沙面结皮形成与微环境变化

研究结果表明沙坡头地区的大气年降尘(d相似文献   

固相萃取与气相色谱⁃质谱法联用测定食用植物油和含脂肪食品中氯丙醇酯的方法验证研究

氯丙醇酯是国际上广泛关注的食品加工过程污染物,其水解产物氯丙醇对人体（特别是婴幼儿）危害风险较大。采用固相萃取与气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）联用技术,对食用植物油和含脂食品中的氯丙醇酯[3-氯-1,2-丙二醇脂肪酸酯（简称3-MCPD酯）和2-氯-1,3-丙二醇脂肪酸酯（简称2-MCPD酯）]进行检测。该方法准确度高（3-MCPD酯和2-MCPD酯的平均回收率分别为98.9%和96.5%)、灵敏度高(3-MCPD酯和2-MCPD酯的检出限分别为0.042 mg·kg^-1和0.058 mg·kg^-1)、重现性好(相对标准偏差均低于5%)。76批次监测样品中,3-MCPD酯和2-MCPD酯的含量分别为0.042~4.865 mg·kg^-1(平均值为0.773 mg·kg^-1)和0.058~2.592 mg·kg^-1(平均值为0.469 mg·kg^-1)。经机构间的协同验证和英国FAPAS样的能力验证,2种氯丙醇酯在0.200~3.000 mg·kg^-1范围内线性良好,为进一步研究奠定了基础,同时也为食品加工企业严格控制生产过程建立了一种可行的检测方法。     

Nature of 2n gamete formation and mode of inheritance in interspecific hybrids of diploid Vaccinium darrowi and tetraploid V. corymbosum

RAPD markers were used to determine the level of heterozygosity transmitted via 2n gametes from V. darrowi selection Florida 4B (Fla 4B) to inter-specific hybrids with tetraploid V. corymbosum cv Bluecrop. The tetraploid hybrid US 75 was found to contain about 70% of Fla 4B's heterozygosity, a value attributed to a first-division restitution (FDR) mode of 2n gamete production. Crossovers during 2n gamete formation were evidenced by the absence of 16 dominant alleles of Fla 4B in US 75, and direct tests of segregation in a diploid population involving Fla 4B. RAPD markers that were present in both Fla 4B and US 75 were used to determine the mode of inheritance in a segregating population of US 75xV. corymbosum cv Bluetta. Thirty-one duplex loci were identified which segregated in a 51 ratio, indicating that US 75 undergoes tetrasomic inheritance.     

Regulation of cellulase synthesis in mycelial fungi: Participation of ATP and cyclic AMP

Summary ATP and cAMP in 4 strains of mycelial fungi were determined by luciferin-luciferase system and HPLC respectively. Cellulase synthesis was subject to the dual control of ATP and cAMP. No matter what carbon sourse was used, cellulase synthesis was repressed if intracellular ATP concentration was over 10^-7mg/ml. Exogenous cAMP could increase cellulase synthesis under depression conditions.     

Structure determination of N-linked oligosaccharides engineered at the CH1 domain of humanized LL2

Two humanized antibody mutants, hLL2HCN1 and hLL2HCN5, engineeredwith CH₁ domain-appended carbohydrates (CHOs) were generatedto facilitate site-specific conjugation of radionudides andanti-cancer drugs to antibodies. Such site-specific conjugationmay minimize the incidence of immunoreactlvity perturbationas is often observed with random conjugation. Since the compositionsand structures of CHOs are important in determining the chemistry,efficiency, and extent of conjugation, the sequences of theCH₁-appended CHOs were determined by exoglycosidase digestionsand fluorophore-assisted CHO electrophoresis (FACE). The CHOspecies attached at HCN1 and HCN5 sites in hLL2HCN1 and IJLL2HCN5,respectively, were distinct from each other, heterogeneous,and extensively processed. All of these CHOs were corefucosylatedcomplex-type oligosaccharides and contained Gal (galactose)and GlcNAc (N-acetylglucosamine) residues in the outer branches.Some of the outer branches were composed of Gal     

Kinetic study on starch hydrolysis using a glucose/maltose sensing system

Summary A dual-enzyme electrode flow injection system that can simultaneously determine glucose and maltose is used for an on-line study of starch hydrolyses catalysed by amylases. With the working system, determinations can be made every 2 minutes. A 10 L sample size with recycled back-flow minimises any loss of the reaction medium. The production, growth and decay of glucose and maltose concentrations during starch hydrolysis under various enzymatic conditions can thus be closely monitored, making it useful for the study of the catalytic kinetics of amylases and in screening and analysing enzyme systems.     

水稻雄核发育途径及游离花粉粒培养的活体观察

(1)在水稻雄核发育中,观察到 A—V、A—G、A—GV 和 B 途径,通常 B 途径占优势。在雄核发育早期,各种发育途径的花粉均有退化现象发生。(2)观察和统计表明,游离核型的多核花粉在发育过程中可转变为多细胞花粉,因而也是有发育前途的。(3)能够启动雄核发育的花粉通常是原生质稠密,在花粉群体中属中等大小(35—40μ)的花粉。多细胞花粉在突破花粉壁前。其细胞壁常常加厚,破壁时整个花粉有突然收缩的现象。(4)多细胞花粉内通常含有一些缓慢运动的小淀粉粒,它们可能积极参与了花粉雄核发育过程中的代谢活动。