No abstract

Photosynthetic organisms have adapted to survive a myriad of extreme environments from the earth’s deserts to its poles, yet the proteins that carry out the light reactions of photosynthesis are highly conserved from the cyanobacteria to modern day crops. To investigate adaptations of the photosynthetic machinery in cyanobacteria to excessive light stress, we isolated a new strain of cyanobacteria, Cyanobacterium aponinum 0216, from the extreme light environment of the Sonoran Desert. Here we report the biochemical characterization and the 2.7 Å resolution structure of trimeric photosystem I from this high-light-tolerant cyanobacterium. The structure shows a new conformation of the PsaL C-terminus that supports trimer formation of cyanobacterial photosystem I. The spectroscopic analysis of this photosystem I revealed a decrease in far-red absorption, which is attributed to a decrease in the number of long- wavelength chlorophylls. Using these findings, we constructed two chimeric PSIs in Synechocystis sp. PCC 6803 demonstrating how unique structural features in photosynthetic complexes can change spectroscopic properties, allowing organisms to thrive under different environmental stresses.

Damage to the nervous system can result in loss of sensory and motor function, paralysis, or even death. To facilitate neural regeneration and functional recovery, researchers have employed biomaterials strategies to address both peripheral and central nervous system injuries. Injectable hydrogels that recapitulate native nerve extracellular matrix are especially promising for neural tissue engineering because they offer more flexibility for minimally invasive applications and provide a growthpermissive substrate for neural cell types. Here, we explore the development of injectable hydrogels derived from decellularized rat peripheral nerves (referred to as "injectable peripheral nerve [iPN] hydrogels"), which are processed using a newly developed sodium deoxycholate and DNase (SDD) decellularization method. We assess the gelation kinetics, mechanical properties, cell bioactivity, and drug release kinetics of the iPN hydrogels. The iPN hydrogels thermally gel when exposed to 37 C in under 20 min and have mechanical properties similar to neural tissue. The hydrogels demonstrate in vitro biocompatibility through support of Schwann cell viability and metabolic activity. Additionally, iPN hydrogels promote greater astrocyte spreading compared to collagen I hydrogels. Finally, the iPN is a promising delivery vehicle of drug-loaded microparticles for a combinatorial approach to neural injury therapies.

X-ray free electron lasers (XFELs) provide ultrashort intense X-ray pulses suitable to probe electron dynamics, but can also induce a multitude of nonlinear excitation processes. These affect spectroscopic measurements and interpretation, particularly for upcoming brighter XFELs.Here we elaborate on the limits to observing classical spectroscopy, where only one photon is absorbed per atom for a Mn 2+ in a light element (O, C, H) environment. X-ray emission spectroscopy (XES) with different incident photon energies, pulse intensities, and pulse durations is presented. A rate equation model based on sequential ionization and relaxation events is used to calculate populations of multiply ionized states during a single pulse and to explain the X-ray induced spectral lines shifts. This model provides easy estimation of spectral shifts, which is essential for experimental designs at XFELs, and illustrates that shorter X-ray pulses will not overcome sequential ionization but can reduce electron cascade effects. TOC GRAPHICS

Full-thickness burns almost always require skin grafting because the severity prevents the natural regenerative process. Here, we illustrate the potential to promote natural skin regeneration utilizing growth factors and regenerative proteins in purified amniotic fluid (PAF). A 24-year-old female suffered from full-thickness burns to her legs resulting from a rogue firework. This initiated a treatment plan involving extensive rehabilitation and skin grafting. Instead, the patient was treated with PAF (4 mL) administered topically over 2 days. Forty-five minutes following application, her pain decreased from 10/10 to 2/10. After two treatments her overall recovery time decreased by 75%–leaving her physicians surprised at the obviated need for skin grafting. Topical PAF relieved pain within minutes, making it easier to clean the affected area, enhancing sleep, and allowing more range of motion and autonomy. The efficiency of PAF to reduce pain allowed the patient to discontinue the use of prescribed hydrocodone, an opioid that is fueling an epidemic of abuse and addiction. Accelerated recovery time allowed the patient to return to work sooner, having broader economic implications on medical costs and personal time off. Finally, PAF enhanced the body’s own capacity to heal itself, avoiding painful and costly grafting and decreasing additional donor site scarring.