二脂酰甘油酰基转移酶基因(DGAT1)的沉默对烟草油脂合成的影响

二脂酰甘油酰基转移酶 (DGAT; EC 2.3.1.20) 是催化三脂酰甘油（TAG）合成的最后也是最关键步骤的酶。TAG是真核细胞中最重要的能量存储形式。在植物中，TAG主要在种子、花粉和许多物种的果实中积累。然而，DGAT1基因的转录本也存在于植物的其它器官中，这些器官包括根、茎、叶、花瓣、花粉囊、未成熟的角果、幼苗以及正在发芽的种子等。迄今为止，许多针对DGAT1基因的研究都集中于DGAT1基因的表达在对种子油脂的积累以及对种子中TAG的脂肪酸组成所起的作用上。在本研究中，我们通过构建烟草DGAT1基因带有内含子的发卡RNA（hpRNA）结构，使之在转基因烟草植株中表达双链RNA（dsRNA），利用RNAi原理达到使烟草内源DGAT1基因沉默的目的。转基因沉默烟草植株的获得将会为更好地研究DGAT1基因的功能奠定基础。本实验不仅研究分析了DGAT1基因的抑制对烟草种子油脂积累的影响，还对表现出沉默性状的转基因植株Sil7的不同器官中TAG的含量以及DGAT1的转录水平等进行了研究分析。此外，通过对转基因烟草不同株系种子中的主要贮藏物质——油脂、蛋白质和糖的含量测定，初步揭示出在烟草种子中三者生物合成代谢之间存在的相关性。主要研究结果如下： 采用烟草DGAT1基因的第615～1293碱基之间679bp的片段构建了能表达发卡RNA（hpRNA）结构的表达载体，并转化烟草（Nicotiana tabacum）Wisconsin 38。Northern杂交分析发现,与野生型对照烟草（WT）相比，在沉默植株的花和发育状态种子中DGAT1基因的转录水平有很大降低，这表明该发卡结构能够高效率地引起烟草DGAT1基因的沉默。此外，在对Sil1至Sil12共12株转基因烟草进行油脂含量分析的结果表明，其中有8株表现出油脂降低的性状，转基因沉默效率达到67％。这表明：利用RNAi的方法可对目标基因进行特异降解来研究基因的功能，因此是一个在研究基因的表达功能上十分有效的方法，而且已成为植物基因工程的有力工具。 为了研究DGAT1基因的沉默对转基因植株不同器官的影响，本实验分析了转基因植株Sil7的不同器官中TAG的含量和脂肪酸组成，并采用RT-PCR方法对野生型对照和转基因植株中DGAT1基因的转录水平进行了比较分析。研究发现，转基因植株不同器官中DGAT1基因转录水平的降低与各器官中TAG含量的减少呈正相关。由此看来，植物中DGAT1的表达水平与植物的各个器官内TAG的含量之间存在着一定的对应关系。此外，在转基因植株Sil7不同器官中依然能够产生TAG，这说明或者DGAT1酶活性丧失而由其它的酶（如DGAT2和PDAT）参与TAG的合成，或者DGAT1酶活性只是部分地受到影响。本实验还对Sil7的根、茎、叶、花瓣和种子中TAG的脂肪酸组成进行了分析，结果发现，与烟草野生型对照相比，在Sil7的这些器官中，除种子中TAG的脂肪酸组成无明显变化外，其余器官中TAG的18:3/18:2脂肪酸比例均有明显升高。 对其中8株转基因烟草种子进行油脂含量分析发现，在转基因烟草中由于DGAT1基因的沉默引起种子中TAG含量的减少，从而引起了种子平均千粒重的下降。而在TAG含量和种子平均千粒重下降的同时，种子中其它贮藏物质－蛋白质和糖类的含量却增加了。该实验结果表明：在烟草种子中TAG的生物合成与蛋白质和糖类物质的合成之间存在着负的相关性。

A novel ultra low power temperature sensor for UHF RFID tag chip

A novel ultra low power temperature sensor for UHF RFID tag chip is presented. The sensor consists of a constant pulse generator, a temperature related oscillator, a counter and a bias. Conversion of temperature to digital output is fulfilled by counting the number of the clocks of the temperature related oscillator in a constant pulse period. The sensor uses time domain comparing, where high power consumption bandgap voltage references and traditional ADCs are not needed. The sensor is realized in a standard 0.18 mu m CMOS process, and the area is only 0.2mm(2). The accuracy of the temperature sensor is +/- 1 degrees C after calibration. The power consumption of the sensor is only 0.9 mu W.

A Novel Low-Power Digital Baseband Circuit for UHF RFID Tag with Sensors

A novel low-power digital baseband circuit for UHF RFID tag with sensors is presented in this paper. It proposes a novel baseband architecture and a new operating scheme to fulfill the sensor functions and to reduce power consumption. It is also compatible with the EPC C1G2 UHF RFID protocol. It adopts some advanced low power techniques for system design and circuit design: adaptive clock-gating, multi-clock domain and asynchronous circuit. The baseband circuit is implemented in 0.18um 1P3M standard CMOS process. ne chip area is 0.28 mm(2) excluding test pads. Its power consumption is 25uW under 1.1V power supply.

[Ru(bpy)(3)](2+)-doped silica nanoparticles within layer-by-layer biomolecular coatings and their application as a biocompatible electrochemiluminescent tag material

[Ru(bpy)(3)](2+)-doped silica (RuSi) nanoparticles were synthesized by using a water/oil microemulsion method. Stable electrochemiluminescence (ECL) was obtained when the RuSi nanoparticles were immobilized on a glassy carbon electrode by using tripropylamine (TPA) as a coreactant. Furthermore, the ECL of the RuSi nanoparticles with layer-by-layer biomolecular coatings was investigated. Squential self-assembly of the polyelectrolytes and biomolecules on the RuSi nanoparticles gave nanocomposite suspensions, the ECL of which decreased on increasing the number of bilayers.

He, Ne and Ar isotope compositions of fluid inclusions in hydrothermal sulfides from the TAG hydrothermal field, Mid-Atlantic Ridge

Helium, rieon and argon isotope compositions of fluid inclusions have been measured in hydrothermal sulfide samples from the TAG hydrothermal field at the Mid-Atlantic Ridge. Fluid-inclusion He-3/He-4 ratios are 2.2-13.3 times the air value (Ra), and with a mean of 7.2 Ra. Comparison with the local vent fluids (He-3/He-4=7.5-8.2 Ra) and mid-ocean ridge basalt values (He-3/He-4=6-11 Ra) shows that the variation range of He-3/He-4 ratios from sulfide-hosted fluid inclusions is significantly large. Values for Ne-20/Ne-22 are from 10.2 to 11.4, which are significantly higher than the atmospheric ratio (9.8). And fluid-inclusion Ar-40/Ar-36 ratios range from 287 to 359, which are close to the atmospheric values (295.5). These results indicate that the noble gases of fluid inclusions in hydrothermal sulfides are a mixture of mantle- and seawater-derived noble gases; the partial mantle-derived components of trapped hydrothermal fluids may be from the lower mantle; the helium of fluid inclusions is mainly from upper mantle; and the Ne and Ar components are mainly from seawater.