John Wiley & Sons, Ltd.     

P–V–T equation of state of rhodium oxyhydroxide

A high pressure X-ray diffraction study of RhOOH was carried out up to 17.44?GPa to investigate the compression behavior of an oxyhydroxide with an InOOH-related structure. A fit to the third-order Birch–Murnaghan equation of state gave K₀?=?208?±?6?GPa, and K′?=?9.4?±?1.3. The temperature derivative of the bulk modulus was found to be ?K/?T?=??0.06?±?0.02?GPa K^?1. The refined parameters for volume thermal expansion were α₀?=?2.7?±?0.3?×?10^?5 K^?1; α₁?=?1.7?±?1.1?×?10^?8 K^?2 in the polynomial form (α(T)?=?α_0?+?α₁(T?300)). Our results show that RhOOH is very incompressible, and has a higher bulk modulus than other InOOH-structured oxyhydroxides (e.g. δ-AlOOH, ε-FeOOH, and γ-MnOOH).     

Performance Check of Vegetation Fluorescence Imaging Lidar through In Vivo and Remote Estimation of Chlorophyll Concentration Inside Plant Leaves

Laser-induced fluorescence imaging lidar was developed for in vivo plant/vegetation monitoring. Fluorescences of poplar tree leaves growing naturally at a distance of 60 m from the lidar were successfully detected as two spectral images at wavelengths of 685 nm and 740 nm. By comparing chlorophyll concentration quantified with high performance liquid chromatography, it was confirmed that the intensity ratio of the two wavelengths was converted into the chlorophyll concentration inside the leaves. The intensity ratio of the images reflected the status of the poplar tree in the process of senescence so well that it was possible to assess the living status of the tree as a numerical value. The performance characteristics and the potential of the laser-induced fluorescence imaging lidar for monitoring the physiological activities of plants and vegetation are described.     

The Kirkwood correlation factor of dense methanol as a function of temperature and pressure under isochoric conditions and its statistical mechanical treatment

Experimental data of dielectric susceptibilities of methanol available in the literature over a wide range of temperature and pressure have been used for constructing a state function of the Kirkwood correlation factor g _K of methanol applicable in the homogeneous fluid region between 298 and 580?K and up to 350?MPa. Results of three isochores at 786.32, 820 and 850 kg m^?3 of this state function have been compared with predictions made by a statistical mechanical theory developed in previous work. The theory is based on an association model of alcohols accounting for the correlation of effective dipole moments of chains of all length as well as ringlike cluster formations. Most of the parameters such as association constants and association enthalpies have been obtained from quantum mechanical ab initio calculations of methanol clusters up to six members, reducing the numbers of adjustable parameters to three association constants and an averaged value of the angle between dipoles. The theory which has turned out to provide excellent results for alcohol + hydrocarbon and alcohol +?CCl₄ liquid mixtures at ambient pressure is also able to predict isochoric values of pure methanol up to a pressure of 350?MPa and temperatures of 570?K without adjusting further parameters in satisfying agreement with experimental data.     

Application of Flow-ESR Techniques for Mechanistic Study of Biological Radical Reactions: HPLC�CESR Spin-Trapping System for Post-Column Evaluation of the Superoxide Radical Scavenging Activity of Column Eluates

A new high-performance liquid chromatography (HPLC)?Celectron spin resonance (ESR) spin-trapping system for post-column on-line detection of the superoxide radical scavenging activity of column eluates was developed. A cyclic nitrone-type spin-trapping reagent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), was used for detection of the superoxide radical, which was produced by riboflavin-dependent photo-reduction of molecular oxygen in the presence of an electron donor. The reaction conditions were optimized by monitoring the ESR signal intensity of the spin-adduct of DMPO. HPLC?CESR chromatographs were recorded for the standard sample solution, which included three phenolic compounds, gallic acid (Gal), 4-hydroxycoumaric acid (Cou), and caffeic acid (Caf).     

A deep insight into the mechanism of the acid‐catalyzed rearrangement of the Z‐phenylhydrazone of 5‐amino‐3‐benzoyl‐1,2,4‐oxadiazole in a non‐polar solvent

The conversion of the Z‐phenylhydrazone of 5‐amino‐3‐benzoyl‐1,2,4‐oxadiazole ( 1a ) into the relevant 1,2,3‐triazole ( 2a) has been quantitatively studied in toluene in the presence of several halogenoacetic acids ( HAA s, 3a – h ). Again, the occurrence of two reaction pathways has been pointed out: they require one or two moles of acid, respectively, thus repeating the situation previously observed in the presence of trichloroacetic acid. The observed rate constant ratios (k_III/k_II) are only slightly affected by the nature of the acid used. To gain a deeper insight into the action of the acids used we have measured the association constants of the HAA s ( 3a – h) with 4‐nitroaniline ( 4 ) in toluene. Also in this case, the formation of two complexes requiring one (K₂) or two (K₃) moles of acid has been evidenced, but now the K₃/K₂ ratios are significantly affected by the strength of the acid examined. The variation of the K₃/K₂ ratios larger than those concerning the k_III/k_II ratios appears useful to enlighten the very nature of the acid‐catalyzed pathways in toluene, which has been elucidated also carrying out the rearrangement in the presence of mixtures of tribromo‐ and trichloro‐acetic acids at different concentrations. Copyright © 2010 John Wiley & Sons, Ltd.