Rational design of pharmaceutical drugs targeting integral membrane G protein-coupled receptors (GPCR) requires thorough understanding of ligand binding and mechanism of activation through high resolution structural studies of purified proteins. Due to inherent conformational flexibility of GPCR, stabilization of these proteins solubilized from cell membranes into detergents is a challenging task. Here, we take advantage of naturally occurring post-translational modifications for stabilization of purified GPCR in detergent micelles. The recombinant cannabinoid CB2 receptor was expressed at high yield in Expi293F mammalian cell cultures, solubilized and purified in Façade detergent. We report superior stability of the mammalian cell-expressed receptor compared to its E.coli-expressed counterpart, due to contributions from glycosylation of the N terminus and palmitoylation of the C terminus of CB2. Finally, we demonstrate that the mammalian Expi293F amino acid labelling kit is suitable for preparation of multi-milligram quantities of high quality, selectively stable isotope-labeled GPCR for studies by nuclear magnetic resonance.

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We consider a submerged fluid-filled cylindrical shell subjected to an external acoustic pulse, and analyze the structure of the field radiated by the shell into the fluids, both external and internal. We first propose a computationally efficient semi-analytical model of the interaction based on the Reissner-Mindlin shell theory combining some of the classical methods of mathematical physics with the finite-difference methodology, and then use the model to simulate the interaction. We demonstrate that the model accurately reproduces the wave structure of the radiated fields seen in the experiments for submerged evacuated shells, namely both the symmetric Lamb waves S0 and the pseudo-Rayleigh waves A0. It is further observed that the internal and external wave patterns associated with the A0 waves exhibit the same alternation of the equiphase lines as the one seen in the experiments for a plate loaded by the fluid on both sides, a result that seems to be particularly relevant in the context of very limited number of experimental images of the radiated field for shells loaded by fluid from both inside and outside. Not less interestingly, we also demonstrate that the Scholte-Stoneley, or A, wave is also reproduced by the model.

We introduce a robust and computationally efficient methodology for numerical simulation of shock-structure interaction. The methodology is based on the use of some of the classical methods of mathematical physics, with the subsequent coupling between the fluid dynamics and structural parts using the finite-difference methodology. In order to demonstrate the versatility of the approach, we apply it to two rather different practically important problems of the interaction between shock waves and submerged cylindrical structures, aiming at providing insights that would be useful to engineers at the pre-design stage. We first consider a submerged cylindrical shell subjected to two consecutive shock waves, and analyze the effect of such loading in the context of both hydrodynamic fields and the structural stresses it induces. The most important result of this analysis is the observation, for certain values of the distance between the wavefronts, of a very significant increase of the maximum stress observed in the structure. Then, we consider a submerged cylindrical shell subjected to a single shock wave, but employ a more advanced shell theory than the one traditionally used, namely, the Reissner-Mindlin theory instead of the Kirchhoff-Love one. We demonstrate that such an advancement of the model not only leads to a very significant improvement of the accuracy of the respective simulations, but also allows for modeling relatively thick shells.