The use of bicistronic vectors, which contain two target genes under one promoter, has been the most common practice for the heterologous production of binary protein complexes. The major problem of this method is the much lower expression of the second gene compared with that of the first gene next to the promoter. We tested a simple idea of whether inclusion of an additional promoter in front of the second gene may remove the problem. Compared with bicistronic vectors, corresponding two-promoter vectors yielded four to nine times larger amounts of the complexes between BCL-2 family proteins, BCL-X L :BAD, BCL-X L :BIM-S, and CED-9:EGL-1 in bacterial cells as a result of significantly increased expression of the second genes in a manner independent of the order of the target genes. With the two-promoter system, we produced two other complexes in large quantity suitable for extensive crystallization trial. The method does not accompany any technical disadvantages, and represents a significant improvement from the conventional method, which should enjoy wide application for the coexpression of binary or higher order protein complexes by extension.
The use of unmanned aerial vehicle (UAV) applications has grown rapidly over the past decade with the introduction of low-cost microelectromechanical system (MEMS)-based sensors that measure angular velocity, gravity, and magnetic field, which are important for an object orientation determination. However, the use of low-cost sensors has also been limited because their readings are easily distorted by unwanted internal and/or external noise signals such as environmental magnetic disturbance, which lead to errors in attitude and heading estimation results. In an extended Kalman filter (EKF) process, this study proposes a method for mitigating the effect of magnetic disturbance on attitude determination by using a double quaternion parameters for representation of orientation states, which decouples the magnetometer from attitude computation. Additionally, an online measurement error covariance matrix tuning system was implemented to reject the impact of magnetic disturbance on the heading estimation. Simulation and experimental tests were conducted to verify the performance of the proposed methods in resolving the magnetic noise effect on attitude and heading. The results showed that the proposed method performed better than complimentary, gradient descent, and single quaternion-based EKF.
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