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We develop the impulsiveness index, a new classification system for solar flares using the Solar Dynamics Observatory/Extreme Ultraviolet Experiment 304 Å Sun-as-a-star light curves. Impulsiveness classifies events based on the duration and intensity of the initial high-energy deposition of energy into the chromosphere. In stellar flareU-band light curves, Kowalski et al. found that impulsiveness is related to quantities such as a proxy for the Balmer jump ratio. However, the lack of direct spatial resolution in stellar flares limits our ability to explain this phenomenon. We calculate impulsiveness for 1368 solar flares between 2010 April and 2014 May. We divide events into categories of low, mid, and high impulsiveness. We find, in a sample of 480 flares, that events with high maximum reconnection rate tend to also have high impulsiveness. For six case studies, we compare impulsiveness to magnetic shear, ribbon evolution, and energy release. We find that the end of the 304 Å light-curve rise phase in these case studies corresponds to the cessation of polarity inversion line (PIL)-parallel ribbon motion, while PIL-perpendicular motion persists afterward in most cases. The measured guide-field ratio for low- and mid-impulsiveness case-study flares decreases about an order of magnitude during the impulsive flare phase. Finally, we find that, in four of the six case studies, flares with higher, more persistent shear tend to have low impulsiveness. Our study suggests that impulsiveness may be related to other properties of the impulsive phase, though more work is needed to verify this relationship and apply our findings to stellar flare physics.

 

Photodynamic hydrogel biomaterials have demonstrated great potential for user-triggered therapeutic release, patterned organoid development, and four-dimensional control over advanced cell fates in vitro. Current photosensitive materials are constrained by their reliance on high-energy ultraviolet light (<400 nm) that offers poor tissue penetrance and limits access to the broader visible spectrum. Here, we report a family of three photolabile material crosslinkers that respond rapidly and with unique tricolor wavelength-selectivity to low-energy visible light (400–617 nm). We show that when mixed with multifunctional poly(ethylene glycol) macromolecular precursors, ruthenium polypyridyl- andortho-nitrobenzyl (oNB)-based crosslinkers yield cytocompatible biomaterials that can undergo spatiotemporally patterned, uniform bulk softening, and multiplexed degradation several centimeters deep through complex tissue. We demonstrate that encapsulated living cells within these photoresponsive gels show high viability and can be successfully recovered from the hydrogels following photodegradation. Moving forward, we anticipate that these advanced material platforms will enable new studies in 3D mechanobiology, controlled drug delivery, and next-generation tissue engineering applications.

 

Abstract Premise The specialized metabolites of plants are recognized as key chemical traits in mediating the ecology and evolution of sundry plant–biotic interactions, from pollination to seed predation. Intra‐ and interspecific patterns of specialized metabolite diversity have been studied extensively in leaves, but the diverse biotic interactions that contribute to specialized metabolite diversity encompass all plant organs. Focusing on two species of Psychotria shrubs, we investigated and compared patterns of specialized metabolite diversity in leaves and fruit with respect to each organ's diversity of biotic interactions. Methods To evaluate associations between biotic interaction diversity and specialized metabolite diversity, we combined UPLC‐MS metabolomic analysis of foliar and fruit specialized metabolites with existing surveys of leaf‐ and fruit‐centered biotic interactions. We compared patterns of specialized metabolite richness and variance among vegetative and reproductive tissues, among plants, and between species. Results In our study system, leaves interact with a far larger number of consumer species than do fruit, while fruit‐centric interactions are more ecologically diverse in that they involve antagonistic and mutualistic consumers. This aspect of fruit‐centric interactions was reflected in specialized metabolite richness—leaves contained more than fruit, while each organ contained over 200 organ‐specific specialized metabolites. Within each species, leaf‐ and fruit‐specialized metabolite composition varied independently of one another across individual plants. Contrasts in specialized metabolite composition were stronger between organs than between species. Conclusions As ecologically disparate plant organs with organ‐specific specialized metabolite traits, leaves and fruit can each contribute to the tremendous overall diversity of plant specialized metabolites. 

Proteins provide essential functional regulation of many bioprocesses across all scales of life; however, new techniques to specifically modulate protein activity within living systems and in engineered biomaterials are needed to better interrogate fundamental cell signalling and guide advanced decisions of biological fate. Here we establish a generalizable strategy to rapidly and irreversibly activate protein function with full spatiotemporal control. Through the development of a genetically encoded and light-activated SpyLigation (LASL), bioactive proteins can be stably reassembled from non-functional split fragment pairs following brief exposure (typically minutes) to cytocompatible light. Employing readily accessible photolithographic processing techniques to specify when, where and how much photoligation occurs, we demonstrate precise protein activation of UnaG, NanoLuc and Cre recombinase using LASL in solution, biomaterials and living mammalian cells, as well as optical control over protein subcellular localization. Looking forward, we expect that these photoclick-based optogenetic approaches will find tremendous utility in probing and directing complex cellular fates in both time and three-dimensional space. 

Hydrogels are extensively employed in healthcare due to their adaptable structures, high water content, and biocompatibility, with FDA‐approved applications ranging from spinal cord regeneration to local therapeutic delivery. However, clinical hydrogels encounter challenges related to inconsistent therapeutic exposure, unmodifiable release windows, and difficulties in subsurface polymer insertion. Addressing these issues, we engineered injectable, biocompatible hydrogels as a local therapeutic depot, utilizing poly(ethylene glycol) (PEG)‐based hydrogels functionalized with bioorthogonal SPAAC handles for network polymerization and functionalization. Our hydrogel solutions polymerize in situ in a temperature‐sensitive manner, persist in tissue, and facilitate the delivery of bioactive therapeutics in subsurface locations. Demonstrating the efficacy of our approach, recombinant anti‐CD47 monoclonal antibodies, when incorporated into subsurface‐injected hydrogel solutions, exhibited cytotoxic activity against infiltrative high‐grade glioma xenografts in the rodent brain. To enhance the gel's versatility, recombinant protein cargos can undergo site‐specific modification with hydrolysable “azidoester” adapters, allowing for user‐defined release profiles from the hydrogel. Hydrogel‐generated gradients of murine CXCL10, linked to intratumorally injected hydrogel solutions via azidoester linkers, resulted in significant recruitment of CD8⁺T‐cells and the attenuation of tumor growth in a “cold” syngeneic melanoma model. This study highlights a highly customizable, hydrogel‐based delivery system for local protein therapeutic administration to meet diverse clinical needs.