Publications (11) View all
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Article: Features of the EAP events on the medium-range evolution process and the mid- and high-latitude Rossby wave activities during the Meiyu period
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ABSTRACT: In this paper, features for the evolution of the East Asia/Pacific (EAP) events and their association with high-and mid-latitude Rossby waves during the Meiyu period are analyzed on the medium-range time scale. It is shown that life cycles of the positive and negative EAP events cannot be simply regarded as “mirror” each other. In the upper troposphere, downward propagations of Rossby wave packets both over high-and mid-latitude regions of Eurasian continent and over the Asian jet region are responsible for generating basic patterns of high-and mid-latitude anomaly centers of the events. In this layer, Rossby wave packets also propagate from the mid-latitude anomaly center to the high-latitude one. In the middle and lower troposphere, the formation of the subtropical anomaly center of the event is mainly attributed to the anomalous convective activity in the tropical Pacific warm pool. The northward Rossby wave energy dispersion from this center is favorable to the enhancement and maintenance of the mid-latitude anomaly center in the same layer. Finally, it might be hypothesized that typical features of the positive and negative EAP events in their mature phase result from the interaction between (or phase-locking of) respective anomalous circulations induced both by quasi-zonal Rossby wave packets embedded in upper troposphere westerly and by quasi-meridional Rossby wave packets in the background flow of the East Asian summer monsoon in the middle and lower troposphere.Chinese Science Bulletin 04/2012; 53(4):610-623. · 1.32 Impact Factor -
Article: Crucial points within the pore as determinants of K⁺ channel conductance and gating.
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ABSTRACT: While selective for K⁺, K⁺ channels vary significantly among their rate of ion permeation. Here, we probe the effect of steric hindrance and electrostatics within the ion conduction pathway on K⁺ permeation in the MthK K⁺ channel using structure-based mutagenesis combined with single-channel electrophysiology and X-ray crystallography. We demonstrate that changes in side-chain size and polarity at Ala88, which forms the constriction point of the open MthK pore, have profound effects on single-channel conductance as well as open probability. We also reveal that the negatively charged Glu92s at the intracellular entrance of the open pore form an electrostatic trap, which stabilizes a hydrated K⁺ and facilitates ion permeation. This electrostatic attraction is also responsible for intracellular divalent blockage, which renders the channel inward rectified in the presence of Ca²⁺. In light of the high structural conservation of the selectivity filter, the size and chemical environment differences within the portion of the ion conduction pathway other than the filter are likely the determinants for the conductance variations among K⁺ channels.Journal of Molecular Biology 04/2011; 411(1):27-35. · 4.00 Impact Factor -
Article: Large‐scale circulation anomalies associated with persistent low temperature over Southern China in January 2008
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ABSTRACT: A pre-existing anticyclonic anomaly over Scandinavia/western Russia played a crucial role in the persistent low temperature event over southern China in January 2008. This anticyclonic anomaly extended eastward along the arctic coast of the Eurasian continent, and then induced the persistent low temperature over southern China. Considering that anticyclonic anomalies over Scandinavia/western Russia rarely extended eastward to central Siberia, the simultaneous presence of this feature along with the vigorous Rossby wave propagation along the African-Asian jet stream is found to be a fundamental factor in the occurrence of the persistent event. Copyright © 2011 Royal Meteorological SocietyAtmospheric Science Letters 03/2011; 12(3):273 - 280. · 1.93 Impact Factor -
Article: Tuning the ion selectivity of tetrameric cation channels by changing the number of ion binding sites.
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ABSTRACT: Selective ion conduction across ion channel pores is central to cellular physiology. To understand the underlying principles of ion selectivity in tetrameric cation channels, we engineered a set of cation channel pores based on the nonselective NaK channel and determined their structures to high resolution. These structures showcase an ensemble of selectivity filters with a various number of contiguous ion binding sites ranging from 2 to 4, with each individual site maintaining a geometry and ligand environment virtually identical to that of equivalent sites in K(+) channel selectivity filters. Combined with single channel electrophysiology, we show that only the channel with four ion binding sites is K(+) selective, whereas those with two or three are nonselective and permeate Na(+) and K(+) equally well. These observations strongly suggest that the number of contiguous ion binding sites in a single file is the key determinant of the channel's selectivity properties and the presence of four sites in K(+) channels is essential for highly selective and efficient permeation of K(+) ions.Proceedings of the National Academy of Sciences 01/2011; 108(2):598-602. · 9.68 Impact Factor -
Article: Structural insight into Ca2+ specificity in tetrameric cation channels.
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ABSTRACT: Apparent blockage of monovalent cation currents by the permeating blocker Ca(2+) is a physiologically essential phenomenon relevant to cyclic nucleotide-gated (CNG) channels. The recently determined crystal structure of a bacterial homolog of CNG channel pores, the NaK channel, revealed a Ca(2+) binding site at the extracellular entrance to the selectivity filter. This site is not formed by the side-chain carboxylate groups from the conserved acidic residue, Asp-66 in NaK, conventionally thought to directly chelate Ca(2+) in CNG channels, but rather by the backbone carbonyl groups of residue Gly-67. Here we present a detailed structural analysis of the NaK channel with a focus on Ca(2+) permeability and blockage. Our results confirm that the Asp-66 residue, although not involved in direct chelation of Ca(2+), plays an essential role in external Ca(2+) binding. Furthermore, we give evidence for the presence of a second Ca(2+) binding site within the NaK selectivity filter where monovalent cations also bind, providing a structural basis for Ca(2+) permeation through the NaK pore. Compared with other Ca(2+)-binding proteins, both sites in NaK present a novel mode of Ca(2+) chelation, using only backbone carbonyl oxygen atoms from residues in the selectivity filter. The external site is under indirect control by an acidic residue (Asp-66), making it Ca(2+)-specific. These findings give us a glimpse of the possible underlying mechanisms allowing Ca(2+) to act both as a permeating ion and blocker of CNG channels and raise the possibility of a similar chemistry governing Ca(2+) chelation in Ca(2+) channels.Proceedings of the National Academy of Sciences 10/2007; 104(39):15334-9. · 9.68 Impact Factor
