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The effects due to steric hindrance on solute-solvent interactions and on diffusion of associated molecules were found by comparing the diffusion coefficients of different aromatic isomers in acetone at 298.2 K; there exists a correlation between the isomeric effects of intermolecular association on diffusion and the molecular scales of overall hydrogen-bond acidity of the isomers studied.
The quantum yield of CO in the laser pulse photolysis of acetone at 248 nm and at 298 K in the pressure range 20-900 mbar (N2) has been measured directly using quantitative infrared diode laser absorption of CO. It is found that the quantum yield of CO shows a significant dependence on total pressure with Phi(CO) decreasing with pressure from around 0.45 at 20 mbar to approximately 0.25 at 900 mbar. From a combination of ab initio quantum chemical calculations on the molecular properties of the acetyl (CH3CO) radical and its unimolecular fragmentation as well as the application of statistical (RRKM) and dynamical calculations we show that CO production results from prompt secondary fragmentation (via(2a)) of the internally excited primary CH3CO* photolysis product with an excess energy of approximately 62.8 kJ mol(-1). Hence, our findings are consistent with a consecutive photochemically induced decomposition model, viz. step (1): CH3COCH3+hv--> CH3CO*+ CH3, step (2a): CH3CO*--> CH3+ CO or step (2b) CH3CO*-(+M)--> CH3CO. Formation of CO via a direct and/or concerted channel CH3COCH3+hv--> 2CH(3)+ CO (1') is considered to be unimportant.
Based on recent detailed quantum mechanical computations of the mechanism of the title reaction and, this paper presents kinetics analysis of the overall rate constant and its temperature dependence, for which ample experimental data are available for comparison. The analysis confirms that the principal channel is the formation of acetonyl radical + H(2)O, while the channel leading to acetic acid is of negligible importance. It is shown that the unusual temperature dependence of the overall rate constant, as observed experimentally, is well accounted for by standard RRKM treatment that includes tunneling. This treatment is applied at the microcanonical level, with chemically activated distribution of entrance species, i.e. using a stationary rather than a thermal distribution that incorporates collisional energy transfer and competition between the redissociation and exit channel. A similar procedure is applied to the isotopic reaction acetone-d6 + OH with equally satisfying results, so that the experimental temperature dependence of the KIE (kinetic isotope effect) is perfectly reproduced. This very good agreement between calculation and experiment is obtained without any fitting to experimental values and without any adjustment of the parameters of calculation.
Freeze-drying procedures were developed to enable collection of tissues from Drosophila flies. The flies were frozen in acetone at -86 or -94 degrees C, and dehydrated therein. After drying, many tissues could be easily taken in entirety and free of neighbouring tissues without action of degradative enzymes. Seven polypeptide species specific to retina, and nine specific to cornea, were identified on two-dimensional electrophoretograms. Phospholipids of the dried tissues could be studied by t.l.c., and phosphatidic acid of the fly head was found to occur predominantly in the retina. Activity of three enzymes in the dried tissues could be assayed. The results of protein, phospholipid and enzyme analyses were corroborated by analyses by 'genetic dissection' using an eyeless mutant line.
The authors have previously isolated a solvent tolerant bacterium, strain G(T), (T = type strain) capable to convert acetone-butanol bioprocess residues into poly-beta-hydroxybutyrate. Strain G(T) was initially identified as Alcaligenes spp by standard bacteriological tests. In this study the taxonomic position of the bacterium was investigated in detail. The 165 rDNA sequence analysis, the G + C content of DNA (56 mol%) and the presence of ubiquinone Q-8 confirmed strain G(T) as a representative of the genus Alcaligenes. In the polyamine pattern of the bacterium putrescine and cadaverine were detected, but only trace amounts of 2-hydroxyputrescine. The extremely low content of 2-hydroxyputrescine is remarkable, since this unique diamine is a common marker for beta-proteobacteria. Phylogenetic analyses of 16S rDNA demonstrated that Alcaligenes sp. G(T) is most closely related to the species Alcaligenes faecalis (99.6% sequence similarity to A. faecalis HR4 and 98.7% sequence similarity to A. faecalis [ATCC 8750T = DSM 30030T]. On the basis of DNA-DNA relatedness (56% similarity), the unique polyamine pattern, the physiological and biochemical differences strain G(T) could be distinguished from the species A. faecalis. Therefore, a new subspecies for the species Alcaligenes faecalis is proposed; Alcaligenes faecalis subsp. parafaecalis subsp. nov.
Isolation of soybean agglutinin (SBA) by the salt fractionation involves excessive amounts of (NH4)2SO4. We have found that SBA could be fractionally precipitated from an aqueous extract by adding acetone (40% final concentration). It is stable under these conditions for minimum 2 h at 5 degrees C and 25 degrees C. Incorporating these results, an improved procedure for the isolation of SBA has been developed. The SBA isolated by this method is obtained in better yield, has 6000 HU/mg protein and is identical to that isolated by the (NH4)2SO4 method as ascertained by chromatographic and electrophoretic comparisons and hapten inhibition assays.
The fatty acid composition of lecithin has been determined separately at the 1- and 2-position in 22 samples of amniotic fluid. Palmitic acid (16:0) was the main fatty acid present at both carbon atom positions throughout the last trimester. Myristic acid (14:0) was present in very small amounts only. There was no evidence of 1-palmitoyl/2-myristoyl lecithin being present in more than trace amounts before 35 weeks of gestation. The positional specificity of the methylation pathway is therefore doubtful. Acetone precipitation of lecithin did not alter the observed fatty acid composition at either position, indicating that this procedure precipitates the different lecithin subspecies in equal proportion, without any preference for disaturated species. This method therefore fails to isolate a lecithin fraction with a specific fatty acid composition.
The ocular irritation responses to 11 different surfactants and two concentrations of acetic acid and sodium hydroxide have been shown to depend on the extent of initial injury, despite marked differences in the processes leading to tissue damage. The purpose of these studies was to determine the extent to which this fundamental relationship applies to other nonsurfactants. Ten microl of acetone (ACT). cyclohexanol (CY), parafluoroaniline (PF), or 37% formaldehyde (FA) was directly applied to the cornea of the right eye of each rabbit. Eyes and eyelids were macroscopically scored for signs of irritation beginning 3 hours after dosing and periodically until recovery or 35 days. Tissues were obtained for light microscopic examination after 3 hours and on days 1, 3, and 35. Initial corneal injury was characterized quantitatively at 3 hours and I day using in vivo confocal microscopy (CM) and by postmortem quantitation of dead corneal epithelial cells and keratocytes using a Live Dead Assay (L/D, Molecular Probes) and scanning laser CM. Corneal changes over time were characterized quantitatively using in vivo CM performed at 3 hours and 1, 3, 7, 14, and 35 days. The changes with ACT were consistent with mild irritation. Corneal injury was limited to the epithelium and superficial stroma, with the mean normalized depth of injury (NDI) being less than 10% with the majority of regions showing no stromal injury. Changes with CY and PF were consistent with moderate to severe irritation, and FA caused severe irritation. Specifically, corneal injury by CY and PF tended to involve the epithelium and anterior stroma, with the mean NDI being 10.4% to 23.8%, while injury with FA involved the epithelium, deep stroma, and at times the endothelium. Interestingly, with FA significantly less injury was observed at 3 hours with a dramatic increase in injury observed at 1 day and thereafter. In conclusion, these results continue to support and extend our hypothesis that ocular irritation is principally defined by the extent of initial injury despite clear differences in the means by which irritants cause tissue damage. We believe this approach can be applied to developing alternative assays based on injury to ex vivo eyes or injury to an in vitro corneal equivalent system.
The biofilter process is a relatively new technology that has been proven more cost-effective than traditional technologies for treating low-strength and some high-strength volatile organic compounds (VOCs) from waste gases. Acetone (AT) and methylacetate (MA) mixtures are commonly encountered from the manufacture of artificial rubber or polyurethane resin. This research attempts to employ a trickle-bed air biofilter (TBAB) for treating AT and MA mixtures under different influent carbon loadings. In the pseudo-steady-states, the elimination capacities of AT and MA increased but the removal efficiencies decreased with increased influent carbon loading. The removal efficiencies of MA were higher than those of AT showing that MA is a preferred substrate in the ATMA waste gas and the differences were enhanced at a high carbon loading. Greater than 95% AT removal and nearly complete MA removal were achieved with influent carbon loadings of AT and MA below 20 and 27 g m(-1) h(-1), respectively. The TBAB appears very efficient for treating ATMA emission with low to medium carbon loadings.
Toluene diisocyanate (TDI) is a widely used raw material in the manufacture of flexible polyurethane foams. Acetone (ACE) and/or methylenechloride (MECL) solvents are the most commonly used solvent-based blowing agents for TDI foams. ACGIH has recommended a TWA exposure limit of 5 ppb for TDI and 500 ppm for ACE. For MECL, OSHA mandates a TWA-exposure limit of 25 ppm. This study evaluated the ability of the organic-vapor respirator cartridges (OVC) to block TDI, as well as the effect of airborne MECL or ACE on the OVCs' efficiency to capture TDI. An aluminum/stainless steel exposure chamber was constructed for simultaneously challenging OVCs in triplicate with a dynamic atmosphere of TDI and ACE or MECL vapor. The challenge atmosphere was generated by combining a TDI-laden nitrogen stream from the headspace of a heated impinger with a humidified stream of the indicated solvent in air. The average challenge concentration for TDI was 275 ppb. The average MECL or ACE concentrations were 547 and 581 ppm, respectively. The challenge atmosphere at room temperature (approximately 24 degrees C) and at 25 or 80 percent relative humidity was drawn through each cartridge at 32 L/min for 40+ hours. During the last 8 hours of the challenge, the atmosphere had only TDI vapor. The pre- and post-cartridge atmospheres were periodically sampled for TDI and solvent. Five tests were conducted--two with MSA and three with North OVCs. Under these extreme test conditions no TDI breakthrough was detected from any OVC. The average-calculated efficiency of the OVCs for TDI was >99.9+ percent. Within the first 6 hours of the challenge the cartridges were saturated with ACE or MECL; nevertheless, continued challenging with TDI and solvents did not cause any TDI breakthrough. The study demonstrates that with an OSHA-compliant respiratory protection program, an OVC can safely be used for 40 hours in most polyurethane foam operations. In typical occupational environments using TDI and solvents, the solvent breakthrough, rather than TDI breakthrough, would be the determining factor for the calculation of respirator cartridge change-out schedules.
A sorptive slurry bioscrubber adds powdered activated carbon (PAC) to a conventional suspended-growth bioscrubber. The activated carbon increases pollutant removal from the gas phase due to adsorption on carbon. The carbon is bioregenerated in the oxidation reactor and recycled to the scrubbing column. A three-stage, conventional bioscrubber was tested with and without carbon. The experiments showed that the PAC improved the removal efficiency of the system and that bioregeneration occurred. At an inlet gas-phase acetone concentration of 50 ppmv, the steady-state removal increased from 88 to 95% when activated carbon was added to the biological slurry.
The increased interest in protective capacity of chemical protective clothing materials has resulted in an increasing number of reports from permeation testing, performed by various test procedures and with permeation cells of different configurations. To make it possible to compare the resultant data, it is necessary to identify what parameters will have a decisive influence on test results. The influence of various carrier gas flow rates on breakthrough time and permeation rate of acetone through gloves made of neoprene was investigated using three permeation cells of different configurations. The breakthrough times were not influenced by cell design or gas flow rate. On the other hand, both cell configuration and gas flow rate influenced the steady-state permeation rate.
Groups of hairless mice were painted with the carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) dissolved in reagent-grade acetone in various doses, dose fractions and concentrations. The animals were examined once a week for an appropriate time period and skin tumors were registered and classified as tumors (all tumors appearing) and as malignant tumors. The results show that dividing a particular dose of DMBA into an increasing number of applications was the factor that had the greatest tumorigenic and carcinogenic effect. This was found for total doses of 100, approximately 50 and approximately 26 micrograms DMBA. Similarly, increasing the size of the dose increased the effect on the tumor and carcinoma crop, but to a less pronounced event than splitting the dose into several fractions. The most striking of these effects was that a single dose of 51.2 micrograms DMBA gave a tumor rate of approximately 40%, whereas the same dose divided into 50 doses of 1 microgram gave a tumor rate of almost 100%. The final tumor yield increased from approximately 45 tumours per 32 animals after a single dose of 51.2 micrograms DMBA to approximately 250 tumors per 32 animals after 50 applications of 1 microgram DMBA. The final number of carcinomas per 32 animals was one carcinoma after a single application of 51.2 micrograms DMBA, and 40 carcinomas after 50 applications of 1 microgram DMBA. The paper includes a discussion on how these findings may be explained in terms of the complicated series of events that constitutes carcinogenesis. If it is biologically plausible to regard agents for which there is sufficient evidence for carcinogenicity in experimental animals as representing a carcinogenic risk to humans, then it may also be plausible and prudent to infer that the dose schedule that represents the highest tumorigenic hazard for mouse skin may generally also be the dose schedule that involves the highest risk for humans. Thus, repeated exposure to small doses may be the most hazardous situation. This is unfortunately the way many human beings are exposed to cigarette smoke, sunshine and carcinogens in food, water, air and at the work place. As shown in a previous paper, an increasing time interval between each dose may also increase the risk.
This study aimed to elucidate the potential correlation between gut microbiota and intrahepatic cholangiocarcinoma (ICC) by investigating their causal relationship, while also exploring the possible role of immune cells as mediators in this association. We first identified gut microbiota based on phylum, class, order, family, and genus level information. Using summary-level data from a Genome-Wide Association Study (GWAS), we performed a 2-sample Mendelian randomization (MR) analysis of ICC and gut microbiota. Furthermore, we used 2-step MR to quantify the proportion of the effect of immune cell-mediated gut microbiota on ICC. MR analysis identified pyruvate fermentation to acetone (PFA) as predicting ICC risk reduction. There was no strong evidence that genetically predicted ICC had an effect on PFA risk. Furthermore, the proportion of genetically predicted PFA mediated by CD25hi CD45RA+ CD4 not Treg %T cell (CCCTT) was 3% (95% CI: 0.93-5.03%). In conclusion, our study established a causal relationship between PFA and ICC. We observed that a minor fraction of this effect was mediated by CCCTT, while the majority of the impact exerted by PFA on ICC remains elusive. However, further investigations are warranted to elucidate the mechanisms underlying the influence of gut microbiota on ICC development.
When crystals of kynostatin (KNI)-272, a highly selective HIV protease inhibitor containing allophenylnorstatine [(2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid], were grown in three different solvent systems (methanol, acetone and dimethylsulfoxide solutions), the local conformations around the hydroxymethylcarbonyl (HMC) moiety, which mimics the structure of the transition state, were similar in all three forms. The peptide backbones were slightly bent, but their structures differed from typical sheets, turns or helixes. Although the isoquinoline ring at the N-terminal showed conformational variations, a remarkable similarity was observed in the C-terminal region, including the HMC moiety. Moreover, the conformational characteristics of the uncomplexed forms resembled those of the inhibitor within the KNI-272-HIV protease complex. This suggests that the structure of the C-terminal region of KNI-272 is rigid or very stable.
The crystal structures of hydroxynitrile lyase from Manihot esculenta (MeHNL) complexed with the native substrate acetone and substrate analogue chloroacetone have been determined and refined at 2.2 A resolution. The substrates are positioned in the active site by hydrogen-bond interactions of the carbonyl O atom with Thr11 OG, Ser80 OG and, to a lesser extent, Cys81 SG. These studies support a mechanism for cyanogenesis as well as for the stereospecific MeHNL-catalyzed formation of (S)-cyanohydrins, which closely resembles the base-catalyzed chemical reaction of HCN with carbonyl compounds.
A highly sensitive gas chromatographic assay was used to measure volatile organic compounds in the breath. Samples of breath from three groups of subjects were studied: normal volunteers (n = 15), acutely intoxicated alcohol abusers (n = 11), and abstinent alcohol abusers (n = 13). Acetone levels were significantly higher in the acutely intoxicated subjects than in the normals (p less than 0.05) or the abstinent alcohol abusers (p less than 0.05). Chromatographic peaks arising from 13 unidentified compounds in the breath were observed; two of these unidentified compounds were observed only in the intoxicated and abstinent alcohol abusers. Statistically significance was achieved in only one unidentified peak; elevated levels of this compound were seen in both acutely intoxicated alcohol abusers (p less than 0.01) and in the abstinent alcohol abusers (p less than 0.01) when they were compared to normal subjects.
Plasminogen activator (PGA), kininogenase (Kase) and benzoyl arginine ethyl ester (BAEe) activities generated in plasminogen-free rat plasma by incubation with acetone (23% v/v) at 22 degrees were purified. The activities passed unadsorbed through columns of DEAE-Sephadex A-50 (pH 7.8) and arginine methylester-Sepharose 4B (pH 8.5). Part of the activities (rat plasma kallikrein) was adsorbed onto a soybean trypsin inhibitor (SBTI)-Sepharose 4B column at pH 8.5. At pH 7.0 a fraction with higher ratios PGA/BAEe esterase and Kase/BAEe esterase was also adsorbed. Both fractions could be eluted with 5 mM sodium hydroxide. The fraction not adsorbed at pH 8.5, but adsorbed at pH 7.0 was designated low molecular weight plasminogen activator (LMr-PGA), a plasminogen activator fraction with higher molecular weight, but without esterase activity being also present (Berstad & Briseid 1982). LMr-PGA was strongly inhibited by tranexamic acid (AMCA) 0.10 mM, whereas the fraction designated rat plasma kallikrein was not. By polyacrylamide gel electrophoresis Mr-values in the range 120,000 to 130,000 were established for native samples of both rat plasma kallikrein and LMr-PGA, whereas Mr-values of 78,000 to 80,000 were established after treatment with SDS.