A CMOS fluorescent detector system for biological experiment is presented. This system integrates a CMOS compatible photodiode, a capacitive trans-impedance amplifier （CTIA）, and a 12 bit pipelined analog-to- digita...A CMOS fluorescent detector system for biological experiment is presented. This system integrates a CMOS compatible photodiode, a capacitive trans-impedance amplifier （CTIA）, and a 12 bit pipelined analog-to- digital converter （ADC）, and is implemented in a 0.18μm standard CMOS process. Some special techniques, such as a ＂contact imaging＂ detecting method, pseudo-differential architecture, dummy photodiodes, and a T-type reset switch, are adopted to achieve low-level sensing application. Experiment results show that the Nwell/Psub photodiode with CTIA pixel achieves a sensitivity of 0.1 A/W at 515 nm and a dark current of 300 fA with 300 mV reverse biased voltage. The maximum differential and integral nonlinearity of the designed ADC are 0.8 LSB and 3 LSB, respectively. With an integrating time of 50 ms, this system is sensitive to the fluorescence emitted by the fluorescein solution with concentration as low as 20 ng/mL and can generate 7 fA photocurrent. This chip occupies 3 mm^2 and consumes 37 mW.展开更多
Eukaryotic membrane proteins, many of which are key players in various biological processes, constitute more than half of the drug targets and represent important candidates for structural studies. In contrast to thei...Eukaryotic membrane proteins, many of which are key players in various biological processes, constitute more than half of the drug targets and represent important candidates for structural studies. In contrast to their physiological significance, only very limited number of eukaryoUc membrane protein structures have been obtained due to the technical challenges in the genera- tion of recombinant proteins. In this review, we examine the major recombinant expression systems for eukaryotic membrane proteins and compare their relative advantages and disadvantages. We also attempted to summarize the recent technical strategies in the advancement of eukaryotic membrane protein purification and crystallization.展开更多
荧光共振能量转移技术(fluorescence resonance energy transfer,FRET)作为一种经典的荧光检测技术,已经广泛运用于生物科学研究中,开发了一系列基于FRET技术的荧光检测探针。半胱氨酸蛋白酶家族(cysteine aspartic acid specific prote...荧光共振能量转移技术(fluorescence resonance energy transfer,FRET)作为一种经典的荧光检测技术,已经广泛运用于生物科学研究中,开发了一系列基于FRET技术的荧光检测探针。半胱氨酸蛋白酶家族(cysteine aspartic acid specific protease,Caspase)在细胞凋亡通路中发挥着十分重要的作用,尤其是位于死亡受体介导的凋亡通路起始位置的Caspase-8,它的激活能引发后续的一系列Caspase酶原的激活并引起细胞的凋亡。因此,Caspase-8活性的检测在细胞凋亡检测中具有非常重要的意义。本文基于蛋白酶类FRET荧光探针原理设计了一个能检测活细胞内Caspase-8活性变化的荧光探针,并且在流式细胞仪上利用FRET技术检测了细胞凋亡诱导剂特异性激活的Caspase-8活性,从而证明了所构建的探针检测Caspase-8活性的有效性和特异性。结果表明,所设计的探针能够特异性地响应细胞凋亡诱导中引起细胞内Caspase-8酶活性的变化,并且能够利用流式细胞技术得以快速定量检测。本研究为在活细胞中检测Caspase-8活性提供了一种更加方便快捷的检测方法。展开更多
基金supported by the Micro/Nanoelectronics Science and Technology Innovation Platform of Fudan University of China
文摘A CMOS fluorescent detector system for biological experiment is presented. This system integrates a CMOS compatible photodiode, a capacitive trans-impedance amplifier （CTIA）, and a 12 bit pipelined analog-to- digital converter （ADC）, and is implemented in a 0.18μm standard CMOS process. Some special techniques, such as a ＂contact imaging＂ detecting method, pseudo-differential architecture, dummy photodiodes, and a T-type reset switch, are adopted to achieve low-level sensing application. Experiment results show that the Nwell/Psub photodiode with CTIA pixel achieves a sensitivity of 0.1 A/W at 515 nm and a dark current of 300 fA with 300 mV reverse biased voltage. The maximum differential and integral nonlinearity of the designed ADC are 0.8 LSB and 3 LSB, respectively. With an integrating time of 50 ms, this system is sensitive to the fluorescence emitted by the fluorescein solution with concentration as low as 20 ng/mL and can generate 7 fA photocurrent. This chip occupies 3 mm^2 and consumes 37 mW.
基金ACKNOWLEDGEMENTS We apologize to colleagues whose work could not be cited due to the scope of this review. We would like to thank members in Yan laboratory for discussions. We thank Brendan Lehnert, Xinlei Sheng, Quanxiu Li, Dan Ma and Xinhui Zhou for critical reading. This work was supported by funds from the National Basic Research Program （973 Program） （No. 2011CB910501）, the National Natural Science Foundation of China （Grant Nos. 31321062-20131319400, 31125009, and 91017011 ）, and funds from Tsinghua-Peking Center for Life Sciences. The research of N.Y. was supported in part by an International Early Career Scientist grant from the Howard Hughes Medical Institute.
文摘Eukaryotic membrane proteins, many of which are key players in various biological processes, constitute more than half of the drug targets and represent important candidates for structural studies. In contrast to their physiological significance, only very limited number of eukaryoUc membrane protein structures have been obtained due to the technical challenges in the genera- tion of recombinant proteins. In this review, we examine the major recombinant expression systems for eukaryotic membrane proteins and compare their relative advantages and disadvantages. We also attempted to summarize the recent technical strategies in the advancement of eukaryotic membrane protein purification and crystallization.
文摘荧光共振能量转移技术(fluorescence resonance energy transfer,FRET)作为一种经典的荧光检测技术,已经广泛运用于生物科学研究中,开发了一系列基于FRET技术的荧光检测探针。半胱氨酸蛋白酶家族(cysteine aspartic acid specific protease,Caspase)在细胞凋亡通路中发挥着十分重要的作用,尤其是位于死亡受体介导的凋亡通路起始位置的Caspase-8,它的激活能引发后续的一系列Caspase酶原的激活并引起细胞的凋亡。因此,Caspase-8活性的检测在细胞凋亡检测中具有非常重要的意义。本文基于蛋白酶类FRET荧光探针原理设计了一个能检测活细胞内Caspase-8活性变化的荧光探针,并且在流式细胞仪上利用FRET技术检测了细胞凋亡诱导剂特异性激活的Caspase-8活性,从而证明了所构建的探针检测Caspase-8活性的有效性和特异性。结果表明,所设计的探针能够特异性地响应细胞凋亡诱导中引起细胞内Caspase-8酶活性的变化,并且能够利用流式细胞技术得以快速定量检测。本研究为在活细胞中检测Caspase-8活性提供了一种更加方便快捷的检测方法。
