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- Pons, A, et al.
(författare)
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Sequential GC/MS analysis of sialic acids, monosaccharides, and amino acids of glycoproteins on a single sample as heptafluorobutyrate derivatives
- 2003
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 42:27, s. 8342-8353
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Tidskriftsartikel (refereegranskat)abstract
- A GUMS procedure was developed for the analysis of all major constituents of glycoproteins. The rationale for this approach is that by using GC/MS analysis of the constituents as heptafluorobutyrate derivatives, it was possible to quantitatively determine the sialic acid, monosaccharide, fatty acids (when present), and the amino acid composition with the sample remaining in the same reaction vessel during the entire procedure. A mild acid hydrolysis was used to liberate sialic acids and was followed by formation of methyl-esters of heptafluorobutyrate (HFB) derivatives. After GC/MS analysis of sialic acids, the remaining material was submitted to acid-catalyzed methanolysis followed by the formation of HFB derivatives. After GUMS analysis of the monosaccharides, the sample was supplemented with norleucine (as internal standard) and hydrolyzed with 6 M HCl followed by the formation of isoamyl-esters of HFB derivatives and GC/MS analysis. His and Trp residues were modified during the step of acid-catalyzed methanolysis, but the resulting derivatives were stable during acid hydrolysis and quantitatively recovered by GUMS analysis. As a result, all constituents of glycoproteins (sialic acids, monosaccharides (or di- and trisaccharides) and amino acids) are identified in the electron impact mode of ionization and quantified using three GUMS analysis in the same chromatographic conditions and using a limited number of reagents, a considerable advantage over previous techniques. This method is very sensitive, all data (qualitative and quantitative) being obtained at the sub-nanomolar level of initial material.
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| 3. |
- Richard, JC, et al.
(författare)
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Respective effects of end-expiratory and end-inspiratory pressures on alveolar recruitment in acute lung injury
- 2003
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Ingår i: Critical Care Medicine. - 1530-0293. ; 31:1, s. 89-92
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Tidskriftsartikel (refereegranskat)abstract
- Objective. A low tidal volume can induce alveolar derecruitment in patients with acute lung injury. This study was undertaken to evaluate whether this resulted mainly from the decrease in tidal volume per se or from the reduction in end-inspiratory plateau pressure and whether there is any benefit in raising the level of positive end-expiratory pressure (PEEP) while plateau pressure is kept constant. Design: Prospective crossover study. Setting: Medical intensive care unit of a university teaching hospital. Patients: Fifteen adult patients ventilated for acute lung injury (PaO2/FIO2, 158 +/- 34 mm Hg; lung injury score, 2.7 +/- 0.6). Interventions: Three combinations were tested: PEEP at the lower inflection point with 6 mL/kg tidal volume, PEEP at the lower inflection point with 10 mL/kg tidal volume, and high PEEP with tidal volume at 6 mL/kg, keeping the plateau pressure similar to the preceding condition. Measurements and Main Results: Pressure-volume curves at zero PEEP and at set PEEP were recorded, and recruitment was calculated as the volume difference between both curves for pressures ranging from 15 to 30 cm H2O. Arterial blood gases were measured for all patients. For a similar PEEP at the lower inflection point (10 +/- 3 cm H2O), tidal volume reduction (10 to 6 mL/kg) led to a significant derecruitment. A low tidal volume (6 mL/kg) with high PEEP (14 +/- 3 cm H2O), however, induced a significantly greater recruitment and a higher PaO2 than the two other strategies. Conclusion. At a given plateau pressure (i.e., similar end-inspiratory distension), lowering tidal volume and increasing PEEP increase recruitment and PaO2.
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