Cloning, sequencing and expression of cDNA for a novel subunit of acetylcholine receptor from calf muscle

The nicotinic acetylcholine receptor (AChR) from fish electric organ has a subunit structure of alpha 2 beta gamma delta, and this is thought to be also the case for the mammalian skeletal muscle AChR. By cloning and sequencing the complementary or genomic DNAs, we have previously elucidated the primary structures of all four subunits of the Torpedo californica electroplax and calf muscle AChR and of the alpha- and gamma-subunits of the human muscle AChR; the primary structures of the gamma-subunit of the T. californica AChR and the alpha-subunit of the Torpedo marmorata AChR have also been deduced elsewhere. We have now cloned DNA complementary to the calf muscle messenger RNA encoding a novel polypeptide (the epsilon-subunit) whose deduced amino-acid sequence has features characteristic of the AChR subunits and which shows higher sequence homology with the gamma-subunit than with the other subunits. cDNA expression studies indicate that the calf epsilon-subunit, as well as the calf gamma-subunit, can replace the Torpedo gamma-subunit to form the functional receptor in combination with the Torpedo alpha-, beta- and delta-subunits.     

甲型H1N1流感病毒流行株基因组进化分析

2009年4月, 北美地区出现甲型H1N1流感疫情, 并且疫情快速扩散至欧亚非三大洲, 风险等级上升至5级. 截止至5月13日, 甲型H1N1流感病毒已扩散至33个国家和地区, 实验室确认病例5728例, 死亡61人. 从NCBI的IRV和GISAID的EpiFluDB数据库下载甲型H1N1流感病毒序列425条, 进行序列比对与进化分析. 分析结果显示: (ⅰ) 当前流行的甲型H1N1流感病毒是一个三重排A型流感病毒: HA, NA, MP, NP和NS来源于猪流感病毒; PB2和PA来源于禽流感病毒; PB1来源于人流感病毒. (ⅱ) 猪流感病毒的来源可细分为: HA, NP和NS来源于H1N1亚型经典猪流感毒株; NA和MP来源于H1N1亚型禽源猪流感毒株. (ⅲ) 甲型H1N1流感病毒在流行扩散过程中没有显著变异, 同时病毒基因组没有发生重排. 本文除了分析美国代表毒株A/California/04/2009(H1N1)外, 还以墨西哥代表毒株A/Mexico/4486/2009(H1N1)为主进行了同源性和进化分析, 地理范围相对较大, 分析结果更具科学性.     

Chemical rescue of cleft palate and midline defects in conditional GSK-3beta mice

Glycogen synthase kinase-3beta (GSK-3beta) has integral roles in a variety of biological processes, including development, diabetes, and the progression of Alzheimer's disease. As such, a thorough understanding of GSK-3beta function will have a broad impact on human biology and therapeutics. Because GSK-3beta interacts with many different pathways, its specific developmental roles remain unclear. We have discovered a genetic requirement for GSK-3beta in midline development. Homozygous null mice display cleft palate, incomplete fusion of the ribs at the midline and bifid sternum as well as delayed sternal ossification. Using a chemically regulated allele of GSK-3beta (ref. 6), we have defined requirements for GSK-3beta activity during discrete temporal windows in palatogenesis and skeletogenesis. The rapamycin-dependent allele of GSK-3beta produces GSK-3beta fused to a tag, FRB* (FKBP/rapamycin binding), resulting in a rapidly destabilized chimaeric protein. In the absence of drug, GSK-3beta(FRB)*(/FRB)* mutants appear phenotypically identical to GSK-3beta-/- mutants. In the presence of drug, GSK-3betaFRB* is rapidly stabilized, restoring protein levels and activity. Using this system, mutant phenotypes were rescued by restoring endogenous GSK-3beta activity during two distinct periods in gestation. This technology provides a powerful tool for defining windows of protein function during development.     

Clathrate nanostructures for mass spectrometry

The ability of mass spectrometry to generate intact biomolecular ions efficiently in the gas phase has led to its widespread application in metabolomics, proteomics, biological imaging, biomarker discovery and clinical assays (namely neonatal screens). Matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization have been at the forefront of these developments. However, matrix application complicates the use of MALDI for cellular, tissue, biofluid and microarray analysis and can limit the spatial resolution because of the matrix crystal size (typically more than 10 mum), sensitivity and detection of small compounds (less than 500 Da). Secondary-ion mass spectrometry has extremely high lateral resolution (100 nm) and has found biological applications although the energetic desorption/ionization is a limitation owing to molecular fragmentation. Here we introduce nanostructure-initiator mass spectrometry (NIMS), a tool for spatially defined mass analysis. NIMS uses 'initiator' molecules trapped in nanostructured surfaces or 'clathrates' to release and ionize intact molecules adsorbed on the surface. This surface responds to both ion and laser irradiation. The lateral resolution (ion-NIMS about 150 nm), sensitivity, matrix-free and reduced fragmentation of NIMS allows direct characterization of peptide microarrays, direct mass analysis of single cells, tissue imaging, and direct characterization of blood and urine.     

Magnetic carbon

The discovery of nanostructured forms of molecular carbon has led to renewed interest in the varied properties of this element. Both graphite and C60 can be electron-doped by alkali metals to become superconducting; transition temperatures of up to 52 K have been attained by field-induced hole-doping of C60 (ref. 2). Recent experiments and theoretical studies have suggested that electronic instabilities in pure graphite may give rise to superconducting and ferromagnetic properties, even at room temperature. Here we report the serendipitous discovery of strong magnetic signals in rhombohedral C60. Our intention was to search for superconductivity in polymerized C60; however, it appears that our high-pressure, high-temperature polymerization process results in a magnetically ordered state. The material exhibits features typical of ferromagnets: saturation magnetization, large hysteresis and attachment to a magnet at room temperature. The temperature dependences of the saturation and remanent magnetization indicate a Curie temperature near 500 K.