PM2.5 10 endotoxin content was significantly correlated with IL-6 production (individual sample means: r = 0.56, p < 0.001; site-specific means: r = 0.92, p < 0.001).
However, we fitted an interaction model involving site as a fixed factor, for the purpose of presenting tables with site-specific means.
Of the elements considered, Fe, Cu, Cr, Mn, Sb, and Ba were positively associated with the AA response induced by PM2.5 10, both when the correlation was based on all 41 samples, and on the nine site-specific means (see Supplemental Material, Table 3).
Further validation is carried out using the site-specific mean pattern associated to field measurements of bridge strains when traversed by a truck population.
For summer morning sampling runs, site-specific mean PM2.5 ranged from 30.0 (SD = 3.3) to 55.1 (SD = 13.0) μg/m.
Linear regression of site-specific mean EC concentration on mean large truck counts predicted an increase of 1.69 microg/m(3) EC per 100 large trucks/hr (SE = 0.37; p = 0.01; R(2) = 0.84).
Endotoxin was present in all of the fine and coarse PM samples, with higher concentrations in PM2.5 10 samples and significant differences in site-specific mean PM2.5 10 endotoxin concentrations [ p = 0.005; see Supplemental Material, Figure 6 (doi:10.1289/ehp.1002105)].
In a first step, we computed the site-specific mean hydrophobicities [ h i ] using Eq. (5), which needs as input the distribution of PE values, i.e. the fraction of sites with c i /< c> in a given range, and the mean and standard deviation of the hydrophobicity, which were obtained from the protein sequences.
During winter mobile air sampling, site-specific mean PM2.5 concentrations varied from 15.8 to 33.8 μg/m (SD = 2.4 and 11.4 μg/m, respectively), and mean PM10 varied from 20.0 to 48.2 μg/m (SD = 2.6 and 22.5 μg/m, respectively).
Note that only the mutation parameters were fitted, whereas the selection parameters β i were calculated from the mutation model and the site-specific mean hydrophobicities given by Eq. (5), which only involves the two parameters A and B. These were calculated from the mean and the standard deviation of the hydrophobicity in the whole set of globular proteins, without any fitting procedure.
MS/MS-based analyses offer the most specific means of site-specific quantitation of protein posttranslational modifications.
