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PubMed1982

Biotransformation of epomediol. I--Isolation and identification of main metabolites in the rat.

The identification of biotransformation products of the new choleretic drug epomediol in rat has been performed by means of mass spectral, proton magnetic resonance and infrared techniques. The drug was administered perorally or intravenously; urine, bile and faeces were collected and the metabolites isolated. In urine, three metabolites were found in addition to the unchanged drug, namely; 1,3,3-trimethyl-2-oxabicyclo[2.2.2]octan-6-hydroxy-7-one, 1,3-dimethyl-2-oxabicyclo[2.2.2]octan-6,7-hydroxy-10-methanol and 1,3,3-trimethyl-2-oxabicyclo[2.2.2.]octan-6-beta-glucuronide-7-ol. In bile only the glucuronide and the unchanged drug were found. Analogously, in faeces the glucuronide and the drug were also identified, but only in trace amounts. This fact may suggest the presence of an enterohepatic circulation of the drug.

Administration, Oral↗
PubMed2004

Peptide and protein separations by capillary electrophoresis in the presence of mono- and diquaternarized diamines.

Two compounds, derivatives of 1,4-diazobicyclo[2,2,2]octane (DABCO), have been evaluated as potential quenchers of silanol interactions with peptides and proteins during their capillary zone electrophoresis (CZE) separations. They are: 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2,2,2]octane iodide (M7C4I) and 1,4-didecyl-1,4-diazoniabicyclo [2,2,2]octane dibromide (C10M7C10). The first compound is known to react with the wall, by forming a covalent bond via alkylation of silanols. On the contrary, the second one (C10M7C10) can only loosely interact with silica due to lack of reactive iodine and to a much too short distance (a C(2)) between the two quaternary nitrogens. Very good peptide maps of protein digests can be obtained in isoelectric glutamic acid (Glu) buffer, at pH 3.52 by utilizing the M7C4I. However, in the case of total tissue extracts, excellent resolution is obtained only with the first eluting part of the analyte spectrum (i.e., peptides and smaller proteins). With larger proteins, interaction with the wall and loss of resolution is experienced. When using the C10M7C10, good resolution of di- and tripeptides is obtained, while a loss of resolution is observed with entire protein digest. M7C4I does not seem to interact with the peptide/protein analytes, and simply repels them from the wall via its positive charges; it is believed that disalt (C10M7C10) acts by interacting with the same compounds, possibly by forming micelles in solution.

Animals↗
PubMed2001

Proline-induced hinges in transmembrane helices: possible roles in ion channel gating.

A number of ion channels contain transmembrane (TM) alpha-helices that contain proline-induced molecular hinges. These TM helices include the channel-forming peptide alamethicin (Alm), the S6 helix from voltage-gated potassium (Kv) channels, and the D5 helix from voltage-gated chloride (CLC) channels. For both Alm and KvS6, experimental data implicate hinge-bending motions of the helix in an aspect of channel gating. We have compared the hinge-bending motions of these TM helices in bilayer-like environments by multi-nanosecond MD simulations in an attempt to describe motions of these helices that may underlie possible modes of channel gating. Alm is an alpha-helical channel-forming peptide, which contains a central kink associated with a Gly-x-x-Pro motif in its sequence. Simulations of Alm in a TM orientation for 10 ns in an octane slab indicate that the Gly-x-x-Pro motif acts as a molecular hinge. The S6 helix from Shaker Kv channels contains a Pro-Val-Pro motif. Modeling studies and recent experimental data suggest that the KvS6 helix may be kinked in the vicinity of this motif. Simulations (10 ns) of an isolated KvS6 helix in an octane slab and in a POPC bilayer reveal hinge-bending motions. A pattern-matching approach was used to search for possible hinge-bending motifs in the TM helices of other ion channel proteins. This uncovered a conserved Gly-x-Pro motif in TM helix D5 of CLC channels. MD simulations of a model of hCLC1-D5 spanning an octane slab suggest that this channel also contains a TM helix that undergoes hinge-bending motion. In conclusion, our simulations suggest a model in which hinge-bending motions of TM helices may play a functional role in the gating mechanisms of several different families of ion channels.

Alamethicin↗
PubMed1984

Effects of organic solvents on lipase for fat splitting.

The effect of organic solvents on the stability and catalytic activity of the microbial lipase from Candida rugosa for hydrolysis of triglyceride (fat splitting) has been examined. The solvents examined were 5 hydrocarbons (n-hexane, n-heptane, n-octane, iso-octane and cyclohexane) and 3 ethers (diethyl-ether, diisopropylether and di-n-butylether). The results revealed that iso-octane and cyclohexane are superior to the other solvents examined for enzymatic fat splitting in organic solvent systems.

Candida↗
PubMedDate not supplied

Separation of alpha-amylase by reversed micellar extraction. Effect of solvent type and cosolvent concentration on the transfer process.

The recovery of alpha-amylase from the crude enzyme preparation by the reversed micellar liquid-liquid extraction was investigated. The reversed micellar solution was formed by dissolving a cationic surfactant Aliquat 336 in six different alkanes (cyclohexane, n-hexane, isooctane, n-octane, n-decane, and n-dodecane) respectively with addition of a cosolvent n-octanol. It was found that a minimal quantity of n-octanol was needed for Aliquat 336 to dissolve in apolar solvent and form reversed micelles. Furthermore, this minimal amount of n-octanol needed was found to be different when Aliquat 336 was dissolved in different alkanes. It tended to increase with the number of carbon atoms in alkane and also depended on the solvent structure. During the forward extraction process, it was revealed that a high value of solubilization of protein in Aliquat 336 reversed micelles could be achieved when four out of the six alkanes (cyclohexane, n-hexane, isooctane, n-octane) were used as the solvent for Aliquat 336. After a full forward and backward extraction cycle, however, a high recovery of both the protein mass and alpha-amylase activity in the stripping solution could be obtained only when two out of the six alkanes (n-hexane and isooctane) were used as the solvent for Aliquat 336. When n-hexane and isooctane were used as the solvent for Aliquat 336, up to 80% of the total alpha-amylase activity in the crude enzyme preparation could be recovered at the end of extraction cycle, meanwhile alpha-amylase could be concentrated about 1.4-fold. In the cases of other four alkanes (cyclohexane, n-octane, n-decane, and n-dodecane) as solvent, most of the alpha-amylase activity in the crude enzyme preparation would be denatured after an extraction cycle.

1-Octanol↗
PubMed1983

Mutagenicity of Nagara river sediment.

The sediments of Nagara river and its bystreams were extracted with ether. The mutagenicities of the extracts were determined by the Ames test with Salmonella typhimurium TA100 with S9 mix. The extracts were fractionated on an activated silica-gel column with four kinds of organic solvent, namely iso-octane, iso-octane:benzene (1:1), benzene:ethyl acetate (1:1) and benzene:methanol (1:1). The highest mutagenicity was observed in the iso-octane-benzene fraction of Arata river by using TA100 with S9 mix. Chemical substances in this fraction were identified by GC-MS and GC, and several kinds of polycyclic aromatic hydrocarbons (PAH) were found. Several peaks were unidentified, but these PAH, especially benzo [b] fluoranthene and benzo [a] pyrene, may contribute substantially to the mutagenicity of this fraction.

Hydrogen-Ion Concentration↗
PubMed1996

The preparation, characterisation and solubility characteristics of a hydrogen-bonded complex between acyclovir and cytosine.

Acyclovir and cytosine form a Crick-Watson hydrogen-bonded complex in dimethylsulphoxide (DMSO). For the complex formation Acyclovir + cytosine reversible complex the equilibrium constant, K, was determined using NMR spectroscopy to be K = 1.00 +/- 0.07 mol-1 dm3 at 21 degrees C in DMSO. The acyclovir-cytosine complex was formed in DMSO, then diluted with octan-1-ol to leave a 95.3% v/v octan-1-ol/47% v/v DMSO solution, and demonstrated a 12-fold increase in the saturated solubility of acyclovir. This was compared to a solution of acyclovir alone treated in the same manner. This suggests that a complex species of acyclovir with cytosine has a greater lipophilic character than acyclovir alone. Attempts to increase the octan-1-ol/water partition coefficient for acyclovir produced no significant increase with the presence of cytosine. It was argued that no complexation would occur in water due to the rapid exchange of the protons that are involved in the hydrogen-bonded complex. Experiments to isolate the solid acyclovir-cytosine Crick-Watson hydrogen-bonded complex were performed. Spectra and T1 relaxation times obtained during subsequent solid-state 13C NMR experiments provided evidence that a solid complex can be isolated.

Acyclovir↗
PubMed2006

Characteristics of bioemulsifier V2-7 synthesized in culture media added of hydrocarbons: chemical composition, emulsifying activity and rheological properties.

The bioemulsifier V2-7 is an exopolysaccharide (EPS) synthesized by strain F2-7 of Halomonas eurihalina and it has the property of emulsifying a wide range of hydrocarbons i.e. n-tetradecane, n-hexadecane, n-octane, xylene mineral light and heavy oils, petrol and crude oil. Characteristics of exopolysaccharide V2-7 produced in media supplemented with various hydrocarbons (n-tetradecane, n-hexadecane, n-octane, xylene, mineral light oil, mineral heavy oil, petrol or crude oil) were studied. Yield production varied from 0.54 to 1.45 g L(-1) according to the hydrocarbon added, in the same way chemical composition, viscosity and emulsifying activity of EPS varied with the culture conditions. Respect to chemical composition, percentage of uronic acids found in exopolymers produced in hydrocarbon media was always higher than that described for V2-7 EPS (1.32%) obtained with glucose. This large amount of uronic acid present could be useful in biodetoxification and waste water treatment. On the other hand, the highest amount of biopolymer was synthesized with mineral light oil, while the most active emulsifiers were those obtained from media added with petrol and n-octane. Furthermore, all EPS were capable of emulsifying crude oil more efficiently than the three chemical surfactants tested as control (Tween 20, Tween 80 and Triton X-100). The capacity of strain F2-7 to grow and produce bioemulsifier in presence of oil hydrocarbons together with the high emulsifying activity and low viscosity power of the biopolymers synthesized in hydrocarbons media could be considered highly beneficial for application of both bioemulsifier and producing strain in bioremediation of oil pollutants.

Biodegradation, Environmental↗
PubMed2004

Determination of important odor-active aldehydes of wine through gas chromatography-mass spectrometry of their O-(2,3,4,5,6-pentafluorobenzyl)oximes formed directly in the solid phase extraction cartridge used for selective isolation.

A method for the quantitative determination of octanal, nonanal, decanal, (E)-2-nonenal and (E, Z)-2,6-nonadienal in wine has been developed. In the proposed method, 200 ml of wine percolate through a solid phase extraction (SPE) cartridge packed with 200 mg of LiChrolut EN resins. The interferences are eluted with 60 ml of an aqueous solution containing 40% of methanol and 1% of NaHCO3. In the same SPE cartridge, the corresponding O-(2,3,4,5,6-pentafluorobenzyl)oximes are formed by letting percolate 2 ml of the reagent solution (5 mg ml(-1)). At room temperature the derivatization goes to completion in 15 min. The derivatives are eluted with 2 ml of dichloromethane, and the extract is concentrated and then analyzed by gas chromatography-mass spectrometry (GC-MS). The percentage of recovery in the isolation process is better than 90% in all cases with the exception of octanal, and is independent of the wine studied. In the cases of octanal, nonanal and decanal, the detection limits of the method are determined by the contamination levels of the reagent itself, and vary between 160 and 380 ng l(-1). For (E)-2-nonenal and (E, Z)-2,6-nonadienal, the detection limits were 12 and 20 and ng l(-1), respectively. The linearity of the method upheld until 10 microg l(-1) and was satisfactory in all cases. The reproducibility of the method is independent of the concentration and ranges from 30 to 190 ng (l(-1). The method has been applied to the analysis of these components in several wine samples. With the exception of (E, Z)-2,6-nonadienal, all the components can reach concentrations above their corresponding odor threshold values.

Aldehydes↗
PubMed2005

The water/n-octane/octyl-beta-D-glucoside/1-octanol system: phase diagrams and phase properties.

The partial phase diagram of D2O/n-octyl-beta-D-alkyl-glucoside(C8G1)/n-octane has been determined at T=25 degrees C. The diagram contains a funnel-shaped micellar phase originating from the water corner of the phase diagram D2O/C8G1 with the stem forming a narrow three-phase region, in which the three phases in equilibrium are two microemulsions of similar composition and an excess oil phase. The microemulsions have been characterized with NMR self-diffusion measurements. At high surfactant concentration and no or low n-octane content, branched micelles exist. As the n-octane content is increased, discrete micelles are formed. Upon further addition of n-octane, the phase separation into two microemulsion phases is induced. Possible mechanisms causing the phase separation are discussed. The phase diagram of D2O/(C8G1)/1-octanol has been determined at 25 degrees C. Ten different phase regions were identified. The phases have been characterized with SAXS and deuterium heavy water NMR, and the swelling of the lamellar phase was investigated with SAXS.

Journal Article↗
PubMed2006

Thermodynamic penalty arising from burial of a ligand polar group within a hydrophobic pocket of a protein receptor.

Here, we examine the thermodynamic penalty arising from burial of a polar group in a hydrophobic pocket that forms part of the binding-site of the major urinary protein (MUP-I). X-ray crystal structures of the complexes of octanol, nonanol and 1,8 octan-diol indicate that these ligands bind with similar orientations in the binding pocket. Each complex is characterised by a bridging water molecule between the hydroxyl group of Tyr120 and the hydroxyl group of each ligand. The additional hydroxyl group of 1,8 octan-diol is thereby forced to reside in a hydrophobic pocket, and isothermal titration calorimetry experiments indicate that this is accompanied by a standard free energy penalty of +21 kJ/mol with respect to octanol and +18 kJ/mol with respect to nonanol. Consideration of the solvation thermodynamics of each ligand enables the "intrinsic" (solute-solute) interaction energy to be determined, which indicates a favourable enthalpic component and an entropic component that is small or zero. These data indicate that the thermodynamic penalty to binding derived from the unfavourable desolvation of 1,8 octan-diol is partially offset by a favourable intrinsic contribution. Quantum chemical calculations suggest that this latter contribution derives from favourable solute-solute dispersion interactions.

Binding Sites↗
PubMed2003

Removal of the internal limiting membrane under perfluorocarbon liquid to treat macular-hole-associated retinal detachment.

PURPOSE: To demonstrate the advantages and efficacy of internal limiting membrane removal under perfluorocarbon liquid in macular-hole-associated retinal detachment. DESIGN: Interventional case series. METHOD: Four patients with macular-hole-associated retinal detachment underwent pars plana vitrectomy, retinal reattachment with endodrainage through the macular hole, perfluoro-n-octane injection to seal the macular hole, indocyanine green injection under the perfluoro-n-octane bubble and removal of the indocyanine green-stained internal limiting membrane. Visual acuity and anatomic results were recorded, with a mean follow-up period of 18 months. RESULTS: Postoperatively, the retina was reattached in all four patients and closure of the macular hole was achieved in three eyes. Visual acuity improved in all eyes. CONCLUSIONS: In retinal detachment resulting from macular hole, staining of the internal limiting membrane with indocyanine green injected under perfluoro-n-octane can facilitate peeling of the membrane without exertion of excessive retinal traction and may prevent passage of indocyanine green into the subretinal space.

Aged↗
PubMed2000

Microemulsion electrokinetic chromatography in suppressed electroosmotic flow environment. Separation of fat-soluble vitamins.

Microemulsion electrokinetic chromatography (MEEKC) was carried out in a pH 2.5 phosphate buffer to effectively suppress the electroosmotic flow (EOF). With 66.6% (w/w) 25 mM phosphate buffer pH 2.5, 20.0% (w/w) 2-propanol, 6.6% (w/w) 1-butanol, 6.0% (w/w) sodium lauryl sulphate (SDS), and 0.8% (w/w) n-octane as the separation medium, the fat-soluble vitamins A palmitate, E acetate, and D3 were baseline separated within 11 min. With strongly suppressed EOF, the polarity of the separation voltage was reversed (positive electrode at the outlet); the n-octane micro droplets surrounded by negatively charged SDS molecules migrated towards the detector. The aqueous part of the microemulsion was modified with 20% (w/w) 2-propanol to improve partition between the n-octane phase and the surrounding aqueous medium. The fat-soluble vitamins were separated in order of decreasing hydrophobicity with a high migration time stability (repeatable within 0.1% RSD). Excellent accuracy and precision were obtained when the system was applied for the determination of vitamin E acetate in commercial vitamin tablets; quantitative data corresponded to 97.0% of label claim, intra-day results varied within 1.72% RSD (n=6), and inter-day results varied within 3.22% RSD (n=5).

Buffers↗
PubMed2001

Surface properties of Ascaris suum eggs: hydrophobic potential and Lewis acid-base interactions.

The cell surface properties of Ascaris suum eggs were investigated to determine the hydrophobic properties of eggs of different origins. Hydrophobic potential measurements were based on adhesion to hydrocarbons. Freshly laid eggs with or without the external coat and eggs that had been stored for 3 months at -20 degrees C were tested. The hydrophobic potential differed according to the hydrocarbon used (hexadecane or octane) and the eggs tested (stored or fresh). The hydrophobic potential with octane was 95% for fresh eggs and 72% for eggs stored at -20 degrees C. Tests with Ascaris eggs with and without an external coat showed similar hydrophobic characteristics; the presence or absence of this external structure did not appear to influence hydrophobic interactions. Acidic interactions also appeared to play no part in the adhesion of eggs to the surface of octane emulsions.

Journal Article↗
PubMed2003

Microemulsion electrokinetic chromatographic analysis of some polar compounds.

This study presents the optimization of a microemulsion electrokinetic chromatographic (MEEKC) electrolyte solution by using UV detection and with the method, simultaneous separations of chemically, biochemically and pharmaceutically related anionic and cationic compounds. Representatives of the compound groups were from isoflavonoids, benzodiazepines, metanephrines, diuretics and peptide hormones. The MEEKC separations under basic conditions were first optimized using a two-component isoflavonoid mixture as the sample and an electrolyte containing 10 mM tetraborate as the main buffer (pH 9.5). The stable microemulsion phase was adjusted with various amounts of octane, 1-butanol and sodium dodecyl sulfate (SDS). An only acidified electrolyte solution used in the study was made of phosphoric acid (pH 1.8) containing octane, SDS and ethyl acetate. The analyses with isoflavonoids showed that electrophoretic mobilities of the investigated compounds were highly related to the concentrations of SDS and 1-butanol with linear and parabolic correlation, respectively. However, addition of octane gave linear correlation only at low concentrations. In most cases four to six structurally related compounds and even 13 diuretics with various polar properties were separated from each other in basic microemulsion medium. The acidified MEEKC electrolyte gave good resolution for anionic metanephrines.

Benzodiazepines↗
PubMed1984

Human liver alcohol dehydrogenase isozymes: reduction of aldehydes and ketones.

The class I (alpha, beta 1, gamma 1, and gamma 2), II (pi), and III (chi) isozymes of human liver alcohol dehydrogenase (ADH) were isolated as electrophoretically homogeneous preparations to examine their kinetics of aldehyde and ketone reduction. While the oxidation of a wide variety of alcohols by ADH has been investigated extensively, the reduction of aldehydes and ketones has received much less attention even though the equilibrium favors the latter process. For each isozyme, the Km and kcat values were measured at pH 7.0 with acetaldehyde, pentanal, octanal, benzaldehyde, and cyclohexanone as substrates. Activity could not be detected with succinic semialdehyde and betaine aldehyde for any of the isozymes. The nonenzymatic hydration, oxidation, and aldol condensation of aldehydes in aqueous solutions present serious experimental obstacles in determining the isozymes' kinetic constants. The effects of these reactions on the enzymatic parameters were studied and compensated for. Michaelis constants for all class I and II isozymes vary by more than 8000-fold, from less than 1 microM for beta 1 gamma 1 and beta 1 beta 1 with octanal to 8.3 mM for pi-ADH for acetaldehyde. However, with any given aldehyde, these values vary by less than 40-fold, and the constants are approximately equal to Km values reported previously for the corresponding alcohols. In contrast, Km values for chi-ADH are extremely high and could be determined accurately only for octanal (75 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Dehydrogenase↗
PubMedDate not supplied

Graph valence shells as molecular descriptors.

We have introduced a new simple structural descriptor for molecules that is based on the count of the valence shells for vertices in molecular graphs. The construction of the new descriptor is illustrated on 2,3-dimethylhexane and is reported for the 18 octane isomers. The relationship of the new descriptor to the path numbers of a graph is discussed. It can be seen that the path counts and the count of valence of neighbor shells are related for paths of length two (and shells of range two). There is no appreciable correlation between the count of the longer paths and the count of the corresponding neighbor valence shells at larger separations. Use of the neighbor valence shells as molecular descriptors is illustrated on the boiling point, the entropy, and the density of octanes. An intriguing situation is observed for regressions involving considered properties of n-octane isomers C8H18 in that the paths of length two, three, and four and the shells of the range two, three, and four give identical multivariate regression statistics. An explanation for this somewhat unusual aspect of MRA (multiple regression analysis) is offered.

Journal Article↗
PubMed2002

Emission of alcohols and carbonyl compounds from a spark ignition engine. Influence of fuel and air/fuel equivalence ratio.

A spark ignition engine was used to study the impact of fuel composition and of the air/fuel equivalence (lambda) ratio on exhaust emissions of alcohols and aldehydes/ketones. Fuel blends contained eight hydrocarbons (n-hexane, 1-hexene, cyclohexane, n-octane, isooctane, toluene, o-xylene, and ethylbenzene (ETB)) and four oxygenated compounds (methanol, ethanol, 2-propanol, and methyl tert butyl ether (MTBE)). Exhaust methanol is principally produced from fuel methanol and MTBE but also from ethanol, 2-propanol, isooctane, and hexane. Exhaust ethanol and 2-propanol are produced only from the respective fuel compounds. Exhaust formaldehyde is mainly produced from fuel methanol, acetaldehyde from fuel ethanol, and propionaldehyde from straight-chain hydrocarbons. Exhaust acroleine comes from fuel 1-hexene, acetone from 2-propanol, n-hexane, n-octane, isooctane, and MTBE. Exhaust crotonaldehyde comes from fuel 1-hexene, cyclohexane, n-hexane, and n-octane, methacroleine from fuel isooctane, and benzaldehyde from fuel aromatics. Light pollutants (C1-C2) are most likely formed from intermediate species which are quite independent of the fuel composition. An increase in A increases the exhaust concentration of acroleine, crotonaldehyde, methacroleine, and decreases these of the three alcohols for the alcohol-blended fuels. The concentration of methanol, formaldehyde, propionaldehyde, and benzaldehyde is a maximum atstoichiometry. The exhaust concentration of acetaldehyde and acetone presents a complex behavior: it increases in some cases, decreases in others, or presents a maximum at stoichiometry. The concentration of four aldehydes (formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde) is also linked with the exhaust temperature and fuel H/C ratio.

Air Pollutants↗