Mechanics of human vocal folds layers during finite strains in tension, compression and shear.

During phonation, human vocal fold tissues are subjected to combined tension, compression and shear loading modes from small to large finite strains. Their mechanical behaviour is however still not well understood. Herein, we complete the existing mechanical database of these soft tissues, by characterising, for the first time, the cyclic and finite strains behaviour of the lamina propria and vocalis layers under these loading modes. To minimise the inter or intra-individual variability, particular attention was paid to subject each tissue sample successively to the three loadings. A non-linear mechanical behaviour is observed for all loading modes: a J-shape strain stiffening in longitudinal tension and transverse compression, albeit far less pronounced in shear, stress accommodation and stress hysteresis whatever the loading mode. In addition, recorded stress levels during longitudinal tension are much higher for the lamina propria than for the vocalis. Conversely, the responses of the lamina propria and the vocalis in transverse compression as well as transverse and longitudinal shears are of the same orders of magnitude. We also highlight the strain rate sensitivity of the tissues, as well as their anisotropic properties.

The effect of hydration on the material and mechanical properties of cellulose nanocrystal-alginate composites.

Alginate is commonly used in the form of hydrogels in biomedical applications. It is known to be highly sensitive to liquid exposure and can degrade or solubilize easily. This study attempts to improve the mechanical and material properties in various humidity conditions and in liquid immersion of thin alginate films with the addition of unmodified and oxidized cellulose nanocrystals (CNCs, CNC-Ts). CNCs and CNC-Ts were added to alginate composites in varying amounts, and the material and mechanical properties were measured in dry, humid, and liquid conditions. It was shown that the properties can be enhanced with the addition of nanocellulose as tested by liquid uptake, and mechanical testing. These results suggest that the addition of TEMPO-oxidized nanocellulose crystals improves the performance and longevity of alginate when exposed to phosphate buffer solution (PBS) compared to deionized water. This improved performance was shown to have a limited effect on the adhesion of mesenchymal stem cells (MSCs) to the surface of the nanocomposites.

A crystallization apparatus for temperature-controlled flow-cell dialysis with real-time visualization.

Many instrumentation developments in crystallization have concentrated on massive parallelization assays and reduction of sample volume per experiment to find initial crystallization conditions. Yet improving the size and diffraction quality of the crystals for diffraction studies often requires decoupling of crystal nucleation and growth. This in turn requires the control of variables such as precipitant and protein concentration, equilibration rate, and temperature, which are all difficult parameters to control in the existing setups. The success of the temperature-controlled batch method, originally developed to grow very large crystals for neutron crystallography, demonstrated that the rational optimization of crystal growth has potential in structural biology. A temperature-controlled dialysis button has been developed for our previous device, and a prototype of an integrated apparatus for the rational optimization of crystal growth by mapping and manipulating temperature-precipitant concentration phase diagrams has been constructed. The presented approach differs from the current paradigm, since it involves serial instead of parallel experiments, exploring multiple crystallization conditions with the same protein sample. The sample is not consumed in the experiment and the conditions can be changed in a reversible fashion, using dialysis with a flowing precipitant reservoir as well as precise temperature control. The control software allows visualization of the crystals, as well as control of the temperature and composition of the crystallization solution. The rational crystallization optimization strategies presented here allow tailoring of crystal size, morphology and diffraction quality, significantly reducing the time, effort and amount of expensive protein material required for structure determination.

In crystallo optical spectroscopy (icOS) as a complementary tool on the macromolecular crystallography beamlines of the ESRF.

The analysis of structural data obtained by X-ray crystallography benefits from information obtained from complementary techniques, especially as applied to the crystals themselves. As a consequence, optical spectroscopies in structural biology have become instrumental in assessing the relevance and context of many crystallographic results. Since the year 2000, it has been possible to record such data adjacent to, or directly on, the Structural Biology Group beamlines of the ESRF. A core laboratory featuring various spectrometers, named the Cryobench, is now in its third version and houses portable devices that can be directly mounted on beamlines. This paper reports the current status of the Cryobench, which is now located on the MAD beamline ID29 and is thus called the ID29S-Cryobench (where S stands for `spectroscopy'). It also reviews the diverse experiments that can be performed at the Cryobench, highlighting the various scientific questions that can be addressed.

REACH: Robotic Equipment for Automated Crystal Harvesting using a six-axis robot arm and a micro-gripper.

In protein crystallography experiments, only two critical steps remain manual: the transfer of crystals from their original crystallization drop into the cryoprotection solution followed by flash-cooling. These steps are risky and tedious, requiring a high degree of manual dexterity. These limiting steps are a real bottleneck to high-throughput crystallography and limit the remote use of protein crystallography core facilities. To eliminate this limit, the Robotic Equipment for Automated Crystal Harvesting (REACH) was developed. This robotized system, equipped with a two-finger micro-gripping device, allows crystal harvesting, cryoprotection and flash-cooling. Using this setup, harvesting experiments were performed on several crystals, followed by direct data collection using the same robot arm as a goniometer. Analysis of the diffraction data demonstrates that REACH is highly reliable and efficient and does not alter crystallographic data. This new instrument fills the gap in the high-throughput crystallographic pipeline.