Multiple flavonoid-binding sites within multidrug resistance protein MRP1

Recombinant nucleotide-binding domains (NBDs) from human multidrug resistance protein MRP1 were overexpressed in bacteria and purified to measure their direct interaction with high-affinity flavonoids, and to evaluate a potential correlation with inhibition of MRP1-mediated transport activity and reversion of cellular multidrug resistance. Among different classes of flavonoids, dehydrosilybin exhibited the highest affinity for both NBDs, the binding to N-terminal NBD1 being prevented by ATP. Dehydrosilybin increased vanadate-induced 8-N₃-[-³²P]ADP trapping, indicating stimulation of ATPase activity. In contrast, dehydrosilybin strongly inhibited leukotriene C₄ (LTC₄) transport by membrane vesicles from MRP1-transfected cells, independently of reduced glutathione, and chemosensitized cell growth to vincristine. Hydrophobic C-isoprenylation of dehydrosilybin increased the binding affinity for NBD1, but outsite the ATP site, lowered the increase in vanadate-induced 8-N₃-[-³²P]ADP trapping, weakened inhibition of LTC₄ transport which became glutathione dependent, and induced some cross-resistance. The overall results indicate multiple binding sites for dehydrosilybin and its derivatives, on both cytosolic and transmembrane domains of MRP1.Received 1 May 2003; received after revision 18 June 2003; accepted 24 June 2003     

Defects in whirlin,a PDZ domain molecule involved in stereocilia elongation,cause deafness in the whirler mouse and families with DFNB31

The whirler mouse mutant (wi) does not respond to sound stimuli, and detailed ultrastructural analysis of sensory hair cells in the organ of Corti of the inner ear indicates that the whirler gene encodes a protein involved in the elongation and maintenance of stereocilia in both inner hair cells (IHCs) and outer hair cells (OHCs). BAC-mediated transgene correction of the mouse phenotype and mutation analysis identified the causative gene as encoding a novel PDZ protein called whirlin. The gene encoding whirlin also underlies the human autosomal recessive deafness locus DFNB31. In the mouse cochlea, whirlin is expressed in the sensory IHC and OHC stereocilia. Our findings suggest that this novel PDZ domain-containing molecule acts as an organizer of submembranous molecular complexes that control the coordinated actin polymerization and membrane growth of stereocilia.     

A new pterosaur (Pterodactyloidea,Tapejaridae) from the Early Cretaceous Jiufotang Formation of western Liaoning,China and its implications for biostratigraphy

In this article we describe a new and exceptionally weel-preserved pterodactyloid pterosaur,Sinopterus dong gen.et sp.nov.from the Jiufotang Formation in western Liaoning Province of northeast China,The new species is referred to the family Tapejaridae,representing its first record outside Brazil.It also represents the earliest occurrence as well as the most complete sketeton of the famil.Some revisions are made about the family according to the mophological observations of the postcranial bones of Sinopterus.Two pterosaur assemblages appear to have existed in the Jehol Group,represented by the lower Yixian Formation and upper Jiufotang Formation,respectively,The lower pterosaur assemblage shows some resembalance to that of the Late Jurassic in Solnhofen (Tithonian)by sharing members of the Pterodactylidae and Anurognathidae.The upper one shows more resemblance to that to the Early Cretaceous Santana Formation (Aptian/Albian) by comprising only pterodactyloids such as the Tapejaridae,The age of the Yixian Formation is younger than that of the Solnhofen lihographic limestone ,and the age of the Jiufotang Formation (Aptian )is slightly older than the Santana Formation.     

Fabrication and characteristics of intrinsic Josephson junctions in Bi<Subscript>2</Subscript>Sr<Subscript>2</Subscript>CaCu<Subscript>2</Subscript>O<Subscript>8+x</Subscript> single crystals

Mesa-structured intrinsic Jospehson junctions are fabricated in Bi2Sr2CaCu2O8 x single crystals.Typical current-voltage characteristics of intrinsic Josephson junctions are observed .which include multiple quasi-particle branches,surface junction with critical current lower than those of inner junctions.and subgap structures on quasi-particle branches,The corresponding physical explanations are also given .The energy gap voltage of the intrinsic Josephson junctions at 30 K is about 20mV Besides,The measured Ic-T relationship agrees quite well with the theoretical computations based on dx′-y′-wave superconductor.Our measured dI/dV-V relationship shows the V-shaped gap structure,obviously differing from the U-shaped gap structure of the s-wave superconductor.     

Equilibrium PT curve of methane hydrates in the presence of AlCl<Subscript>3</Subscript>

Using an experimental transparent sapphire high-pressure cell,three-phase (methane hydrate AlCl3 solution methane )equilibrium conditions of methane hydrates in the aqueous solution containing AlCl3 have been investigated under conditions of temperature from 272.15 to 278.15K and pressure from 4.040 to 8.382 MPa ,It could be clearly verified that AlCl3 is of stronger inhibitive effect than that observed for other electrolytes,such as KCl,CaCl2 ,at the same mole fraction,The induction time of the methane hydrate fromation becomes longer when the water activity decreases with the increase of ion charge numbers.Methane hydrates tend to crystallize more easily with higher concentration (AlCl3 concentration of 18%) than lower one (AlCl3 concentration of 10%) in the same electriclyte solution ,An empirical exponential equation is presented to calculate the equilibrium temperature and pressure of methane hydrate stable occurrence ,and to correlate the measured data for aqueous AlCl3 solution .The results show that there was infinitely small discrepance between the theoretical computed values and the data oberseved in actual experiments.     

Characterization of a calmodulin binding protein kinase from<Emphasis Type="Italic">Arabidopsis thalian</Emphasis>

A full-length calmodulin binding protein kinase cDNA ,AtCBK1 ,from Arabidopsis has been isolated by screening of an Arabidopsis cDNA library and by 5′-RACE-Northern blot and in situ hybridization indicated that the expression of AtCBK1 was more abundant in the vascular bundles and the meristems than in other tissues,The phylogenetic analyses revenl that AtCBK1 is different from animal CaMKs and it falls into CRK subgroup,indicating that they may come from different ancestors,The result suggests that AtCBK1 encoldes a CaM-binding serine/threonine protein kinase.     

Cloning and enzymology analysis of farnesyl pyrophosphate synthase gene from a superior strain of<Emphasis Type="Italic">Artemisia annua</Emphasis> L.

A cDNA(af1) encoding farnesyl pyrophosphate synthase AaFPS1(FPS,EC2.5.1.1/EC2.5.1.10) from a high yield Artemisia annua strain 025 has heen cloned from its cDNA library .Sequence analysis showed that the cDNA encoded a protein of 343 amino acid (aa) residues with molecular weight of 39 kD.Deduced aa sequence of the cDNA was similar to FPS from other plants,yeast and mammals,containing 5 conserved domains found in both prenyl trans-ferase and polyprenyl synthase,The expression of the cDNA in Escherichia coli showed measurable specific activity of FPS in vitro.The enzyme was purified by ion exchange chromatography and its kinetics was measured ,These results would further promote the molecular regulation of artemisnin biosynthesis.     

Population information extraction in Chaohu watershed based on RS and GIS

It is always difficult to extract population information of small watershed during the region environment assessment.The report adopted compound areal interpolation to study the population in Chaohu watershed with the GIS technique and landuse interpretation data from remote sensing.The result indicated that the method is effective to extract population information of small watershed.     

Geological records of marine environmental changes in the southern Okinawa Trough

Indexes of sediment grain size,sedimentation rates,geochemical composition,heavy,minerals,benthic foraminiferal fauna,indicator species of the Kuroshio Current,paleo-SST and carbonate dissolution of core E017 conformably suggest a great marine environmental change occurring at about 10.1-9.2cal.kaBP in the southern Okinawa Trough,which may correspond to the strengthening of the Kuroshio Warm Current and re-entering the Okinawa Trough through the sea area off northeast Taiwan.The invasion of Kuroshio current has experienced a process of gradual strengthening and then weakening,and its intensity became more fluctuation during the last 5000 years.Compared to the transition of sediment grain size,geochemical composition and heavy minerals,the foraminiferal faunas show a 900-year lag,which may indicate that the invasion of Kuroshio Current and the consequent sea surface and deep-water environmental chanages is a gradual process,and fauna has an obvious lag compared to environment altering.The carbonate dissolution of the Okinawa Trough has had an apparent strengthening since 9.2cal.kaBP,and reached a maximum in the late 3000 years,which may be caued by the deep-water environmental changes due to the invasion of Kuroshio Current.     

Reconstruction of surface ocean water <Emphasis Type="Italic">p</Emphasis>CO<Subscript>2</Subscript>(aq) in Nansha area,the South China Sea during the last 30 ka

The reconstruction of pCO2 in the tropic ocean is one of the most important issues to understand global climatic changes.In this study,the high-resolution stratigraphic analysis of core 17962 was conducted,which is Iocated in the southern South China Sea(SCS).The contents of sedimentary organic matter,the stable carbon isotopic composition of sedimentary organic matter,and the δ^13C values of black carbon and terrigenons n-alkanes were determined.And the δ^13Cwc value of carbon derived from aquatic was calculated.On the basis of δ^13Corg-pCO2equation proposed by Popp et al.(1989),we estimated the pCO2 in the Nansha area,SCS,since the last glaciation using δ^13Cwc instead of δ^13Corg.The results show that the average pCO2 was estimated at 240 ppm V during the last glaciation,and at 320ppm V in the Holocene.A comparison of surface sea pCO2 with the atmosphere CO2 recorded in the Vostok ice core,indicates that CO2 in surface water of the southern SCS could emit into atmosphere during the last 30ka.