Time-resolved serial femtosecond crystallography reveals early structural changes in channelrhodopsin

X線自由電子レーザーを用いて、光照射によるチャネルロドプシンの構造変化の過程を捉えることに成功. 京都大学プレスリリース. 2021-03-26.Channelrhodopsins (ChRs) are microbial light-gated ion channels utilized in optogenetics to control neural activity with light . Light absorption causes retinal chromophore isomerization and subsequent protein conformational changes visualized as optically distinguished intermediates, coupled with channel opening and closing. However, the detailed molecular events underlying channel gating remain unknown. We performed time-resolved serial femtosecond crystallographic analyses of ChR by using an X-ray free electron laser, which revealed conformational changes following photoactivation. The isomerized retinal adopts a twisted conformation and shifts toward the putative internal proton donor residues, consequently inducing an outward shift of TM3, as well as a local deformation in TM7. These early conformational changes in the pore-forming helices should be the triggers that lead to opening of the ion conducting pore

An experimental study on promotion of burning velocity of powder-gas hybrid combustion in a stagnation-point flow

An experimental study was made on burning velocity in powder-gas hybrid combustion in order to investigate the determination factor to alter the burning velocity caused by the addition of power in the premixed gas. A burner system was newly developed to visualize the dynamic flame behavior originally stabilized in a stagnation point flow field. Using the system, the instantaneous burning velocity and burning area by powder loading were obtained and analyzed. It was found that the burning velocity and burning area varied substantially in accordance with the powder loading amount. Data analyses exhibited that a positive correlation was found between them, suggesting that wrinkling shall be a major cause to alter the burning velocity. To understand the mechanism of wrinkle formation, the change of the flow field ahead of the flame with powder loading was measured. It is suggested that the wrinkles could be attributed to the pyrolysis gases evolved in the preheating zone, which could both increase the local burning velocity by increasing the local equivalence ratio and change the flow field due to the divergence flow generated by each powder. Further study would be needed to confirm the suggested mechanism

Solution Properties of Amphiphilic Alternating Copolymers of <i>N</i>‑Ethylmaleimide and 2‑Hydroxyethyl Vinyl Ether: Thermoresponsiveness in Alcohols and Cosolvency Phenomenon in Binary Ethanol/Water Solutions

We discovered unique solution properties, including cosolvency of an amphiphilic alternating copolymer comprising hydrophobic N-ethylmaleimide (EMIm) and hydrophilic 2-hydroxyethyl vinyl ether (HEVE). The solubility of polymers is greatly affected by the balance of polymer–polymer interaction and polymer–solvent interaction, and an amphiphilic alternating sequence is attractive for achieving unique solubility. We synthesized the alternating copolymers P(EMIm/HEVE) by reversible addition-fragmentation chain transfer polymerization to investigate the solubility in a variety of solvents. The obtained polymers exhibited the upper-critical-solution-temperature-type miscibility behavior in various alcohols, and the insoluble-to-soluble transition temperature varied depending on the alcohol structure: bulkier and more hydrophobic alcohol resulted in a higher transition temperature. Furthermore, P(EMIm/HEVE) was shown to be soluble in the mixture of ethanol and water, despite being insoluble in each solvent at room temperature. This cosolvency phenomenon was probably due to the change in the local composition of ethanol and water around the polymer