Prediction of Vertical Tail Buffet Using CFD/CSD Coupling Method

The vertical tail buffet induced by the vortex breakdown flow is numerically investigated. The unsteady flow is calculated by solving the RANS equations. The structural dynamic equations are decoupled in the modal coordinates. The radial basis functions (RBFs) are employed to generate the deformation mesh. The buffet response of the flexible tail is predicted by coupling the three sets of equations. The results show that the presence of asymmetry flow on the inner and outer surface of the tail forced the structural deflection offsetting the outboard. The frequency of the 2nd bending mode of the tail structure meets the peak frequency of the pressure fluctuation upon the tail surface, and the resonance phenomenon was observed. Therefore, the 2nd bending responses govern the flow field surrounding the vertical tail. Finally, the displacement of the vertical tail is small, while the acceleration with a large quantitation forces the vertical tail undergoing severe addition inertial loads.

Development of a Bionic Dolphin Flexible Tail Experimental Device Driven by a Steering Gear

In order to study the mechanism of the tail swing of the bionic dolphin, a flexible tail experimental device based on a steering engine was developed. This study was focused on the common three joint steering gear and its use in a bionic dolphin tail swing mechanism, and it was found that the bionic dolphin driven by the steering gear had the problem of excessive stiffness. In order to solve this problem, we designed a bionic dolphin tail swing mechanism. The tail swing mechanism was designed rationally through the combination of a steering gear drive and two flexible spines. Analysis of kinematic and dynamic modeling was further completed. Through simulation using, the research on the bionic dolphin tail swing mechanism was verified. Experiments showed that the swing curve formed by the steering gear-driven bionic dolphin tail swing mechanism with two flexible spines fit the real fish body wave curve better than the original bionic dolphin tail swing mechanism.

Bioinspired Monolithically Designed Compliant Swimming Robots

As technology advances and enables us to design and realize complex systems using new materials and manufacturing methods, biologically inspired robots in every aspect of engineering have attracted much attention in the last few decades. This paper presents the design and motion analysis of monolithically designed two compliant swimming robots that are actuated and controlled by single motor. Each design incorporates large deflecting compliant members and rigid levers to transfer the input torque to the different parts on the mechanism. While the first design integrates flexible tail to perform swimming motion, the second design adopts snapping type motion for the same action. Both mechanisms are 3D printed and tested for forward motion. The first robot has a constant speed of 0.68 BL/s while the second has an average speed of 0.6 BL/s. Kinematic model using pseudo rigid body modeling (PRBM) is derived to calculate the load-deflection curves of the flexible tail for Design I, finite element analysis for deflection analysis are performed for Design II.

Architecture of the flexible tail tube of bacteriophage SPP1

Bacteriophage SPP1 is a double-stranded DNA virus of the Siphoviridae family that infects the bacterium Bacillus subtilis. This family of phages features a long, flexible, non-contractile tail that has been difficult to characterize structurally. Here, we present the atomic structure of the tail tube of phage SPP1. Our hybrid structure is based on the integration of structural restraints from solid-state nuclear magnetic resonance (NMR) and a density map from cryo-EM. We show that the tail tube protein gp17.1 organizes into hexameric rings that are stacked by flexible linker domains and, thus, form a hollow flexible tube with a negatively charged lumen suitable for the transport of DNA. Additionally, we assess the dynamics of the system by combining relaxation measurements with variances in density maps.

Protective anti-prion antibodies in human immunoglobulin repertoires

Prion immunotherapy may hold great potential, but antibodies against certain PrP epitopes can be neurotoxic. Here we identified >6000 PrP-binding antibodies in a synthetic human Fab phage display library, 49 of which we characterized in detail. Antibodies directed against the flexible tail of PrP conferred neuroprotection against infectious prions. We then mined published repertoires of circulating B cells from healthy humans and found antibodies similar to the protective phage-derived antibodies. When expressed recombinantly, these antibodies exhibited anti-PrP reactivity. Furthermore, we surveyed 48’718 samples from 37’894 hospital patients for the presence of anti-PrP IgGs, and found 21 high-titer individuals. The clinical files of these individuals did not reveal any enrichment of specific pathologies, suggesting that anti-PrP autoimmunity is innocuous. The existence of protective anti-prion antibodies in unbiased human immunological repertoires, combined with the reported lack of such antibodies in carriers of disease-associated PRNP mutations, suggests a link to the low incidence of spontaneous prion diseases in human populations.

A staphylococcal cyclophilin carries a single domain and unfolds via the formation of an intermediate that preserves cyclosporin A binding activity

Cyclophilin (Cyp), a peptidyl-prolyl cis-trans isomerase (PPIase), acts as a virulence factor in many bacteria including Staphylococcus aureus. The enzymatic activity of Cyp is inhibited by cyclosporin A (CsA), an immunosuppressive drug. To precisely determine the unfolding mechanism and the domain structure of Cyp, we have investigated a chimeric S. aureus Cyp (rCyp) using various probes. Our limited proteolysis and the consequent analysis of the proteolytic fragments indicate that rCyp is composed of one domain with a short flexible tail at the C-terminal end. We also show that the urea-induced unfolding of both rCyp and rCyp-CsA is completely reversible and proceeds via the synthesis of at least one stable intermediate. The secondary structure, tertiary structure, and the hydrophobic surface area of no intermediate are fully identical to those of other intermediate or the related native protein. Further analyses reveal no loss of CsA binding activity in rCyp intermediate. The thermodynamic stability of rCyp was also significantly increased in the presence of CsA, recommending that this protein could be employed to screen new CsA derivatives in future.