A solvent-controlled photoresponsive ionic hydrogen-bonded organic framework for encryption applications.

Two novel ionic hydrogen-bonded organic frameworks (iHOF-17 and iHOF-18) were obtained by integrating organosulfonic acids with amidine salts. Among them, iHOF-18 exhibits fast, reversible, and high-contrast UV-induced photochromic properties, and this property is solvent-controlled. This work provides valuable insights for designing advanced anti-counterfeiting techniques and encryption applications.

Charge-Assisted Ionic Hydrogen-Bonded Organic Frameworks: Designable and Stabilized Multifunctional Materials.

Hydrogen-bonded organic frameworks (HOFs) are a class of crystalline framework materials assembled by hydrogen bonds. HOFs have the advantages of high crystallinity, mild reaction conditions, good solution processability, and reproducibility. Coupled with the reversibility and flexibility of hydrogen bonds, HOFs can be assembled into a wide diversity of crystalline structures. Since the bonding energy of hydrogen bonds is lower than that of ligand and covalent bonds, the framework of HOFs is prone to collapse after desolventisation and the stability is not high, which limits the development and application of HOFs. In recent years, numerous stable and functional HOFs have been developed by π-π stacking, highly interpenetrated networks, charge-assisted, ligand-bond-assisted, molecular weaving, and covalent cross-linking. Charge-assisted ionic HOFs introduce electrostatic attraction into HOFs to improve stability while enriching structural diversity and functionality. In this paper, we review the development, the principles of rational design and assembly of charge-assisted ionic HOFs, and introduces the different building block construction modes of charge-assisted ionic HOFs. Highlight the applications of charge-assisted ionic HOFs in gas adsorption and separation, proton conduction, biological applications, etc., and prospects for the diverse design of charge-assisted ionic HOFs structures and multifunctional applications.

A single photoreceptor splits perception and entrainment by cotransmission.

Vision enables both image-forming perception, driven by a contrast-based pathway, and unconscious non-image-forming circadian photoentrainment, driven by an irradiance-based pathway1,2. Although two distinct photoreceptor populations are specialized for each visual task3-6, image-forming photoreceptors can additionally contribute to photoentrainment of the circadian clock in different species7-15. However, it is unknown how the image-forming photoreceptor pathway can functionally implement the segregation of irradiance signals required for circadian photoentrainment from contrast signals required for image perception. Here we report that the Drosophila R8 photoreceptor separates image-forming and irradiance signals by co-transmitting two neurotransmitters, histamine and acetylcholine. This segregation is further established postsynaptically by histamine-receptor-expressing unicolumnar retinotopic neurons and acetylcholine-receptor-expressing multicolumnar integration neurons. The acetylcholine transmission from R8 photoreceptors is sustained by an autocrine negative feedback of the cotransmitted histamine during the light phase of light-dark cycles. At the behavioural level, elimination of histamine and acetylcholine transmission impairs R8-driven motion detection and circadian photoentrainment, respectively. Thus, a single type of photoreceptor can achieve the dichotomy of visual perception and circadian photoentrainment as early as the first visual synapses, revealing a simple yet robust mechanism to segregate and translate distinct sensory features into different animal behaviours.

Resveratrol and Sir2 Reverse Sleep and Memory Defects Induced by Amyloid Precursor Protein.

Resveratrol (RES), a natural polyphenolic phytochemical, has been suggested as a putative anti-aging molecule for the prevention and treatment of Alzheimer's disease (AD) by the activation of sirtuin 1 (Sirt1/Sir2). In this study, we tested the effects of RES and Sirt1/Sir2 on sleep and courtship memory in a Drosophila model by overexpression of amyloid precursor protein (APP), whose duplications and mutations cause familial AD. We found a mild but significant transcriptional increase of Drosophila Sir2 (dSir2) by RES supplementation for up to 17 days in APP flies, but not for 7 days. RES and dSir2 almost completely reversed the sleep and memory deficits in APP flies. We further demonstrated that dSir2 acts as a sleep promotor in Drosophila neurons. Interestingly, RES increased sleep in the absence of dSir2 in dSir2-null mutants, and RES further enhanced sleep when dSir2 was either overexpressed or knocked down in APP flies. Finally, we showed that Aß aggregates in APP flies were reduced by RES and dSir2, probably via inhibiting Drosophila ß-secretase (dBACE). Our data suggest that RES rescues the APP-induced behavioral deficits and Aß burden largely, but not exclusively, via dSir2.

Water-Induced Single-Crystal to Single-Crystal Transformation of Ionic Hydrogen-Bonded Organic Frameworks with Enhanced Proton Conductivity.

Two ionic hydrogen-bonded organic frameworks (iHOF-10, iHOF-11) were prepared using 1,1'-diamino-4,4'-bipyridine diiodide (Dbpy ⋅ 2I) and tetrakis(4-sulfophenyl)ethylene (H4 TPE). With increasing RH and temperature, water molecules induce single crystal to single crystal (SCSC) transformation of iHOF-10, resulting in the formation of iHOF-11. At 90 °C, 98 % RH, the proton conductivity of iHOF-11 (7.03×10-3  S cm-1 ) is 2.09 times higher than iHOF-10 (3.37×10-3  S cm-1 ). At 50 °C, 98 % RH, iHOF-11 (9.49×10-4  S cm-1 ) is 19.06 times higher than iHOF-10 (4.98×10-5  S cm-1 ). The proton conductivity shows water molecules enter the crystal and induce crystal transformation and reorganization of the hydrogen bonding structure, thus increasing the proton conductivity and stability.

Poly[bis-(µ2-N,N-di-methyl-formamide-κ2 O:O)bis-(µ4-thio-phene-2,5-di-carboxyl-ato-κ4 O:O':O'':O''')dicobalt(II)].

The asymmetric unit of the title three-dimensional metal-organic hybrid compound, [Co2(C6H2O4S)2(C3H7NO)2] n , comprises two cobalt(II) cations, one residing on a twofold axis and the other on a centre of inversion, one thio-phene-2,5-di-carboxyl-ate (tdc2-) ligand and one coordinating di-methyl-formamide (DMF) solvent mol-ecule. Both of the cobalt(II) cations exhibit an octa-hedral coordination environment from the four carboxyl O atoms of the tdc2- anions in a µ 4-κ 1:κ 1:κ 1:κ 1 fashion and two O atoms from DMF. A pair of carboxyl O atoms and one DMF molecule connect the adjacent cobalt(II) cations into an infinite chain, leading to a rod-spacer framework with rhombus-window channels, yet no residual solvent-accessible voids are present because the coordinating DMF molecules are oriented into the potential channels.

An extra-clock ultradian brain oscillator sustains circadian timekeeping.

The master circadian clock generates 24-hour rhythms to orchestrate daily behavior, even running freely under constant conditions. Traditionally, the master clock is considered self-sufficient in sustaining free-running timekeeping via its cell-autonomous molecular clocks and interneuronal communications within the circadian neural network. Here, we find a set of bona fide ultradian oscillators in the Drosophila brain that support free-running timekeeping, despite being located outside the master clock circuit and lacking clock gene expression. These extra-clock electrical oscillators (xCEOs) generate cell-autonomous ultradian bursts, pacing widespread burst firing and promoting rhythmic resting membrane potentials in clock neurons via parallel monosynaptic connections. Silencing xCEOs disrupts daily electrical rhythms in clock neurons and impairs cycling of neuropeptide pigment dispersing factor, leading to the loss of free-running locomotor rhythms. Together, we conclude that the master clock is not self-sufficient to sustain free-running behavior rhythms but requires additional endogenous inputs to the clock from the extra-clock ultradian brain oscillators.

Hybrid Nafion Membranes of Ionic Hydrogen-Bonded Organic Framework Materials for Proton Conduction and PEMFC Applications.

As the high-power density and environmentally friendly energy resources, proton exchange membrane fuel cells (PEMFCs) have a promising future in portable power generation. Herein, the hybrid Nafion membranes of ionic hydrogen-bonded organic frameworks (iHOFs) for PEMFC applications are demonstrated. By adjusting the position of sulfonic groups on naphthalene disulfonic acid compounds, four iHOFs with different types of hydrogen bonds were synthesized successfully based on 1,1'-diamino-4,4'-bipyridylium and naphthalene disulfonic acid. The formation of hydrogen bond interactions between amino and sulfonate groups provides a rich hydrogen bond network, which makes such iHOFs have high conductivity, and the maximum value is 2.76 × 10-3 S·cm-1 at 100 °C and 98% RH. Besides, composite membrane materials were obtained by mixing Nafion and iHOFs, and the maximum proton conductivity values can achieve 1.13 × 10-2 S·cm-1 for 6%-iHOF-3/Nafion and 2.87 × 10-3 S·cm-1 for 6%-iHOF-4/Nafion membranes at 100 °C under 98% RH. Through the H2/O2 fuel cell performance test by using iHOF/Nafion as the solid electrolyte, the maximum power and current density values of hybrid membranes are 0.36 W·cm-2 and 1.10 A·cm-2 for 6%-iHOF-3/Nafion and 0.42 W·cm-2 and 1.20 A·cm-2 for 6%-iHOF-4/Nafion at 80 °C and 100% RH. This work provides a practicable approach for establishing high-performance proton exchange hybrid membranes by doping high proton-conducting iHOFs into the Nafion matrix.

Controllable Strategy for Metal-Organic Framework Light-Driven [2 + 2] Cycloaddition Reactions via Solvent-Assisted Linker Exchange.

Flexible olefinic trans-1,2-bis(4-pyridyl)ethene linkers were postsynthetically introduced into the metal-organic frameworks (MOFs) containing parallel rigid 4,4'-bipyridine linkers with a spacing of less than 4.2 Å by the linker exchange strategy, and then, the MOF satisfied Schmidt criteria could be obtained. Eventually, MOF products connected by cyclobutane derivatives were formed by the photochemical [2 + 2] cycloaddition reaction under UV irradiation.

Cationic Nonporous Macrocyclic Organic Compounds for Multimedia Iodine Capture.

Over the past two decades, progress in chemistry has generated various types of porous materials for removing iodine (129 I or 131 I) that can be formed during nuclear energy generation or nuclear waste storage. However, most studies for iodine capture are based on the weak host-guest interactions of the porous materials. Here, we present two cationic nonporous macrocyclic organic compounds, namely, MOC-1 and MOC-2, in which 6I- and 8I- were as counter anions, for highly efficient iodine capture. MOC-1 and MOC-2 were formed by reacting 1,1'-diamino-4,4'-bipyridylium di-iodide with 1,2-diformylbenzene or 1,3-diformylbenzene, respectively. The presence of a large number of I- anions results in high I2 affinity with uptake capacities up to 2.15 g ⋅ g-1 for MOC-1 and 2.25 g ⋅ g-1 for MOC-2.

Apo-Opsin and Its Dark Constitutive Activity across Retinal Cone Subtypes.

Retinal rod and cone photoreceptors mediate vision in dim and bright light, respectively, by transducing absorbed photons into neural electrical signals. Their phototransduction mechanisms are essentially identical. However, one difference is that, whereas a rod visual pigment remains stable in darkness, a cone pigment has some tendency to dissociate spontaneously into apo-opsin and retinal (the chromophore) without isomerization. This cone-pigment property is long known but has mostly been overlooked. Importantly, because apo-opsin has weak constitutive activity, it triggers transduction to produce electrical noise even in darkness. Currently, the precise dark apo-opsin contents across cone subtypes are mostly unknown, as are their dark activities. We report here a study of goldfish red (L), green (M), and blue (S) cones, finding with microspectrophotometry widely different apo-opsin percentages in darkness, being ∼30% in L cones, ∼3% in M cones, and negligible in S cones. L and M cones also had higher dark apo-opsin noise than holo-pigment thermal isomerization activity. As such, given the most likely low signal amplification at the pigment-to-transducin/phosphodiesterase phototransduction step, especially in L cones, apo-opsin noise may not be easily distinguishable from light responses and thus may affect cone vision near threshold.

Color-Tuning and Near-Sunlight White Emission in Highly Stable Rod-Spacer MOFs with Defective Dicubane Based Lead(II)-Carboxyl Chains.

The active lone pair electron effect and highly flexible coordination geometry of Pb2+ prevented the rational construction of metal-organic frameworks (MOFs) but promoted excellent fluorescence tuning. The regulation on organic and alkali templates facilitated the assemblies of three new Pb-MOFs: [Pb2(pia)2(DMA)]·DMA (1), [Pb2(pia)2(DMF)]·1.5DMF (2), and [Pb2(pia)2(DMF)]·NEt3 (3). They were rigid rod-spacer and double-walls frameworks, which possess defective dicubane [Pb4O6] based metal-carboxyl chains constructed from both semidirected and holodirected Pb2+ ions. These MOFs exhibited thermal stability up to 370 °C and unprecedented chemical stability in H2O and acidic (pH 2) and alkaline (pH 12) aqueous solutions, found for the first time in Pb-MOFs. A single-phase and rare-earth-free white-emitting phosphor, 1, was screen out, which showed a near-sunlight and human-vision-friendly broadband spectrum covering the full visible region, possessing the close-to-pure-white chromaticity coordinates of (0.332, 0.347), a near-daylight color temperature of 5696 K, and a high color rendering index of 95. The replacement of DMF as apical ligand and guest in 2 resulted in an intrinsic single and narrow emission at 562 nm with yellow color. The convenient yellow-and-blue color-tuning until white for 2 was realized by either solution or solid blending with blue-emissive H2pia, benefited from their highly matched excitation spectra. Using large NEt3 as template guest induced great framework distortion for 3 and led to white emission with chromaticity coordinates of (0.302, 0.294), stemming from nonequivalent dual emission at 450 and 545 nm. In-depth structure analysis revealed intra-/interchain Pb···Pb interactions in the lead(II)-carboxyl chains greatly affected the photochemical output.

A fivefold linker length reduction in an interpenetrated metal-organic framework via sequential solvent-assisted linker exchange.

A sequential solvent-assisted linker exchange (SSALE) method was used to contract the unit cell dimensions of an interpenetrated layer-pillared Zn-MOF. The 15.3 Å N,N'-di-4-pyridylnaphthalenetetracarboxydiimide (DPNDI) pillar was replaced stepwise by 9.4 Å trans-1,2-bis(4-pyridyl)ethene (BPE) and 2.8 Å pyrazine (PYZ). Notably, the sequential transformations lead to more than five times reduction in the linker size, which is the largest change in linker size by the SALE method so far.

Near sunlight continuous broadband white-light emission by single-phase Zn(ii)-1,3,5-benzenetricarboxylate MOFs.

A new white light MOF was constructed from low-cost 1,3,5-benzenetricarboxylate and nontoxic Zinc(ii) ions. The compound possessed the most sophisticated crystallographic asymmetric unit containing sixteen metal ions and twelve ligands. Near sunlight and human eye friendly white-light emission under a wide ultraviolet radiation range of 300 to 390 nm was observed for this photoemitter, without the use of expensive rare earth and complicated organic ligands.

Physiological response and miRNA-mRNA interaction analysis in the head kidney of rainbow trout exposed to acute heat stress.

The rainbow trout is a cold-water fish cultured in China. Heat stress has a serious impact on the summer survival and the yield of rainbow trout. A better understanding of the regulatory response of rainbow trout to heat stress will help in determining the relationship between heat stress signaling pathways and adaption mechanisms and help contribute to breeding new high-temperature tolerant strains of rainbow trout. In this study, the 48-h median lethal temperature (48h-LT50) of rainbow trout was determined as 22.5°C. We developed control (16°C) and heat-treated (22.5°C) groups and extracted RNA from the head kidney tissues for high-throughput sequencing to study the microRNA (miRNA) expression profiles. Twelve up-regulated and five down-regulated miRNAs were identified between the control and heat-treated groups. A total of 22 target genes were predicted for 6 of the differentially expressed miRNAs, including 31 negative miRNA-mRNA interactions. Important regulatory pathways under heat stress are related to the metabolism and immune responses of the rainbow trout. Our findings provide preliminary data for investigating the high-temperature molecular mechanism of the rainbow trout and can help producers to reduce the economic losses caused by high temperature weather.

Mechanosensory circuits coordinate two opposing motor actions in Drosophila feeding.

Mechanoreception detects physical forces in the senses of hearing, touch, and proprioception. Here, we show that labellar mechanoreception wires two motor circuits to facilitate and terminate Drosophila feeding. Using patch-clamp recordings, we identified mechanosensory neurons (MSNs) in taste pegs of the inner labella and taste bristles of the outer labella, both of which rely on the same mechanoreceptor, NOMPC (no mechanoreceptor potential C), to transduce mechanical deflection. Connecting with distinct brain motor circuits, bristle MSNs drive labellar spread to facilitate feeding and peg MSNs elicit proboscis retraction to terminate feeding. Bitter sense modulates these two mechanosensory circuits in opposing manners, preventing labellar spread by bristle MSNs and promoting proboscis retraction by peg MSNs. Together, these labeled-line circuits enable labellar peg and bristle MSNs to use the same mechanoreceptors to direct opposing feeding actions and differentially integrate gustatory information in shaping feeding decisions.

Hub-organized parallel circuits of central circadian pacemaker neurons for visual photoentrainment in Drosophila.

Circadian rhythms are orchestrated by a master clock that emerges from a network of circadian pacemaker neurons. The master clock is synchronized to external light/dark cycles through photoentrainment, but the circuit mechanisms underlying visual photoentrainment remain largely unknown. Here, we report that Drosophila has eye-mediated photoentrainment via a parallel pacemaker neuron organization. Patch-clamp recordings of central circadian pacemaker neurons reveal that light excites most of them independently of one another. We also show that light-responding pacemaker neurons send their dendrites to a neuropil called accessary medulla (aMe), where they make monosynaptic connections with Hofbauer-Buchner eyelet photoreceptors and interneurons that transmit compound-eye signals. Laser ablation of aMe and eye removal both abolish light responses of circadian pacemaker neurons, revealing aMe as a hub to channel eye inputs to central circadian clock. Taken together, we demonstrate that the central clock receives eye inputs via hub-organized parallel circuits in Drosophila.

Odor-evoked inhibition of olfactory sensory neurons drives olfactory perception in Drosophila.

Inhibitory response occurs throughout the nervous system, including the peripheral olfactory system. While odor-evoked excitation in peripheral olfactory cells is known to encode odor information, the molecular mechanism and functional roles of odor-evoked inhibition remain largely unknown. Here, we examined Drosophila olfactory sensory neurons and found that inhibitory odors triggered outward receptor currents by reducing the constitutive activities of odorant receptors, inhibiting the basal spike firing in olfactory sensory neurons. Remarkably, this odor-evoked inhibition of olfactory sensory neurons elicited by itself a full range of olfactory behaviors from attraction to avoidance, as did odor-evoked olfactory sensory neuron excitation. These results indicated that peripheral inhibition is comparable to excitation in encoding sensory signals rather than merely regulating excitation. Furthermore, we demonstrated that a bidirectional code with both odor-evoked inhibition and excitation in single olfactory sensory neurons increases the odor-coding capacity, providing a means of efficient sensory encoding.

Diverse dissolution-recrystallization structural transformations and sequential Förster resonance energy transfer behavior of a luminescent porous Cd-MOF.

Metal-organic frameworks (MOFs) with light-harvesting building blocks provide an excellent platform to study energy transfer in networks with well-defined structures. Here, we report the synthesis, dissolution-recrystallization structural transformation (DRST) and the Förster resonance energy transfer (FRET) properties of a 2D microporous MOF {[Cd2(L1)3(Hdabco)2]·5DMAc·6H2O}n (Cd-MOF, 1). Complex 1 can be dissolved in water and three other products with different dimensions recrystallized from the aqueous solution under diverse reaction conditions were obtained. Due to the porosity and excellent blue luminescence properties of complex 1, we also studied the FRET process between 1 and guest dyes. Two distinct organic dye molecules viz., acridine orange (AO) and rhodamine B (RhB), are encapsulated in 1 which has honeycomb-type nanochannels, and their influence on fluorescence emission has also been studied. The microporous complex 1 in (AO + RhB)@1 serves as an energy funnel that harvests high energy excitation and channels it onto AO and then onto RhB. The steady-state fluorescence and fluorescence dynamics of emission reveal successfully the process of stepwise vectorial energy transfer. Therefore, MOFs could be a class of promising host materials to be further explored in the field of energy transfer between MOF-host and organic guests.

Dimerization of visual pigments in vivo.

It is a deeply engrained notion that the visual pigment rhodopsin signals light as a monomer, even though many G protein-coupled receptors are now known to exist and function as dimers. Nonetheless, recent studies (albeit all in vitro) have suggested that rhodopsin and its chromophore-free apoprotein, R-opsin, may indeed exist as a homodimer in rod disk membranes. Given the overwhelmingly strong historical context, the crucial remaining question, therefore, is whether pigment dimerization truly exists naturally and what function this dimerization may serve. We addressed this question in vivo with a unique mouse line (S-opsin(+)Lrat(-/-)) expressing, transgenically, short-wavelength-sensitive cone opsin (S-opsin) in rods and also lacking chromophore to exploit the fact that cone opsins, but not R-opsin, require chromophore for proper folding and trafficking to the photoreceptor's outer segment. In R-opsin's absence, S-opsin in these transgenic rods without chromophore was mislocalized; in R-opsin's presence, however, S-opsin trafficked normally to the rod outer segment and produced functional S-pigment upon subsequent chromophore restoration. Introducing a competing R-opsin transmembrane helix H1 or helix H8 peptide, but not helix H4 or helix H5 peptide, into these transgenic rods caused mislocalization of R-opsin and S-opsin to the perinuclear endoplasmic reticulum. Importantly, a similar peptide-competition effect was observed even in WT rods. Our work provides convincing evidence for visual pigment dimerization in vivo under physiological conditions and for its role in pigment maturation and targeting. Our work raises new questions regarding a potential mechanistic role of dimerization in rhodopsin signaling.