Co-flow injection for serial crystallography at X-ray free-electron lasers.

Serial femtosecond crystallography (SFX) is a powerful technique that exploits X-ray free-electron lasers to determine the structure of macro-molecules at room temperature. Despite the impressive exposition of structural details with this novel crystallographic approach, the methods currently available to introduce crystals into the path of the X-ray beam sometimes exhibit serious drawbacks. Samples requiring liquid injection of crystal slurries consume large quantities of crystals (at times up to a gram of protein per data set), may not be compatible with vacuum configurations on beamlines or provide a high background due to additional sheathing liquids present during the injection. Proposed and characterized here is the use of an immiscible inert oil phase to supplement the flow of sample in a hybrid microfluidic 3D-printed co-flow device. Co-flow generation is reported with sample and oil phases flowing in parallel, resulting in stable injection conditions for two different resin materials experimentally. A numerical model is presented that adequately predicts these flow-rate conditions. The co-flow generating devices reduce crystal clogging effects, have the potential to conserve protein crystal samples up to 95% and will allow degradation-free light-induced time-resolved SFX.

Beginning with biology: "Aspects of cognition" exist in the service of the brain's overall function as a resource-regulator.

Lieder and Griffiths rightly urge that computational cognitive models be constrained by resource usage, but they should go further. The brain's primary function is to regulate resource usage. As a consequence, resource usage should not simply select among algorithmic models of "aspects of cognition." Rather, "aspects of cognition" should be understood as existing in the service of resource management.

Exercise Similarly Facilitates Men and Women's Selective Attention Task Response Times but Differentially Affects Memory Task Performance.

Previous research has found that acute, moderate-intensity physical exercise enhances selective attention and memory and that men and women show differential performance on tasks measuring these skills. Although exercise and participant sex have been examined separately, it remains unknown whether acute, moderate-intensity exercise differentially affects men and women's selective attention and memory encoding and retrieval. Participants in the present study completed two 10-min sessions of either moderate-intensity exercise comprised of jumping rope alternating with walking in place or an active control protocol comprised of watching wellness videos alternating with walking in place. Each participant completed a selective attention task and a task assessing recognition and object location memory immediately after exercising. Exercise was related to overall faster performance during the selective attention task, with no differences in men and women's performance. Women showed better recognition memory compared to men. Exercise specifically improved object location memory among men, but only among participants who completed the memory task second. These findings suggest that acute, moderate-intensity exercise differentially affects men and women's memory, which may be related to complex interactions between exercise, sex hormones, and the neurotrophin BDNF.

Hydrogen production by a hyperthermophilic membrane-bound hydrogenase in water-soluble nanolipoprotein particles.

Hydrogenases constitute a promising class of enzymes for ex vivo hydrogen production. Implementation of such applications is currently hindered by oxygen sensitivity and, in the case of membrane-bound hydrogenases (MBHs), poor water solubility. Nanolipoprotein particles (NLPs) formed from apolipoproteins and phospholipids offer a novel means of incorporating MBHs into a well-defined water-soluble matrix that maintains the enzymatic activity and is amenable to incorporation into more complex architectures. We report the synthesis, hydrogen-evolving activity, and physical characterization of the first MBH-NLP assembly. This may ultimately lead to the development of biomimetic hydrogen-production devices.