A cDNA encoding a sigma-class glutathione S-transferase of the locust, Locusta migratoria manilensis （LmGSTs1）, was cloned by reverse transcriptase-polymerase chain reaction. The 830 bp-long cDNA encoded a 615 bp op...A cDNA encoding a sigma-class glutathione S-transferase of the locust, Locusta migratoria manilensis （LmGSTs1）, was cloned by reverse transcriptase-polymerase chain reaction. The 830 bp-long cDNA encoded a 615 bp open reading frame （204 amino acid polypeptide）, which exhibited the structural motif and domain organization characteristic of GST sigma-class. It revealed 59, 57, 57, and 56% identities to sigma-class GSTs from Blattella germanica, Gryllotalpa orientalis, Nasonia vitripennis, and Pediculus humanus corporis, respectively. A recombinant protein （LmGSTs1） was functionally expressed in Escherichia coli cells in a soluble form and purified to homogeneity. LmGSTs1 was able to catalyze the biotranslation of glutathione with 1-chloro-2,4-dinitrobenzene, a model substrate for GSTs, as well as with p-nitro-benzyl chloride. Its optimal activity was observed at pH 8.0 and at 30℃. Incubation for 30 min at temperatures below 50℃ scarcely affected the activity. The I50 of reactive blue （RB） was 18.5 μmol L-1. In the presence of 0.05 mmol L-1 ethacrynic acid （ECA）, LmGSTs1 showed （81±3）% of the original activities.展开更多
在闭环结构D类放大器中,反馈回路中的DAC对放大器的整体性能有着很大的影响在考虑到实际应用的情况下,本文提出了一个应用于反馈回路的DAC,它是基于Sigma-Delta的一个连续时间三阶调制器,在MATLAB环境下结合放大器输出的PWM信号与调制...在闭环结构D类放大器中,反馈回路中的DAC对放大器的整体性能有着很大的影响在考虑到实际应用的情况下,本文提出了一个应用于反馈回路的DAC,它是基于Sigma-Delta的一个连续时间三阶调制器,在MATLAB环境下结合放大器输出的PWM信号与调制器的信号传输方程(STF)进行联合仿真,获得了较好的效果。其动态范围(DR)能够达到101 d B,信号对噪声和失真比(SNDR)达到72 d B。展开更多
A digital input class-D audio amplifier with a sixth-order pulse-width modulation （PWM） modulator is presented. This modulator moves the PWM generator into the closed sigma-delta modulator loop. The noise and distor...A digital input class-D audio amplifier with a sixth-order pulse-width modulation （PWM） modulator is presented. This modulator moves the PWM generator into the closed sigma-delta modulator loop. The noise and distortions generated at the PWM generator module are suppressed by the high gain of the forward loop of the sigma-delta modulator. Therefore, at the output of the modulator, a very clean PWM signal is acquired for driving the power stage of the class-D amplifier. A sixth-order modulator is designed to balance the performance and the system clock speed. Fabricated in standard 0.18 μm CMOS technology, this class-D amplifier achieves 110 dB dynamic range, 100 dB signal-to-noise rate, and 0.0056% total harmonic distortion plus noise.展开更多
基金supported by the Funds for International Cooperation and Exchange of the National Natural Science Foundation of China (30810103907)the National Natural Science Foundation of China (30870302)+2 种基金the Public Welfare Fund for Agriculture, Ministry of Agriculture, China (200903021)the China Postdoctoral Science Foundation (Special Program, 201003656 Regular Program, 20090451359)
文摘A cDNA encoding a sigma-class glutathione S-transferase of the locust, Locusta migratoria manilensis （LmGSTs1）, was cloned by reverse transcriptase-polymerase chain reaction. The 830 bp-long cDNA encoded a 615 bp open reading frame （204 amino acid polypeptide）, which exhibited the structural motif and domain organization characteristic of GST sigma-class. It revealed 59, 57, 57, and 56% identities to sigma-class GSTs from Blattella germanica, Gryllotalpa orientalis, Nasonia vitripennis, and Pediculus humanus corporis, respectively. A recombinant protein （LmGSTs1） was functionally expressed in Escherichia coli cells in a soluble form and purified to homogeneity. LmGSTs1 was able to catalyze the biotranslation of glutathione with 1-chloro-2,4-dinitrobenzene, a model substrate for GSTs, as well as with p-nitro-benzyl chloride. Its optimal activity was observed at pH 8.0 and at 30℃. Incubation for 30 min at temperatures below 50℃ scarcely affected the activity. The I50 of reactive blue （RB） was 18.5 μmol L-1. In the presence of 0.05 mmol L-1 ethacrynic acid （ECA）, LmGSTs1 showed （81±3）% of the original activities.
文摘在闭环结构D类放大器中,反馈回路中的DAC对放大器的整体性能有着很大的影响在考虑到实际应用的情况下,本文提出了一个应用于反馈回路的DAC,它是基于Sigma-Delta的一个连续时间三阶调制器,在MATLAB环境下结合放大器输出的PWM信号与调制器的信号传输方程(STF)进行联合仿真,获得了较好的效果。其动态范围(DR)能够达到101 d B,信号对噪声和失真比(SNDR)达到72 d B。
基金supported by the National High Technology Research and Development Program of China(No.2012AA012301)the National Natural Science Foundation of China(No.61171001)
文摘A digital input class-D audio amplifier with a sixth-order pulse-width modulation （PWM） modulator is presented. This modulator moves the PWM generator into the closed sigma-delta modulator loop. The noise and distortions generated at the PWM generator module are suppressed by the high gain of the forward loop of the sigma-delta modulator. Therefore, at the output of the modulator, a very clean PWM signal is acquired for driving the power stage of the class-D amplifier. A sixth-order modulator is designed to balance the performance and the system clock speed. Fabricated in standard 0.18 μm CMOS technology, this class-D amplifier achieves 110 dB dynamic range, 100 dB signal-to-noise rate, and 0.0056% total harmonic distortion plus noise.
