Surface activity of thymol: implications for an eventual pharmacological activity

In the present work, we studied the ability of thymol to affect the organization of model membranes and the activity of an intrinsic membrane protein, the GABA(A) receptor (GABA(A)-R). In this last aspect, we tried to elucidate if the action mechanism of this terpene at the molecular level, involves its binding to the receptor protein, changes in the organization of the receptor molecular environment, or both. The self-aggregation of thymol in water with a critical micellar concentration approximately = 4 microM and its ability to penetrate in monomolecular layers of soybean phosphatidylcholine (sPC) at the air-water interface, even at surface pressures above the equilibrium, lateral pressure of natural bilayers were demonstrated. Thymol affected the self-aggregation of Triton X-100 and the topology of sPC vesicles. It also increased the polarity of the membrane environment sensed by the electrochromic dye merocyanine. A dipolar moment of 1.341 Debye was calculated from its energy-minimized structure. Its effect on the binding of [3H]-flunitrazepam ([3H]-FNZ) to chick brain synaptosomal membranes changed qualitatively from a tendency to the inhibition to a clear activatory regime, up on changing the phase state of the terpene (from a monomeric to a self-aggregated state). Above its CMC, thymol increased the affinity of the binding of [3H]-FNZ (K(d-control)= 2.9, K(d-thymol)= 1.7 nM) without changing the receptor density (B(max-control)= 910, B(max-thymol)= 895 fmol/mg protein). The activatory effect of thymol on the binding of [ [3H]-FNZ was observed even in the presence of the allosteric activator gamma-aminobutyric acid (GABA) at a concentration of maximal activity, and was blocked by the GABA antagonist bicuculline. Changes in the dipolar arrangement and in the molecular packing of GABA(A)-R environment are discussed as possible mediators of the action mechanism of thymol.     

A contribution to the trace analysis of high-purity iron by atomic spectrometry (flame-AAS, furnace-AAS, ICP-OES)

Summary Various possibilities for the determination of trace impurities in high-purity iron by atomic spectrometry were investigated in detail. For Ba, Bi, Cd, Co, Cr, Cu, Mn, Ni, Pb, Ti and V, flame AAS, furnace AAS and ICP-OES were firstly evaluated in terms of their power of detection. Detection limits in the g/g-range could be achieved by direct determination. For determination in the ng/g-range a removal of iron by a solvent extraction technique prior to the instrumental measurement was required. The power of detection of direct determination, and of combined procedures were compared with regard to routine applicability and a minimization of systematic errors.     

Particle-size analysis of latexes by classical and small-angle spectrodissymmetry

The spectral dependence of classical and small-angle dissymmetryZ in polydispersions containing spherical particles with lognormal distribution was theoretically studied. It has been found, for instance, for polystyrene latex that small-angle dissymmetry may be used for determining the distribution parameters in systems with particle medial radius 60–700 nm on the basis of measurements ofZ (10°/5°( at two wavelengths of radiation. For particles outside this interval and by use of working relationships of classical dissymmetry only the application of a wide range of wavelengths comes into consideration by distribution analysis.     

Zwei neue pentacyclische dimere des cycloheptatriens

Titanium - catalyzed dimerization of cycloheptatriene affords pentacyclo[7.5.0.0^2,8.0^5,14.0^7,11]tetradeca-3,12-diene, $\text{3}$, and pentacyclo[8.4.0.0^3,7.0^4,14.0^6,11]tetradeca-8,12-diene, $\text{4}$. By heating, $\text{3}$ is converted quantitatively into $\text{4}$.     

Nitrogen bridgehead compounds part 14. Acylation of ethyl 6-methyl-4-oxo- -6,7,8,9-tetrahydro-pyrido(1,2-a)pyrimidine-3-carboxilate with isocyanates

The 9-carbamoyl derivatives /$\text{3}$–$\text{9}$/ can be prepared from title compound /$\text{1}$/ with isocyanates /$\text{2}$/. $\text{3}$–$\text{9}$ are mixtures of the cis /Z/ and trans /E/ imines and the enamine /e/. The equilibrium depends on the substituents R,X and on the solvent.     

Characterization of ion-implanted silicion by Rutherford backscattering spectrometry and ellipsometry

It is demonstrated that the information obtained by Rutherford backscattering spectrometry and channeling technique can substantially help in the construction of a realistic optical model for the ellipsometry of ion-implanted silicon. In the case of fully amorphous ion-bombarded layers, the ellipsometry is a fast, non-destructive and contactless method to estimate the thickness of these films. For buried and partially disordered layers a qualitative interpretation of different trajectories in the - plance can be given on the basis of channeling measurements.     

Ion-pair extraction of pentacaine from biological materials

Simple and rapid extraction method for quantitative and selective isolation of the new local anesthetic pentacaine from biological materials is proposed. The technique of ion-pair formation was found to be more effective than usual access using the extraction of the nonionized species. The extraction yield of the unchanged molecule³H-pentacaine after double extraction and single scrubbing was found to be more than 90%. The radiochemical purity was over 90%. The method appears suitable for pharmacokinetic studies in the animal body.     

Flow injection spectrophotometric determination of boron in ceramic materials

A flow injection spectrophotometric method for the determination of boron in ceramic materials is described. The method is based on spectrophotometric measurement of the decrease in the pH produced by the reaction between boric acid and mannitol in the presence of an acid-base indicator. A bichannel FI (flow injection) manifold in which the sample solutions were injected into deionized water (at pH 5.4) and the stream was later merged with the reagent stream (a mannitol solution containing 1x10(-4) mol l(-1) bromocresol green at pH 5.4), was used. Transient signals were monitored at 616 nm. A theoretical model which describes the dependence between the absorbance values and boric acid concentration is presented. The model predicts a non linear dependence between the absorbance or increment in absorbance and the boric acid concentration. In contrast, the model predicts a linear dependence between the inverse of the absorbance values and the boric acid concentration. The calibration graphs (1/A vs mug ml(-1) B(2)O(3)) were linear over the range 1-30 mug ml(-1) of B(2)O(3). The relative standard deviations were 0.7 and 0.4% for 4 and 8 mug ml(-1) of B(2)O(3), respectively. The limit of detection was 0.02 mug ml(-1) of B(2)O(3) (3sigma criterium). The method was used to determine boron in nine ceramic materials with very different nominal boron compositions. The results were compared with those obtained using a potentiometric titration method as reference method. No significant differences (at 95% probability level) were found between the proposed and reference methods. The method is rapid, reliable, precise and free of interferences.     

Prediction of the net retention volumes in gas chromatography using porous polymers coated with different stationary phases

Summary A new expression which permits the prediction of the net retention volumes in gas chromatography with column packings of coated porous polymers is reported. The porous polymers Chromosorb 101 and Chromosorb 102 were used as supports and squalane, Ethofat and Carbowax 20M as stationary phases at three different column temperatures of 80°C, 100°C and 150°C. Several organic compounds of various polarity were used as test compounds and the net retention volumes, V_Ntheor, have been calculated according to this new expression. The V_Ntheor values were compared with the experimental net retention volumes, V_Nexp, and it was found that the difference between these two values is dependent on the type of compound and column packing. Nevertheless, the elution order could be predicted in most cases.     

Collection of selected reaction monitoring and full scan data on a time scale suitable for target compound quantitative analysis by liquid chromatography/tandem mass spectrometry

A hybrid linear ion trap/triple quadrupole mass spectrometer was used to demonstrate the value of collecting full scan qualitative data during quantitative analysis of target compounds. We present examples of the additional information that can be obtained from plasma samples analyzed primarily for target compound concentrations. This information includes detection of circulating metabolites, dosing vehicle, interfering matrix components, and potential interfering drug conjugates. Additionally, the quantitative results from selected reaction monitoring (SRM) analysis and from combined full scan and SRM analysis (SRM/EMS) were compared. The quantitative data in both scan modes are acceptable in terms of sensitivity, accuracy and precision. One can conclude from this work that the hybrid linear ion trap/triple quadrupole mass analyzer can provide in a single analysis both useful qualitative data, and accurate and precise quantitative data from the samples routinely prepared and analyzed for target drug concentrations.