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At least 1,621 records · Page 90Linked to original sources
PubMed2002

Flow-injection electrospray ionization mass spectrometry of crude cell extracts for high-throughput bacterial identification.

Flow-injection electrospray ionization mass spectrometry (FI-ESI-MS) of unfractionated cell-free extracts obtained from bacterial cells suspended in a solvent mixture was investigated as a rapid analytical method for reproducible, high-throughput bacterial identification. Five bacterial strains (two Escherichia coli, two Bacillus spp. and one Brevibacillus laterosporus) were studied in this investigation. Axenically grown bacterial cells were suspended in an acidic organic solvent and the cell-free extract was sequentially injected into a solvent flow stream that was sprayed into the ionization chamber of the ESI-MS. The spectra produced contained reproducible information, which was useful for discriminating between the bacteria. Tandem mass spectrometry was used to characterize further the peaks, and at least three classes of macromolecules, namely phospholipids, glycolipids, and proteins, were found to contribute most to the spectral information. Bacterial extracts stored under different conditions gave very similar mass spectra for each of the five bacterial strains, indicating that the extracts were stable even at room temperature for up to 24 h, with no loss of information content, which has obvious implications for automated high-throughput analysis. An analysis of the components of the extracting solvent mixture and their effects on the spectral information showed that acetonitrile contributes most significantly to the extraction process and hence to the information content of the spectra.

Bacteria↗
PubMed2003

Fourier transform ion cyclotron resonance mass spectrometry with NanoLC/microelectrospray ionization and matrix-assisted laser desorption/ionization: analytical performance in peptide mass fingerprint analysis.

Protein identifications by peptide mass fingerprint analyses with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were performed using microelectrospray ionization coupled to nano liquid chromatography (NanoLC), as well as using matrix-assisted laser desorption/ionization (MALDI). Tryptic digests of bovine serum albumin (BSA), diluted down to femtomole quantities, have been desalted by fast NanoLC under isocratic elution conditions as the high resolving power of FT-ICR MS enables peptides to be separated during the mass analysis stage of the experiment. The high mass accuracy achieved with FT-ICR MS (a few ppm with external calibration) facilitated unambiguous protein identification from protein database searches, even when only a few tryptic peptides of a protein were detected. Statistical confidence in the database search results was further improved by internal calibration due to increased mass accuracy. Matrix-assisted laser desorption/ionization and micro electrospray ionization (ESI) FT-ICR showed good mass accuracies in the low femtomole range, yet a better sensitivity was observed with MALDI. However, in higher femtomole ranges slightly lower mass accuracies were observed with MALDI FT-ICR than with microESI FT-ICR due to scan-to-scan variations of the ion population in the ICR cell. Database search results and protein sequence coverage results from NanoLC FT-ICR MS and MALDI FT-ICR MS, as well as the effect of mass accuracy on protein identification for the peptide mass fingerprint analysis are evaluated.

Animals↗
PubMed2006

Multiplexed two-dimensional liquid chromatography for MALDI and nanoelectrospray ionization mass spectrometry in proteomics.

We developed a multiplexed two-dimensional separation system based on reversed phase (RP)--strong cation exchange (SCX) chromatography as a front-end device for matrix-assisted laser desorption ionization (MALDI) or nanoelectrospray ionization (nanoESI) mass spectrometry. Tryptic peptide mixtures were fractionated on a reversed-phase HPLC column, and each fraction was loaded onto multiplexed SCX microcolumns. Because this second chromatography was carried out in parallel, the analysis time is independent of the fraction number in the first RP-HPLC separation. The resultant samples were desalted/concentrated and eluted onto a MALDI plate with matrix-containing elution solutions in parallel, or eluted with optimized solutions for nanoESI and loaded onto nanoESI sprayers by an automated instrument. The soluble portion of HCT116 lysate was digested and fractionated using a 48-plexed chromatography system. Approximately 1000 unique peaks were detected in MALDI-MS with 3000 MS/MS spectra, while 724 peptides with ultrahigh peptide mass accuracy (sub-ppm error) were identified in nanoESI-FTICR mass spectrometry with five integrated selected ion monitoring scans. Since MS measurement with this off-line LC-LC approach is not restricted by continuous LC elution, it is expected to be useful especially in cases where repeated analysis with different scan modes or long-term data acquisition is required.

Chromatography, Liquid↗
PubMed1998

A controlled trial of timed bright light and negative air ionization for treatment of winter depression.

BACKGROUND: Artificial bright light presents a promising nonpharmacological treatment for seasonal affective disorder. Past studies, however, have lacked adequate placebo controls or sufficient power to detect group differences. The importance of time of day of treatment--specifically, morning light superiority--has remained controversial. METHODS: This study used a morning x evening light crossover design balanced by parallel-group controls, in addition to a nonphotic control, negative air ionization. Subjects with seasonal affective disorder (N = 158) were randomly assigned to 6 groups for 2 consecutive treatment periods, each 10 to 14 days. Light treatment sequences were morning-evening, evening-morning, morning-morning, and evening-evening (10,000 lux, 30 min/d). Ion density was 2.7 x 10(6) (high) or 1.0 x 10(4) (low) ions per cubic centimeter (high-high and low-low sequences, 30 min/d in the morning). RESULTS: Analysis of depression scale percentage change scores showed low-density ion response to be inferior to all other groups, with no other group differences. Response to evening light was reduced when preceded by treatment with morning light, the sole sequence effect. Stringent remission criteria, however, showed significantly higher response to morning than evening light, regardless of treatment sequence. CONCLUSIONS: Bright light and high-density negative air ionization both appear to act as specific antidepressants in patients with seasonal affective disorder. Whether clinical improvement would be further enhanced by their use in combination, or as adjuvants to medication, awaits investigation.

Air Ionization↗
PubMed1999

Comparative mass spectrometric analyses of Photofrin oligomers by fast atom bombardment mass spectrometry, UV and IR matrix-assisted laser desorption/ionization mass spectrometry, electrospray ionization mass spectrometry and laser desorption/jet-cooling photoionization mass spectrometry.

Photofrin (porfimer sodium) is a porphyrin derivative used in the treatment of a variety of cancers by photodynamic therapy. This oligomer complex and a variety of porphyrin monomers, dimers and trimers were analyzed with five different mass spectral ionization techniques: fast atom bombardment, UV and IR matrix-assisted laser desorption/ionization, electrospray ionization, and laser desorption/jet-cooling photoionization. All five approaches resulted in very similar oligomer distributions with an average oligomer length of 2.7 +/- 0.1 porphyrin units. In addition to the Photofrin analysis, this study provides a side-by-side comparison of the spectra for the five different mass spectrometric techniques.

Dihematoporphyrin Ether↗
PubMed1996

Interaction of ionizing radiation with topotecan in two human tumor cell lines.

The effect of topotecan, a topoisomerase I inhibitor, on ionizing radiation-induced cytotoxicity was studied in 2 human tumor cell lines characterized by a different expression of the target enzyme. The cytotoxicity of topotecan alone or in combination with radiation was assessed in exponentially growing non-small-cell lung cancer (H460) and glioblastoma (GBM) cells using the colony-forming assay. An isobologram method was used to evaluate the treatment interaction. An apparent supra-additive effect in cell killing following drug-radiation-combined treatment was observed only in GBM cells exposed to topotecan for 24 hr. In the case of H460 cells, interaction varied from a strong infra-additive effect at low radiation doses to a slight supra-additive effect when cells were exposed to radiation doses greater than 3 Gy. Northern blot analysis indicated that topoisomerase I expression in H460 cells was 8-fold higher than that of GBM cells. Although the H460 cell line exhibited an increased sensitivity to topotecan, only in the GBM cell line (which expressed a lower level of topoisomerase I) did the drug potentiate the radiation cytotoxicity. The observation that the radiosensitization by topotecan was related to topoisomerase I level is consistent with a putative role of the enzyme in processes involved in the repair of radiation damage. It is conceivable that the modulation of enzyme function results in an effective reduction of cellular capability for repair of radiation damage only if the enzyme is not over-expressed. Although a precise role of topoisomerase I in the cellular response to ionizing radiations (in particular, in DNA repair) remains to be documented, such results suggest the potential interest of topoisomerase I inhibitors in combination with radiation therapy for tumors expressing low topoisomerase I levels.

Antineoplastic Agents↗
PubMed1998

Determination of n-hexane metabolites by liquid chromatography/mass spectrometry. 1. 2,5-hexanedione and other phase I metabolites in untreated and hydrolyzed urine samples by atmospheric pressure chemical ionization.

The capabilities of atmospheric pressure chemical ionization liquid chromatography/mass spectrometry (APCI-LC/MS) were investigated for the analysis of urinary 2,5-hexanedione (2,5-HD) and for the identification and characterization of other n-hexane Phase I metabolites in hydrolized urine samples. Chromatography was performed under reversed phase conditions at 0.75 mL min-1 flow rate. The ionization of 2,5-HD and other n-hexane metabolites was obtained in positive ion mode. After optimization of several interface parameters, the linearity, sensitivity and precision of the method were determined operating in the selected ion monitoring mode. Detection limits were 0.02 and 0.05 mg L-1 in water and urine respectively, with linear calibration curves in the 0.05-10 L-1 concentration range. Repeatability and both intra-day and inter-day precision were determined at two concentration levels (0.5 and 5.0 mg L-1), and relative standard deviations were in the 1.3%-5.3% range. The method was applied to the quantitative analysis of 2,5-HD in urine samples from an external Quality Assurance Programme for Organic Solvent Metabolites. Moreover, the metabolites 5-hydroxy-2-hexanone, 2,5-hexanediol and 4,5-dihydroxy-2-hexanone were identified and confirmed in hydrolyzed urine of rats exposed to n-hexane.

Air Ionization↗
PubMed1998

Matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry analysis of blue copper proteins. Azurin and mavicyanin.

Two copper proteins azurin-1 and azurin-2 were isolated from denitrifying bacteria Alcaligenes xylosoxidans GIFU1051, and the mass spectrometric analysis of the proteins were carried out by both matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray ionization (ESI). The mass spectrometric analysis was also carried out with the recombinant zucchini protein mavicyanin, which was obtained by expression in Escherichia coli. All the proteins were detected as positive ions with the copper atom being eliminated. The molecular weights were determined as 14,017.6 for azurin-1, 13,807.6 for azurin-2 and 11,808.8 for mavicyanin. The observed molecular weight of azurin-1 agrees within two daltons with that calculated from the amino acid composition. Azurin-2 was found to have one different amino acid residue when compared with the known azurin-2 isolated from A. xylosoxidans NCIB11015. The measured molecular weight for the recombinant mavicyanin agrees within two daltons with that of calculated from the amino acid composition of the native protein; therefore, the recombinant mavicyanin is identical to the native protein.

Azurin↗
PubMed2000

Mass spectrometric study of randomly methylated beta-cyclodextrins using ionspray, atmospheric pressure chemical ionization and matrix-assisted laser desorption/ionization.

Mixtures of methylated beta-cyclodextrins were characterized using three different methods of mass spectrometry: ionspray, atmospheric pressure chemical ionization (APCI) and matrix-assisted laser desorption/ionization (MALDI). Each of these methods allows a fast and simple determination of the degree of substitution, and can provide evidence for differences in the methylation of batches which have very similar global degrees of substitution. The three methods are in good qualitative agreement, but there are systematic differences in the quantitative results for the percentages of the various methylated molecules present in a batch. This is attributed to ionization yields which increase with the number of methyl groups, with different slopes for the different methods.

Atmospheric Pressure↗
PubMedDate not supplied

Hormesis: an adaptive expectation with emphasis on ionizing radiation.

Non-linear fitness gradients with maxima between extremes are expected for any environmental variable to which free-living populations are exposed. For exceedingly toxic agents, including ionizing radiation, such deviations from linearity are close to zero exposure and are conventionally called hormesis. Accordingly, hormesis is an extreme version of the non-linear fitness gradients for general environmental stresses such as temperature fluctuations, for which maximum fitness occurs at the moderate temperature fluctuations to which free-living populations are most commonly exposed. Some metabolic reserves should occur under moderate temperature stresses because of the need for pre-adaptation enabling survival during exposure to occasional periods of more extreme stress, especially at species borders where selection for stress resistance is likely to be most intense. Because heat shock proteins are induced by all stresses, adaptation to extreme temperatures should translate into adaptation to other stresses. Consequently, metabolic reserves from adaptation to extreme temperatures in the past should translate into protection from correlated abiotic stresses, especially in human populations where modern cultural processes are now ameliorating exposure to extreme stresses. Ambient and man-made radiations of non-catastrophic dimensions should therefore lead to stress-derived radiation hormesis. Other stresses can, in principle, be incorporated into this model. Accordingly, evolutionary and ecological considerations suggest two components of hormesis in relation to ionizing radiation: background radiation hormesis based upon the background exposure to which all organisms on earth are subjected; and stress-derived radiation hormesis. Exposure under stress-derived radiation hormesis is considerably larger than under background radiation hormesis, so significant deleterious effects from non-catastrophic radiation normally may be impossible to detect. Suggestions are provided for testing such postulated deviations from the commonly assumed linear no-threshold (LNT) hypothesis for the biological consequences of exposure to radiation.

Adaptation, Physiological↗
PubMed2000

Determination of lodenosine and its major metabolite in human plasma by liquid chromatography/electrospray ionization tandem mass spectrometry.

A sensitive and selective method for the determination of 2'-beta-fluoro-2',3'-dideoxyadenosine (lodenosine, F-ddA), an experimental anti-AIDS drug, and its major metabolite, 2'-beta-fluoro-2',3'-dideoxyinosine (F-ddI), in human plasma was developed and validated. The procedure employs two internal standards and a simple ultrafiltration step followed by chromatography on a Betasil C(18) minibore column. An in-line valve is used to remove salts before reaching the ion source. Detection is by electrospray ionization tandem mass spectrometry with selected reaction monitoring. The method has a limit of quantitation of 4 ng ml(-1) (16 nM) for F-ddA and 8 ng ml(-1) (32 nM) for F-ddI with a linear range up to 2000 ng ml(-1) (7.9 microM) for each. Predicted concentrations from a three-day validation study were within 5% of the nominal values for F-ddA and 16% for F-ddI. Intra- and inter-assay precision, as measured by relative standard deviation, was 13% or better for both compounds. To achieve good reproducibility, many variables related to the electrospray ionization were optimized for both precision and sensitivity. The method was successfully employed to analyze samples and evaluate plasma pharmacokinetics from a Phase I clinical trial.

Anti-HIV Agents↗
PubMed2000

Direct analysis by electrospray ionization tandem mass spectrometry of mixtures of phosphatidyldiacylglycerols from Lactobacillus.

Electrospray ionization followed by collision-induced dissociation in a quadrupole ion trap mass spectrometer of mixtures of deprotonated phosphatidyldiacylglycerols afforded a group of three diagnostic ions of convenient abundance for each phosphatidyldiacylglycerol (PG) present in the mixture. Thus, it was possible to determine unmistakably the identity and substitution positions (sn-1 or sn-2) for both acyl groups of each PG present in the mixture. The method also allows the study of isomeric mixtures of PG and mixtures containing minor amounts of some PG from crude extracts of Lactobacillus acidophillus. The present results improve those of previous studies using fast atom bombardment and electrospray ionization tanden mass spectrometry, in which it was reported that it was possible to differentiate the identity and position of the sn-2 acyl substituent only by the presence of one ion, with variable abundance.

Lactobacillus acidophilus↗
PubMed2001

Involvement of the hepatocyte growth factor/scatter factor receptor c-met and of Bcl-xL in the resistance of oropharyngeal cancer to ionizing radiation.

The activation of cytoplasmic signal transduction pathways by a number of growth factors and their tyrosine-kinase receptors, including hepatocyte growth factor/scatter factor (HGF/SF) and its receptor c-met, exerts an inhibitory influence on apoptosis induced by ionizing radiation in vitro. The clinical relevance of the aforementioned ligand-receptor pair, of Bcl-xL, which is targeted by HGF/SF/c-met signaling, and of Bcl-2, was assessed by evaluating their predictive and prognostic impact in a cohort of 97 patients with radically irradiated squamous cell cancers of the oropharynx. Immunohistochemical expression of c-met and Bcl-xL was correlated with decreased rates of complete remission of the primary tumor in both the univariate (c-met: P = 0.01; Bcl-xL: P = 0.001) and multivariate analyses. Expression of c-met was, moreover, a significant and independent predictor of impaired local failure-free survival (P = 0.003), disease-free survival (P = 0.003) and overall survival (p = 0.001). Bcl-2 expression was, on the other hand, associated with a favorable outcome, in terms of both local failure-free survival (P = 0.01) and overall survival (P = 0.001). In accordance with in vitro data, c-met and Bcl-xL appear to be involved in the resistance of oropharyngeal cancers to ionizing radiation, and may therefore represent attractive targets for radiosensitization.

Aged↗
PubMed2000

Determination of the site of glucuronidation in an N-(3,5-dichlorophenyl)succinimide metabolite by electrospray ionization tandem mass spectrometry following derivatization to picolinyl esters.

Derivatization using 3-pyridylcarbinol coupled with liquid chromatography electrospray ionization tandem mass spectrometry (LC/MS/MS) was used to characterize a novel Phase II metabolite of the nephrotoxic agricultural fungicide, N-(3,5-dichlorophenyl)succinimide (NDPS). A glucuronide conjugate of N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) was identified in the urine from a rat dosed with [14C]NDPS. However, 2-NDHSA contains an aliphatic hydroxyl group and a carboxylic acid group, both of which are potential sites for glucuronidation. Mass spectrometry alone was unable to distinguish between these possibilities. Since the position of glucuronidation may be important in the mechanism of NDPS-induced nephrotoxicity, chemical derivatization in conjunction with mass spectrometry was used to characterize the glucuronide. The 2-NDHSA glucuronide conjugate was isolated from rat urine, derivatized with 3-pyridylcarbinol, and the derivatized metabolite was then analyzed by LC/MS/MS. Two known NDPS metabolites, 2-NDHSA and N-(3,5-dichlorophenyl)succinamic acid (NDPSA), were also isolated from rat urine and derivatized similarly. 3-Pyridinylcarbinol reacted rapidly with the carboxylic acid groups and formation of the picolinyl esters increased the ionization potential under positive ion conditions. The urinary glucuronide of 2-NDHSA was identified as an alcohol-linked glucuronide by examination of the molecular ions and the collision-induced dissociation (CID) product ion spectra of the derivatized products. When used in combination with mass spectrometry, derivatization of carboxylic acids with 3-pyridylcarbinol provided useful mass fragmentations and is a rapid way to obtain structural information about the position of glucuronidation of NDPS metabolites.

Animals↗
PubMed2000

Estimation of genome damage after exposure to ionizing radiation and ultrasound used in industry.

The application of ionizing radiation in industry for nondestructive testing entails a specific framework of working conditions that include field work, facilities with different radioactive sources, maintenance thereof without halting production, use of nonionizing radiation, and exposure to chemical agents. The present study gives an estimation of recent genome damage in two groups of subjects using chromosome aberration assay and micronucleus assay. The first group was exposed to (192)Ir and the second was simultaneously exposed to (192)Ir and ultrasound. The results show that both groups had higher values of chromosome aberrations and micronucleus frequency than controls. The group of examinees exposed both to (192)Ir and ultrasound had significantly more chromatid breaks, acentric fragments, and dicentric chromosomes, and had a significantly higher frequency of micronuclei than subjects exposed to (192)Ir only. The study suggests that the detected differences in the genome damage may be attributed to the action of ultrasound. This study confirms the dosimetry data for ionizing radiation, which indicate that the methods used in industrial radiography and the usage of nonionizing radiation entail an increased health risk. In the absence of personal dosimeters for nonionizing radiation and chemical agents, biomonitoring provides reliable parameters for estimation of genome damage and may lead to improvements in working conditions and radiation safety programs.

Adult↗
PubMed2002

Structural effects on the formation of proton and alkali metal ion adducts of apolar, neutral peptides: electrospray ionization mass spectrometry and Ab initio theoretical studies.

Apolar, neutral peptides have been shown to ionize extremely well under the conditions used for electrospray ionization mass spectrometry (ESIMS). Peptides for which the conformations have been independently determined in solution and in crystals have been examined by ESIMS. Studies of peptide helices ranging from 7 to 18 residues reveal that shorter helices yield exclusively singly charged ions, while in larger helices multiply charged species are detectable. Multiple sites for protonation/metallation are introduced in the helix by proline insertion or by changing the chirality in the residue. The preferred site of cation binding to helices may be the C-terminus end, where three free CO groups are available for chelation. Ab initio and DFT calculations at several levels have been carried out for the binding of H+, Li+, Na+, and K+ to CHO-(Gly)3)-OMe. The results reveal that metallation in helices is favoured by chelation to carbonyl groups at the C-terminus, while protonation involved two carbonyl groups and thus favour a 10-membered cyclic hydrogen-bonded structure. In -strands, metallation/protonation occurs at isolated carbonyl groups. Collision induced fragmentation of hydrophobic peptides under ESI conditions reveals that helix fragmentation occurs predominantly from the C-terminus, while in -hairpins cleavage occurs simultaneously at multiple sites.

Amino Acids, Neutral↗
PubMed2000

Exposure to ionizing radiation in children undergoing Amplatzer device placement to close atrial septal defects.

To evaluate exposure to ionizing radiation during Amplatzer device occlusion, a prospective study was performed to measure surface entrance radiation dose by thermoluminescent dosimetry (TLD). Between June 1998 and April 1999, dosimetry was carried out on 12 patients with Amplatzer device occlusion of atrial septal defects (n = 10) or Fontan fenestration (n =) and 12 age-matched patients who underwent diagnostic catherization. TLD chips were placed at the posterior (PA) and right lateral (LA) chest wall as well as the thyroid (TH) and gonadal (GN) regions. The Amplatzer group had a median age of 6.4 yr (2.4-12.4 yr) and a median weight of 23.7 kg (15.6-28.9 kg), which were similar (p = NS) to those of the control group, who had a median age of 7.9 yr (3.3-16.2 yr) and a median weight of 29.9 kg (10.6-58.0 kg). Device placement was successful in 11 of 12 patients; one device was removed owing to partial obstruction of the right-upper pulmonary vein. Fluoroscopy times were also similar in the Amplatzer group (23.5 +/- 2.1 min) and the control group (16.4 +/- 3.1 min; P = NS). The measured surface entrance doses of the Amplatzer group was similar (p = NS) to those of the control group in all four regions: PA (4.96 +/- 1.88 vs. 6.07 +/- 2.16 cGy), LA (5.22 +/- 1.68 vs. 3.13 +/- 1.25 cGy), TH (0.92 +/- 0.14 vs. 0.69 +/- 0.09 cGy), and GN (0.20 +/- 0.00 vs. 0.22 +/- 0.01cGy). Fluoroscopy times and measured surface entrance doses of ionizing radiation in patients undergoing Amplatzer device occlusion are similar to those in patients undergoing routine diagnostic catheterization.

Cardiac Catheterization↗
PubMed2003

Nested case-control study of external ionizing radiation dose and mortality from dementia within a pooled cohort of female nuclear weapons workers.

BACKGROUND: A prior investigation of this cohort of female nuclear workers found increased deaths from mental disorders, including dementia. The present study estimates the effect of workplace exposures to ionizing radiations and other hazards on mortality from dementia. METHODS: A nested case-control study within a pooled cohort of 67,976 female nuclear workers compared 91 cases of death from dementia with 910 controls. Adjusted odds ratios (ORs) were employed to estimate the effects of maximum annual and total lifetime radiation doses on the occurrence of dementia in 168 monitored workers. RESULTS: Both maximum annual (OR = 2.11, 95% confidence interval (CI) = 0.98, 4.40) and total lifetime radiation doses (OR = 2.09, 95% CI = 1.02, 4.29) were associated with death from dementia. Significant dose-response trends were present for both exposures. CONCLUSIONS: Occupational exposure to ionizing radiation (IR) may be associated with increased risk of death from dementia in female workers. Since these findings are based on a small number of cases, replication with a larger case sample should be pursued.

Adolescent↗