SEARCH · PubMed Health

Results for “CYCLOPROPANE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources

PubMed1997

MMAS-1, the branch point between cis- and trans-cyclopropane-containing oxygenated mycolates in Mycobacterium tuberculosis.

The proportion of mycolic acid containing trans-substituents at the proximal position of the meromycolate chain is an important determinant of fluidity of the mycobacterial cell wall and is directly related to the sensitivity of mycobacterial species to hydrophobic antibiotics. MMAS-1, an enzyme encoded in the gene cluster responsible for the biosynthesis of methoxymycolates, was overexpressed in Mycobacterium tuberculosis and shown to result in the overproduction of trans-cyclopropane and trans-olefin-containing oxygenated mycolic acids. MMAS-1 converted a cis-olefin into a trans-olefin with concomitant introduction of an allylic methyl branch in a precursor to both the methoxy and ketone-containing mycolic acids. In addition to an increase in the amount of trans-mycolate, MMAS-1 expression resulted in a substantial increase in the amount of ketomycolate produced relative to methoxymycolate. Thus MMAS-1 may act at a complex branch point where expression of this enzyme directly affects the cis- to trans-ratio and indirectly affects the keto to methoxy ratio. Overexpression of MMAS-1 resulted in a substantially slower growth rate at moderately elevated temperature, decreased thermal stability of the cell wall as measured by differential scanning calorimetry, and an increased permeability to chenodeoxycholate. These results provide experimental evidence for the intermediacy of trans-olefinic mycolate precursors in trans-cyclopropane formation and suggest that increasing the proportion of the polar ketomycolate subclass may exert a significant fluidizing effect on the cell wall.

Bacterial Proteins↗

PubMed2003

Reaction intermediate structures of 1-aminocyclopropane-1-carboxylate deaminase: insight into PLP-dependent cyclopropane ring-opening reaction.

The pyridoxal 5'-phosphate-dependent enzymes have been evolved to catalyze diverse substrates and to cause the reaction to vary. 1-Aminocyclopropane-1-carboxylate deaminase catalyzes the cyclopropane ring-opening reaction followed by deamination specifically. Since it was discovered in 1978, the enzyme has been widely investigated from the mechanistic and physiological viewpoints because the substrate is a precursor of the plant hormone ethylene and the enzymatic reaction includes a cyclopropane ring-opening. We have previously reported the crystal structure of the native enzyme. Here we report the crystal structures of the two reaction intermediates created by the mutagenesis complexed with the substrate. The substrate was validated in the active site of two forms: 1). covalent-bonded external aldimine with the coenzyme in the K51T form and 2). the non-covalent interaction around the coenzyme in the Y295F form. The orientations of the substrate in both structures were quite different form each other. In concert with other site-specific mutation experiments, this experiment revealed the ingenious and unique strategies that are used to achieve the specific activity. The substrate incorporated into the active site is reactivated by a two-phenol charge relay system to lead to the formation of a Schiff base with the coenzyme. The catalytic Lys51 residue may play a novel role to abstract the methylene proton from the substrate in cooperation with other factors, the carboxylate group of the substrate and the electron-adjusting apparatuses of the coenzyme.

Binding Sites↗

PubMed1979

Cyclopropane and Caesarean section.

In a prospective study 589 patients were anaesthetized by the inhalation of cyclopropane 40% for 2--3 min. Relaxation was provided with suxamethonium and anaesthesia was maintained with cyclopropane 7.5%. The series was divided into four groups: patients in optimal condition (96 elective (group 1), 164 emergency (group 3)) and those not in optimal condition (75 elective (group 2), 254 emergency (group 4)). All infants from groups 1 and 3 had high Apgar scores, and all survived. Infants in groups 2 and 4 had lower Apgar scores, eight and 96 respectively were depressed, and 10 and 20 died because of obstetric and neonatal factors unrelated to the anaesthesia. Respiratory distress syndrome (RDS) developed in 44 infants. Among 29 infants in whom the birth weight was less than 2.5 kg the mortality was 31%, whereas no death occurred in mature infants. RDS was significantly more frequent after elective than after emergency surgery. Neonatal depression was independent of the length of the induction-delivery interval, which averaged 13.3 min. The frequency of awareness was 1.5%.

Anesthesia, Inhalation↗

PubMed1979

Mutagenicity of inhalation anaesthetics: trichloroethylene, divinyl ether, nitrous oxide and cyclopropane.

The mutagenic potential of trichloroethylene, divinyl ether, nitrous oxide and cyclopropane was assessed in vitro by microbial assay employing two histidine-dependent strains of Salmonella typhimurium, TA1535 and TA100. Anaesthetic agents in various concentrations were incubated with bacteria in the presence or absence of an enzyme system prepared from enzyme-induced rat liver. Nitrous oxide and cyclopropane were not mutagenic, whereas divinyl ether gave a strongly positive response. Results for trichloroethylene were equivocal. These and previous studies with the salmonella system, together with mutagenicity studies using different test systems, indicate that modern inhalation anaesthetic agents are unlikely to be mutagenic.

Anesthesia, Inhalation↗

PubMed1999

Synthesis of carbocyclic nucleosides bearing a cyclopropane ring.

A carbocyclic cyclopropane fused nucleoside, 9-(c-4-hydroxymethylbicyclo[3.1.0]hex-r-2-yl)-9H-adenine, has been efficiently synthesized from 2-azabicyclo-[2.2.1]hex-5-en-3-one (ABH) in 6 steps, namely cyclopropanation, -reductive amide cleavage (RAC) reaction and adenine ring construction.

Antiviral Agents↗

PubMed1987

Explosive anaesthetic agents. A regional survey on the use of ether and cyclopropane.

A total of 156 consultant anaesthetists in the North East Thames Regional Health Authority were circulated with a questionnaire on their personal use of ether and cyclopropane and their attitudes towards restriction or withdrawal of these agents: 144 completed questionnaires were received (92% response). Four anaesthetists (3%) claimed to use ether regularly at least once a month and 27 anaesthetists (19%) felt that their anaesthetic practice would suffer if ether were withdrawn. Cyclopropane had 62 regular users (43%) and 65 anaesthetists (45%) felt that their practice would suffer if it were withdrawn. Ninety-two anaesthetists (64%) were prepared to confine their use of explosive agents to either the anaesthetic room or the operating room; of these, three-quarters favoured the anaesthetic room. There were few notable differences in the pattern of use of explosive agents between anaesthetists with more than 21 years in the specialty and those with less than 21 years.

Anesthesia, Inhalation↗

PubMed1984

Cryosensitivity of Escherichia coli and the involvement of cyclopropane fatty acids.

Strains of Escherichia coli proficient and deficient in cylopropane fatty acid synthesis were compared for fatty acid content, cryosensitivity, presence of freeze-thaw-induced wall and membrane damage, resistance to detergent-stimulated lysis and tolerance to salt and detergents during growth. The mutant populations synthesized much less cyclopropane fatty acids and were more resistant than the wild type to freezing and thawing in saline only, exhibiting less viability loss and less wall and membrane damage. While the resistance of the mutants to NaCl was unaltered, their detergent resistance was decreased under both growth and non-growth conditions. Although these physiological changes were associated with a lower cyclopropane fatty acid content in the mutant strains, it is proposed that the responses were due to the altered membrane fluidity of the mutants due to changes in their unsaturated fatty acid content.

Cyclopropanes↗

PubMed1971

Role of the chemoreceptor trigger zone in cyclopropane induced emesis in dogs.

Inhalation of cyclopropane in dogs, by the closed circuit method, for a fixed period, produced an emetic response during recovery from anaesthesia. Bilateral surgical ablation of the emetic chemoreceptor trigger zone of the area postrema rendered the dogs refractory to several times (3-6) the threshold emetic dose of cyclopropane.

Anesthetics↗

PubMed2004

Two-pore-domain K+ channels are a novel target for the anesthetic gases xenon, nitrous oxide, and cyclopropane.

Nitrous oxide, xenon, and cyclopropane are anesthetic gases that have a distinct pharmacological profile. Whereas the molecular basis for their anesthetic actions remains unclear, they behave very differently to most other general anesthetics in that they have little or no effect on GABAA receptors, yet strongly inhibit the N-methyl-d-aspartate subtype of glutamate receptors. Here we show that certain members of the two-pore-domain K+ channel superfamily may represent an important new target for these gaseous anesthetics. TREK-1 is markedly activated by clinically relevant concentrations of nitrous oxide, xenon, and cyclopropane. In contrast, TASK-3, a member of this family that is very sensitive to volatile anesthetics, such as halothane, is insensitive to the anesthetic gases. We demonstrate that the C-terminal cytoplasmic domain is not an absolute requirement for the actions of the gases, although it clearly plays an important modulatory role. Finally, we show that Glu306, an amino acid that has previously been found to be important in the modulation of TREK-1 by arachidonic acid, membrane stretch and internal pH, is critical for the activating effects of the anesthetic gases.

Anesthetics, Inhalation↗

PubMed1986

Methyl sterol and cyclopropane fatty acid composition of Methylococcus capsulatus grown at low oxygen tensions.

Methylococcus capsulatus contained extensive intracytoplasmic membranes when grown in fed-batch cultures over a wide range of oxygen tensions (0.1 to 10.6%, vol/vol) and at a constant methane level. Although the biomass decreased as oxygen levels were lowered, consistently high amounts of phospholipid and methyl sterol were synthesized. The greatest amounts of sterol and phospholipid were found in cells grown between 0.5 and 1.1% oxygen (7.2 and 203 mumol/g [dry weight], respectively). While sterol was still synthesized in significant amounts in cells grown at 0.1% oxygen, the major sterol product was the dimethyl form. Analysis by capillary gas chromatography-mass spectrophotometry showed that the phospholipid esterified fatty acids were predominantly 16:0 and 16:1 and that the hexadecenoates consisted of cis delta 9, delta 10, and delta 11 isomers. At low oxygen tensions, the presence of large amounts (25%) of cyclopropane fatty acids (cy 17:0) with the methylene groups at the delta 9, delta 10, and delta 11 positions was detected. Although the delta 9 monoenoic isomer was predominant, growth at low oxygen levels enhanced the synthesis of the delta 10 isomers of 16:1 and cy 17:0. As the oxygen level was increased, the amount of cyclopropanes decreased, such that only a trace of cy 17:0 could be detected in cells grown at 10.6% oxygen. Although M. capsulatus grew at very low oxygen tensions, this growth was accompanied by changes in the membrane lipids.

Cyclopropanes↗

PubMed1983

Comparison of the effects of acid and base hydrolyses on hydroxy and cyclopropane fatty acids in bacteria.

The cellular fatty acid compositions of Legionella oakridgensis, Brucella suis, Pseudomonas aeruginosa, and Francisella tularensis were compared after base hydrolysis (saponification), acid hydrolysis, and acid methanolysis procedures were used to release the fatty acids. The branched-chain, unsaturated, saturated, and ester-linked hydroxy acids were released as effectively with saponification at 100 degrees C for 30 min as with acid hydrolysis or acid methanolysis at 85 degrees C for 16 h. Although the amide-linked hydroxy acids were released more effectively by acid hydrolysis or acid methanolysis, these methods degraded the cyclopropane fatty acids, producing a number of new peaks or artifacts in the chromatograms. Cyclopropane fatty acids were not degraded by saponification, and at least 50% of the hydroxy acids were released when the cells were saponified with 15% NaOH in 50% aqueous methanol. Thus, the results show that saponification for 30 min at 100 degrees C with 15% NaOH, followed by methylation is an excellent method for routine fatty acid analysis of bacteria and for screening cultures whose identity and fatty acid composition are unknown.

Bacteria↗

PubMed1991

Measuring the lipid content of live animals using cyclopropane gas.

The cyclopropane technique was validated, and it accurately estimated the lipid mass of six pond turtles (Trachemys scripta). This technique provided more accurate estimates of lipid mass and lipid-free mass (by difference) than other nonfatal techniques. This technique was accurate despite the turtles' low lipid contents (0.71-3.5% of body mass), variable water contents (65-74% of body mass), and variable body temperatures (approximately 23-31 degrees C). A computer model of the cyclopropane technique revealed that an analytical error of 1% in variables measured (e.g., body water content and body temperature) may cause errors of less than 1-6% in lipid estimates.

Animals↗

PubMed1999

Synthesis of conformationally restricted analogs of baclofen, a potent GABAB receptor agonist, by the introduction of a cyclopropane ring.

Conformationally restricted analogs of baclofen (2), i.e., 5, 6, and their enantiomers ent-5, and ent-6, the conformations of which were restricted by introducing a cyclopropane ring, were designed as potential GABAB receptor ligands. Reaction of (R)-epichlorohydrin [(R)-7] and (4-chlorophenyl)acetonitrile in the presence of NaNH2 in benzene/tetrahydrofuran gave chiral cyclopropane derivatives 11 and 12, which were then converted into the target compounds 5 and 6, respectively. Their corresponding enantiomers, ent-5 and ent-6, were also synthesized starting from (S)-epichlorohydrin [(S)-7].

Animals↗

PubMed2001

Lewis acid-promoted cycloaddition reaction of cyclopropanes with allylsilanes.

The treatment of cyclopropanes having donor and acceptor substituents at the vicinal positions on the cyclopropane ring with a Lewis acid readily generates a 1,3-zwitterion, which reacted with allylsilanes to produce cycloadducts and allylic products. It was found that the yield of the cycloadduct depends on the steric demand of the alkyl substituents on the silicon atom.

Allyl Compounds↗

PubMed1990

Metabolism of illudin S, a toxic principle of Lampteromyces japonicus, by rat liver. I. Isolation and identification of cyclopropane ring-cleavage metabolites.

1. Illudin S, a toxic principle of the basidiomycete Lampteromyces japonicus, was incubated with rat liver 9000 g supernatant and its metabolites studied. 2. Two metabolites, M1 and M2, were isolated and identified as cyclopropane ring-cleavage compounds by n.m.r., i.r. and mass spectral analyses. Moreover, M2 contained a chlorine atom. 3. On the basis of detailed analyses of the 2D n.m.r. spectra and differential nuclear Overhauser effect experiments, the previous assignments of the cyclopropane carbons of illudin S were revised.

Animals↗

PubMed1984

Use of cyclopropane to test generality of anesthetic requirement in the elderly.

The minimum alveolar concentration (MAC) of cyclopropane was determined in young (mean age, 32 yr; n = 16) and older (mean age, 81 yr; n = 12) surgical patients. Cyclopropane requirement was 23% lower in the elderly (P less than 0.01). This reduction in anesthetic requirement with age is similar to that reported previously for halothane and isoflurane and supports the thesis of a general effect of age on anesthetic requirement.

Adult↗

PubMed2001

Synthesis and characterization of germanium, tin, phosphorus, iron, and rhodium complexes of tris(pentafluorophenyl)corrole, and the utilization of the iron and rhodium corroles as cyclopropanation catalysts.

The germanium(IV), tin(IV). and phosphorus(v) complexes of tris(pentafluorophenyl)corrole were prepared and investigated by electrochemistry for elucidation of the electrochemical HOMO-LUMO gap of the corrole and the spectroscopic characteristics of the corrole pi radical cation. This information was found to be highly valuable for assigning the oxidation states in the various iron corroles that were prepared. Two iron corroles and the rhodium(I) complex of an N-substituted corrole were fully characterized by X-ray crystallography and all the transition metal corroles were examined as cyclopropanation catalysts. All iron (except the NO-ligated) and rhodium corroles are excellent catalysts for cyclopropanation of styrene, with the latter displaying superior selectivities. An investigation of the effect of the oxidation state of the metal and its ligands leads to the conclusion that for iron corroles the catalytically active form is iron(III), while all accesible oxidation states of rhodium are active.

Journal Article↗

PubMed2003

Mechanisms of electrochemically-induced retro-cyclopropanation reactions of fullerene derivatives using digital simulations.

Three C(60) derivatives, 1, 2 and 3, have been studied by cyclic voltammetry (CV) under high vacuum in anhydrous tetrahydrofuran (THF). The CV behavior was essentially similar to that already observed for other cyclopropanated fullerene derivatives. After the second reduction processes all compounds undergo a chemical reaction that generates another electroactive species. This "new" chemical species is likely to be the compound with the cyclopropane ring open. Differences in CV behavior were observed for the different addends. Electrochemical data obtained at different scan rates for a given potential window, were fit with the BAS digital simulation program, DigiSim. The purpose of this study was to probe the proposed mechanisms and to obtain reliable estimations of the kinetic constants for the homogeneous chemical reactions taking place during the CV experiments. Calculations at the PM3 level lend additional support to the conclusions derived from digital simulations. The proposed mechanism is similar for all the compounds and involves two main chemical reactions in a reversible square scheme.

Journal Article↗