Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.55 (PTR)
 433 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Frequency-domain photothermal radiometry (FD-PTR or PTR) is used to detect mechanical holes and demineralized enamel in the interproximal contact area of extracted human teeth. Thirty-four teeth are used in a series of experiments. Preliminary tests to detect mechanical holes created by dental burs and 37% phosphoric acid etching for 20 s on the interproximal contact points show distinct differences in the signal. Interproximal contact areas are demineralized by using a partially saturated acidic buffer system. Each sample pair is examined with PTR before and after micromachining or treating at sequential treatment periods spanning 6 h to 30 days. Dental bitewing radiographs showed no sign of demineralized lesion even for samples treated for 30 days. Microcomputer tomography (micro-CT), transverse microradiography (TMR), and scanning electron microscopy (SEM) analyses are performed. Although micro-CT and TMR measured mineral losses and lesion depths, only SEM surface images showed visible signs of treatment because of the minimal extent of the demineralization. However, the PTR amplitude increased by more than 300% after 80 h of treatment. Therefore, PTR is shown to have sufficient contrast for the detection of very early interproximal demineralized lesions. The technique further exhibits excellent signal reproducibility and consistent signal changes in the presence of interproximal demineralized lesions, attributes that could lead to PTR as a reliable probe to detect early interproximal demineralization lesions. Modulated luminescence is also measured simultaneously, but it shows a lower ability than PTR to detect these interproximal demineralized lesions.
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PMID:Detection of interproximal demineralized lesions on human teeth in vitro using frequency-domain infrared photothermal radiometry and modulated luminescence. 1761 36

The gastronomic relevance and high price of white truffle are related mainly to its unique aroma. Here we evaluate, for the first time, the possibility of characterizing in a rapid and non-destructive way the aroma of white truffles based on proton transfer reaction mass spectrometry (PTR-MS). We indicate that anonymous PTR-MS fingerprinting allows sample classification and we also compare qualitatively and quantitatively PTR-MS data with measurements made by solid-phase microextraction gas chromatography (SPME-GC) of the same samples under the same conditions. PTR-MS fragmentation data of truffle-relevant compounds are also published here for the first time. Most of the sulfur-containing compounds detected by GC and relevant for white truffle aroma have a high positive correlation with single PTR-MS peaks. Our work indicates that, after preliminary comparison with GC data, PTR-MS is a new tool for the rapid, quantitative and non-invasive characterization of white truffle by direct headspace injection without any pre-concentration.
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PMID:Rapid white truffle headspace analysis by proton transfer reaction mass spectrometry and comparison with solid-phase microextraction coupled with gas chromatography/mass spectrometry. 1763 68

The present work shows the possibilities and limitations in modeling release kinetics of volatile organic compounds (VOCs) from roasted and ground coffee by applying physical and empirical models such as the diffusion and Weibull models. The release kinetics of VOCs were measured online by proton transfer reaction-mass spectrometry (PTR-MS). Compounds were identified by GC-MS, and the contribution of the individual compounds to different mass fragments was elucidated by GC/PTR-MS. Coffee samples roasted to different roasting degrees and ground to different particle sizes were studied under dry and wet stripping conditions. To investigate the accuracy of modeling the VOC release kinetics recorded using PTR-MS, online kinetics were compared with kinetics reconstituted from purge and trap samplings. Results showed that uncertainties in ion intensities due to the presence of isobaric species may prevent the development of a robust mathematical model. Of the 20 identified compounds, 5 were affected to a lower extent as their contribution to specific m/z intensity varied by <15% over the stripping time. The kinetics of these compounds were fitted using physical and statistical models, respectively, the diffusion and Weibull models, which helped to identify the underlying release mechanisms. For dry stripping, the diffusion model allowed a good representation of the release kinetics, whereas for wet stripping conditions, release patterns were very complex and almost specific for each compound analyzed. In the case of prewetted coffee, varying particle size (approximately 400-1200 microm) had no significant effect on the VOC release rate, whereas for dry coffee, the release was faster for smaller particles. The absence of particle size effect in wet coffee was attributed to the increase of opened porosity and compound diffusivity by solubilization and matrix relaxation. To conclude, the accurate modeling of VOC release kinetics from coffee allowed small variations in compound release to be discriminated. Furthermore, it evidenced the different aroma compositions that may be obtained depending on the time when VOCs are recovered.
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PMID:Release kinetics of volatile organic compounds from roasted and ground coffee: online measurements by PTR-MS and mathematical modeling. 1799 91

In Drosophila and vertebrates, Hedgehog (Hh) signalling is mediated by a cascade of genes, which play essential roles in cell proliferation and survival, and in patterning of the embryo, limb buds and organs. In C. elegans, this pathway has undergone considerable evolutionary divergence; genes encoding homologues of key pathway members, including Hh, Smoothened, Cos2, Fused and Suppressor of Fused, are absent. Surprisingly, over sixty proteins (i.e. WRT, GRD, GRL, and QUA), encoded by a set of genes collectively referred to as the Hh-related genes, and two co-orthologs (PTC-1,-3) of fly Patched, a Hh receptor, are present in C. elegans. Several of the Hh-related proteins are bipartite and all can potentially generate peptides with signalling activity, although none of these peptides shares obvious sequence similarity with Hh. In addition, the ptc-related (ptr) genes, which are present in a single copy in Drosophila and vertebrates and encode proteins closely related to Patched, have undergone an expansion in number in nematodes. A number of functions, including roles in molting, have been attributed to the C. elegans Hh-related, PTC and PTR proteins; most of these functions involve processes that are associated with the trafficking of proteins, sterols or sterol-modified proteins. Genes encoding other components of the Hh signalling pathway are also found in C. elegans, but their functions remain to be elucidated.
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PMID:Homologs of the Hh signalling network in C. elegans. 1805 Apr 69

We demonstrate the use of an aldehyde scrubber system to resolve isobaric aldehyde/alkene interferences in a proton transfer reaction mass spectrometer (PTR-MS) by selectively removing the aldehydes from the gas mixture without loss of quantitative information for the alkene components. The aldehyde scrubber system uses a bisulfite solution, which scrubs carbonyl compounds from the gas stream by forming water-soluble carbonyl bisulfite addition products, and has been evaluated using a synthetic mixture of acrolein and isoprene. Trapping efficiencies of acrolein exceeded 97%, whereas the transmission efficiency of isoprene was better than 92%. Quantification of the PTR-MS response to acrolein was validated through an intercomparison study that included two derivatization methods, dinitrophenylhydrazine (DNPH) and O-(4-cyano-2-ethoxybenzyl)hydroxylamine (CNET), and a spectroscopic method using a quantum cascade laser infrared absorption spectroscopy (QCL) instrument. Finally, using cigarette smoke as a complex matrix, the acrolein content was assessed using the scrubber and compared with direct QCL-based detection.
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PMID:Laboratory evaluation of an aldehyde scrubber system specifically for the detection of acrolein. 1806 60

The methodology of solid phase microextraction (SPME) with O-(2,3,4,5,6)-pentafluorobenzylhydroxylamine hydrochloride (PFBHA) on-fiber derivatization for the determination of carbonyls has been applied to the photo-oxidation of benzene and toluene carried out in the EUPHORE chambers. This work focuses on the results obtained for a number of highly reactive carbonyls, crucial in the determination of branching ratios and confirmation of the carbonylic route. The observed yields and kinetic behavior were compared to simulations with the Master Chemical Mechanism model, version 3.1 (MCMv3.1). The following yields were measured in the toluene system: glyoxal, (37 +/- 2)%; methylglyoxal, (37 +/- 2)%; 4-oxo-2-pentenal, > (13.8 +/- 1.5)%; and total butenedial, (13 +/- 7)% (cis-butenedial, (6 +/- 3)%; trans-butenedial, (7 +/- 4)%]. For benzene, the experimental glyoxal yields were (42 +/- 3) and (36 +/- 2)% for the two successive experiments (September 24 and 25, 2003), (17 +/- 9)% for total butenedial [(8 +/- 4)% cis-butenedial and (9 +/- 5)% trans-butenedial (September 24, 2003)] and (15 +/- 6)% total butenedial (September 25, 2003) [(7 +/- 3) and (7 +/- 3)% for the cis and trans isomers, respectively]. PTR-MS estimations for butenedial also allowed the two isomers of butenedial to be distinguished, but the measurements showed signs of interference from other products. The results presented confirm the fast ring cleavage and provide further experimental confirmation of the dicarbonylic route.
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PMID:Experimental confirmation of the dicarbonyl route in the photo-oxidation of toluene and benzene. 1820 Aug 64

A robust and reproducible model was developed to predict the sensory profile of espresso coffee from instrumental headspace data. The model is derived from 11 different espresso coffees and validated using 8 additional espressos. The input of the model consists of (i) sensory profiles from a trained panel and (ii) on-line proton-transfer reaction mass spectrometry (PTR-MS) data. The experimental PTR-MS conditions were designed to simulate those for the sensory evaluation. Sixteen characteristic ion traces in the headspace were quantified by PTR-MS, requiring only 2 min of headspace measurement per espresso. The correlation is based on a knowledge-based standardization and normalization of both datasets that selectively extracts differences in the quality of samples, while reducing the impact of variations on the overall intensity of coffees. This work represents a significant progress in terms of correlation of sensory with instrumental results exemplified on coffee.
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PMID:When machine tastes coffee: instrumental approach to predict the sensory profile of espresso coffee. 1822 Mar 71

A method for analysis of volatile organic compounds (VOCs) from microbial cultures was established using proton transfer reaction-mass spectrometry (PTR-MS). A newly developed sampling system was coupled to a PTR-MS instrument to allow on-line monitoring of VOCs in the dynamic headspaces of microbial cultures. The novel PTR-MS method was evaluated for four reference organisms: Escherichia coli, Shigella flexneri, Salmonella enterica, and Candida tropicalis. Headspace VOCs in sampling bottles containing actively growing cultures and uninoculated culture medium controls were sequentially analyzed by PTR-MS. Characteristic marker ions were found for certain microbial cultures: C. tropicalis could be identified by several unique markers compared with the other three organisms, and E. coli and S. enterica were distinguishable from each other and from S. flexneri by specific marker ions, demonstrating the potential of this method to differentiate between even closely related microorganisms. Although the temporal profiles of some VOCs were similar to the growth dynamics of the microbial cultures, most VOCs showed a different temporal profile, characterized by constant or decreasing VOC levels or by single or multiple peaks over 24 h of incubation. These findings strongly indicate that the temporal evolution of VOC emissions during growth must be considered if characterization or differentiation based on microbial VOC emissions is attempted. Our study may help to establish the analysis of VOCs by on-line PTR-MS as a routine method in microbiology and as a tool for monitoring environmental and biotechnological processes.
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PMID:On-line monitoring of microbial volatile metabolites by proton transfer reaction-mass spectrometry. 1824 41

Activated alpha-smooth muscle actin (alpha-SMA)-positive hepatic stellate cells (HSCs) are pericytes responsible for fibrosis in chronic liver injury. The glial fibrillary acidic protein (GFAP), commonly expressed by astrocytes in the central nervous system, is expressed in vivo in the liver in a subpopulation of quiescent stellate cells. In the rat, increased GFAP expression in the acute response to injury and down-regulation in the chronic response have been observed, whereas reports concerning GFAP expression in human liver are still conflicting. We investigated the utility of GFAP compared to alpha-SMA as an immunohistochemical marker of early activated HSCs in chronic and posttransplant recurrent hepatitis C and correlated GFAP expression with vascular remodeling and fibrosis progression. With immunohistochemistry and a semiquantitative scoring system, the expression of GFAP and alpha-SMA in HSCs and the microvessel density were analyzed in biopsies from normal livers obtained from cadaveric donors [donor liver (DL); n = 21] and from livers from posttransplant hepatitis C virus recurrent hepatitis (HCV-PTR) patients (n = 19), hepatitis C virus chronic hepatitis (HCV-CH) patients, (n = 12), and hepatitis C virus cirrhosis (HCV-C) patients (n = 16). The percentage of alpha-SMA-positive HSCs was significantly higher in the HCV-PTR, HCV-CH, and HCV-C groups compared to the DL group (P < 0.01). The percentage of GFAP-positive HSCs was significantly higher in the HCV-PTR group compared to the DL, HCV-C (P < 0.01), and HCV-CH (P < 0.05) groups and in the HCV-CH group compared to the DL group (P < 0.01), inversely correlating with the extent of fibrosis and microvessel density (P < 0.01). In the HCV-PTR group, the percentage of GFAP-positive HSCs correlated with fibrosis progression (P < 0.01). In conclusion, GFAP could represent a useful marker of early activation of HSCs in HCV-CH and seems to predict fibrosis progression in HCV-PTR.
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PMID:Glial fibrillary acidic protein as an early marker of hepatic stellate cell activation in chronic and posttransplant recurrent hepatitis C. 1850 67

Contemporary literature lacks a definition of prior antibiotic exposure which captures all patients at risk of developing piperacillin-tazobactam-resistant Pseudomonas aeruginosa (PTR-PA). The results indicated that individual antibiotics that are associated with PTR-PA differ depending on the definition of prior antibiotic exposure utilized. When the specific antibiotic used was replaced by the number of prior exposures, the number of exposures was the only variable associated with an increased risk of antibiotic resistance at each time threshold.
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PMID:Relationship between various definitions of prior antibiotic exposure and piperacillin-tazobactam resistance among patients with respiratory tract infections caused by Pseudomonas aeruginosa. 1851 18


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