RESUMEN
The following four commercial sulfur dioxide passive monitors were tested for performance and realiability: DuPont Pro-Tek C-20 air monitoring badges; MSA Vaporgard Dosimeter tubes; REAL BioBadges; and 3M Sulfur Dioxide Nutshell monitors. The experiments conducted were designed to test factors critical to the operation of passive samplers: accuracy and precision; capacity; stability; analytical recovery; and the effects of exposure time, concentration, humidity, face velocity, orientation, chemical interference, and temperature. The DuPont Pro-Tek badges performed satisfactorily for all the factors tested, and the REAL BioBadges performed satisfactorily except for the instability of the SO2/tetrachloromercurate complex when stored. An alternate monitoring system, REAL BioBadges containing deionized water absorbent had a limited capacity. Only the MSA dosimeters exhibited unsatisfactory performance. The 3M Nutshell monitor was withdrawn by the manufacturer after only partial evaluation.
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Dióxido de Azufre/análisis , Exposición a Riesgos Ambientales , Humanos , Concentración Máxima AdmisibleRESUMEN
During removal of sprayed-on asbestos coating workers are exposed to high airborne fiber concentrations. The true protection of negative pressure respirators under working conditions was evaluated during an asbestos abatement project. A modification allowing air sampling inside the mask is described. The values for samples collected inside a full-face mask ranged between 0.4 and 5% of the concentrations measured outside. These values were considerably lower than those found inside a half-mask.
Asunto(s)
Amianto/efectos adversos , Equipos de Seguridad/normas , Dispositivos de Protección Respiratoria/normas , Amianto/análisis , Estudios de Evaluación como Asunto , Humanos , Máscaras/normas , Concentración Máxima AdmisibleRESUMEN
The light-harvesting bacteriochlorophyll-carotenoid-protein complex B800--850 has been isolated from membranes of the phototroph-negative mutant strain Y5 of Rhodopseudomonas capsulata. The three polypeptides of the complex have been found to be soluble in chloroform-methanol (1:1, v/v) in the presence of 0.1 M ammonium acetate. They were extracted from the complex and separated by gel filtration on Sephadex LH-60 in the same solvent mixture. Minimum molecular weights based on amino acid composition are 12 000, 9300, and 5100. Values previously determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis are 14 000, 10 000 and 8000. The two smaller polypeptides (polarities 31% and 39%) are completely soluble in chloroform/methanol/ammonium acetate while the largest and most polar (41%) polypeptide is only partially soluble. The largest polypeptide contains no tryptophan. The middle polypeptide contains no cysteine and arginine, while the small polypeptide lacks cysteine. Methionine is shown to be the amino terminus for the small and middle polypeptides by two independent methods (Edman degradation and dansylation). Both methods also indicated that the N terminus of the 14 000 polypeptide seems to be blocked. Partial N-terminal amino acid sequences were obtained for the two smaller polypeptides. No homology between the two proteins was observed.
Asunto(s)
Proteínas Bacterianas/aislamiento & purificación , Bacterioclorofilas/aislamiento & purificación , Carotenoides/aislamiento & purificación , Clorofila/análogos & derivados , Rhodopseudomonas/análisis , Aminoácidos/análisis , Luz , Sustancias Macromoleculares , Peso Molecular , Mutación , Péptidos/análisisRESUMEN
A hydrophobic, lipid- and pigment-free polypeptide from the chromatophore membrane of Rhodospirillum rubrum was spread from chloroform/methanol, pyridine and formic acid solutions at an air-water interface. Surface pressure versus area isotherms of the monolayers formed at the interface were partially dependent upon the spreading solvent used. From the surface area at 20 dynes/cm compression, an average molecular area of 12.9 nm2/molecule was calculated for a polypeptide monolayer spread from chloroform/methanol. Multilayers built up on germanium plates at different surface pressures were subjected to attenuated total reflection infrared spectroscopy. In all cases the amide I and II absorption bands were typical of alpha-helical and random conformations. Electron microscopy of transferred monolayers replicated by rotary platinum shadowing revealed domains of regular texture in specimens prepared at 20 dynes/cm. Such domains were virtually absent in specimens prepared at 10 and 30 dynes/cm. Light optical diffractometry of the ordered arrays yielded a smallest repetitive area of 13.5 nm2 which agrees well with the molecular area obtained from the monolayer surface. Although no drastic changes in secondary structure were detected in the course of this study, some conformational changes are indicated by solvent-dependent differences in the surface pressure versus area isotherms.