434 research outputs found
Seasonal variation of phytoplankton community assembly processes in Tibetan Plateau floodplain
Uncovering the mechanisms underlying phytoplankton community assembly remains a major challenge in freshwater ecology. The roles of environmental filtering and spatial processes in shaping phytoplankton metacommunity in Tibetan floodplain ecosystems under various hydrological conditions are still unclear. Here, multivariate statistics and a null model approach were used to compare the spatiotemporal patterns and assembly processes of phytoplankton communities in the river-oxbow lake system of Tibetan Plateau floodplain between non-flood and flood periods. The results showed that phytoplankton communities had significant seasonal and habitat variations, with the seasonal variations being more remarkable. Phytoplankton density, biomass, and alpha diversity were distinctly lower in the flood than non-flood period. The habitat differences (rivers vs. oxbow lakes) in phytoplankton community were less pronounced during the flood than non-flood period, most likely due to the increased hydrological connectivity. There was a significant distance-decay relationship only in lotic phytoplankton communities, and such relationship was stronger in the non-flood than flood period. Variation partitioning and PER-SIMPER analysis showed that the relative role of environmental filtering and spatial processes affecting phytoplankton assemblages varied across hydrological periods, with environmental filtering dominating in the non-flood period and spatial processes in the flood period. These results suggest that the flow regime plays a key role in balancing environmental and spatial factors in shaping phytoplankton communities. This study contributes to a deeper understanding of ecological phenomena in highland floodplains and provides a theoretical basis for floodplain ecosystem maintenance and ecological health management.Peer reviewe
Genetic Meta-Structure Search for Recommendation on Heterogeneous Information Network
In the past decade, the heterogeneous information network (HIN) has become an
important methodology for modern recommender systems. To fully leverage its
power, manually designed network templates, i.e., meta-structures, are
introduced to filter out semantic-aware information. The hand-crafted
meta-structure rely on intense expert knowledge, which is both laborious and
data-dependent. On the other hand, the number of meta-structures grows
exponentially with its size and the number of node types, which prohibits
brute-force search. To address these challenges, we propose Genetic
Meta-Structure Search (GEMS) to automatically optimize meta-structure designs
for recommendation on HINs. Specifically, GEMS adopts a parallel genetic
algorithm to search meaningful meta-structures for recommendation, and designs
dedicated rules and a meta-structure predictor to efficiently explore the
search space. Finally, we propose an attention based multi-view graph
convolutional network module to dynamically fuse information from different
meta-structures. Extensive experiments on three real-world datasets suggest the
effectiveness of GEMS, which consistently outperforms all baseline methods in
HIN recommendation. Compared with simplified GEMS which utilizes hand-crafted
meta-paths, GEMS achieves over performance gain on most evaluation
metrics. More importantly, we conduct an in-depth analysis on the identified
meta-structures, which sheds light on the HIN based recommender system design.Comment: Published in Proceedings of the 29th ACM International Conference on
Information and Knowledge Management (CIKM '20
Interaction of Flavonoids from Woodwardia unigemmata with Bovine Serum Albumin (BSA): Application of Spectroscopic Techniques and Molecular Modeling Methods
Phytochemical investigation on the methanol extract of Woodwardia unigemmata resulted
in the isolation of seven flavonoids, including one new flavonol acylglycoside (1). The structures of
these compounds were elucidated on the basis of extensive spectroscopic analysis and comparison
of literature data. The multidrug resistance (MDR) reversing activity was evaluated for the isolated
compounds using doxorubicin-resistant K562/A02 cells model. Compound 6 showed comparable
MDR reversing effect to verapamil. Furthermore, the interaction between compounds and bovine
serum albumin (BSA) was investigated by spectroscopic methods, including steady-state fluorescence,
synchronous fluorescence, circular dichroism (CD) spectroscopies, and molecular docking approach.
The experimental results indicated that the seven flavonoids bind to BSA by static quenching
mechanisms. The negative ∆H and ∆S values indicated that van der Waals interactions and hydrogen
bonds contributed in the binding of compounds 2–6 to BSA. In the case of compounds 1 and 7
systems, the hydrophobic interactions play a major role. The binding of compounds to BSA causes
slight changes in the secondary structure of BSA. There are two binding sites of compound 6 on BSA
and site I is the main site according to the molecular docking studies and the site marker competitive
binding assayThis work was supported by the Natural Science Foundation of China (81502921) and the
Young Scholars Program of Shandong University (2015WLJH50).Peer Reviewe
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Phosphorylation-Dependent 14-3-3 Binding to LRRK2 Is Impaired by Common Mutations of Familial Parkinson's Disease
Background: Recent studies show that mutations in Leucine Rich Repeat Kinase 2 (LRRK2) are the cause of the most common inherited and some sporadic forms of Parkinson's disease (PD). The molecular mechanism underlying the pathogenic role of LRRK2 mutations in PD remains unknown.Methodology/Principal Findings: Using affinity purification and mass spectrometric analysis, we investigated phosphorylation sites and binding proteins of LRRK2 purified from mouse brain. We identified multiple phosphorylation sites at N-terminus of LRRK2 including S910, S912, S935 and S973. Focusing on the high stoichiometry S935 phosphorylation site, we developed an anti-pS935 specific antibody and showed that LRRK2 is constitutively phosphorylated at S935 in various tissues (including brain) and at different ages in mice. We find that 14-3-3 proteins (especially isoforms γ and η) bind LRRK2 and this binding depends on phosphorylation of S935. The binding of 14-3-3, with little effect on dimer formation of LRRK2, confers protection of the phosphorylation status of S935. Furthermore, we show that protein kinase A (PKA), but not LRRK2 kinase itself, can cause the phosphorylation of LRRK2 at S935 in vitro and in cell culture, suggesting that PKA is a potential upstream kinase that regulates LRRK2 function. Finally, our study indicates that the common PD-related mutations of LRRK2, R1441G, Y1699C and G2019S, decrease homeostatic phosphorylation levels of S935 and impair 14-3-3 binding of LRRK2.Conclusions/Significance: LRRK2 is extensively phosphorylated in vivo, and the phosphorylation of specific sites (e.g. S935) determines 14-3-3 binding of LRRK2. We propose that 14-3-3 is an important regulator of LRRK2-mediated cellular functions. Our study suggests that PKA, a cAMP-dependent kinase involved in regulating dopamine physiology, is a potential upstream kinase that phosphorylates LRRK2 at S935. Furthermore, the reduction of phosphorylation/14-3-3 binding of LRRK2 due to the common familial PD-related mutations provides novel insight into the pathogenic mechanism of LRRK2-linked PD.</p
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