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Activation of voltage-gated calcium channels at presynaptic terminals leads to local increases in calcium and the fusion of synaptic vesicles containing neurotransmitter. Presynaptic output is a function of the density of calcium channels, the dynamic properties of the channel, the distance to docked vesicles, and the release probability at the docking site. We demonstrate that at Caenorhabditis elegans neuromuscular junctions two different classes of voltage-gated calcium channels, CaV2 and CaV1, mediate the release of distinct pools of synaptic vesicles. CaV2 channels are concentrated in densely packed clusters ~250 nm in diameter with the active zone proteins Neurexin, α-Liprin, SYDE, ELKS/CAST, RIM-BP, α-Catulin, and MAGI1. CaV2 channels are colocalized with the priming protein UNC-13L and mediate the fusion of vesicles docked within 33 nm of the dense projection. CaV2 activity is amplified by ryanodine receptor release of calcium from internal stores, triggering fusion up to 165 nm from the dense projection. By contrast, CaV1 channels are dispersed in the synaptic varicosity, and are colocalized with UNC-13S. CaV1 and ryanodine receptors are separated by just 40 nm, and vesicle fusion mediated by CaV1 is completely dependent on the ryanodine receptor. Distinct synaptic vesicle pools, released by different calcium channels, could be used to tune the speed, voltage-dependence, and quantal content of neurotransmitter release. 

While planktonic microbes play key roles in the coastal oceans, our understanding of heterotrophic microeukaryotes’ ecology, particularly their spatiotemporal patterns, drivers, and functions, remains incomplete. In this study, we focus on a ubiquitous marine fungus-like protistan group, the Labyrinthulomycetes, whose biomass can exceed that of bacterioplankton in coastal oceans but whose ecology is largely unknown. Using quantitative PCR and amplicon sequencing of their 18S rRNA genes, we examine their community variation in repeated five-station transects across the nearshore-to-offshore surface waters of North Carolina, United States. Their total 18S rRNA gene abundance and phylotype richness decrease significantly from the resource-rich nearshore to the oligotrophic offshore waters, but their Pielou’s community evenness appears to increase offshore. Similar to the bacteria and fungi, the Labyrinthulomycete communities are significantly structured by distance from shore, water temperature, and other environmental factors, suggesting potential niche partitioning. Nevertheless, only several Labyrinthulomycete phylotypes, which belong to aplanochytrids, thraustochytrids, or unclassified Labyrinthulomycetes, are prevalent and correlated with cohesive bacterial communities, while more phylotypes are patchy and often co-occur with fungi. Overall, these results complement previous time-series observations that resolve the Labyrinthulomycetes as persistent and short-blooming ecotypes with distinct seasonal preferences, further revealing their partitioning spatial patterns and multifaceted roles in coastal marine microbial food webs. 

The stability of metal–organic frameworks (MOFs) in water affects their ability to function as chemical catalysts, their capacity as adsorbents for separations in water vapor presence, and their usefulness as recyclable water harvesters. Here, we have examined water stability of four node-modified variants of the mesoporous MOF, NU-1000, namely formate-, Acac-, TFacac-, and Facac-NU-1000, comparing these with node-accessible NU-1000. These NU-1000 variants present ligands grafted to NU-1000's hexa-Zr( iv )-oxy nodes by displacing terminal aqua and hydroxo ligands. Facac-NU-1000, containing the most hydrophobic ligands, showed the greatest water stability, being able to undergo at least 20 water adsorption/desorption cycles without loss of water uptake capacity. Computational studies revealed dual salutary functions of installed Facac ligands: (1) enhancement of framework mechanical stability due to electrostatic interactions; and (2) transformation and shielding of the otherwise highly hydrophilic nodes from H-bonding interactions with free water, presumably leading to weaker channel-stressing capillary forces during water evacuation – consistent with trends in free energies of dehydration across the NU-1000 variants. Water harvesting and hydrolysis of chemical warfare agent simulants were examined to gauge the functional consequences of modification and mechanical stabilization of NU-1000 by Facac ligands. The studies revealed a harvesting capacity of ∼1.1 L of water vapor per gram of Facac-NU-1000 per sorption cycle. They also revealed retention of catalytic MOF activity following 20 water uptake and release cycles. This study provides insights into the basis for node-ligand-engendered stabilization of wide-channel MOFs against collapse during water removal.