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PubMed2003

Atmospheric chemistry of nonanal.

During the Southern Oxidants Study 1999 field campaign at Dickson, TN, we conducted measurements of the n-aldehydes propanal, pentanal, hexanal, heptanal, octanal, and nonanal. Propanal and nonanal tended to have the largest concentrations, with afternoon maxima of approximately 0.3 ppb. These aldehydes typically represented a significant fraction of the VOC reactivity defined as k(OH)[VOC]. However, this information is misleading with regard to the impact of these aldehydes on ozone formation, as their oxidation can represent a significant NOx sink. Motivated by the relatively large nonanal concentrations, we conducted a laboratory study of the products of the nonanal + OH reaction. The OH + nonanal reaction rate constant was determined via the relative rate technique and found to be 3.6 (+/- 0.7) x 10(-11) cm3 molecule(-1) s(-1). Under conditions of high [NO2]/[NO], we determined that 50 +/- 6% of OH-nonanal reaction occurs via abstraction of the aldehydic H-atom through measurement of the peroxynonanyl nitrate yield. We also studied the production of organic nitrates from OH reaction with nonanal in the presence of NO. As expected, a major product (20% at large [NO]/[NO2]) of this reaction was 1-nitrooxy octane. We calculate that the branching ratio for 1-nitrooxy octane formation from peroxyoctyl radicals is 0.40 +/- 0.05. On the basis of these measurements, we find that for more than 50% of the time OH reacts with nonanal (for midday summer conditions) an organic nitrate or PAN compound is formed, making this important atmospheric aldehyde an effective NOx sink.

Air Pollutants↗
PubMed2003

Fluorous catalysis under homogeneous conditions without fluorous solvents: a "greener" catalyst recycling protocol based upon temperature-dependent solubilities and liquid/solid phase separation.

The thermomorphic fluorous phosphines P((CH(2))(m)()(CF(2))(7)CF(3))(3) (m = 2, 1a; m = 3, 1b) exhibit ca. 600-fold solubility increases in n-octane between -20 (1a = 0.104 mM) and 80 degrees C (63.4 mM) and 1500-fold solubility increases between -20 and 100 degrees C (151 mM). They catalyze conjugate additions of alcohols to methyl propiolate under homogeneous conditions in n-octane at 65 degrees C and can be recovered by simple cooling and precipitation and used again. This avoids the use of fluorous solvents during the reaction or workup, which are expensive and can leach in small amounts. Teflon shavings can be used to mechanically facilitate recycling, and (31)P NMR analyses indicate >97% phosphorus recovery (85.2% 1a, 12.2% other). (19)F NMR analyses show that 2.3% of the (CF(2))(7)CF(3) moieties of 1a leach, in some form, into the n-octane (value normalized to phosphorus). 1a similarly catalyzes additions in the absence of solvent. Yield data match or exceed those of reactions conducted under fluorous/organic liquid/liquid biphase conditions. The extra methylene groups render 1b more nucleophilic than 1a and, thus, a more active catalyst. The temperature dependence of the solubility of 1a is measured in additional solvents and compared to that of the nonfluorous phosphine PPh(3).

Journal Article↗
PubMed2005

Partitioning behavior of Alkan-1-ols between milkfat and aqueous phases as influenced by temperature.

Partitioning of volatile compounds between lipid and aqueous phases may influence flavor perception and availability to participate in flavor-generating reactions. The objective of this research was to characterize the partitioning of short-chain alkan-1-ols between milkfat and aqueous phases, as influenced by temperature, as compared to an octan-1-ol/water biphasic system (Log P). Temperature has a positive, but nonlinear, influence on Log P values for alkan-1-ols. There is an approximately 1 log decrease in Log P values of milkfat/water as compared to octan-1-ol/water systems; similar trends were observed across chain length. Temperature has a greater effect on alkan-1-ol partitioning in milkfat/water systems than octan-1-ol/water. The latter observation is primarily attributed to the solidification of milkfat at temperatures below 40 degrees C and the resulting reduction in liquid lipid solvent volume.

Alcohols↗
PubMed1999

Novel 1,3-dioxanes from apple juice and cider.

Extracts obtained by XAD solid-phase extraction of apple juice and cider were separated by liquid chromatography on silica gel. Several new 1,3-dioxanes including the known 2-methyl-4-pentyl-1,3-dioxane and 2-methyl-4-[2'(Z)-pentenyl]-1,3-dioxane, were identified in the nonpolar fractions by GC/MS analysis and confirmed by chemical synthesis. The enantioselective synthesis of the stereoisomers of the 1,3-dioxanes was performed using (R)- and (R,S)-octane-1,3-diol and (R)- and (R,S)-5(Z)-octene-1,3-diol as starting material. Comparison with the isolated products indicated that the natural products consisted of a mixture of (2S,4R) and (2R,4R) stereoisomers in the ratio of approximately 10:1, except for 1,3-dioxanes generated from acetone and 2-butanone. It is assumed that the 1, 3-dioxanes are chemically formed in the apples and cider from the natural apple ingredients (R)-octane-1,3-diol, (R)-5(Z)-octene-1, 3-diol, (3R,7R)- and (3R,7S)-octane-1,3,7-triol, and the appropriate aldehydes and ketones, which are produced either by the apples or by yeast during fermentation of the apple juice.

Beverages↗
PubMed1992

N-modified analogues of cocaine: synthesis and inhibition of binding to the cocaine receptor.

Cocaine methiodide (2), N-norcocaine (1b), N-benzyl-N-norcocaine (1c), and N-nor-N-acetylcocaine (1d) were synthesized and evaluated for their ability to inhibit binding of [3H]-3 beta-(4-fluorophenyl)tropane-2 beta-carboxylic acid methyl ester (WIN 35,428) to the cocaine receptor. The study showed that removal of the N-methyl group to give 1b, or replacement with the larger N-benzyl group to give 1c, has a relatively small effect on binding potency. In contrast, replacement of the N-methyl group by the acetyl moiety to give 1d, or the addition of a methyl group to give 2, reduces affinity for the receptor by a large factor. In order to gain preliminary information concerning the importance of the nitrogen location on the tropane ring system, the receptor binding affinity of 8-methyl-8-azabicyclo[3.2.1]octan-3 beta-ol benzoate (5, beta-tropacocaine) was compared to that of the isomeric 6-methyl-6-azabicyclo[3.2.1]octan-3 beta-ol benzoate (4d). The fact that both compounds have similar binding affinities for the cocaine receptor suggests that 3 beta-(benzoyloxy)-6-methyl-6-azabicyclo[3.2.1] octane-2-carboxylic acid methyl ester, which is isomeric with cocaine, may possess binding potency similar to cocaine.

Analgesics↗
PubMed1991

Synthesis, molecular modeling studies, and muscarinic receptor activity of azaprophen analogues.

Synthesis, radioligand binding, and pharmacologic activities of a series of muscarinic receptor ligands including and related to azaprophen (6-methyl-6-azabicyclo[3.2.1]octan-3 alpha-ol 2,2-diphenylpropionate, 1) have been measured to determine activity and selectivity for muscarinic receptor subtypes. Pharmacologic affinities of antagonists were determined as pA2 values for antagonism of methacholine-induced tension responses in guinea pig ileum. Binding affinities were measured by competition against [3H]QNB binding in guinea pig ileum, rat heart and brain, and m1- or m3-transfected Chinese hamster ovary (CHO) cells. The efficacies of muscarinic agonists in brain were determined by the ratio of binding affinities against [3H]QNB or [3H]NMS and [3H]oxotremorine-M ([3H]Oxo-M). Nine muscarinic antagonists, including azaprophen, did not discriminate significantly between the subtypes of muscarinic receptors. KI values for receptor binding for azaprophen (1) were between 8.81 x 10(-11) and 4.72 x 10(-10) M in ileum, heart, brain, and m1- or m3-transfected CHO cells. The alpha- and beta-benzilate esters 5 and 6 are as potent as azaprophen, and diphenylacetate esters 3 and 4 and N-(6)-benzyl alpha-isomer 7 are less potent than azaprophen. Significant stereoselectivity was exhibited with (+)-azaprophen being approximately 200 times more potent than the (-)-enantiomers and the 3 beta-ol isomer 2 being ca. 50 times less potent than azaprophen in all systems. A molecular modeling-molecular mechanics study was conducted to account for the difference. Putative muscarinic agonists (analogues and isomers of 6-methyl-6-azabicyclo[3.2.1]octan-3-ol acetate) did not discriminate muscarinic receptor subtypes with KI values between 2.77 x 10(-6) and 4.33 x 10(-5) M without significant stereoselectivity in the systems examined. The most active analogue was (1R,3R,5S)-6-[1(R)-phenylethyl]-6-azabicyclo[3.2.1]octan-3 alpha-ol acetate. However, efficacies of these putative agonists were in general very low.

Animals↗
PubMed2002

Insights into regioselective oxy (-O-) and imino (-NH-) group insertions of 3-nortricyclanone.

Lactam 4-azatricyclo[3.2.1.0(2,7)]octan-3-one (16a) was proven to be formed in a previously reported reaction that claimed production of lactam 3-azatricyclo[3.2.1.0(2,7)]octan-4-one (17a). In a related reaction, bicyclo[3.1.0]hex-2-ene-endo-6-carbonitrile (15), lactam (16a), and novel hydroxycarbonitriles 19-21 were selectively formed when 3-nortricyclanone (1) was treated with aqueous hydroxylamine-O-sulfonic acid (HOSA). Since nitrile 15 neither hydrolyzed nor underwent intramolecular Ritter reaction under these conditions, mechanisms involving Beckmann rearrangement of 3 to nitrilium ion 9 (normal) and Beckmann fragmentation of 3 to cation 8 (abnormal) were investigated using semiempirical calculations. When alkaline HOSA was employed, lactams 16a and 17a were formed in a 1:2 ratio, perhaps via oxaziridine 6a. A similar selectivity was observed using an NH(3)/NaOCl reagent solution, which afforded lactone 4-oxatricyclo[3.2.1.0(2,7)]octan-3-one (16b) in addition to both lactams. Consequently, the Baeyer-Villiger oxidation of 1 with NaOCl gave 16b exclusively. Finally, the Schmidt reaction of ketone 1 gave only the lactam 17a, via cyclopropyl migration, and the same fragmentation products obtained from the acidic HOSA reaction. Migration selectivities are rationalized in terms of nucleofugacity, electronic effects, cyclopropyl regulation, and MO theory.

Journal Article↗
PubMed2004

Determining partition constants of polar organic molecules between the oil/interfacial and water/interfacial regions in emulsions: a combined electrochemical and spectrometric method.

We have developed a new approach for estimating distributions of polar additives in opaque, surfactant based, macroemulsions based on the pseudophase model for homogeneous micellar and microemulsion solutions. The distribution of a polar additive, such as an antioxidant, AO, within emulsions is expressed in terms of two partition constants, one between the oil and interfacial regions, P(O)I, and the other between the water and interfacial regions, P(W)I. To estimate values for P(O)I and P(W)I requires fitting two independent data sets with two independent mathematical relations and solving equations simultaneously for the two parameters. The experimental protocols were developed for determining the partition constants of tertbutylhydroquinone, TBHQ, in a stirred emulsion composed of octane, dilute aqueous acid, and hexaethyleneglycol monododecyl ether, C12E6. One data set was obtained by electrochemical determination of the observed rate constant, k(obs), for reaction of TBHQ with an arenediazonium ion probe as a function of C12E6 volume fraction. The second data set was obtained by determining the partition constant, P(O)W, of TBHQ between octane and water in the absence of surfactant by UV-visible spectrometry. TBHQ is almost 30 times more soluble in water than octane: P(O)W = 27.5. The values of the partition constants in the emulsion are P(O)I = 1.84 x 10(4) and P(W)I = 6.73 x 10(2). The partition constants were used to estimate the fraction of TBHQ in each region; for example, 96% of the TBHQ is located in the interfacial region at 0.02 volume fraction of C12E6. Our approach is quite general and should be applicable to any polar organic compound that reacts with the arenediazonium ion probe in emulsions composed of virtually any type of oil and surfactant. Comparisons of the rate constants for reaction of the antioxidant in the interfacial region of the emulsion, which can be obtained from the electrochemical results, may lead to a scale of antioxidant efficiency that is independent of the distribution of the antioxidant in the emulsion.

Journal Article↗
PubMed2005

Measurements of molecular and thermal diffusion coefficients in ternary mixtures.

Thermal diffusion coefficients in three ternary mixtures are measured in a thermogravitational column. One of the mixtures consists of one normal alkane and two aromatics (dodecane-isobutylbenzene-tetrahydronaphthalene), and the other two consist of two normal alkanes and one aromatic (octane-decane-1-methylnaphthalene). This is the first report of measured thermal diffusion coefficients (for all species) of a ternary nonelectrolyte mixture in literature. The results in ternary mixtures of octane-decane-1-methylnaphthalene show a sign change of the thermal diffusion coefficient for decane as the composition changes, despite the fact that the two normal alkanes are similar. In addition to thermal diffusion coefficients, molecular diffusion coefficients are also measured for three binaries and one of the ternary mixtures. The open-end capillary-tube method was used in the measurement of molecular diffusion coefficients. The molecular and thermal diffusion coefficients allow the estimation of thermal diffusion factors in binary and ternary mixtures. However, in the ternaries one also has to calculate phenomenological coefficients from the molecular diffusion coefficients. A comparison of the binary and ternary thermal diffusion factors for the mixtures comprised of octane-decane-1-methylnaphthalene reveals a remarkable difference in the thermal diffusion behavior in binary and ternary mixtures.

Journal Article↗
PubMed1998

Hydration for a series of hydrocarbons.

The hydrophobic hydration in a series of hydrocarbons is probed by using molecular dynamics simulations. The solutes considered range from methane to octane. Examination of the shapes of the hydration shell suggests that there is no single stable structure surrounding these solutes. The structure of the water molecules around the solute is not significantly perturbed, even for octane, and the hydrogen bond network is essentially preserved. The solutes are accommodated in the voids of the tetrahedral network of water in such a way as to leave the local environment almost intact. The hydrophobic hydration arises primarily because of the plasticity of the hydrogen bond network. Even for octane we find very little evidence for water-mediated interactions between nonbonded carbon atoms, leading us to suggest that the transition to globular conformations can only occur for very long, linear hydrocarbon chains.

Hydrocarbons↗
PubMed1994

Evaluation of anterior segment tolerance to short-term intravitreal perfluoron.

PURPOSE: A study was performed to evaluate corneal and anterior segment toxicity from short-term (24-hour) intravitreal use of perfluoro-n-octane. METHODS: Forty aphakic, vitrectomized eyes of pigmented rabbits underwent intravitreal injection of either 0.5 ml of perfluoro-n-octane (Perfluoron; Infinitech, St. Louis, MO; treated) or 0.5 ml balanced saline solution (control). Perfluoron was allowed to remain in the vitreous cavity for 24 hours. Serial measurements of corneal pachymetry and pneumotonometry were performed at 1, 4, 12, and 24 hours after injection. After 24 hours, endothelial cell morphology and barrier function were evaluated. RESULTS: No significant differences in corneal thickness or intraocular pressure were noted between the two groups at any of the time points studied, and no differences in endothelial cell density/hexagonality or endothelial cell barrier function were observed 24 hours after injection. CONCLUSIONS: In the absence of sustained corneal contact, no evidence of significant acute corneal or anterior segment toxicity was observed in response to short-term intravitreal perfluoro-n-octane in aphakic, vitrectomized rabbit eyes.

Animals↗
PubMed2005

Hydrogen bonding patterns in the cocrystals of 5-nitrouracil with several donor and acceptor molecules.

: Cocrystals of 5-nitrouracil with solvent molecules, dioxane, pyridine, DMSO, formamide and ethanol as well as with piperazine, N, N'-dimethylpiperazine, 3-aminopyridine and diazabicyclo [2.2.2]octane obtained by deliberate inclusion, have been examined by X-ray crystallography. The tape structure found in the parent centric form of nitrouracil is retained with some modifications in the cocrystals with dioxane, piperazine, diazabicyclo [2.2.2]octane, N,N'-dimethylpiperazine, pyridine and DMSO, with the guest molecules forming alternate tapes. In cocrystals involving formamide, ethanol and 3-aminopyridine, the molecular tapes exhibit mixed compositions. The observed bonding patterns have been classified into six schemes. Interestingly, quadruple type hydrogen bonding patterns are seen in cocrystals containing 3-aminopyridine or ethanol and water, while a network of acyclic tetrahedral pentamers of water is found in the cocrystal containing diazabicyclo [2.2.2]octane and water.

Journal Article↗
PubMed1999

Synthesis of (1-azabicyclo[3.3.0]octanyl)methyl-substituted aromatic heterocycles and their muscarinic activity.

In our development of drugs effective against Alzheimer's disease, we have researched a series of aromatic compounds having a characteristic cyclic amine, 1-azabicyclo[3.3.0]octane ring. In this report, we describe synthesis of a series of aromatic heterocycles with the 1-azabicyclo[3.3.0]octane ring and their pharmacological evaluation. 3-Amino-5-(1-azabicyclo[3.3.0]octan-5-yl)methyl-1,2,4-oxadiazole (2b) showed the highest M1 selectivity.

Animals↗
PubMed2000

Efficient synthesis of a key intermediate of DV-7751 via optical resolution or microbial reduction.

Two efficient and practical methods of synthesis of the C-10 substituent of DV-7751 (1), a novel quinolone carboxylic acid, were established. The first method utilizes an optical resolution of racemic 8-amino-6-benzyl-6-azaspiro[3.4]octane (13), while the second employs an enantioselective microbial reduction of 6-benzyl-5,8-dioxo-6-azaspiro[3.4]octane (8b). The enantiomeric excess of (S)-8-amino-6-benzyl-6-azaspiro[3.4]octane (11) with each method of synthesis is greater than 96%.

Anti-Infective Agents↗
PubMed2004

Characteristic odor components of Citrus reticulata Blanco (ponkan) cold-pressed oil.

Citrus reticulata Blanco (ponkan) cold-pressed oil and its oxygenated fraction were studied by analytical (GC and GC/MS) and sensory analyses. The monoterpene group was predominant, accounting for more than 89.6% (w/w), of which limonene was the most abundant (80.3%). Among the oxygenated compounds, octanal and decanal were the major ones among 12 aldehydes accounting for >1.5%; six alcohols were identified with a total concentration of >0.7%, while oxides, ketones and esters did not quantitatively or qualitatively contribute to the oil. Sniffing the ponkan cold-pressed oil and its oxygenated fraction demonstrated that octanal and decanal were the characteristic odor components of ponkan. Reconstruction of the ponkan aroma model and its sensory evaluation by a hedonic test were performed, showing that, in addition to octanal and decanal which played important roles, (R)-(+)-limonene contributed to the aroma model as a background component, making the aroma model very similar to that of the original.

Alcohols↗
PubMed2006

Dual signal transduction mediated by a single type of olfactory receptor expressed in a heterologous system.

Controversy exists over the relationship between the cAMP and IP3 pathways in vertebrate olfactory signal transduction, as this process is known to occur by either of the two pathways. Recent studies have shown that a single olfactory neuron responds to both cAMP- and IP3-producing odorants, suggesting the existence of an olfactory receptor protein that can recognize both ligands. In this study we found that the rat olfactory receptor I7, stably expressed in HEK-293 cells, triggers the cAMP pathway upon stimulation by a specific odorant (octanal) at concentrations lower than 10(-4) M; however, the receptor triggers both pathways at higher concentrations. This indicates that a single olfactory receptor, stimulated by a single pathway-inducing odorant, can evoke both pathways at high odorant concentrations. Using this heterologous system, both the dose-dependent response and receptor I7 specificity were analyzed. The dose-dependent Ca2+ response curve, which also includes the release of Ca2+ ions from internal stores at high odorant concentrations, was not monotonous, but had a local maximum and minimum with 10(-10) and 10(-7) M octanal, respectively, and reached a plateau at 10(-2) M octanal. The specificity of the I7 receptor was lower when exposed to higher concentrations of odorants.

Animals↗
PubMed1985

Cell surface hydrophobicity of Bifidobacterium bifidum subsp. pennsylvanicum.

The possible role of lipoteichoic acid with respect to cell surface properties of Bifidobacterium bifidum subsp. pennsylvanicum was studied. Standard suspensions of bacteria were mixed with octane or xylene. B. bifidum subsp. pennsylvanicum was shown to possess a strongly hydrophobic cell surface. Hydrophobicity of the bacteria could be reduced by treatment with trypsin, pepsin (at pH 4.5), HCl and penicillin. The latter treatment resulted in an increased excretion of lipoteichoic acid. Albumin was capable of inhibiting the adherence to octane when it was present in the assay buffer. The data suggest that both protein and lipoteichoic acid may be involved in cell surface hydrophobicity. A great divergence in cell surface properties was observed within the genus Bifidobacterium.

Bifidobacterium↗
PubMed2006

Structural investigation of syringomycin-E using molecular dynamics simulation and NMR.

Syringomycin-E (SR-E) is a cyclic lipodepsinonapeptide produced by certain strains of the bacterium Pseudomonas syringae pv. syringae. It shows inhibitory effects against many fungal species, including human pathogens. Its primary biological target is the plasma membrane, where it forms channels comprised of at least six SR-E molecules. The high-resolution structure of SR-E and the structure of the channels are currently not known. In this paper, we investigate in atomic detail the molecular features of SR-E in water by NMR and in water and octane by molecular dynamics simulation (MD). We built a model of the peptide and examined its structure in water and octane in 200 ns MD simulations both with and without distance restraints derived from NMR NOE data. The resulting trajectories show good agreement with the measured NOEs and circular dichroism data from the literature and provide atomistic models of SR-E that are an important step toward a better understanding of the antifungal and antibacterial activity of this peptide.

Biophysical Phenomena↗