61 research outputs found
Efficient extracellular expression of transpeptidase sortase A in Pichia pastoris
No full textIn order to achieve efficient extracellular expression of Sortase A (SrtA), various strategies in Pichia pastoris system were applied in this study. Among different constructed recombinant strains, the SMD1168 strain integrated 5.7 copies of srtA gene under control of AOX1 promoter was proved to be the best strain for the extracellular SrtA expression. After the optimization of fermentation conditions (induction 72 h at 28 degrees C, initial pH 6.0, supplemented with 1.5% methanol), the highest yield and activity of extracellular SrtA reached 97.8 mg/L and 131.9 U/mL at the shake-flask level, respectively. This is the first report on the efficient secretory expression of SrtA in P. pastoris and the yield of SrtA is the maximum compared with previous reports. In addition, the transpeptidation activity of extracellular SrtA was confirmed by the successful immobilization of enhanced green fluorescent protein (EGFP) onto Gly(3)-polystyrene beads. (C) 2017 Elsevier Inc. All rights reserved.National Natural Science Foundation of China [21472070]; Project for Jiangsu Scientific and Technological Innovation Team; Fund for Jiangsu Distinguished Professorship Program; Jiangsu Postdoctoral Science Foundation [1402070C]; State Key Laboratory of Natural and Biomimetic Drugs [K20140216]; Priority Academic Program Development of Jiangsu Higher Education Institutions; 111 Project [111-2-06]; Jiangsu province "Collaborative Innovation Center for Advanced Industrial Fermentation" industry development programSCI(E)ARTICLE132-13813
Hybrid interface for human robot interaction
No full textTo better interact with robots, human robot interfaces should decode human intent reliably. There are multiple possible communication channels for such interfaces. In this thesis, we seek to develop hybrid interfaces for human-robot interaction, focusing on integrating cues from electroencephalography (EEG), eye gaze, force, and the environment. First, we describe a hybrid EEG/gaze-based brain computer interaction system. Past work has shown that it is possible to use motor imagery to decode the subject's voluntary intent. However, system accuracy is limited by the low signal-to-noise ratio of EEG signals. We investigated combining motor imagery with eye gaze to improve system performance. We demonstrated a hybrid interface for a robot arm that enables subjects to perform a pick and place task. We found that the integration of EEG with eye gaze significantly improved system performance over either cue in isolation. Second, we addressed the problem of estimating 3D gaze location in a world-centric coordinate system. The key challenge in 3D gaze tracking is to estimate the depth along the line of sight. We solved this problem by integrating the gaze estimates with information about the environmental structure represented by a point-cloud representation from an RGBD camera. We implemented the algorithm on both remote and head-mounted eye trackers. We tested the proposed system in a human-human collaborative assembly task. Next, we developed a gaze-based upper limb rehabilitation system. Unlike previous works focusing mainly on the mechanical design, we proposed a gaze-modulated admittance control strategy that integrates gaze estimates with force estimates. Our system has the flexibility to be configured into different working modes to fit patient needs at different injury stages: a passive mode for the acute phase, an assistive mode for the sub-acute phase, and an active mode for the chronic phase. To keep the patient engaged, we designed a fishing game and implemented the algorithm on a planar robot. We also developed an immersive gaze-controlled painting task in virtual reality. Finally, we investigated using single-trial EEG signal to distinguish between target and non-target faces presented in a rapid serial visual presentation paradigm. Unlike the past work on event-related-potentials (ERP) detection, which averaged multiple trials, here we focused on the more challenging task of detecting the target using a single-trial EEG signal. We used a convolutional neural network for classification, resulting in performance surpassing that of the support vector machine (SVM) algorithm, which has been commonly used in ERP detection tasks.</p
Gaze awareness improves collaboration efficiency in a collaborative assembly task
No full textIn building human robot interaction systems, it would be helpful to understand how humans collaborate, and in particular, how humans use others’ gaze behavior to estimate their intent. Here we studied the use of gaze in a collaborative assembly task, where a human user assembled an object with the assistance of a human helper. We found that the being aware of the partner’s gaze significantly improved collaboration efficiency. Task completion times were much shorter when gaze communication was available, than when it was blocked. In addition, we found that the user’s gaze was more likely to lie on the object of interest in the gaze-aware case than the gaze-blocked case. In the context of human-robot collaboration systems, our results suggest that gaze data in the period surrounding verbal requests will be more informative and can be used to predict the target object.</p
Gaze-controlled Robot-assisted Painting in Virtual Reality for Upper-limb Rehabilitation
No full textStroke is the leading cause of adult disability. Robot-assisted rehabilitation systems show great promise for motor recovery after a stroke. In this work, we present a gazecontrolled robotic system for upper limb rehabilitation. Subjects perform a painting task in virtual reality. We designed a novel and challenging painting task to encourage motivation and engagement, as these are critical factors in treatment efficacy. Because the robotic system can be programmed to provide varying amounts of assistance or resistance to the subject, it can be applied to a wide range of patients at different phases of recovery. We describe here the system configured in two modes: resistive control and hierarchical control. The former is designed for later stages of recovery, where the patient's impaired limb has recovered some function. It can be configured to provide varying degrees of resistance by adjusting the properties of an admittance controller. The latter targets patients in more acute phases, where the impaired limb is less responsive. It provides a combination of assistive and corrective control. We pilot tested our system on 10 able-bodied subjects. Our results show that the system can provide varying degrees of resistive control, and that the integration of high level control modulated by gaze can improve engagement. These results suggest that the system may provide a more engaging environment for a wide range of rehabilitative therapies than currently available.</p
User Engagement Correlates Better with Behavioral than Physiological Measures in a Virtual Reality Robotic Rehabilitation System
No full textRobotic systems to assist with movement rehabil-itation are transitioning from providing fixed pre-programmed assistance towards adaptive challenge-oriented strategies that present patients with tasks that are demanding yet achiev-able. This promotes active engagement, which is crucial for stimulating neural plasticity and promoting recovery. While it has been well established that varying the challenge level can affect user engagement, measuring engagement during task performance has received less attention. To investigate this issue, we developed a virtual reality (VR) robotic system for upper limb rehabilitation using a line-tracing task that measures physiological and behavioral signals. Challenge level can be modulated by introducing force noise disturbance. We con-ducted a preliminary study on 12 participants, measuring user engagement and physiological/behavioral signals at different noise (challenge) levels. Our findings align with the predictions of flow channel theory. Engagement peaks at an intermediate challenge level. While past work considered only physiological measures, our results reveal that behavioral measures are better correlated with user engagement. Physiological measures correlate better with arousal. This work takes a step toward systems that dynamically adapt task parameters to optimize user engagement.</p
Maximally steerable mixed state based on the linear steering inequality and the Clauser-Horne-Shimony-Holt–like steering inequality
No full textSortase A-mediated on-resin peptide cleavage and in situ ligation: an efficient one-pot strategy for the synthesis of functional peptides and proteins
No full textA one-pot approach combining Sortase A mediated on-resin peptide cleavage, activation and in situ ligation was developed and was employed to synthesize dual functional peptides, modify peptides with lipid, biotin and PEG, as well as protein N-terminal labeling in high efficiency.</p
Immobilization of Staphylococcus aureus Sortase A on Chitosan Particles and Its Applications in Peptide-to-Peptide Ligation and Peptide Cyclization
No full textChitosan macro-particles prepared by the neutralization method were applied to Sortase A (SrtA) immobilization using glutaraldehyde as a crosslinking agent. The particles were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Response surface methodology (RSM) was employed to optimize the immobilization process. An average specific activity of 3142 U (mg protein)−1 was obtained under optimized immobilization conditions (chitosan concentration 3%, SrtA concentration 0.5 mg·mL−1, glutaraldehyde concentration 0.5%, crosslinking and immobilization at 20 °C, crosslinking for 3 h, and an immobilization time of 8 h). The transpeptidase activity of immobilized SrtA was proved by a peptide-to-peptide ligation with a conversion yield approximately at 80%, and the immobilized catalyst was successfully reused for five cycles without obvious activity loss. Moreover, the scale-up capability of using immobilized SrtA to catalyze a head-to-tail peptide cyclization was investigated in a batch reaction and the conversion yield was more than 95% when using 20 mg of peptide as a substrate
Efficient expression of sortase A from Staphylococcus aureus in Escherichia coli and its enzymatic characterizations
No full textEffect of stellate ganglion block on perioperative myocardial injury following thoracoscopic surgery for lung cancer (SGBMI): protocol for a single-centre, randomised controlled trial
No full textIntroduction Myocardial injury is a common complication of thoracoscopic surgery. The stellate ganglion block is believed to affect myocardial oxygen consumption. The Stellate Ganglion Block and Myocardial Injury (SGBMI) trial aims to test the hypothesis that stellate ganglion block can reduce the incidence of perioperative myocardial injury in patients undergoing thoracoscopic surgery for lung cancer.Methods and analysis The SGBMI trial is a double-blind, randomised trial comparing the effects of a stellate ganglion block and a sham procedure in patients with cardiovascular risk factors undergoing thoracoscopic surgery. The exclusion criteria include procedure-related contraindications and severe heart failure. The stellate ganglion block or sham procedures will be performed preoperatively. The primary outcome is myocardial injury within 30 days of the follow-up. The main safety outcomes are sepsis, infection and procedure-related complications. We will enrol 248 patients to ensure at least 80% power for the evaluation of the primary outcome. The primary results of the SGBMI trial are expected to be announced by the year 2027.Ethics and dissemination Ethical approval for the study is obtained from the Ethics Committee of the Shanghai Pulmonary Hospital (approval number: L22-394). Written informed consent will be obtained from all participating patients. The publication of results in a peer-reviewed journal and presentations at conferences are anticipated.Trial registration number ChiCTR2300071469 (registered on 16 May 2023)
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