Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Complex Mixtures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 307 records · Page 17Linked to original sources
PubMed2002

Application of (1)h NMR and multivariate statistics for screening complex mixtures: quality control and authenticity of instant coffee.

Principal components analysis (PCA) followed by linear discriminant analysis (LDA) of the nuclear magnetic resonance (NMR) spectra from 98 instant spray-dried coffees, obtained from 3 different producers, correctly attributed 99% of the samples to their manufacturer. Blind testing of the PCA model with a further 36 samples of instant coffee resulted in a 100% success rate in identifying the samples from the 3 manufacturers. Coffees from one manufacturer were also assigned into 2 groups using these techniques, and the compound 5-(hydroxymethyl)-2-furaldehyde was identified as the primary marker of differentiation.

Analysis of Variance↗
PubMed2003

Multitarget affinity/specificity screening of natural products: finding and characterizing high-affinity ligands from complex mixtures by using high-performance mass spectrometry.

In this work we describe a high-throughput screening approach based on electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR) that rapidly interrogates the noncovalent interaction between RNA-based drug targets and components derived from a bacterial natural product library. The screening process detects molecules present in the natural product library that bind to a synthetic RNA target that mimics the prokaryotic 16S rRNA A-site, while simultaneously measuring specificity for the synthetic A-site target using a control RNA target that lacks the critical structural element of the A-site construct. This screening approach known as multitarget affinity/specificity screening (MASS) demonstrated the expected binding of paromomycin from a fractionated natural product library derived from Streptomyces rimosus sp. paromomycinus. A new molecule was observed to bind with specificity to the 16S A-site RNA construct. MS/MS characterization of this species yielded partial structural information suggesting it is an aminoglycoside consisting of a paromomycin core with one or more modified rings. This work demonstrates the tremendous utility of MASS for screening natural product fractions against macromolecular targets.

Base Sequence↗
PubMedDate not supplied

Differences in the tumorigenic activity of a pure hydrocarbon and a complex mixture following ingestion: benzo[a]pyrene vs manufactured gas plant residue.

The tumorigenic activity of manufactured gas plant residue (MGP) was evaluated in female A/J mice using a F0927 basal gel diet system. Adulterated diets containing MGP (0.10% or 0.25%) or benzo[a]pyrene (B[alpha]P; 16 or 98 ppm) were fed for 260 days. A negative control group was maintained on a nonadulterated basal gel diet. Mice dosed with a single ip injection of 1.79 mg of B[a]P in a tricaprylin vehicle and maintained on a NIH-07 pellet diet were positive controls. In addition, a nontreated group of mice and a group dosed with vehicle only were maintained on a NIH-07 pellet diet and used as negative controls. Animal body weight and consumption of MGP and B[a]P were monitored throughout the study. Ingestion of a 0.10 or 0.25% MGP adulterated diet resulted in 70 and 100% of the mice developing lung tumors with a multiplicity of 1.19 and 12.17 tumors/mouse, respectively. Mice maintained on a 0.10% MGP diet consumed 0.7 g of MGP containing 1.8 mg of B[a]P while those fed a 0.25% MGP diet ingested 1.5 g of MGP containing 4.2 mg of B[a]P. The incidence of lung tumors in mice fed only B[a]P was considerably lower than that observed for animals fed a MGP diet. A diet containing 98 ppm B[a]P produced a significant incidence of tumor-bearing mice with 52% developing lung tumors. The multiplicity observed in these animals, however, was not significant at 0.59 tumors/mouse. A diet containing 16 ppm B[a]P did not produce a significant tumorigenic response in lung. Animals fed a 16 or 98 ppm B[a]P diet consumed a total of 11 and 67 mg of B[a]P, respectively. A single ip dose of B[alpha]P (1.79 mg in 0.25 mL of tricaprylin) resulted in 100% lung tumorigenesis with a multiplicity of 15.79 tumors/mouse. In contrast to observed induction of lung tumors, no forestomach tumors were detected in any animal fed a 0.10 or 0.25% MGP adulterated diet. However, ingestion of a diet containing only 16 or 98 ppm of B[a]P resulted in 20 and 100% of the mice developing forestomach tumors, respectively. The multiplicity for forestomach tumors was 0.24 and 4.22 tumors/mouse, respectively. The incidence of forestomach carcinomas in tumor bearing mice was 8 and 52%, respectively. The ip administration of 1.79 mg of B[a]P resulted in an 83% forestomach tumor incidence having a multiplicity of 1.83 tumors/mouse. Forestomach carcinomas were induced in 34% of the mice exhibiting forestomach tumors. These data indicate that chronic ingestion of MGP- or B[a]P-adulterated diets produces significant differences in the tumorigenic response of female A/J mouse forestomach and lung tissues.

Adenocarcinoma↗
PubMed1997

Determination of complex mixtures of airborne isocyanates and amines. Part 3. Methylenediphenyl diisocyanate, methylenediphenylamino isocyanate and methylenediphenyldiamine and structural analogues after thermal degradation of polyurethane.

A method is presented for the determination of isocyanates in polymeric methylenediphenyl diisocyanate (MDI) and related compounds formed during the thermal decomposition of polyurethane (PUR). Derivatization of isocyanates was performed in impinger flasks containing dibutylamine (DBA) with the formation of urea derivatives. Compounds containing amine groups were then derivatized with ethyl chloroformate (ET to give urethane derivatives. Reversed-phase liquid chromatography, with a gradient flow rate of 40 milligrams min-1 and mass spectrometry in the electrospray mode monitoring positive ions was studied. Injection volumes of up to 10 milligrams of the sample were made possible by using column focusing. 1,5-Naphthyldiisocyanate-DBA and 1,5-naphthyldiamine-ET derivatives were used as internal standards. Virtually linear calibration curves were obtained for 4,4'-MDI-DBA and 4,4'-methylenediphenyldiamine-ET (MDA-ET) and the correlation coefficients were 0.9952-0.9964 (n = 14). The precision for five injections of samples spiked with 4,4'-MDA-ET, and 4,4'-MDI-DBA ar concentrations of 50 nmol ml-1 was 2.76 and 2.55%, respectively. The instrumental detection limit, defined as three times the noise, was 4 fmol of MDI-DBA and 50 fmol of MDA-ET injected. In chromatograms of polymeric MDI derivatized with diethylamine, dipropylamine and DBA, the presence of several structural isomers and analogues in polymeric MDI was demonstrated. In the chromatograms of thermal decomposition products of MDI-PUR, in addition to isocyanates, related amino isocyanates and amines were also observed.

Air Pollutants, Occupational↗
PubMed1998

Determination of complex mixtures of airborne isocyanates and amines. Part 5. Determination of low molecular weight aliphatic isocyanates as dibutylamine derivatives.

A method is presented for the determination of low molecular weight aliphatic isocyanates, methyl isocyanate (MIC), ethyl isocyanate (EIC), propyl isocyanate (PIC) and butyl isocyanate (BIC), as their dibutylamine (DBA) derivatives. The method is based on sampling in midget impinger flasks containing 10 ml of 0.01 mol l-1 DBA in toluene (as in Parts 1-4 in this series). The samples are analysed using liquid chromatography-electrospray mass spectrometry (LC-ESP-MS) or gas chromatography-mass spectrometry using chemical ionisation with ammonia, monitoring positive ions (GC-PCI). Quantification was effected by monitoring the molecular ions MH+. Aliquots of 10 ml of toluene solutions containing 0.01 mol l-1 DBA were spiked with 0.03-0.85 microgram of MIC-, EIC-, PIC- and BIC-DBA. The correlation coefficients for LC-ESP-MS were in the range 0.9952-0.9999 (n = 14). The repeatability (RSD) was in the range 0.37-1.2% (0.12-0.34 microgram ml-1, n = 10). The instrumental detection limit for MIC was about 15 micrograms l-1, which corresponds to about 0.5 microgram m-3 in a 15 l air sample. The correlation coefficients for GC-PCI were in the range 0.9913-0.9990. The repeatability (RSD) was in the range 1.1-4.9% (0.12-0.34 microgram ml-1, n = 10). The instrumental detection limit for MIC was about 0.2 microgram l-1, which corresponds to about 0.05 microgram m-3 in a 15 l air sample. Using electron ionisation, the instrumental detection limit for MIC was about 10 micrograms l-1. No derivatisation reaction losses were seen when the derivatization reaction between PIC and DBA took place in the presence of morpholine, propylamine, ethanol, phenol and water. When mineral wool with a phenol-formaldehyde-urea resin was thermally degraded, 0.1% m/m of MIC was released. In air samples taken on top of a new electric oven insulated with mineral wool, MIC was found in the range 0.1-3 mg m-3. No MIC in air was found from a pre-heated oven.

Air Pollutants, Occupational↗
PubMed2000

Resolution of benzo[a]pyrene in complex mixtures of other polycyclic aromatic hydrocarbons. Comparison of two spectrofluorimetric methods applied to water samples.

Two spectrofluorimetric methods, second-derivative constant-energy synchronous luminescence (SDCESL) and constant-wavelength synchronous luminescence (CWSL) in combination with multiple linear regression (MLR), for the quantification of benzo[a]pyrene (BaP) at sub-ng mL-1 levels, in the presence of benzo[b]fluoranthene (BbFt), benzo[k]fluoranthene (BkFt), benzo[ghi]perylene (BghiP) and indeno[1,2,3-cd]pyrene (IP), were developed and compared in detail. SDCESL presents lower limits of detection and quantification than CWSL/MLR and also gives more exact and precise results for levels close to the quantification limit. For BaP, SDCESL achieved quantification limits of 0.019 ng mL-1 in river waters and 0.007 ng mL-1 in drinking waters. This work offers a sensitive, precise, accurate, rapid, simple and economic methodology for monitoring BaP in waters for public consumption, meeting all the requirements of the EC Directive 98/83/CE that fixes the maximum admissible limit for this polycyclic aromatic hydrocarbon in drinking waters at of 0.010 ng mL-1.

Benzo(a)pyrene↗
PubMed2000

In vitro cloning of complex mixtures of DNA on microbeads: physical separation of differentially expressed cDNAs.

We describe a method for cloning nucleic acid molecules onto the surfaces of 5-micrometer microbeads rather than in biological hosts. A unique tag sequence is attached to each molecule, and the tagged library is amplified. Unique tagging of the molecules is achieved by sampling a small fraction (1%) of a very large repertoire of tag sequences. The resulting library is hybridized to microbeads that each carry approximately 10(6) strands complementary to one of the tags. About 10(5) copies of each molecule are collected on each microbead. Because such clones are segregated on microbeads, they can be operated on simultaneously and then assayed separately. To demonstrate the utility of this approach, we show how to label and extract microbeads bearing clones differentially expressed between two libraries by using a fluorescence-activated cell sorter (FACS). Because no prior information about the cloned molecules is required, this process is obviously useful where sequence databases are incomplete or nonexistent. More importantly, the process also permits the isolation of clones that are expressed only in given tissues or that are differentially expressed between normal and diseased states. Such clones then may be spotted on much more cost-effective, tissue- or disease-directed, low-density planar microarrays.

Cloning, Molecular↗
PubMedDate not supplied

Suppression of arylamine toxicity in the Fischer-344 rat following ingestion of a complex mixture.

The toxic effects of a mixture of 2-aminoanthracene (2-AA), benzanthracene (BA), and dinitropyrene isomers (DNP), and the toxic effects of these compounds individually, were investigated in the Fischer-344 rat following dietary exposure via a powdered basal diet. Animals were sacrificed at 14-, 30-, and 80-days of dietary exposure. Exposure to dietary 2-AA alone induced anorexia, cachexia, variable mortality, and altered serum chemistry profiles in the F-344 rat. Reduced lymphocyte counts were also shown in rats exposed to 2-AA. A temporal pattern of effect of 2-AA dietary exposure was observed in the progression of hepatic lesions in exposed animals. Dietary exposure to either DNP isomers or BA at a 10-fold higher concentration in the diet, relative to 2-AA, did not induce detectable toxic responses. However, exposure of rats to a mixture of 2-AA, BA, and DNP isomers (100 mg/kg, 1.0 g/kg, and 1.0 g/kg of diet, respectively) resulted in the attenuation of toxic effects when compared to exposure of F-344 rats to 2-AA alone. These results indicate that the toxic effects of 2-AA are suppressed by co-administration of DNP and BA and suggest that compound interactions need to be considered when predicting the toxic potential of specific environmental pollutants.

Alanine Transaminase↗
PubMed1992

Analysis of complex mixtures of vapors in ambient air by fast-gas chromatography.

The use of Fast-GC was investigated for the separation and analysis of mixtures of organic vapors in ambient air. Mixtures of up to 34 components were separated and total analysis times ranged from 8 to 100 seconds. Analyses were performed using both flame ionization and electron capture detectors. Up to 950 effective theoretical plates per second were produced when the flame ionization detector was used, and up to 300 per second when the electron capture detector was used. Theoretical predictions of optimal analysis conditions and of column performance matched experimental results.

Air↗
PubMed2005

Biofilter treatment of volatile organic compound emissions from reformulated paint: complex mixtures, intermittent operation, and startup.

Two biofilters were operated to treat a waste gas stream intended to simulate off-gases generated during the manufacture of reformulated paint. The model waste gas stream consisted of a five-component solvent mixture containing acetone (450 ppm(v)), methyl ethyl ketone (12 ppm(v)), toluene (29 ppm(v)), ethylbenzene (10 ppm(v)), and p-xylene (10 ppm(v)). The two biofilters, identical in construction and packed with a polyurethane foam support medium, were inoculated with an enrichment culture derived from compost and then subjected to different loading conditions during the startup phase of operation. One biofilter was subjected to intermittent loading conditions with contaminants supplied only 8 hr/day to simulate loading conditions expected at facilities where manufacturing operations are discontinuous. The other biofilter was subjected to continuous contaminant loading during the initial start period, and then was switched to intermittent loading conditions. Experimental results demonstrate that both startup strategies can ultimately achieve high contaminant removal efficiency (>99%) at a target contaminant mass loading rate of 80.3 g m(-3) hr(-1) and an empty bed residence time of 59 sec. The biofilter subjected to intermittent loading conditions at startup, however, took considerably longer to reach high performance. In both biofilters, ketone components (acetone and methyl ethyl ketone) were, more rapidly degraded than aromatic hydrocarbons (toluene, ethylbenzene, and p-xylene). Scanning electron microscopy and plate count data revealed that fungi, as well as bacteria, populated the biofilters.

Air Pollution↗
PubMedDate not supplied

Quantifying the toxic and mutagenic activity of complex mixtures with Salmonella typhimurium.

The toxicity and mutagenicity of 11 compounds individually and in mixtures were quantified in Salmonella typhimurium strains TA98, TA100, and TA1537 by a modification of the Ames spot test. The distance (millimeters) from the center of the petri dish to the bacterial growth front represented the toxic response. When mutagenicity occurred, the distance from the inner radius to the outer radius of the mutagenic growth represented the mutagenic response. Multiple regression analysis was used to quantify the toxicity and mutagenicity of individual compounds in the mixtures. The results indicate that the effects of compounds in mixtures are generally additive.

Azaserine↗
PubMed1976

Effect of essential and nonessential fatty acids in complex mixture on fatty acid composition of liver lipids.

Linoleate, linolenate, arachidonate, docosahexenoate and six other fatty acids were major components of 24 ester preparations fed as 5% of the diet for 60 days to groups of male white rats. The experiment was designed so as to provide that all major fatty acid components were independent of each other in the sense that the intake of each was poorly correlated with the intake of any of the others. Fatty acid compositions of liver lipids were determined and were related to the composition of the diet lipids. Linolenate and docosahexaenoate contents of diet and tissue revealed the same relationships reported previously from experiments in which individual pure acid esters were added to a fat-free diet. Linoleate, when fed in lipid mixtures, was more effective in raising the linoleate concentration in liver lipids than when fed alone, but this increase did not change the shape of the dose-response curve or the estimated nutritional requirement. Large amounts of fish oil in the diet tended to depress the arachidonate concentration in tissue lipids.

Animals↗