PubMed · 11432703
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R E Clement, P W Yang. 2001-06-15. Environmental analysis.. https://doi.org/10.1021/ac0103930
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We have developed two solid-phase microextraction (SPME) methods, coupled with gas chromatography, for quantitatively analysing the major Eucalyptus leaf terpene, 1,8-cineole, in both expired air and blood from the common brushtail possum (Trichosurus vulpecula). In-line SPME sampling (5 min at 20 degrees C room temperature) of excurrent air from an expiratory chamber containing a possum dosed orally with 1,8-cineole (50 mg/kg) allowed real-time semi-quantitative measurements reflecting 1,8-cineole blood concentrations. Headspace SPME using 50 microl whole blood collected from possums dosed orally with 1,8-cineole (30 mg/kg) resulted in excellent sensitivity (quantitation limit 1 ng/ml) and reproducibility. Blood concentrations ranged between 1 and 1380 ng/ml. Calibration curves were prepared for two concentration ranges (0.05-10 and 10-400 ng/50 microl) for the analysis of blood concentrations. Both calibration curves were linear (r(2)=0.999 and 0.994, respectively) and the equations for the two concentration ranges were consistent.
Fluorescent and modified dark-field microscopies were used to investigate the phase behavior of physiologically relevant lipid/protein monomolecular films containing surfactant protein C(SP-C). Synthetic human SP-C(1-34) was labeled at its N-terminus using the fluorescent probe 6-(((4(4,4-difluoro-5-(2-thienyl)-4-bora-3a,4a-diaza-s-indacene-3-yl)phenoxy)acetyl)amino)hexanoic acid (BODIPY/TR-X). Using dual fluorescent labeling (lipid and protein) in the monolayers, we have correlated (at physiologically small concentrations of the protein) the lipid phase separation and protein distribution in situ. A comparison of the lipid and protein dye fluorescent micrographs indicates that SP-C(1-34) is preferentially associated with the disordered lipid phase. Three concepts arise from our results. (1) The presence of SP-C alone does not result in the complete dissolution of condensed phase domains in a fashion that we have previously reported for the entire hydrophobic surfactant protein (SP-B/C) fraction (Biophys. J. 77 (1999) 903). Rather, the use of relatively high amounts ( approximately 10 wt.%) of the labeled SP-C protein is needed to reproduce the fluorescence monolayer morphology previously observed for small concentrations ( approximately 1 wt.%) of the natural SP-B/C mixture. (2) Scattered light, dark-field microscopy performed using grazing angle laser illumination reveals the presence of surface-associated, three-dimensional (3D) structures of micrometer-sized dimensions when the labeled BODIPY/TR-X:SP-C(1-34) protein is included in the monolayer, as previously observed with the naturally isolated SP-B/C mixture. The 3D structures are associated exclusively with the presence of the SP-C protein in disordered monolayer phases. (3) To explain these results, we have derived a molecular model accounting for the structure and physico-chemical properties of the SP-C protein in terms of its energetics. The molecular events involved in the SP-C-mediated production of the 3D surface particles are explained using the analogy of a simple molecular machine, namely a loaded spring. This interpretation is supported by an energetic analysis that suggests the major factor contributing to the formation of the 3D particles is the energy liberated by re-expansion of the surrounding phospholipid film into the area vacated by the SP-C protein as it re-orients away from the surface.
As part of the Atmospheric Exchange Over Lakes and Oceans Study (AEOLOS), air-water exchange fluxes of polychlorinated biphenyls (PCBs) were determined along a transect in the Baltimore Harbor from the Inner Harbor of Baltimore, MD, to the mainstem of the northern Chesapeake Bay to assess the overall contributions of urban source PCBs through air-water exchange and their impacts on coastal waters. Six sites were sampled during three intensive sampling periods in June 1996, February 1997, and July 1997 and at two sites (urban and rural) every ninth day between March 1997 and March 1998 to measure spatial and temporal variability in the PCB air-water exchange fluxes. During the intensive sampling campaigns, net total PCB (t-PCBs) volatilization fluxes ranged between 5 and 2120 ng m(-2) day(-1), varying on both temporal and spatial scales. Volatilization fluxes were highest in February, driven by high winds and elevated dissolved PCB concentrations. Throughout the annual sampling period, t-PCB volatilization fluxes were similar between urban (130 microg m(-2) yr(-1)) and rural (120 microg m(-2) yr(-1)) sites. Approximately 10% of the dissolved t-PCB inventory in the water column in Baltimore Harbor exchanges with the atmosphere each day. From air-water exchange alone, the estimated residence time of dissolved t-PCBs in the harbor is approximately 10 days (estimated hydraulic residence time of water in the harbor is between 7 and 14 days), indicating that air-water exchange is an efficient removal mechanism of t-PCBs from urban coastal waters. Furthermore, the annual flux of t-PCBs volatilizing from Baltimore Harbor is approximately 12% of the gas-phase t-PCB inventory over the water, and at the northern Chesapeake Bay site, the t-PCB flux is approximately 40% of the gas-phase t-PCB inventory. This suggests that air-water exchange of t-PCBs has the potential to be a significant source of PCBs to the rural atmosphere.