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A strategy is presented for the synthesis of crystalline porous covalent organic frameworks via topology-templated polymerization. The template is based on imine-linked frameworks and their (001) facets seed the C=C bond formation reaction to constitute 2D sp2 carbon-conjugated frameworks. This strategy is applicable to templates with different topologies, enables designed synthesis of frameworks that cannot be prepared via direct polymerization, and creates a series of sp2 carbon frameworks with tetragonal, hexagonal, and kagome topologies. The sp2 carbon frameworks are highly luminescent even in the solid state and exhibit topology-dependent π transmission and exciton migration; these key fundamental π functions are unique to sp2 carbon-conjugated frameworks and cannot be accessible by imine-linked frameworks, amorphous analogues, and 1D conjugated polymers. These results demonstrate an unprecedented strategy for structural and functional designs of covalent organic frameworks.

Attracted by the numerous regulatory functions of double-helical biopolymers such as DNA, many researchers have synthesized various double-helical systems. A recently synthesized double-stranded helical oligomer covalently bridged by rotary boronate esters (BBDD) was shown to undergo helix-inversion that might serve as platform to design rotor systems. However, the detailed helix-inversion mechanism could not be investigated experimentally. Direct molecular dynamics simulations based on density-functional tight-binding energies and gradients computed on-the-fly reveal that disentanglement to the unraveled form and following exchange of the twisted terminal trimethylsilyl (TMS) groups are prerequisites for the observed helix-inversion. The potential of mean force confirms that the originally assumed "concurrent" rotation of the boronate esters and the helix-inversion involves shorter time scale "step-wise" processes, triggered by the disentanglement and exchange of the TMS groups. These results indicate that inversion dynamics of double-helical molecules such as BBDD may be controllable by chemical fine-tuning of the terminal groups. © 2019 Wiley Periodicals, Inc.

Density functional theory (DFT) is a widely used methodology for the computation of molecular and electronic structure, and we confirm that B3LYP and the high-level ab initio G3B3 method are in excellent agreement for the lowest-energy isomers of the 16 glucose epimers. Density-functional tight-binding (DFTB) is an approximate version of DFT with typically comparable accuracy that is 2 to 3 orders of magnitude faster, therefore generally very suitable for processing large numbers of complex structures. Conformational isomerism in sugars is well known to give rise to a large number of isomer structures. On the basis of a comprehensive study of glucose epimers in vacuo and aqueous solution, we found that the performance of DFTB is on par to B3LYP in terms of geometrical parameters excluding hydrogen bonds and isomer energies. However, DFTB underestimates both hydrogen bonding interactions as well as torsional barriers associated with rotations of the hydroxy groups, resulting in a counterintuitive overemphasis of hydrogen bonding in both gas phase as well as in water. Although the associated root mean squared deviation from B3LYP within epimer isomer groups is only on the order of 1 kcal/mol, this deviation affects the correct assignment of major isomer ordering, which span less than 10 kcal/mol. Both second- as well as third-order DFTB methods are exhibiting similar deviations from B3LYP. Even after the inclusion of empirical dispersion corrections in vacuum, these deviations remain for a large majority of isomer energies and geometries when compared to dispersion-corrected B3LYP.

Transformation of carbon dioxide to high value-added chemicals becomes a significant challenge for clean energy studies. Here a stable and conductive covalent organic framework was developed for electrocatalytic carbon dioxide reduction to carbon monoxide in aqueous solution. The cobalt(II) phthalocyanine catalysts are topologically connected via robust phenazine linkage into a two-dimensional tetragonal framework that is stable under boiling water, acid, or base conditions. The 2D lattice enables full π conjugation along x and y directions as well as π conduction along the z axis across the π columns. With these structural features, the electrocatalytic framework exhibits a faradaic efficiency of 96 %, an exceptional turnover number up to 320 000, and a long-term turnover frequency of 11 412 hour-1 , which is a 32-fold improvement over molecular catalyst. The combination of catalytic activity, selectivity, efficiency, and durability is desirable for clean energy production.

Calpain-1 and calpain-2 are involved in the regulation of several signaling pathways and neuronal functions in the brain. Our recent studies indicate that calpain-1 is required for hippocampal synaptic plasticity, including long-term depression (LTD) and long-term potentiation (LTP) in field CA1. However, little is known regarding the contributions of calpain-1 to cerebellar synaptic plasticity. Low frequency stimulation (LFS, 5 Hz, 5 min)-induced LTP at parallel fibers to Purkinje cell synapses was markedly impaired in cerebellar slices from calpain-1 knock-out (KO) mice. Application of a selective calpain-2 inhibitor enhanced LFS-induced LTP in both wild-type (WT) and calpain-1 KO mice. Three protocols were used to induce LTD at these synapses: LFS (1 Hz, 15 min), perfusion with high potassium and glutamate (K-Glu) or dihydroxyphenylglycine (DHPG), a mGluR1 agonist. All three forms of LTD were impaired in calpain-1 KO mice. DHPG application stimulated calpain-1 but not calpain-2 in cerebellar slices, and DHPG-induced LTD impairment was reversed by application of a protein phosphatase 2A (PP2A) inhibitor, okadaic acid. As in hippocampus, BDNF induced calpain-1 activation and PH domain and Leucine-rich repeat Protein Phosphatase 1/suprachiasmatic nucleus oscillatory protein (PHLPP1/SCOP) degradation followed by extracellular signal-regulated kinase (ERK) activation, as well as calpain-2 activation leading to degradation of phosphatase and tensin homolog deleted on chromosome ten (PTEN) in cerebellar slices. The role of calpain-1 in associative learning was evaluated in the delay eyeblink conditioning (EBC). Calpain-1 KO mice exhibited significant learning impairment in EBC during the first 2 days of acquisition training. However, after 5 days of training, the percentage of conditioned responses (CRs) between calpain-1 KO and WT mice was identical. Both calpain-1 KO and WT mice exhibited typical extinction patterns. Our results indicate that calpain-1 plays critical roles in multiple forms of synaptic plasticity and associative learning in both hippocampus and cerebellum.

SummaryA CAPN1 missense mutation in Parson Russell Terrier dogs is associated with spinocerebellar ataxia. We now report that homozygous or heterozygous CAPN1-null mutations in humans result in cerebellar ataxia and limb spasticity in four independent pedigrees. Calpain-1 knockout (KO) mice also exhibit a mild form of ataxia due to abnormal cerebellar development, including enhanced neuronal apoptosis, decreased number of cerebellar granule cells, and altered synaptic transmission. Enhanced apoptosis is due to absence of calpain-1-mediated cleavage of PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1), which results in inhibition of the Akt pro-survival pathway in developing granule cells. Injection of neonatal mice with the indirect Akt activator, bisperoxovanadium, or crossing calpain-1 KO mice with PHLPP1 KO mice prevented increased postnatal cerebellar granule cell apoptosis and restored granule cell density and motor coordination in adult mice. Thus, mutations in CAPN1 are an additional cause of ataxia in mammals, including humans.

Covalent organic frameworks (COFs) offer ordered π structures that are useful for developing light-emitting materials. However, most COFs are weak in luminescence. Here we report the conversion of less emissive COFs into light-emitting materials via a pinpoint surgery on the pore walls. Deprotonation of the N–H bond to form an anionic nitrogen species in the hydrazone linkage can eliminate the nitrogen-related fluorescence quenching pathway. The resulting COF enhances the fluorescence in a linear proportion to the progress of deprotonation, achieving a 3.8-fold improved emission. This pinpoint N–H cleavage on the pore walls can be driven only by the fluoride anion while other halogen anions, including chloride, bromide, and iodide, remain inactive, enabling the selective fluorescence switch-on sensing of the fluoride anion at a ppb level.

Objective This study examined the effectiveness of Chinese martial arts in reducing reactive and proactive aggressive behavior among schoolchildren with a cluster-randomized trial. Methods A screening questionnaire was completed by 3511 schoolchildren of Grades 2 to 5 from 13 sites in Hong Kong. We shortlisted 298 children who scored z ≥ 1 on the total score of the Reactive-Proactive Aggression Questionnaire in their respective sites to participate in the experiment. They were divided into 31 clusters that were blinded and randomly assigned to one of the 4 conditions: skills only, philosophy only, skills and philosophy, and physical fitness (placebo). Subjects were assessed at baseline, posttraining, and 6 months after training using aggression scales. Results Results from the linear mixed model indicated that the time × training interaction effects were significant for aggressive behavior (reactive and proactive), delinquent behavior, anxiety/depression, and attention problems. Although all measures declined in all conditions over time, only the skills-and-philosophy condition showed a significant reduction at posttraining and/or 6-month follow-up compared with the placebo. Conclusion The results provided a theoretical proof for the relationship between aggression and sport involvement combined with children's moral reasoning. This study gives practical implications to intervention that solely playing sports or teaching moral lessons is not effective enough for high-risk schoolchildren with aggressive behavior. However, combined traditional Chinese martial arts skills and moral philosophy training could be considered in the school curriculum to reduce school violence and facilitate creation of harmonious schools.

Climbing fiber (CF) input to the cerebellum is thought to instruct associative motor memory formation through its effects on multiple sites within the cerebellar circuit. We used adeno-associated viral delivery of channelrhodopsin-2 (ChR2) to inferior olivary neurons to selectively express ChR2 in CFs, achieving nearly complete transfection of CFs in the caudal cerebellar lobules of rats. As expected, optical stimulation of ChR2-expressing CFs generates complex spike responses in individual Purkinje neurons (PNs); in addition we found that such stimulation recruits a network of inhibitory interneurons in the molecular layer. This CF-driven disynaptic inhibition prolongs the postcomplex spike pause observed when spontaneously firing PNs receive direct CF input; such inhibition also elicits pauses in spontaneously firing PNs not receiving direct CF input. Baseline firing rates of PNs are strongly suppressed by low-frequency (2 Hz) stimulation of CFs, and this suppression is partly relieved by blocking synaptic inhibition. We conclude that CF-driven, disynaptic inhibition has a major influence on PN excitability and contributes to the widely observed negative correlation between complex and simple spike rates. Because they receive input from many CFs, molecular layer interneurons are well positioned to detect the spatiotemporal patterns of CF activity believed to encode error signals. Together, our findings suggest that such inhibition may bind together groups of Purkinje neurons to provide instructive signals to downstream sites in the cerebellar circuit.

Cognitive functions show many alternative outcomes and great individual variation during normal aging. We examined learning over the adult life span in CBA mice, along with morphological and electrophysiological substrates. Our aim was to compare cerebellum-dependent delay eyeblink classical conditioning and hippocampus-dependent contextual fear conditioning in the same animals using the same conditioned and unconditioned stimuli for eyeblink and fear conditioning. In a subset of the behaviorally tested mice, we used unbiased stereology to estimate the total number of Purkinje neurons in cerebellar cortex and pyramidal neurons in the hippocampus. Several forms of synaptic plasticity were assessed at different ages in CBA mice: long-term depression (LTD) in both cerebellum and hippocampus and NMDA-mediated long-term potentiation (LTP) and voltage-dependent calcium channel LTP in hippocampus. Forty-four CBA mice tested at one of five ages (4, 8, 12, 18, or 24 months) demonstrated statistically significant age differences in cerebellum-dependent delay eyeblink conditioning, with 24-month mice showing impairment in comparison with younger mice. These same CBA mice showed no significant differences in contextual or cued fear conditioning. Stereology indicated significant loss of Purkinje neurons in the 18- and 24-month groups, whereas pyramidal neuron numbers were stable across age. Slice electrophysiology recorded from an additional 48 CBA mice indicated significant deficits in LTD appearing in cerebellum between 4 and 8 months, whereas 4- to 12-month mice demonstrated similar hippocampal LTD and LTP values. Our results demonstrate that processes of aging impact brain structures and associated behaviors differentially, with cerebellum showing earlier senescence than hippocampus.

In contrast to our increasingly detailed understanding of how synaptic plasticity provides a cellular substrate for learning and memory, it is less clear how a neuron's voltage-gated ion channels interact with plastic changes in synaptic strength to influence behavior. We find, using generalized and regional knockout mice, that deletion of the HCN1 channel causes profound motor learning and memory deficits in swimming and rotarod tasks. In cerebellar Purkinje cells, which are a key component of the cerebellar circuit for learning of correctly timed movements, HCN1 mediates an inward current that stabilizes the integrative properties of Purkinje cells and ensures that their input-output function is independent of the previous history of their activity. We suggest that this nonsynaptic integrative function of HCN1 is required for accurate decoding of input patterns and thereby enables synaptic plasticity to appropriately influence the performance of motor activity.

A commentary on A theory of cerebellar cortex by Marr, D. (1969). J. Physiol. 202, 437–470. A commentary on A theory of cerebellar function by Albus, J. S. (1971). Math. Biosci. 10, 25–61. Four decades ago, Marr and Albus suggested that the climbing fiber (CF) pathway from the inferior olive (IO) to the cerebellum instructs the cellular changes necessary for motor learning (Marr, 1969; Albus, 1971). Subsequent work has confirmed that CFs can drive specific forms of associative motor learning (Gilbert and Thach, 1977; Mauk et al., 1986; Raymond et al., 1996; Jirenhed et al., 2007; Medina and Lisberger, 2008) and has detailed how CFs trigger learning-related forms of synaptic plasticity in Purkinje neurons (PNs) (Linden et al., 1991; Linden and Connor, 1995; Coesmans et al., 2004). Yet, it is widely believed that associative motor learning, such as eyeblink conditioning (Lavond and Steinmetz, 1989; Perrett et al., 1993; Medina and Mauk, 1999; Jorntell and Ekerot, 2002; Ohyama et al., 2006; Shutoh et al., 2006) and vestibulo-ocular reflex (VOR) adaptation (Miles and Lisberger, 1981; Boyden et al., 2004) result from distinct forms of synaptic plasticity that are coordinated at multiple sites within the cerebellar circuit, an idea formalized in several reviews (Raymond et al., 1996; Boyden et al., 2004; Gao et al., 2012). This raises a central question regarding how CFs coordinates plasticity at multiple sites. Simply stated, how do CFs teach? To address this larger question it is useful to focus on three previously hypothesized sites of associative synaptic plasticity within the cerebellar circuit. At each, the CF is believed to instruct heterosynaptic forms of plasticity by driving changes in the strengths of other excitatory inputs, however, the direction of change triggered by CF activity, i.e., long-term depression (LTD) or long-term potentiation (LTP), is different at each site (Figure ​(Figure1A).1A). The best described example of CF teaching, and the main focus of the Marr/Albus hypothesis, occurs at the parallel fiber (PF)-to-PN synapse. In mature PNs the single CF input generates a salient and distinctive signal—a cell wide burst termed the complex spike (Eccles et al., 1964)—which instructs heterosynaptic LTD in those PFs that are coactivated with CFs [blue starburst, Figure ​Figure1A;1A; (Wang et al., 2000; Hansel et al., 2001; Coesmans et al., 2004; Safo and Regehr, 2008)]. Albus also conjectured that CFs could drive plasticity at a second site, proposing heterosynaptic LTP of PF inputs to a subset of molecular layer interneurons [MLIs; red starburst in cortex, Figure ​Figure1A;1A; (Albus, 1971)]. From the perspective of the PN, Albus considered CF enhancement of PF-to-MLI synapses as equivalent to “negative PF synaptic weights.” Considering the fact that PNs spontaneously pacemake at rates up to ~80 Hz (Hausser and Clark, 1997; Raman et al., 1997), PF-to-MLI LTP makes it possible to instruct learned pauses in PN spiking, something that PF LTD on its own cannot accomplish. Although this form of associative plasticity has yet to be demonstrated, there is evocative in vivo evidence that indirectly supports it (Jorntell and Ekerot, 2002). The final site at which CFs might instruct plasticity is at mossy fiber (MF)-to-deep cerebellar nucleus neuron (DCN) synapses (red starburst in the deep nuclei, Figure ​Figure1A).1A). Much theoretical and experimental work supports the notion that MF-to-DCN synapses strengthen during associative learning (Miles and Lisberger, 1981; Lavond and Steinmetz, 1989; Perrett et al., 1993; Chen et al., 1996; Raymond et al., 1996; Garcia and Mauk, 1998; Medina and Mauk, 1999; Ohyama et al., 2006; Shutoh et al., 2006), and some of these studies indicate that plasticity in the cortex may precede or consolidate plasticity in the DCN (Ohyama et al., 2006; Shutoh et al., 2006; Wulff et al., 2009). The predicted consequence of all three forms of plasticity is to increase DCN excitability in response to particular patterns of MF/PF inputs. While it is generally accepted that CFs drive associative LTD of PFs, it is not clear whether CFs drive the associative forms of LTP during learning (i.e., PF LTP at the MLIs and MF LTP at the DCN). Perhaps relatedly, there is also some debate to whether any one of these forms of plasticity, including PF LTD (Schonewille et al., 2011), are necessary for motor learning. Figure 1 The CF pathway and associative motor learning. (A) Schematic of the proposed sites (colored bursts) within the cerebellar circuit where CFs might teach during associative motor learning. The blue burst denotes CF driven LTD of PFs, while the red bursts ... In an effort to better understand the mechanistic details of how CFs participate in cerebellar learning, we have exploited optogenetic and pharmacological approaches to selectively manipulate CF signals. Using adeno-associated viral delivery of ChR2-eYFP to IO neurons we are able to transfect CFs with high efficiency and specificity in the rat (Figure ​(Figure1B;1B; Mathews et al., 2012). Optical activation then gives rise to “pure” CF signals generated at the key sites within the cerebellar circuit identified in Figure ​Figure1A.1A. This approach shows that MLIs are cooperatively excited by several CFs, giving rise to a robust, CF-driven, feed-forward inhibition that can in turn lead to a transient, synchronous pause in multiple PNs (dashed line, Figure ​Figure1A).1A). The CF excitation of MLIs shows cooperativity in part because it can result from the indirect spillover of glutamate from multiple CFs to an MLI, a phenomenon first described by Barbour and colleagues (Szapiro and Barbour, 2007). In this way our observations suggest that MLIs might read out population activity in many CFs (Bell and Kawasaki, 1972; Welsh et al., 1995; Lang et al., 1999; Marshall and Lang, 2009; Mukamel et al., 2009; Ozden et al., 2009), and that synchronous CF input to modules of PNs would result in synchronous pauses in PN spiking. In such a model, CF-dependent pauses in groups of PNs could then serve as proxy teaching signals in the DCN. In complimentary experiments we have used specific pharmacological tools to manipulate a component of the CF signal, the post-complex spike pause in simple spike firing rate. Two very different compounds (1-EBIO, a positive modulator of calcium activated K+ channels, or ZD 7288, an inhibitor of hyperpolarization activated cation channels) were each demonstrated to prolong the post-complex spike pause (Maiz et al., 2012). Either of these drugs infused into the cerebellar cortex during eyeblink conditioning resulted in markedly faster learning (Maiz et al., 2012). We hypothesize that prolongation of the CF-associated pause drives faster learning by facilitating associative LTP of MF inputs to DCN neurons (see Figure ​Figure1A).1A). Considering the NMDA receptor dependence of MF to DCN plasticity, it is straightforward to imagine how a pause in descending PN inhibition could associatively drive the types of LTP that have been described in vitro (Pugh and Raman, 2006, 2009). A critical step in understanding cerebellar learning is to explain how CFs, or other teaching signals, coordinate learning-related changes within the circuit. The experiments described here address important questions about the biology of the CF and how it might operate as a teaching signal. Related questions include whether CFs give rise to distinctive postsynaptic signals at those sites in the circuit where they have been hypothesized as teachers, and whether CFs trigger heterosynaptic, associative forms of plasticity that might contribute to learned motor behaviors. The striking anatomical organization of the cerebellar cortex coupled with the remarkable properties of the CF contact on PNs led to the insightful conjecture of Marr and Albus more than 40 years ago. Our observations are consistent with CFs exerting control over multiple sites within the cerebellar circuit, in part through indirect actions read out by MLIs or groups of PNs, a picture that brings to mind the aphorism from the Talmud, “When you teach your son, you teach your son's son.” Future experiments utilizing a wide breadth of classical and novel techniques, like those mentioned here will be required to determine just how paternalistic the CF is, and whether it broadens its influence in an analogous way.

The calcium/calmodulin-dependent protein kinase type IV (CaMKIV) is highly expressed in cerebellar cortical granule cells and deep nuclear neurons in the cerebellum. It mediates the phosphorylation and activation of the cAMP-dependent response element binding protein (CREB). In several paradigms CREB-dependent transcription is required for cellular events underlying long-term memory processes. Also, CaMKIV deficiency results in impaired long-term depression (LTD) induction in cerebellar cortex. To investigate the function of CaMKIV in the cerebellum, Wild-type (WT) and CaMKIV KO mice were tested with delay eyeblink conditioning. KO and WT mice did not differ in acquisition, but the KO mice showed a significantly lower conditioned response (CR) percentage than the WT mice in the retention testing and retraining period. The CR peak latencies for the two groups did not differ in acquisition but were shorter for the KO mice in the testing period. No significant differences were found between KO and WT mice in spontaneous eyeblink activity, auditory brainstem response (ABR) amplitudes, and tail-flick latency. The results suggest an important role for CaMKIV in long-term memory in the cerebellum.

Long-term potentiation (LTP) and long-term depression (LTD) are arguably two of the most widely discussed cellular plasticity mechanisms for learning and memory. However, the extent to which they are required for behavioral plasticity and learning is not clear. In this issue of Neuron, Boyden et al. use mice lacking CaMKIV and Hansel et al. use mice lacking alphaCaMKII to assess the contribution of LTD to cerebellar learning.