A wireless sEMG-based body-machine interface for assistive technology devices

Assistive technology (AT) tools and appliances are being more and more widely used and developed worldwide to improve the autonomy of people living with disabilities and ease the interaction with their environment. This paper describes an intuitive and wireless surface electromyography (sEMG) based body-machine interface for AT tools. Spinal cord injuries at C5-C8 levels affect patients' arms, forearms, hands, and fingers control. Thus, using classical AT control interfaces (keypads, joysticks, etc.) is often difficult or impossible. The proposed system reads the AT users' residual functional capacities through their sEMG activity, and converts them into appropriate commands using a threshold-based control algorithm. It has proven to be suitable as a control alternative for assistive devices and has been tested with the JACO arm, an articulated assistive device of which the vocation is to help people living with upper-body disabilities in their daily life activities. The wireless prototype, the architecture of which is based on a 3-channel sEMG measurement system and a 915-MHz wireless transceiver built around a low-power microcontroller, uses low-cost off-the-shelf commercial components. The embedded controller is compared with JACO's regular joystick-based interface, using combinations of forearm, pectoral, masseter, and trapeze muscles. The measured index of performance values is 0.88, 0.51, and 0.41 bits/s, respectively, for correlation coefficients with the Fitt's model of 0.75, 0.85, and 0.67. These results demonstrate that the proposed controller offers an attractive alternative to conventional interfaces, such as joystick devices, for upper-body disabled people using ATs such as JACO

Étude de la structure des protéines de soie d'araignée par spectroscopie de vibration

Tableau d'honneur de la Faculté des études supérieures et postdoctorales, 2011-2012Le fil de soie d'araignée est un matériau structural ayant des propriétés mécaniques de résistance et d'endurance exceptionnelles. Récemment, Nexia Biotechnologies Inc. a réussi à produire en grande quantité les deux protéines recombinantes (MaSpI et MaSpII) qui composent la soie d'araignée. Un défi important est de pouvoir convertir ces protéines en biomatériaux ayant les propriétés mécaniques désirées, ces dernières étant fortement dépendantes du processus de filage. In vivo, le filage de la soie implique le passage d'une solution protéique concentrée contenue dans la glande à travers une filière conduisant à une fibre insoluble. La conformation des protéines dans la glande serait déterminante pour l'optimisation de ce processus. Dans la première partie de notre projet, nous avons étudié pour la première fois la conformation des protéines de soie d'araignée in situ à l'intérieur de la glande ampullacée majeure ainsi que des deux protéines recombinantes en solution. À cette fin, nous avons utilisé des techniques sensibles à la conformation des protéines comme la spectromicroscopie Raman, la spectroscopie infrarouge et le dichroïsme circulaire vibrationnel (VCD). Les données obtenues par VCD montrent la présence d'hélices 3₁ gauche de type polyproline II (PPH), d'hélices a et de structures désordonnées. La présence de PPII pourrait influencer fortement le processus de filage. En effet, les angles dièdres de la structure PPII et des feuillets, p étant proches, la transition d'un état à l'autre nécessiterait peu d'énergie. La caractérisation des propriétés d'auto-assemblage des protéines recombinantes a également été effectuée. Ces résultats devraient conduire à une meilleure compréhension des paramètres qui gouvernent le processus de filage naturel des protéines de soie. Dans la deuxième partie du projet, nous avons étudié par spectromicroscopie Raman la conformation et l'orientation des protéines de soie dans différents types de fibres produites de l'araignée Araneus diadematus. Les résultats obtenus nous ont permis d'établir des corrélations entre la structure de la soie et les propriétés mécaniques des fibres

Structure and mechanical properties of spider silk films at the air-water interface.

International audienceThe kinetics of adsorption of solubilized spider major ampullate (MA) silk fibers at the air-water interface and the molecular structure and mechanical properties of the interfacial films formed have been studied using various physical techniques. The data show that Nephila clavipes MA proteins progressively adsorb at the interface and ultimately form a highly cohesive thin film. In situ infrared spectroscopy shows that as soon as they reach the interface the proteins predominantly form β sheets. The protein secondary structure does not change significantly as the film grows, and the amount of β sheet is the same as that of the natural fiber. This suggests that the final β-sheet content is mainly dictated by the primary structure and not by the underlying formation process. The measure of the shear elastic constant at low strain reveals a very strong, viscous, cohesive assembly. The β sheets seem to form cross-links dispersed within an intermolecular network, thus probably playing a major role in the film strength. More importantly, the molecular weight seems to be a crucial factor because interfacial films made from the natural proteins are ~7 times stronger and ~3 times more viscous than those obtained previously with shorter recombinant proteins. Brewster angle microscopy at the air-water interface and transmission electron microscopy of transferred films have revealed a homogeneous organization on the micrometer scale. The images suggest that the structural assembly at the air-water interface leads to the formation of macroscopically solid and highly cohesive networks. Overall, the results suggest that natural spider silk proteins, although sharing similarities with recombinant proteins, have the particular ability to self-assemble into ordered materials with exceptional mechanical properties

Unexpected differences in the behavior of ovotransferrin at the air-water interface at pH 6.5 and 8.0.

International audienceAdsorption of purified apo-ovotransferrin at the air-water interface was studied by ellipsometry, surface tension, polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and shear elastic constant measurements. No significant difference was observed between pH 6.5 and 8.0 as regards the final value of surface concentration and surface pressure. However at low concentration, a weak barrier to adsorption is evidenced at pH 6.5 and confirmed by PM-IRRAS measurements. At a pH where the protein net charge is negative (pH 8.0), the behavior of ovotransferrin at the air-water interface is more influenced by charge effects rather than bulk concentration effects. At this pH, the interface exhibits a low shear elastic constant and a spectral signature not usual for globular proteins

Surface properties and conformation of Nephila clavipes spider recombinant silk proteins at the air-water interface.

International audienceThe dragline fiber of spiders is composed of two proteins, the major ampullate spidroins I and II (MaSpI and MaSpII). To better understand the assembly mechanism and the properties of these proteins, the adsorption behavior of the recombinant proteins of the spider Nephila clavipes produced by Nexia Biotechnologies Inc. has been studied at the air-water interface using ellipsometry, surface pressure, rheological, and infrared measurements. The results show that the adsorption is more rapid and more molecules are present at the interface for MaSpII than for MaSpI. MaSpII has thus a higher affinity for the interface than MaSpI, which is consistent with its higher aggregation propensity in water. The films formed at the interface consist of networks containing a high content of intermolecular beta-sheets as revealed by the in situ polarization modulation infrared absorption reflection spectra. The infrared results further demonstrate that, for MaSpI, the beta-sheets are formed as soon as the proteins adsorb to the interface while for MaSpII the beta-sheet formation occurs more slowly. The amount of beta-sheets is lower for MaSpII than for MaSpI, most likely due to the presence of proline residues in its sequence. Both proteins form elastic films, but they are heterogeneous for MaSpI and homogeneous for MaSpII most probably as a result of a more ordered and slower aggregation process for MaSpII. This difference in their mechanism of assembly and interfacial behaviors does not seem to arise from their overall hydrophobicity or from a specific pattern of hydrophobicity, but rather from the longer polyalanine motifs, lower glycine content, and higher proline content of MaSpII. The propensity of both spidroins to form beta-sheets, especially the polyalanine blocks, suggests the participation of both proteins in the silk's beta-sheet crystallites

Deep Intronic FGF14 GAA Repeat Expansion in Late-Onset Cerebellar Ataxia

BACKGROUND: The late-onset cerebellar ataxias (LOCAs) have largely resisted molecular diagnosis. METHODS: We sequenced the genomes of six persons with autosomal dominant LOCA who were members of three French Canadian families and identified a candidate pathogenic repeat expansion. We then tested for association between the repeat expansion and disease in two independent case-control series - one French Canadian (66 patients and 209 controls) and the other German (228 patients and 199 controls). We also genotyped the repeat in 20 Australian and 31 Indian index patients. We assayed gene and protein expression in two postmortem cerebellum specimens and two induced pluripotent stem-cell (iPSC)-derived motor-neuron cell lines. RESULTS: In the six French Canadian patients, we identified a GAA repeat expansion deep in the first intron of FGF14, which encodes fibroblast growth factor 14. Cosegregation of the repeat expansion with disease in the families supported a pathogenic threshold of at least 250 GAA repeats ([GAA]≥250). There was significant association between FGF14 (GAA)≥250 expansions and LOCA in the French Canadian series (odds ratio, 105.60; 95% confidence interval [CI], 31.09 to 334.20; P<0.001) and in the German series (odds ratio, 8.76; 95% CI, 3.45 to 20.84; P<0.001). The repeat expansion was present in 61%, 18%, 15%, and 10% of French Canadian, German, Australian, and Indian index patients, respectively. In total, we identified 128 patients with LOCA who carried an FGF14 (GAA)≥250 expansion. Postmortem cerebellum specimens and iPSC-derived motor neurons from patients showed reduced expression of FGF14 RNA and protein. CONCLUSIONS: A dominantly inherited deep intronic GAA repeat expansion in FGF14 was found to be associated with LOCA. (Funded by Fondation Groupe Monaco and others.)