Anion-catalyzed dissolution of NO2 on aqueous microdroplets.

Fifty-seven years after NO(x) (NO + NO(2)) were identified as essential components of photochemical smog, atmospheric chemical models fail to correctly predict *OH/HO(2)* concentrations under NO(x)-rich conditions. This deficiency is due, in part, to the uncertain rates and mechanism for the reactive dissolution of NO(2)(g) (2NO(2) + H(2)O = NO(3)(-) + H(+) + HONO) in fog and aerosol droplets. Thus, state-of-the-art models parametrize the uptake of NO(2) by atmospheric aerosol from data obtained on "deactivated tunnel wall residue". Here, we report experiments in which NO(3)(-) production on the surface of microdroplets exposed to NO(2)(g) for approximately 1 ms is monitored by online thermospray mass spectrometry. NO(2) does not dissolve in deionized water (NO(3)(-) signals below the detection limit) but readily produces NO(3)(-) on aqueous NaX (X = Cl, Br, I) microdroplets with NO(2) uptake coefficients gamma that vary nonmonotonically with electrolyte concentration and peak at gamma(max) approximately 10(-4) for [NaX] approximately 1 mM, which is >10(3) larger than that in neat water. Since I(-) is partially oxidized to I(2)(*-) in this process, anions seem to capture NO(2)(g) into X-NO(2)(*-) radical anions for further reaction at the air/water interface. By showing that gamma is strongly enhanced by electrolytes, these results resolve outstanding discrepancies between previous measurements in neat water versus NaCl-seeded clouds. They also provide a general mechanism for the heterogeneous conversion of NO(2)(g) to (NO(3)(-) + HONO) on the surface of aqueous media.

Electrospray mass spectrometric detection of products and short-lived intermediates in aqueous aerosol microdroplets exposed to a reactive gas.

The intermediates ISO3- (m/z=207) and IS2O3- (m/z=239) generated in aqueous (NaI/Na2S2O3) microdroplets traversing dilute O3 gas plumes are detected via online electrospray mass spectrometry within approximately 1 ms, and their stabilities gauged by collisionally induced dissociation. The simultaneous detection of anionic reactants and the S2O62-, HSO4-, IO3-, and I3- products as a function of experimental conditions provides evidence of genuinely interfacial reaction kinetics. Although O3(aq) reacts about 3 times faster with I- than with S2O32- in bulk solution, only S2O32- is significantly depleted in the interfacial layers of [I-]/[S2O32-]=10 microdroplets below [O3(g)] approximately 50 ppm.

Global inorganic source of atmospheric bromine.

A few bromine molecules per trillion (ppt) causes the complete destruction of ozone in the lower troposphere during polar spring and about half of the losses associated with the "ozone hole" in the stratosphere. Recent field and aerial measurements of the proxy BrO in the free troposphere suggest an even more pervasive global role for bromine. Models, which quantify ozone trends by assuming atmospheric inorganic bromine (Bry) stems exclusively from long-lived bromoalkane gases, significantly underpredict BrO measurements. This discrepancy effectively implies a ubiquitous tropospheric background level of approximately 4 ppt Bry of unknown origin. Here, we report that I- efficiently catalyzes the oxidation of Br- and Cl- in aqueous nanodroplets exposed to ozone, the everpresent atmospheric oxidizer, under conditions resembling those encountered in marine aerosols. Br- and Cl-, which are rather unreactive toward O3 and were previously deemed unlikely direct precursors of atmospheric halogens, are readily converted into IBr2- and ICl2- en route to Br2(g) and Cl2(g) in the presence of I-. Fine sea salt aerosol particles, which are predictably and demonstrably enriched in I- and Br-, are thus expected to globally release photoactive halogen compounds into the atmosphere, even in the absence of sunlight.

FBR murine osteosarcoma virus. II. Nucleotide sequence of the provirus reveals that the genome contains sequences acquired from two cellular genes.

The complete nucleotide sequence of the FBR proviral DNA has been determined. The provirus of 3791 nucleotides (specifying a genome of 3284 bases) encodes a single gag- fos fusion product of 554 amino acids. The fos portion of the gene lacks the sequences which code for the first 24 and the last 98 amino acids of the 380-amino acid mouse c- fos gene product. In addition, the coding region has sustained three in-frame deletions, one in the p30gag portion, and two in the fos region, as compared to the sequences of AKR-MLV and the c- fos gene, respectively. The gene product terminates in sequences, termed v-fox, that are present in uninfected mouse DNA at loci unrelated to the c- fos gene. The c-fox gene(s) is expressed as an abundant class of polyadenylated RNA in normal mouse tissues.

Growth of normal and neoplastic mouse mammary epithelial cells in primary culture: stimulation by conditioned medium from mouse mammary fibroblasts.

Conditioned medium obtained from mouse mammary fibroblasts markedly stimulated both DNA synthesis and cell proliferation in primary monolayer cultures of mouse mammary tumor cells. Growth of normal mammary epithelial cells from virgin female mice was likewise stimulated by the conditioned medium. The growth-stimulating activity was absent in conditioned media from 3T3 cells, 3T6 cells, mouse embryonic and lung fibroblasts, mammary tumor cells and normal mammary epithelial cells. Stimulation of DNA synthesis in mammary tumor cells was also observed with epidermal growth factor (EGF), although the effect was less than that observed with the conditioned medium. Receptor studies using 125I-labeled EGF further showed that the specific binding of EGF to mammary tumor cells was not inhibited by the conditioned medium. The molecular weight of the growth-stimulating activity in mammary fibroblast-conditioned medium was estimated to be approximately 100,000 daltons by Sephadex G-200 column chromatography. These observations suggest that mammary fibroblasts, which constitute the stroma of the mammary gland, produce a mammary epithelial cell growth factor(s) distinct from EGF.