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  • Breum Honore posted an update 6 hours, 51 minutes ago

    The timing of T&M (before vs after shimming) turned out to be critically important sufficient time is required to achieve full-temperature equilibrium relative to thermal gradients in the air inside the probe and the sample. Achievable accuracy across different NMR solvents varies with differences in thermal conductivity and leads to 2% or greater errors. With matching solvents, the demonstrated accuracy of ∼1.0% underscores the feasibility of EC-qHNMR as a highly practical research tool.The construction of three-dimensional covalent organic frameworks (3D COFs) has proven to be very challenging, as their synthetic driving force mainly comes from the formation of covalent bonds. To facilitate the synthesis, rigid building blocks are always the first choice for designing 3D COFs. Ko143 In principle, it should be very appealing to construct 3D COFs from flexible building blocks, but there are some obstacles blocking the development of such systems, especially for the designed synthesis and structure determination. Herein, we reported a novel highly crystalline 3D COF (FCOF-5) with flexible C-O single bonds in the building block backbone. By merging 17 continuous rotation electron diffraction data sets, we successfully determined the crystal structure of FCOF-5 to be a 6-fold interpenetrated pts topology. Interestingly, FCOF-5 is flexible and can undergo reversible expansion/contraction upon vapor adsorption/desorption, indicating a breathing motion. Moreover, a smart soft polymer composite film with FCOF-5 was fabricated, which can show a reversible vapor-triggered shape transformation. Therefore, 3D COFs constructed from flexible building blocks can exhibit interesting breathing behavior, and finally, a totally new type of soft porous crystals made of pure organic framework was announced.Metformin as a hypoglycemic drug for antidiabetic treatment has emerged as a multipotential drug for many disease treatments such as cognitive disorders, cancers, promoting weight loss. However, overdose uptake may upregulate the hepatic H2S level, subsequently leading to serious liver injury and toxicity. Therefore, developing intelligent second near-infrared (NIR-II) emitting nanoprobes by using endogenous H2S as a smart trigger for noninvasive highly specific in situ monitoring of the metformin-induced hepatotoxicity is highly desirable, which is rarely explored. Herein, an endogenous H2S activated orthogonal NIR-II emitting myrica rubra-like nanoprobe based on NaYF4Gd/Yb/Er@NaYF4Yb@SiO2 coated with Ag nanodots was explored for highly specific in vivo ratiometrically monitoring of hepatotoxicity. The designed nanoprobes were mainly uptaken by the liver and subsequently converted to NaYF4Gd/Yb/Er@NaYF4Yb@SiO2@Ag2S via in situ sulfuration reaction triggered by the overexpressed endogenous H2S in the injured liver tissues, finally leading to a turn-on orthogonal emission centered at 1053 nm (irradiation by 808 nm laser) and 1525 nm (irradiation by 980 nm laser). The designed nanoprobe presents a high detection limit down to 0.7 nM of H2S. More importantly, the in situ highly specific ratiometric imaging of the metformin-induced hepatotoxicity was successfully achieved by using the activatable orthogonal NIR-II emitting probe. Our results provide an NIR-II ratiometric fluorescence imaging strategy for highly sensitive/specific diagnosis of hepatotoxicity levels induced by metformin.Spider silk is a protein material that exhibits extraordinary and nontrivial properties such as the ability to soften and decrease its length by up to ∼60% upon exposure to high humidity. This process is commonly called supercontraction and is the result of a transition from a highly oriented glassy phase to a disoriented rubbery phase. In this work, we derive a microscopically motivated and energy-based model that captures the underlying mechanisms that give rise to supercontraction. We propose that the increase in relative humidity and the consequent wetting of a spider silk have two main consequences (1) the dissociation of hydrogen bonds and (2) the swelling of the fiber. From a mechanical viewpoint, the first consequence leads to the formation of rubbery domains. This process is associated with an entropic gain and a loss of orientation of chains in the silk network, which motivates the contraction of the spider silk. The swelling of the fiber is accompanied by the extension of chains in order to accommodate the influx of water molecules. Supercontraction occurs when the first consequence is more dominant than the second. The model presented in this work allows us to qualitatively track the transition of the chains from glassy to rubbery states and determine the increase in entropy, the loss of orientation, and the swelling as the relative humidity increases. We also derive explicit expressions for the stiffness and the mechanical response of a spider silk under given relative humidity conditions. To illustrate the merit of this model, we show that the model is capable of capturing several experimental findings. The insights from this work can be used as a microstructural design guide to enable the development of new materials with unique spider-like properties.Detection of environmental pollutants is crucial to safeguard ecological and public health. Here, we report a modular biosensing approach for the detection of contaminants based on the regulation of a minimal DNA signal amplifier and transducer circuit by allosteric transcription factors and their cognate ligands. We leverage the competition between allosteric proteins and an endonuclease to modulate cascade toehold-mediated strand displacement reactions, which are triggered in the presence of specific effectors and sustained by the endonuclease. We built two optical biosensors for the detection of tetracyclines and macrolides in water using repressors TetR and MphR, respectively. We demonstrate that our minimal, fast, and single-step biosensors can successfully detect antibiotics in nanomolar levels and apply them to report the presence of spiked-in antibiotics in water samples in a matter of minutes, suggesting great potential for monitoring of water contaminants.

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