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Photosystem I (PS I) has a symmetric structure with two highly similar branches of pigments at the center that are involved in electron transfer, but shows very different efficiency along the two branches. We have determined the structure of cyanobacterial PS I at room temperature (RT) using femtosecond X-ray pulses from an X-ray free electron laser (XFEL) that shows a clear expansion of the entire protein complex in the direction of the membrane plane, when compared to previous cryogenic structures. This trend was observed by complementary datasets taken at multiple XFEL beamlines. In the RT structure of PS I, we also observe conformational differences between the two branches in the reaction center around the secondary electron acceptors A1A and A1B. The π-stacked Phe residues are rotated with a more parallel orientation in the A-branch and an almost perpendicular confirmation in the B-branch, and the symmetry breaking PsaB-Trp673 is tilted and further away from A1A. These changes increase the asymmetry between the branches and may provide insights into the preferential directionality of electron transfer.

We report 3D coherent diffractive imaging (CDI) of Au/Pd core-shell nanoparticles with 6.1 nm spatial resolution with elemental specificity. We measured single-shot diffraction patterns of the nanoparticles using intense x-ray free electron laser pulses. By exploiting the curvature of the Ewald sphere and the symmetry of the nanoparticle, we reconstructed the 3D electron density of 34 core-shell structures from these diffraction patterns. To extract 3D structural information beyond the diffraction signal, we implemented a super-resolution technique by taking advantage of CDI's quantitative reconstruction capabilities. We used high-resolution model fitting to determine the Au core size and the Pd shell thickness to be 65.0 ± 1.0 nm and 4.0 ± 0.5 nm, respectively. We also identified the 3D elemental distribution inside the nanoparticles with an accuracy of 3%. To further examine the model fitting procedure, we simulated noisy diffraction patterns from a Au/Pd core-shell model and a solid Au model and confirmed the validity of the method. We anticipate this super-resolution CDI method can be generally used for quantitative 3D imaging of symmetrical nanostructures with elemental specificity.

The possibilities offered by catalytic γ-Al2O3 substrates are explored, and the mechanism governing graphene formation thereon is elucidated using both numerical simulations and experiments. The growth scheme offers metal-free synthesis at low temperature, grain-size customization, large-area uniformity of electrical properties, single-step preparation of graphene/dielectric structures, and readily detachable graphene. We quantify based on thermodynamic principles the activation energies associated with graphene nucleation/growth on γ-Al2O3, verifying the low physical and chemical barriers. Importantly, we derive a universal equation governing the adsorption-based synthesis of graphene over a wide range of temperatures in both catalytic and spontaneous growth regimes. Experimental results support the equation, highlighting the catalytic function of γ-Al2O3 at low temperatures. The synthesized graphene is manually incorporated as a 'graphene sticker' into an ultrafast mode-locked laser. [ABSTRACT FROM AUTHOR]

Although surgery and radiation are beneficial for treating cancer, they can also lead to malfunctions of the lymphatic system such as secondary lymphedema. This abnormality of the lymphatic system is characterized by severe swelling, adipogenesis, inflammation, and fibrosis in the lymphedematous region. Moreover, the proliferation of fibrotic tissue in the lymphedematous region generates edema that is no longer spontaneously reversible. No treatment for fibrosis has been validated in patients with lymphedema. In our efforts to develop a therapeutic agent for lymphedema fibrosis, we used a newly established mouse hind limb model. Previous studies have demonstrated that hyaluronic acid accumulates in the lymphedematous region. Thus, we challenged mice with of hyaluronidase (HYAL), with the aim of reducing fibrogenesis. After subcutaneous injections in the lymphedematous mouse leg every two days, the volume of lymphedema had reduced significantly by 7 days post-operation. Histochemical analysis indicated that collagen accumulation and myofibroblast differentiation were decreased in epidermal tissues after HYAL injection. Moreover, it was associated with upregulation of interferon-gamma, increased numbers of Th1 cells, and downregulation of interleukin-4 and interleukin-6 in the lymphedematous region and spleen. These results indicate that hydrolysis of hyaluronic acid can boost an anti-fibrotic immune response in the mouse lymphedema model.