Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 2 de 2
Mais filtros

Base de dados
Intervalo de ano de publicação
Proc Natl Acad Sci U S A ; 113(21): 5828-34, 2016 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-26944081


Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25° restricts the satellite coverage to ∼25% of the world area in a single day.

PLoS One ; 10(9): e0138151, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26398213


Lipids and lipid-metabolizing esterases/lipases are highly important for the mycobacterial life cycle and, possibly, for mycobacterial virulence. In this study, we expressed 10 members of the Lip family of Mycobacterium tuberculosis. Among the 10 proteins, LipL displayed a significantly high enzymatic activity for the hydrolysis of long-chain lipids. The optimal temperature for the lipase activity of LipL was demonstrated to be 37°C, and the optimal pH was 8.0. The lipase active center was not the conserved motif G-x-S-x-G, but rather the S-x-x-K and GGG motifs, and the key catalytic amino acid residues were identified as G50, S88, and K91, as demonstrated through site-directed mutagenesis experiments. A three-dimensional modeling structure of LipL was constructed, which showed that the GGG motif was located in the surface of a pocket structure. Furthermore, the subcellular localization of LipL was demonstrated to be on the mycobacterial surface by Western blot analysis. Our results revealed that the LipL protein could induce a strong humoral immune response in humans and activate a CD8+ T cell-mediated response in mice. Overall, our study identified and characterized a novel lipase denoted LipL from M. tuberculosis, and demonstrated that LipL functions as an immunogen that activates both humoral and cell-mediated responses.

Lipase/imunologia , Mycobacterium tuberculosis/enzimologia , Sequência de Aminoácidos , Animais , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Clonagem Molecular , Detergentes/farmacologia , Genes Bacterianos , Humanos , Concentração de Íons de Hidrogênio , Lipase/química , Camundongos Endogâmicos BALB C , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Proteínas Mutantes/metabolismo , Mycobacterium tuberculosis/genética , Homologia Estrutural de Proteína , Frações Subcelulares/enzimologia , Especificidade por Substrato/efeitos dos fármacos , Temperatura