Chemically etched open tubular and monolithic emitters for nanoelectrospray ionization mass spectrometry.
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We have developed a new procedure for fabricating fused-silica emitters for electrospray ionization-mass spectrometry (ESI-MS) in which the end of a bare fused-silica capillary is immersed into aqueous hydrofluoric acid, and water is pumped through the capillary to prevent etching of the interior. Surface tension causes the etchant to climb the capillary exterior, and the etch rate in the resulting meniscus decreases as a function of distance from the bulk solution. Etching continues until the silica touching the hydrofluoric acid reservoir is completely removed, essentially stopping the etch process. The resulting emitters have no internal taper, making them much less prone to clogging compared to, e.g., pulled emitters. The high aspect ratios and extremely thin walls at the orifice facilitate very low flow rate operation; stable ESI-MS signals were obtained for model analytes from 5-microm-diameter emitters at a flow rate of 5 nL/min with a high degree of interemitter reproducibility. In extensive evaluation, the etched emitters were found to enable approximately four times as many LC-MS analyses of proteomic samples before failing compared with conventional pulled emitters. The fabrication procedure was also employed to taper the ends of polymer monolith-containing silica capillaries for use as ESI emitters. In contrast to previous work, the monolithic material protrudes beyond the fused-silica capillaries, improving the monolith-assisted electrospray process. (+info)
Structural and immunochemical studies of O-specific polysaccharide of Proteus vulgaris 5/43 belonging to OX19 group (O-variants).
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O-specific polysaccharide was obtained on mild acid degradation of lipopolysaccharide of Proteus vulgaris 5/43 belonging to OX19 (O-variants). It was found to contain D-glucose, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2,6-dideoxy-L-glucose (QuiNAc, N-acetyl-L-quinovosamine) in the ratio of about 1:2:1, the last-named sugar being rather uncommon for bacterial antigens. A computer-assisted 13C-NMR-based analysis, methylation analysis, and selective cleavage with anhydrous hydrogen fluoride and dilute hydrochloric acid were applied for structural elucidation of the polysaccharide and the following structure was established:----2)-beta-D-Glcp-(1----6)-alpha-D-GlcpNAc-(1----3)- alpha-L-QuipNAc-(1----3)-beta-D-GlcpNAc-(1----. Serological studies of the O-antigen and oligosaccharides derived therefrom revealed the importance of the trisaccharide fragment beta-D-Glcp-(1----6)-alpha-D-GlcpNAc-(1----3)-alpha-L- QuipNAc in manifesting the antigenic specificity. Serological cross-reactions were demonstrated between lipopolysaccharides of P. vulgaris 5/43, 8/44, and OX19 strains. (+info)
N-glycans of the porcine nematode parasite Ascaris suum are modified with phosphorylcholine and core fucose residues.
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In recent years, the glycoconjugates of many parasitic nematodes have attracted interest due to their immunogenic and immunomodulatory nature. Previous studies with the porcine roundworm parasite Ascaris suum have focused on its glycosphingolipids, which were found, in part, to be modified by phosphorylcholine. Using mass spectrometry and western blotting, we have now analyzed the peptide N-glycosidase A-released N-glycans of adults of this species. The presence of hybrid bi- and triantennary N-glycans, some modified by core alpha1,6-fucose and peripheral phosphorylcholine, was demonstrated by LC/electrospray ionization (ESI)-Q-TOF-MS/MS, as was the presence of paucimannosidic N-glycans, some of which carry core alpha1,3-fucose, and oligomannosidic oligosaccharides. Western blotting verified the presence of protein-bound phosphorylcholine and core alpha1,3-fucose, whereas glycosyltransferase assays showed the presence of core alpha1,6-fucosyltransferase and Lewis-type alpha1,3-fucosyltransferase activities. Although, the unusual tri- and tetrafucosylated glycans found in the model nematode Caenorhabditis elegans were not found, the vast majority of the N-glycans found in A. suum represent a subset of those found in C. elegans; thus, our data demonstrate that the latter is an interesting glycobiological model for parasitic nematodes. (+info)
Effect of surface treatment on the shear bond strength of a resin-based cement to porcelain.
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The purpose of this in vitro study was to evaluate the effect of different surface treatments on the shear bond strength of a resin-based cement to porcelain. Sixty pairs of 50% aluminous porcelain discs were fabricated. In each pair, one disc measured 6 mm in diameter X 3 mm thickness (A) and the other measured 3 mm in diameter X 3mm thickness (B). The specimens were randomly assigned to 6 groups (n=10 pairs of discs), according to the surface treatment: etching with 10% hydrofluoric acid for 2 or 4 min (G1 and G2); 50-microm particle aluminum oxide sandblasting for 5 s (G3); sandblasting followed by etching for 2 or 4 min (G4 and G5) and control--no treatment (G6). A silane agent was applied to the treated surface of both discs of each pair. Bistite II DC dual-cure resin cement was applied and the B discs were bonded to their respective A discs. Specimens were stored in distilled water at 37 degrees C for 24 h and were tested in shear strength at a crosshead speed of 2 mm/min. Means in MPa were: G1: 14.21 +/- 4.68; G2: 8.92 +/- 3.02; G3: 10.04 +/- 2.37; G4: 12.74 +/- 5.15; G5: 10.99 +/- 3.35; G6: 6.09 +/- 1.84. Data were compared by one-way ANOVA and Tukey's test at 5% significance level. Bond strength recorded after 2-min acid etching was significantly higher than 4-min etching (p<0.05) and control (p<0.05), but did not differ significantly from sandblasting alone (p>0.05) or followed by etching for 2 or 4 min (p>0.05). Within the limitations of an in vitro study, it may be concluded that 2-min hydrofluoric acid etching produced a favorable micromechanical retention that enhanced resin cement bond strength to porcelain. (+info)
Adherence of oral streptococci to salivary glycoproteins.
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We used an overlay method to study the ability of human salivary glycoproteins to serve as receptors for several strains of streptococci that colonize the oral cavity. Parotid and submandibular-sublingual salivas were collected as ductal secretions, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and transferred to nitrocellulose membranes. The resulting blots were overlaid with [35S]methionine-labeled bacteria, and salivary components to which the bacteria bound were detected by autoradiography. Potential glycoprotein receptors were identified for 8 of the 16 strains tested. In three cases (Streptococcus sanguis 72-40 and 804 and Streptococcus sobrinus OMZ176), highly specific interactions with a single salivary component were detected. Removal of sialic acid residues from the low-molecular-weight salivary mucin prevented adherence of one of these strains (S. sanguis 72-40), suggesting that this saccharide either mediates binding or is a critical component of the receptor site. In the remaining five strains (Streptococcus gordonii G9B and 10558, S. sanguis 10556, and Streptococcus oralis 10557 and 72-41), interactions with multiple salivary components, including the low-molecular-weight salivary mucin, highly glycosylated proline-rich glycoproteins, and alpha-amylase, were detected. These results suggest that some oral streptococci can bind specifically to certain of the salivary glycoproteins. The interactions identified may play an important role in governing bacterial adherence and clearance within the oral cavity. (+info)
Effect of acetic NaF solutions on fluoride-containing dental restorative materials.
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The aim of this study was to evaluate the effect of acetic NaF solutions on fluoride-containing restorative materials. As the pH value of solution decreased, the degree of microhardness change in restorative materials increased- regardless of product. Dyract AP (DA) and F2000 (F2) (polyacid-modified resin composites) showed the greatest decrease in microhardness after immersion for three days. Similarly, as the pH value decreased, volumetric weight change (loss) increased in all products. DA and F2 showed the greatest--but similar-weight change in pH 3.5 solution among the products. In terms of color change, most specimens showed a slight color change after immersion for one and three days-regardless of pH value. However, F2 in pH 3.5 solution showed a noticeable color change (deltaE*=2.1). In terms of surface morphology, specimens in distilled water showed only minor surface modification. However, in pH 3.5 solution, DA and F2 showed randomly propagating cracks, while Solitaire 2 and Tetric Ceram (resin composites) lost many fillers less than 2 microm in size. (+info)
The tissue distribution of fluoride in a fatal case of self-poisoning.
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The purpose of this paper is to report a case of fluoride poisoning along with a discussion of poisoning characteristics, analytical procedures, and a review of previous reports of fatal intoxications with analytical data. A case of suicidal ingestion of 40 mL of a rust removal agent containing hydrofluoric acid and ammonium fluoride by a 33-year-old white male is presented. He had an organic personality disorder with residual schizophrenia and previous suicide attempts with therapeutic drugs and cleaning products. At admission, he presented with a Glasgow coma score of 3, third degree atrioventricular block, and asystole. Resuscitation efforts were performed during which the patient suffered two episodes of ventricular fibrillation followed by asystole. In spite of advanced resuscitation efforts and the administration of calcium chloride, he died 2.5 h after the ingestion. Analytical data in the hospital showed calcium levels of 3.1 mg/dL and metabolic acidosis. Internal findings were erosive gastritis, brain edema, and pulmonary and hepatic congestion. Quantitation of fluoride was performed using an ion-selective electrode for the anion. Disposition of fluoride in the different tissues was as follows: peripheral blood, 19.4 mg/L; urine, 670 mg/L; vitreous humor, 2.5 mg/L; liver, 40.0 mg/kg; kidney, 60.0 mg/kg; lung, 17.5 mg/kg; brain, 2.5 mg/kg; spleen, 30.0 mg/kg; bone, 0.5 mg/ kg; and gastric content, 1120 mg/L (67 mg total). Validation of the analytical method was performed using different spiked tissues, in a range of concentrations from 2.4 to 475 mg/L or mg/kg, and submitting them to dilution (1:25) to avoid the matrix effect and to bring these concentrations to the range of the aqueous calibration curve (0.19-19 mg/L). Limits of detection and quantitation were 0.02 and 0.1 mg/L, respectively. The linearity of the method, for all studies tissues, was excellent, with r(2) values of 0.999. Accuracy and precision were within 10.5% and 5.7%, respectively. Fluoride analyses using the ion selective electrode are simple, sensitive, and rapid. This report provides an extensive tissue distribution study of fluoride after a well documented case of acute poisoning. Based on the autopsy findings, patient history, toxicology results, and previously reported data the forensic pathologists ruled that the cause of death was due to a fluoride poisoning, and the manner of death was listed as suicide. (+info)
Limited efficacy of calcium and magnesium in a porcine model of hydrofluoric acid ingestion.
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OBJECTIVE: This investigation evaluated the effectiveness of calcium and magnesium in treating oral hydrofluoric acid (HF) poisoning. METHODS: The controlled laboratory investigation used anesthetized pigs. Subjects received HF via NG tube, titrated to abolish electrocardiographic abnormalities. The untreated group received saline infusion. The treatment group received serial injections of calcium chloride (CaCl2) and magnesium chloride (MgCl2). A third group received oral infusions of Calcium fluoride (CaF2). We measured heart rate, QRS interval, pH, bicarbonate, calcium, magnesium, and potassium. The Wilcoxon Rank Sum test was used to compare intra- and inter-subject differences. RESULTS: Fatality occurred in all pigs receiving HF. Compared to the untreated group, trends for the treatment group were toward a larger amount of HF to produce fatality (83.1 +/- 17.5 grams vs. 37.7 +/- 16.1 grams, p = 0.08), to cause QRS prolongation (72.5 +/- 25.8vs. 33.8 +/- 14.9 grams, p = 0.08), and to lower potassium at mortality (4.9 +/- 0.7 vs. 8.7 +/- 2.7 mEq/L, p = 0.08). No major changes in calcium (-1.0 +/- 0.7 mEq/L) or magnesium (0.4 +/- 0.6 mEq/L) occurred in the untreated group. Tachycardia developed in all pigs and ventricular arrhythmias occurred in 2 of 3 pigs of both groups [CaF2 administration caused no QRS prolongation or ventricular arrhythmias and had no effect on laboratory parameters]. CONCLUSION: CaCl2 and MgCl2 replacement delayed but did not prevent fatality and QRS prolongation. Although this result suggests Ca++ and Mg++ may be beneficial in the treatment of systemic HF toxicity, factors other than hypocalcemia and hypomagnesemia play a role in toxicity. (+info)