Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human serum lipoproteins and egg yolk lecithin liposomes are able to solubilize large amounts of n-hexane and n-octane. At the maximum water solubility of n-octane the mole ratio of alkane to lipoprotein was 65 for high density lipoprotein (holo-HDL) and 900 for low density lipoprotein (holo-LDL). Alkane binding to lipid-free apo-HDL is negligible compared to alkane solubility in holo-HDL. Alkane solubility in the lipoproteins and liposomes is thermodynamically consistent with the simple soution of hydrocarbon in the hydrophobic regions of these particles. The unitary free energies of alkane transfer are similar to values previously observed for detergent micelles but are less favorable by 0.8 kcal/mol from the free energy of transfer to liquid hydrocarbon. It is concluded that the thermodynamics of alkane transfer to the lipoproteins resembles that found for detergent micelles or liposomes rather than that anticipated for an "oil drop" (i.e. liquid hydrocarbon).
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PMID:Hydrophobic interaction of alkanes with liposomes and lipoproteins. 16 99

An analytical method for the measurement of quaternary ammonium compounds in biological fluids has been developed. Samples are prepared by forming the corresponding iodides, which are extracted and isolated. The residue is taken into n-hexane or into water and part of the solution obtained is injected onto the gas chromatograph where thermal degradation takes place. The methyl iodide released is measured by a 63Ni electron capture detector. This method is quite sensitive and detects with good reliability and reproducibility as little as 10(-14) mole quaternary ammonium compound.
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PMID:Simplified detection of quaternary ammonium compounds by gas chromatography. 85

Direct esterifications using a nylon-immobilized lipase from Candida cylindracea were carried out in batch and continuous-flow reactors. The immobilized enzyme was effective in catalyzing the synthesis of ethylpropionate, isoamylpropionate, and isoamylbutyrate. With ethanol dissolved in hexane as a substrate, the maximum initial esterification rate was 0.02 mole/(h x g of immobilized protein), but the enzyme was stable only when the substrate concentrations were lower than 0.2 M. With isoamyl alcohol in hexane as a substrate, esterification rates as high as 0.085 mole/(h x g of immobilized protein) were observed and the immobilized enzyme was stable over a much broader concentration range. However, in this case, the use of a solvent, such as hexane, was not necessary for esterification, and the enzyme could be employed in equimolar acid/alcohol mixtures. A packed-bed reactor was operated successfully for the continuous synthesis of esters. The reactor was stable for long periods of time, and the steady-state performance could be accurately predicted on the basis of batch reaction experiments.
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PMID:Synthesis of esters using a nylon-immobilized lipase in batch and continuous reactors. 136 90

The possibility of regulating the retention and selectivity of monoalkyl- and polymethyl-substituted aromatic hydrocarbons in normal-phase high-performance liquid chromatography was investigated by modifying the non-polar (hexane) mobile phase with halide derivatives of hydrocarbons. Dichloromethane, chloroform, carbon tetrachloride and ethyl bromide were employed as modifiers. The decrease in relative retention for small mole fractions of modifier in the eluent increased with decrease in the polarity. The retention mechanism of the aromatic hydrocarbons is discussed. Chromatograms for the group separation of diesel fuel aromatic hydrocarbons are presented.
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PMID:Peculiarities of aromatic hydrocarbon retention in normal-phase high-performance liquid chromatography with eluents containing halide derivatives. 208 83

Dextromoramide and pethidine were separated and identified by thin-layer chromatography on silica gel, using ammonia and methanol (1.5:100) as the mobile phase, after previous extraction with dicthyl ether or with a mixture of n-hexane and isoamyl alcohol (98.5:1.5) from blood alkalized to pH 10.3 Dextromoramide can be revealed on the chromatograms in the amount of 0.5 micrograms and pethidine in the amount of 1 micrograms using the Dragendorff reagent. Reversed-phase TLC proved less sensitive. High-performance liquid chromatography on the column of LiChrosorb RP-18 was applied to the determination of dextromoramide in blood after extraction with diethyl ether, using methanol--phosphate buffer pH 4.5 (95:5) as the mobile phase. The determination range was of 0.5-5.0 micrograms per 2 cm3 of blood plasma (1.26.10(-8)-1.26.10(-7) mole/dm3).
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PMID:[Chromatographic identification and analysis of dextromoramide in the plasma by the method of high performance liquid chromatography]. 263 68

The relations between the single high affinity binding sites for azapropazone, phenylbutazone, chlorpropamide, sulfathiazole, and iophenoxate and the binding regions of human serum albumin represented by the marker ligands diazepam, phenol red, salicylate, and warfarin were examined by a series of competition experiments. Binding was determined by equilibrium dialysis at pH 7.0. In order to ensure an accurate analysis of the competition experiment, the number of moles of ligand bound per mole of protein was usually 0.4 or less to minimize ligand binding to weaker sites. Furthermore, binding of both ligands was determined in all experiments (except for iophenozate). None of the test ligands competed with diazepam for a common high affinity binding site, but, surprisingly, they were all able to displace two or three of the other marker ligands according to a competitive scheme. These findings show, first, the existence of a particular serum albumin region for high affinity binding of diazepam. Secondly, they imply that it is not necessary to assume the existence of new drug binding regions beyond those existing for phenol red, salicylate, and warfarin. On the contrary, the relatively many examples of competitive binding indicate that the binding regions represented by the last-mentioned three marker ligands are placed quite close to each other in the albumin molecule in a common region, which is suggested to be located at subdomains 1C and 2A-B. The region must be relatively large, because in some cases independent high affinity binding of pairs of ligands is observed. It is probably also rather flexible, inasmuch as no clear relation could be found between the chemical structure of the test ligands and the two or three marker ligands with which they compete. Correlations between primary association constants and partition coefficients for both marker ligands and test ligands, in the unionized forms, between n-hexane or 1-octanol and aqueous media showed that hydrophobic forces are important for the binding processes. However, the data also showed that other attractive forces must be operative as well.
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PMID:Evidence for a large and flexible region of human serum albumin possessing high affinity binding sites for salicylate, warfarin, and other ligands. 341 20

Oxidation of p-nitro- and p-dimethylaminomethyl derivatives of benzylamine, catalyzed by amine oxidases from human placenta and blood serum, was studied. The amine oxidase activity was estimated by means of a spectrophotometric procedure involving measurement of aldehyde formed during the reaction after extraction with hexane. For extraction of benzaldehyde and p-nitrobenzaldehyde in the samples HCl was added up to the concentration of 0.17 M and for extraction of p-dimethylaminomethyl benzaldehyde--NaHCO3 up to the 0.5 M concentration. The reaction products were extracted with a yield of 94%, 83% and 78% respectively; molar extinction coefficients for aldehydes at the maximal absorption were equal to 13,080 (241 mn), 16,520 (258 nm), and 11,547 (248 nm), respectively. Analysis of the oxidative reactions using inhibitors Lilly 51,641, deprenyl, aminoguanidine and semicarbazide showed that monoamine oxidase of the A type (95%) and benzylamine oxidase (7%) catalyzed oxidation of 0.1 mM p-nitrobenzylamine in mitochondria and microsomes but oxidation of the substrate at 1 mM concentration was catalyzed by monoamine oxidase of the B type (20% in mitochondria and 35% in microsomes). In the soluble fraction oxidation of p-nitrobenzylamine was catalyzed mainly by diamine oxidase (55%); monoamine oxidase of the A type catalyzed oxidation of 30% of the amine, benzylamine oxidase-15%. The molecular activity of the mitochondrial monoamine oxidase of the A type with p-nitrobenzylamine as a substrate was equal to 61 nmol of the product per 1 mole of the enzyme per 1 min.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Oxidation of p-nitrobenzylamine and p-dimethylaminomethylbenzylamine by amine oxidases from the human placenta and serum]. 370 5

The theromdynamic pKa values for doxepin and its metabolite desmethyldoxepin were determined by the solubility method to be 8.96 and 9.75, respectively at 25 degrees. The intrinsic solubilities for doxepin and desmethyldoxepin were linearly dependent upon ionic strength. The intrinsic solubilities at zero ionic strength and 25 degrees were determined to be 1,13 x 10(-4) M for doxepin and 3.95 x 10(-4) M for desmethyldoxepin. The solubility experiment was repeated at different temperatures and a constant ionic strength of 0.167 M. The change in enthalpy (6.71 kcal/mole) and entropy (-4.16 cal/mole degrees K) of solution for doxepin was determined from a van't Hoff plot for this nonideal system. The apparent partition coefficient between hexane and water for the doxepin free base was determined to be 13,615 at an ionic strength of 0.067 M.
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PMID:Solubility and ionization characteristics of doxepin and desmethyldoxepin. 706 43

The hydrophobicity profiles across phosphatidylcholine (PC)-cholesterol bilayer membranes were estimated in both frozen liposome suspensions and fluid-phase membranes as a function of alkyl chain length, unsaturation, and cholesterol mole fraction. A series of stearic acid spin labels, with the probe attached to various positions along the alkyl chain, cholesterol-type spin labels (cholestane and androstane spin labels), and Tempo-PC were used to examine depth-dependent changes in local hydrophobicity, which is determined by the extent of water penetration into the membrane. Local hydrophobicity was monitored primarily by observing the z component of the hyperfine interaction tensor (Az) of the nitroxide spin probe in a frozen suspension of the membrane at -150 degrees C and was further confirmed in the fluid phase by observing the rate of collision of Fe(CN)6(3-) with the spin probe in the membrane using saturation recovery ESR. Saturated-PC membranes show low hydrophobicity (high polarity) across the membrane, comparable to 2-propanol and 1-octanol, even at the membrane center where hydrophobicity is highest. Longer alkyl chains only make the central hydrophobic regions wider without increasing the level of hydrophobicity. Introduction of a double bond at C9-C10 decreases the level of water penetration at all locations in the membrane, and this effect is considerably greater than the cis configuration than with the trans configuration. Incorporation of cholesterol (30 mol %) dramatically changes the profiles; it decreases hydrophobicity (increases water penetration) from the polar headgroup region to a depth of approximately C7 and C9 for saturated- and unsaturated-PC membranes, respectively, which is about where the bulky rigid steroid ring structure of cholesterol reaches in the membrane. Membrane hydrophobicity sharply increases at these positions from the level of methanol to the level of pure hexane, and hydrophobicity is constant in the inner region of the membrane. Thus, formation of effective hydrophobic barriers to permeation of small polar molecules requires alkyl chain unsaturation and/or cholesterol. The thickness of this rectangular hydrophobic barrier is less than 50% of the thickness of the hydrocarbon regions. Results obtained in dioleoyl-PC-cholesterol membranes in the fluid phase are similar to those obtained in frozen membranes. These results correlate well with permeability data for water and amino acids in the literature.
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PMID:Hydrophobic barriers of lipid bilayer membranes formed by reduction of water penetration by alkyl chain unsaturation and cholesterol. 801 34

An approach to reproduce the solubility profile of a drug in several solvent mixtures showing two solubility maxima is proposed in this work. The solubility of sulphamethoxypyridazine was determined at 25 degrees C in several mixtures of varying polarity (hexane:ethyl acetate, ethyl acetate:ethanol and ethanol:water). Sulphamethoxypyridazine was chosen as a model drug because of its proton-donor and proton-acceptor properties. A plot of the mole fraction of the drug vs the solubility parameter of the solvent mixtures shows two solubility peaks. The two peaks found for sulphamethoxypyridazine demonstrate the chameleonic effect as described by Hoy and suggest that the solute-solvent interaction does not vary uniformly from one mixture to another. The different behaviour of the drug in mixtures of two proton-donor and proton-acceptor solvents (alcohol and water), and in mixtures of one proton acceptor (ethyl acetate) and one proton donor-proton acceptor (ethanol) is rationalized in terms of differences in the proton donor-acceptor ability of the solvent mixtures. An approach based on the acidic and basic partial solubility parameters together with the Hildebrand solubility parameter of the solvent mixtures is developed to reproduce the experimental results quantitatively. The equation predicts the two solubility maxima as found experimentally, and the calculated values closely correspond to the experimental values through the range composition of the solvent mixtures. These results show that the chameleonic effect can be described in a quantitative way in terms of Lewis acid-base interactions; this approach can assist the product formulator to choose the proper solvent mixture for a new drug.
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PMID:Predicting the solubility of drugs in solvent mixtures: multiple solubility maxima and the chameleonic effect. 802 22


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