SEARCH · Search PubMed
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.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A simple, sensitive technique for detecting proteolytic enzyme zones on electrophoretograms by making contact print zymograms is described. The method is applicable to electrophoretograms prepared on a variety of support media, immunoelectrophoretograms or isoelectric focusing patterns on various media. The contact print zymograms are prepared by placing unfixed, unstained electrophoretograms in contact with a thin film of casein which has diffused into a layer of agarose supported by a hydrophilic polyester film. After staining the casein film with Coomassie blue, the proteolytic zones are detected as clear zones against a blue background. The method can detect as little as 9 ng of trypsin. The utility of the method is illustrated by detection of the proteinase enzymes in thermophilic actinomycete antigen preparations separated by polyacrylamide electrophoresis, crossed immunoelectrophoresis and isoelectric focusing on agarose and granulated dextran supports.
The Finney harmonic mean model for joint toxicity of ingredients in mixtures can be used to estimate the toxicity of the neat compound if each component can be substituted in potency-adjusted-doses for any of the other components. Chemical analysis of constituent substances and their associated concentrations and relative toxicological potency values (computed according to the RApid Screening of Hazard (RASH) method) were used to compare the toxicities as predicted from ingredients of cigarette smoke, PAHs in diesel exhaust, asphalt, coal tar, pitch, and creosote with the measured toxicities of the corresponding neat mixtures. Accuracy for cigarette smoke condensate, coal tar, pitch, and creosote were within a factor of three based on the PAH fraction; asphalt was within a factor of 18; but the PAH fraction of diesel particulate was again found to be inadequate to describe the composite toxicity of diesel emissions.
A novel way is presented for determination of the stoichiometry of ribosomal proteins in the ribosome. The 70S E. coli r-proteins, completely separated on a two-dimensional gel system, were used throughout our experiments. The method is based on our previous observation that the amount of Coomassie R bound to a protein molecule is directly proportional to the number of positive charges on that protein. By plotting the amount of bound Coomassie as a function of the number of positive charges of each r-protein, and relating the experimental amount of the dye bound to each r-protein to the value obtained from the linear regression line based on all (a total of some 50 proteins), one can obtain the molar concentration of every protein in the ribosome. A parallel experiment can be carried out, which relates the radioactivity contributed by 3H-labeled amino acid in each r-protein to its amino acid content in that molecule. The two sets of data, which are completely independent of each other, are well correlated. Further verification of the validity of our procedure is provided by the fact that we found the known proportions of four copies of L7/L12 and one copy of S6 per ribosome. The rationale behind the present study was our finding that recalculation of Hardy's data (Hardy, S.J.S. (1975) Mol. Gen. Genet. 140, 253-274), with the accurate molecular weight value of the r-proteins provided by Giri et al. (Adv. Protein Chem. (1984) 36, 1-78), raises some doubt with regard to his experimental results, although we agree with his final conclusion that E. coli ribosome is homogeneous with respect to its proteins.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
It is well recognized in industrial and environmental health that man is exposed simultaneously to more than one chemical. Interaction may take place in the metabolism of chemicals absorbed in combination or in sequence, especially when the chemicals share similar chemical structures. It is further conceivable that the extent of possible metabolic interaction will depend on the intensity of exposure. Moreover, the metabolism of chemicals may be modified by social habits, especially smoking. No systemic and comprehensive studies however have been reported in literature, possibly because the combinations of the chemicals are various and the exposure intensities vary greatly. In a survey of factories where workers were exposed to either benzene alone (20 ppm as GM and 86 ppm as max.), toluene alone (38 and 86 ppm) or a combination of both, the urinary levels of phenol (a metabolite of benzene) and hippuric acid (that of toluene) were significantly lower among the co-exposed workers as compared with the levels in workers who were exposed to either benzene or toluene alone (Inoue et al. (1988) Int. Arch. Occup. Environ. Health 60, 15-20). In contrast, a similar factory survey on the workers exposed to a mixture of toluene (3 ppm as GM) and xylenes (3 ppm for the sum of the 3 isomers) revealed that increments in urinary hippuric acid and methylhippuric acid levels were equal to the values after individual exposure (Huang et al. (1994) Occup. Environ. Med. 51, 42-46). Furthermore, the hippuric acid levels in the urine of workers exposed to toluene (18 ppm as GM) were not reduced by the co-exposure to MEK (16 ppm) or IPA (7 ppm) (Ukai et al. (1994) Occup. Environ. Med. 51, 523-529). In a human volunteer study with repeated exposures, metabolic interaction took place when the subjects were exposed to a combination of 95 ppm toluene and 80 ppm xylenes (mostly m-isomer), whereas no interaction was detected after the exposure to a combination of 50 ppm toluene and 40 ppm xylenes (Tardif et al. (1991) Int. Arch. Occup. Environ. Health 63, 279-284). From the observation it appears likely that due caution should be exercised when the intensity of the combined exposure is high but not necessarily so when the exposure is low. The threshold remains yet to be established.
Increasing recognition of the important roles served by membrane phospholipids in cellular metabolic and signal transduction processes has stimulated interest in examining potential phospholipid abnormalities in patients with psychiatric disorders. This report describes a method, based on several novel modifications of existing techniques, for concurrently analyzing nanomolar amounts of nine phospholipid classes in a single aliquot of membrane extract. With this method, diverse phospholipid classes are first separated by two-dimensional thin-layer chromatography, and then determined using two-dimensional scanning laser densitometry. The method is able to quantitate even small amounts of specific phospholipid classes, corresponding to < 10 ng of lipid phosphorus. The sensitivity of this method allows it to be readily applied to clinical studies involving membranes from cell types that are obtainable only in small quantities.
Explore the source record for details and available documents.
The development of a two-dimensional liquid chromatographic system requires a process of assessment that can yield an optimum performing system with minimal experimental evaluation. Information Theory and a geometric approach to Factor Analysis are two techniques that when used in combination, provide important information on the expected two-dimensional performance. In the present study, we compare the predicted separation performance of two-dimensional systems that have been subjected to analysis by Information Theory and Factor Analysis to that of actual chromatographic separation performance. Our test separation comprised a mixture of 32 oligostyrene structural isomers and stereoisomers. The optimal combination as determined by Information Theory and Factor Analysis consisted of a C18 column with a methanol mobile phase in the first dimension and a carbon clad zirconia column with an acetonitrile mobile phase in the second dimension. This system was also shown to be the most successful practical system when a heart-cutting approach was employed. The practical results were in total agreement with the results from Information Theory and Factor Analysis. The number of isomers resolved using this system was 27. A second system, namely one comprising of a C18 column and methanol mobile phase in the first dimension and a carbon clad zirconia column with a methanol mobile phase in the second dimension was also predicted to be a system with high separation potential. However, practical assessment of this system did not realise the theoretical predictions, largely due to the long separation times required in the second dimension. Furthermore, all combinations that employed a C18 column with an acetonitrile mobile phase in the first dimension failed to realise the theoretical separation potential due to high solute crowding, low orthogonality and a disordered arrangement of bands along the first separation axis. This was also predicted by the theoretical assessment.
Fast GC separations of a broad range of analytes are demonstrated using a capillary column coated with a novel immobilized ionic liquid (IIL) stationary phase. Both completely cross-linked and partially cross-linked columns were evaluated, yielding approximately 1600 and approximately 2000 theoretical plates per meter, respectively. Enhanced separation is demonstrated using a dual-column ensemble comprised of an IIL column, a commercially coated Rtx-1 column, and a pneumatic valve connecting the inlet to the junction point between the two columns. Enhanced separation of 20 components, with two sets of co-eluting peaks is shown in approximately 150 s, while sacrificing only a length of time equivalent to the sum of the stop flow pulses, or about 15.5 s. A novel application of a band trajectory model that shows band position as a function of analysis time as analytes move through the column ensemble is employed to determine pulse application times. The model predicts component retention times within a few seconds. Another method of selectivity enhancement of the IIL stationary phase-coated columns is demonstrated using a differential mobility spectrometer (DMS) that provides a second dimension separation based on ion mobility in a high-frequency electrical field. The DMS is able to separate all but one set of co-eluting components from the IIL column. The separation of 13 components found in the headspace above U.S. currency is demonstrated using the IIL column in a dual-column ensemble as well as with the DMS.
Explore the source record for details and available documents.
Among the "inadvertent" environmental pollutants are polychlorinated biphenyls, terphenyls, quadphenyls, naphthalenes, diphenyl ethers, dibenzofurans, dibenzo-p-dioxins and benzenes. Mixtures of these classes of compounds also occur in commercial products such as transformer fluids. To analyze such mixtures, gas chromatography--mass spectrometry may be combined with pre-fractionation on basic and acidic alumina columns and semi-quantitative perchlorination techniques. These procedures are illustrated for synthetic mixtures as well as for two samples of stored transformer fluid. Although the described procedure is mainly intended to be applied to the characterization of the major class components of such mixtures, it is also applicable to the determination of trace components such as the dibenzofurans in commercial polychlorinated biphenyls. The mass spectral techniques permit the simultaneous patterning, or "fingerprinting", of the compounds comprising each major class of chlorinated aromatics present.
Explore the source record for details and available documents.
A variety of approaches have been required in order to achieve the resolution of large fragments from cyanogen bromide (CNBr) digests of Inc k chain (an immunoglobulin light chain), human serum albumin (HSA) and four of its mutants. Reversed-phase high-performance liquid chromatography (RP-HPLC) under different conditions failed to resolve the Inc k chain digest; the three CNBr fragments (3.1, 6.7 and 13.7 kDa) were separated in a homogeneous form by gel HPLC. Five of the seven CNBr fragments (ranging from 3.4 to 20.0 kDa) obtained from CNBr cleavage of HSA can be resolved by a single reversed-phase HPLC step; separation of the other two requires modification of the eluent composition. Some structural features of the peptides seem to influence their chromatographic behaviour; by examining the elution patterns from albumin mutants, the sequence-related contribution of single amino acid residues is apparent.