Effect of monovalent cations on the binding of amino acids to cholesterol.

The nature of the interaction between amino acids and cholesterol was shown by reversed-phase thin-layer chromatography (RP-TLC) in the presence of monovalent cations of different concentration. The degree of interaction between amino acids and cholesterol was affected by different salt solutions and by applying cholesterol to the chromatographic plates at higher concentration. The relative strength of interaction was determined by statistical evaluation of the results in each case.

The in vitro biosynthesis and stability measurement with agyl-glycuronide isoformes of the main metabolite of ipriflavone.

The formation and stability of 1-beta-glucuronide conjugate of the main metabolite of ipriflavone [7-(1-carboxy-ethoxy)-isoflavone] (CI)--were studied by using liver microsomes, hepatocytes, and isolated perfused liver of untreated and 3-methylcholanthrene (MC) treated dog and rat, and human liver microsomes. MC treatment enhanced the rate of conjugation twice as much as that of the control in the microsomes of both dogs and rats. Conjugation of CI by microsomes results in two metabolites, both sensitive to pH and temperature.

Classification of chili powders by thin-layer chromatography and principal component analysis.

Silica gel, aluminium oxide, diatomaceous earth, polyamide, cyano, diol and amino plates have been tested for their capacity to separate the color pigments of six chili powders of different origin by both adsorption and reversed-phase thin-layer chromatography. The plates were evaluated at 340 and 440 nm wavelengths. Best separation of color pigments was obtained on impregnated diatomaceous earth layer using acetone-water 17:3 v/v eluent.

Liquid chromatography of natural pigments.

The newest results in the application of various liquid chromatographic techniques for the analysis of natural pigments in pure state and in complicated matrices are compiled. The methods employed for the separation and quantitative determination of the different pigment classes (flavonoids, coumarins, chlorophylls, etc.) are described and critically evaluated.

Charge-transfer chromatographic study of the interaction of antibiotics with cetyltrimethylammonium bromide.

The interaction of 20 antibiotics with the cationic surfactant cetyltrimethylammonium bromide (CTAB) was studied by charge-transfer reversed-phase chromatography carried out on impregnated alumina layers using water-methanol mixtures as eluents. The lipophilicity and specific hydrophobic surface area of antibiotics and the relative strength of their interaction with CTAB was calculated. CTAB interacted with 10 antibiotics the antibiotic--CTAB complex generally being more hydrophilic than the uncomplexed molecule.

Relationship between the retention characteristics on an alumina column and physico-chemical parameters of some environmental pollutants.

The retention behavior of 16 environmental pollutants was studied on alumina and porous graphitized carbon (PGC) columns using n-hexane as eluent. The relationship between the logarithm of the capacity factors determined on the alumina column and the physico-chemical characteristics of the solutes was elucidated by principal component analysis (PCA) followed by two-dimensional nonlinear mapping. The 12 original variables can be reduced to four with only a 10% loss of information.

Determination of the relative impact of chromatographic conditions and solute structures on the retention behaviour of non-ionic surfactants in RP-HPLC.

The retention behaviour of non-ionic surfactants containing different hydrophobic moiety and various lengths of polar ethylene oxide chain was studied on RP-8 and RP-18 columns using methanol and acetonitrile as organic modifiers. The relative impact of the chromatographic conditions on the retention strength was determined using stepwise regression analysis. Non-ionic surfactants can be separated according to the character of the hydrophobic moiety, but not according to the length of the polar ethylene oxide chain.

Effect of salt concentration and pH on the hydrophobicity parameters of surfactants studied by TLC and spectral mapping technique.

The lipophilicity and specific hydrophobic area of 56 surfactants having different hydrophobic moiety and different length of ethylene oxide chain were determined by reversed-phase thin-layer chromatography and the strength and selectivity of the effect of sodium chloride and pH on the hydrophobicity parameters was elucidated using spectral mapping technique followed by two-dimensional nonlinear mapping. In each instance significant linear correlations were found between the lipophilicity and specific hydrophobic surface area of surfactants suggesting that from a chromatographic point of view they behave as a homologous series of solutes. It was established that the strength of the effect of both salt concentration and pH is relatively low and the selectivity of their influence on the hydrophobicity parameters is markedly different.

Relationship between retention characteristics and physicochemical parameters of solutes on porous graphitized carbon column.

The retention of 44 barbituric acid derivatives was determined on porous graphitized carbon (PGC) column using dioxane water mixtures as eluents. Linear correlations were calculated between the logarithm of the capacity factor and the dioxane concentration in the eluent. Free Wilson analysis combined with stepwise regression analysis was used to elucidate the role of individual substituents in the retention behaviour.

Inclusion complex formation of steroidal drugs with hydroxypropyl-beta-cyclodextrin studied by charge-transfer chromatography.

The interaction between 17 steroidal drugs and hyroxypropyl-beta-cyclodextrin (HPbetaBCD) was determined by charge-transfer chromatography and the relative strength of interaction was calculated. HPbetaCD interacted with each steroidal drugs decreasing the hydrophobicity of the guest molecules. The relative strength of interaction considerably depended on the structure of the drug molecule.

Separation of steroidal drugs on porous graphitized carbon column.

The retention time of 11 steroidal drugs was determined on a porous graphitized carbon (PGC) column using water tetrahydrofuran mixtures as eluents. Linear correlations were calculated between the logarithm of the capacity factor (k') and the tetrahydrofuran concentration in the eluent. To find the molecular parameters significantly influencing the retention the intercept and slope values of the above relationship were correlated with the physicochemical characteristics of steroidal drugs using principal component analysis (PCA).

Bimodal action of furosemide on convulsant [3H]EBOB binding to cerebellar and cortical GABA(A) receptors.

Picrotoxinin-sensitive binding of a convulsant 4'-ethynyl-4-n[2,3-3H2]propyl-bicycloorthobenzoate ([3H]EBOB) to gamma-aminobutyric acid type A (GABA(A)) receptors was characterized in rat cerebrocortical and cerebellar membranes. The non-penetrating organic anions, furosemide and niflumate, in spite of their structural similarities, exerted differential effects on [3H]EBOB binding. Furosemide, a loop diuretic and a specific antagonist of a cerebellar GABA(A) receptor population, and GABA decreased the inhibitory potencies of each other in the cerebellum, while enhanced them in the cortex.

Phenoxyacetic acids: separation and quantitative determination.

The various chromatographic methods suitable for the separation and quantitative determination of phenoxyalkyl acid herbicides in environmental samples are reviewed, with special emphasis being placed on sample preparation methods such as liquid-liquid, solid-phase and supercritical fluid extractions. Techniques are classified (high-performance liquid chromatography, gas-liquid chromatography, capillary zone electrophoresis, micellar electrokinetic chromatography) and discussed separately. The advantages and disadvantages of the various preparation and separation methods and their combinations are evaluated.

A stilbene from the roots of leuzea carthamoides.

From the roots of Leuzea carthamoides, (E)-3,3'-dimethoxy-4, 4'-dihydroxystilbene (1) has been isolated and its structure elucidated by means of NMR spectroscopy, including HMQC and HMBC measurements, mass spectrometry, and X-ray crystallography.

Differential effects of thiocyanate on the binding thermodynamics of bicuculline methiodide versus SR95531 (gabazine) to the gamma-aminobutyric acid receptor-ionophore complex.

The temperature dependence of the binding of [3H]SR 95531 (Gabazine), an antagonist of gamma-aminobutyric acid (GABA(A)) receptors, was studied in synaptosomal membranes of rat brain in the presence of 50 mM KSCN. The displacing potencies of the antagonists bicuculline methiodide and Gabazine were determined at five temperatures between 0 degrees and 37 degrees. Van't Hoff plots of the displacing potencies were analyzed by linear regression in the presence and absence of thiocyanate.

Comparison of partial least-square method and canonical correlation analysis in a quantitative structure-retention relationship study.

The retention of 7 monotetrazolium and 9 ditetrazolium salts was determined on alumina and reversed-phase (RP) alumina layers using n-hexane-1-propanol and water-1-propanol mixtures as eluents. The retention capacity and the specific surface area of solutes in contact with the stationary phases were calculated. The relationship between retention characteristics and physicochemical parameters of solutes was elucidated by canonical correlation analysis and partial least-square regression analysis.

Stability of Asp-Pro bond under high and low energy collision induced dissociation conditions in the immunodominant epitope region of herpes simplex virion glycoprotein D.

A series of truncated Herpes simplex virion peptides studied by fast atom bombardment mass spectrometry under high and low energy collision induced dissociation conditions showed preferential fragmentation of the aspartyl-proline amide bond, compared to other peptide bonds. Electrospray ionization investigation proved that this favoured fragmentation can not be attributed to only the known proline effect, as a change from Asp to Asn in the peptide yielded an Asn-Pro bond which was found to be stable under the same ionization conditions. This mass spectrometric behaviour is in good agreement with the observation that DP bonds are sensitive to acidic conditions.

Effect of salts on the interaction of oxidized glutathione with dibasic amino acids.

The interaction of oxidized glutathione (GSSG) with dibasic amino acids was studied with charge-transfer chromatography carried out on unimpregnated cellulose layers in the absence and presence of LiCl, NaCl, KCl, MgCl2 and CaCl2. GSSG decreased in each case the apparent lipophilicity of dibasic amino acids, indicating some type of interaction. Calculations proved that the strength of GSSG - dibasic amino acid interaction decreases with increasing concentration of salts suggesting a hydrophilic character of interaction.

Quantitative structure-retention relationship study of tetrazolium salts on alumina support.

The retention of 7 monotetrazolium and 9 ditetrazolium salts was determined on alumina and reversed-phase (RP) alumina layers using n-hexane-2-propanol and water-2-propanol mixtures as eluents. The retention capacity and the specific surface area of solutes in contact with the stationary phases were calculated. Quantitative structure-retention relationship calculations indicated that the retention capacity of solutes on RP alumina layers depended not only on the molecular hydrophobicity but also on the hydrogen-donor and acceptor properties.

Spectral components of cytosolic [Ca2+] spiking in neurons.

We show here, by means of evolutionary spectral analysis and synthesis of cytosolic Ca2+ ([Ca2+]c) spiking observed at the single cell level using digital imaging fluorescence microscopy of fura-2-loaded mouse cerebellar granule cells in culture, that [Ca2+]c spiking can be resolved into evolutionary spectra of a characteristic set of frequencies. Non-delayed small spikes on top of sustained [Ca2+]c were synthesized by a main component frequency, 0.132+/-0.

Ipriflavone as an inhibitor of human cytochrome P450 enzymes.

1. Reduction of theophylline metabolism and elimination were observed in a theophylline-treated patient during ipriflavone administration. After withdrawal of ipriflavone, the serum theophylline level decreased to an extent similar to that found before administration of ipriflavone.

Species differences in metabolism of panomifene, an analogue of tamoxifen.

In vitro metabolism of panomifene (E-1,2-diphenyl-1--4-(2-(2-hydroxyethyl-amino)-ethoxy)-phenyl--3,3,3- trifluoropropene), a novel antiestrogen against hormone dependent tumors, has been investigated using liver microsomes from mouse, rat, dog, and human. Hydroxylation and side chain modifications were the routes of panomifene metabolism. Microsomal biotransformation showed some qualitative similarities, but several differences were observed in the metabolic profiles of the four species tested.

Surface Coverage and Its Determination: Role of Acid-Base Interactions in the Surface Treatment of Mineral Fillers.

The role of acid-base interactions in the nonreactive surface treatment of mineral fillers was studied by a dissolution method. The effect of treatment on the surface properties of CaCO3 covered with stearic acid was determined by ESCA measurements and by the calculation of the basicity of the treated fillers. The dissolution measurements were carried out in twelve different solvents.

Inhibition of gamma-aminobutyric acid uptake by bicuculline analogues.

Enantiomers of norbicuculline, (+)[1S,9R] and (-)[1R,9S]erythro-1-[1'-(4',5'-methylenedioxyphthalidyl)]-6,7-meth ylenedioxy-1,2,3,4-tetrahydroisoquinoline and of the N-methyl derivatives {(+)[1S,9R] and (-)[1R,9S]bicuculline} were found to inhibit the progress of the gamma-aminobutyric acid transporter-mediated uptake of 40 microM [14C]gamma-aminobutyric acid into native plasma membrane vesicles from the rat cerebral cortex at 30 degrees C. The values for the dissociation constants of the reversible inhibition, relative to (+)[1S,9R]bicuculline, in order of increasing inhibition, were: (-)[1R,9S]bicuculline, 3.3; (+)[1S,9R]-bicuculline, 1.