Reconstitution of RNA cap methylation reveals different features of SARS-CoV-2 and SARS-CoV methyltransferases.

Cap RNA methylations play important roles in the replication, evasion of host RNA sensor recognition, and pathogenesis. Coronaviruses possess both guanine N7- and 2'-O-ribose methyltransferases (N7-MTase and 2'-O-MTase) encoded by nonstructural protein (nsp) 14 and nsp16/10 complex, respectively. In this study, we reconstituted the two-step RNA methylations of N7-MTase and 2'-O-MTase of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vitro and demonstrated its common and different features in comparison with that of SARS-CoV. We revealed that the nsp16/10 2'-O-MTase of SARS-CoV-2 has a broader substrate selectivity than the counterpart of SARS-CoV and can accommodate both unmethylated and uncapped RNA substrates in a sequence-independent manner. Most intriguingly, the substrate selectivity of nsp16/10 complex is not determined by the apoenzyme of nsp16 MTase but by its cofactor nsp10. These results provide insight into the unique features of SARS-CoV-2 MTases and may help develop strategies to precisely intervene in the methylation pathway and pathogenesis of SARS-CoV-2.

Synthesis and Characterization of U≡C Triple Bonds in Fullerene Compounds.

Despite decades of efforts, the actinide-carbon triple bond has remained an elusive target, defying synthesis in any isolable compound. Herein, we report the successful synthesis of uranium-carbon triple bonds in carbide-bridged bimetallic [U≡C-Ce] units encapsulated inside the fullerene cages of C72 and C78. The molecular structures of UCCe@C2n and the nature of the U≡C triple bond were characterized through X-ray crystallography and various spectroscopic analyses, revealing very short uranium-carbon bonds of 1.921(6) and 1.930(6) Å, with the metals existing in their highest oxidation states of +6 and +4 for uranium and cerium, respectively. Quantum-chemical studies further demonstrate that the C2n cages are crucial for stabilizing the [UVI≡C-CeIV] units through covalent and coordinative interactions. This work offers a new fundamental understanding of the elusive uranium-carbon triple bond and informs the design of complexes with similar bonding motifs, opening up new possibilities for creating distinctive molecular compounds and materials.

PACT inhibits the replication of SARS-CoV-2 through the blockage of GSK-3ß-N-nsp3 cascade.

The protein activator of protein kinase R (PKR) (PACT) has been shown to play a crucial role in stimulating the host antiviral response through the activation of PKR, retinoic acid-inducible gene I, and melanoma differentiation-associated protein 5. Whether PACT can inhibit viral replication independent of known mechanisms is still unrevealed. In this study, we show that, like many viruses, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) hijacks GSK-3ß to facilitate its replication. GSK-3ß-induced phosphorylation on N protein increased the interaction between N protein and nsp3. Thus, GSK-3ß-N-nsp3 cascade promotes viral replication. Although SARS-CoV-2 can sabotage the activation of AKT, the upstream proteins suppressing the activation of GSK-3ß, we found that the host can use PACT, another protein kinase, instead of AKT to decrease the activity of GSK-3ß and the interaction between PACT and GSK-3ß is enhanced upon viral infection. Moreover, PACT inhibited the activity of GSK-3ß independent of its well-studied double-stranded RNA binding and PKR activating ability. In summary, this study identified an unknown function of PACT in inhibiting SARS-CoV-2 replication through the blockage of GSK-3ß-N-nsp3 cascade.

Spike substitution T813S increases Sarbecovirus fusogenicity by enhancing the usage of TMPRSS2.

SARS-CoV Spike (S) protein shares considerable homology with SARS-CoV-2 S, especially in the conserved S2 subunit (S2). S protein mediates coronavirus receptor binding and membrane fusion, and the latter activity can greatly influence coronavirus infection. We observed that SARS-CoV S is less effective in inducing membrane fusion compared with SARS-CoV-2 S. We identify that S813T mutation is sufficient in S2 interfering with the cleavage of SARS-CoV-2 S by TMPRSS2, reducing spike fusogenicity and pseudoparticle entry. Conversely, the mutation of T813S in SARS-CoV S increased fusion ability and viral replication. Our data suggested that residue 813 in the S was critical for the proteolytic activation, and the change from threonine to serine at 813 position might be an evolutionary feature adopted by SARS-2-related viruses. This finding deepened the understanding of Spike fusogenicity and could provide a new perspective for exploring Sarbecovirus' evolution.

Incentive strategy of safe and intelligent production in assembled steel plants from the perspective of evolutionary game.

Due to the numerous cross-operations and poor information communication, it is easy to cause production safety accidents in traditional assembled steel plants. The transformation and upgrading of smart production in the assembly steel plants is helpful to improve the efficiency of safety management. In order to effectively reduce the safety risks in the production of assembled steel components, this paper integrates policy incentives and safety supervision, constructs an evolutionary game model between the government and assembled steel producers, and analyzes the strategic evolution rules and stability conditions of stakeholders through the replication dynamics equation. Moreover, based on the empirical simulation of the Fuzhou X Steel Structure Plant project, the effectiveness of the evolutionary model incentive strategy setting is verified. The results show that whether an assembled steel plants adopt a smart management strategy or not is influenced by the government's incentive subsidy mechanism, penalty mechanism, the benefits and costs generated by traditional/ smart management, the probability and loss of safety accidents and other factors. The conclusion is important for upgrading the safety management mode, improving the safety production efficiency and constructing the safety supervision system of the assembled steel smart plant.

Association between migraine and epilepsy: a meta-analysis.

Background: Epidemiological studies have demonstrated a comorbid association between migraine and epilepsy. However, despite the long history of this association, the exact nature of the relationship between migraine and epilepsy remains largely unresolved. Therefore, it is crucial to conduct a meta-analysis in order to thoroughly investigate the relationship between migraine and epilepsy. Methods: Odds ratios (ORs) or relative risks (RRs) and 95% confidence intervals (CIs) regarding association between migraine and epilepsy were summarized using STATA 12.0 software. Results: There was an 80% increase in the lifetime prevalence of migraine among patients with epilepsy, compared to those without epilepsy with a random effects model (OR/RR: 1.80, 95% CI: 1.35 to 2.40, I2 = 97.5%, p < 0.001). There was an 80% increase in the lifetime prevalence of epilepsy among patients with migraine, compared to those without migraine with a random effects model (OR/RR: 1.80, 95% CI: 1.43 to 2.25, I2 = 80.6%, p < 0.001). Conclusions: It is important to note the comorbid association between migraine and epilepsy examined in the study.

A charged diatomic triple-bonded U≡N species trapped in C82 fullerene cages.

Actinide diatomic molecules are ideal models to study elusive actinide multiple bonds, but most of these diatomic molecules have so far only been studied in solid inert gas matrices. Herein, we report a charged U≡N diatomic species captured in fullerene cages and stabilized by the U-fullerene coordination interaction. Two diatomic clusterfullerenes, viz. UN@Cs(6)-C82 and UN@C2(5)-C82, were successfully synthesized and characterized. Crystallographic analysis reveals U-N bond lengths of 1.760(7) and 1.760(20) Å in UN@Cs(6)-C82 and UN@C2(5)-C82. Moreover, U≡N was found to be immobilized and coordinated to the fullerene cages at 100 K but it rotates inside the cage at 273 K. Quantum-chemical calculations show a (UN)2+@(C82)2- electronic structure with formal +5 oxidation state (f1) of U and unambiguously demonstrate the presence of a U≡N bond in the clusterfullerenes. This study constitutes an approach to stabilize fundamentally important actinide multiply bonded species.

Genome-Wide Analysis of the Indispensable Role of Non-structural Proteins in the Replication of SARS-CoV-2.

Understanding the process of replication and transcription of SARS-CoV-2 is essential for antiviral strategy development. The replicase polyprotein is indispensable for viral replication. However, whether all nsps derived from the replicase polyprotein of SARS-CoV-2 are indispensable is not fully understood. In this study, we utilized the SARS-CoV-2 replicon as the system to investigate the role of each nsp in viral replication. We found that except for nsp16, all the nsp deletions drastically impair the replication of the replicon, and nsp14 could recover the replication deficiency caused by its deletion in the viral replicon. Due to the unsuccessful expressions of nsp1, nsp3, and nsp16, we could not draw a conclusion about their in trans-rescue functions. Our study provided a new angle to understand the role of each nsp in viral replication and transcription, helping the evaluation of nsps as the target for antiviral drug development.

UCN@Cs(6)-C82: An Encapsulated Triangular UCN Cluster with Ambiguous U Oxidation State [U(III) versus U(I)].

Understanding the chemical behavior of actinide elements is essential for the effective management and use of actinide materials. In this study, we report an unprecedented η2 (side-on) coordination of U by a cyanide in a UCN cluster, which was stabilized inside a C82 fullerene cage. UCN@Cs(6)-C82 was successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray crystallography, cyclic voltammetry, spectroscopy, and theoretical calculations. The bonding analysis demonstrates significant donation bonding between CN- and uranium, and covalent interactions between uranium and the carbon cage. These effects correlate with an observed elongated cyanide C-N bond, resulting in a rare case where the oxidation state of uranium shows ambiguity between U(III) and U(I). The discovery of this unprecedented triangular configuration of the uranium cyanide cluster provides a new insight in coordination chemistry and highlights the large variety of bonding situations that uranium can have.

Synthesis and Characterization of Two Isomers of Th@C82: Th@C2v(9)-C82 and Th@C2(5)-C82.

Actinide endohedral fullerenes have demonstrated remarkably different physicochemical properties compared to their lanthanide analogues. In this work, two novel isomers of Th@C82 were successfully synthesized, isolated, and fully characterized by mass spectrometry, X-ray single crystallography, UV-vis-NIR spectroscopy, Raman spectroscopy, and cyclic voltammetry. The molecular structures of the two isomers were determined unambiguously as Th@C2v(9)-C82 and Th@C2(5)-C82 by single-crystal X-ray diffraction analysis. Raman and UV-vis-NIR spectroscopies further confirm the assignment of the cage isomers. Electrochemical gaps suggest that both Th@C2v(9)-C82 and Th@C2(5)-C82 possess a stable closed-shell electronic structure. The computational results further confirm that Th@C2v(9)-C82 and Th@C2(5)-C82 exhibit a unique four-electron charge transfer from the metal to the carbon cage and are among the most abundant isomers of Th@C82.

Th@D5h(6)-C80: a highly symmetric fullerene cage stabilized by a single metal ion.

A novel endohedral metallofullerene (mono-EMF), Th@D5h(6)-C80, has been successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray diffraction, UV-vis-NIR and Raman spectroscopy and cyclic voltammetry. Single crystal XRD analysis unambiguously assigned the fullerene cage as D5h(6)-C80, the first example in which the highly symmetric cage is stabilized by a single metal ion. The combined experimental and theoretical studies further reveal that the D5h(6)-C80 cage, known only for its stabilization by 6-electron transfer, is stabilized by the 4-electron transfer from the encapsulated Th ion for the first time.

Characterization of a strong covalent Th3+-Th3+ bond inside an Ih(7)-C80 fullerene cage.

The nature of the actinide-actinide bonds is of fundamental importance to understand the electronic structure of the 5f elements. It has attracted considerable theoretical attention, but little is known experimentally as the synthesis of these chemical bonds remains extremely challenging. Herein, we report a strong covalent Th-Th bond formed between two rarely accessible Th3+ ions, stabilized inside a fullerene cage nanocontainer as Th2@Ih(7)-C80. This compound is synthesized using the arc-discharge method and fully characterized using several techniques. The single-crystal X-Ray diffraction analysis determines that the two Th atoms are separated by 3.816 Å. Both experimental and quantum-chemical results show that the two Th atoms have formal charges of +3 and confirm the presence of a strong covalent Th-Th bond inside Ih(7)-C80. Moreover, density functional theory and ab initio multireference calculations suggest that the overlap between the 7s/6d hybrid thorium orbitals is so large that the bond still exists at Th-Th separations larger than 6 Å. This work demonstrates the authenticity of covalent actinide metal-metal bonds in a stable compound and deepens our fundamental understanding of f element metal bonds.

A non-isolated pentagon rule C82 cage stabilized by a stretched Sc3N cluster.

A novel cluster fullerene, Sc3N@Cs(39 663)-C82, has been synthesized and characterized. Crystallograpic charaterization unambiguously determines the non-IPR cage structure of Cs(39 663)-C82. Structural analyses further reveal that the Sc3N cluster is notably stretched to facilitate the interaction with the non-IPR fullerene cage.

Crystallographic and spectroscopic characterization of a mixed actinide-lanthanide carbide cluster stabilized inside an Ih(7)-C80 fullerene cage.

A mixed actinide-lanthanide cluster fullerene, Sc2UC@Ih(7)-C80, was isolated and fully characterized. For the first time, the single crystal X-ray crystallographic analysis confirms a novel actinide-lanthanide cluster Sc2UC stabilized inside an Ih(7)-C80 cage. Moreover, the U[double bond, length as m-dash]C double bond distance is 2.01 Å, the shortest U[double bond, length as m-dash]C bond confirmed by crystallography so far.

U2N@I h(7)-C80: fullerene cage encapsulating an unsymmetrical U(iv)[double bond, length as m-dash]N[double bond, length as m-dash]U(v) cluster.

For the first time, an actinide nitride clusterfullerene, U2N@I h(7)-C80, is synthesized and fully characterized by X-ray single crystallography and multiple spectroscopic methods. U2N@I h(7)-C80 is by far the first endohedral fullerene that violates the well-established tri-metallic nitride template for nitride clusterfullerenes. The novel U[double bond, length as m-dash]N[double bond, length as m-dash]U cluster features two U[double bond, length as m-dash]N bonds with uneven bond distances of 2.058(3) Å and 1.943(3) Å, leading to a rare unsymmetrical structure for the dinuclear nitride motif. The combined experimental and theoretical investigations suggest that the two uranium ions show different oxidation states of +4 and +5. Quantum-chemical investigation further reveals that the f1/f2 population dominantly induces a distortion of the U[double bond, length as m-dash]N[double bond, length as m-dash]U cluster, which leads to the unsymmetrical structure. A comparative study of U2X@C80 (X = C, N and O) reveals that the U-X interaction in U[double bond, length as m-dash]X[double bond, length as m-dash]U clusters can hardly be seen as being formed by classical multiple bonds, but is more like an anionic central ion X q- with biased overlaps with the two metal ions, which decrease as the electronegativity of X increases. This study not only demonstrates the unique bonding variety of actinide clusters stabilized by fullerene cages, showing different bonding from that observed for the lanthanide analogs, it also reveals the electronic structure of the U[double bond, length as m-dash]X[double bond, length as m-dash]U clusters (X = C, N and O), which are of fundamental significance to understanding these actinide bonding motifs.

Synthesis and characterization of carbene derivatives of Th@C 3v(8)-C82 and U@C 2v(9)-C82: exceptional chemical properties induced by strong actinide-carbon cage interaction.

Chemical functionalization of endohedral metallofullerenes (EMFs) is essential for the application of these novel carbon materials. Actinide EMFs, a new EMF family member, have presented unique molecular and electronic structures but their chemical properties remain unexplored. Here, for the first time, we report the chemical functionalization of actinide EMFs, in which the photochemical reaction of Th@C 3v(8)-C82 and U@C 2v(9)-C82 with 2-adamantane-2,3'-[3H]-diazirine (AdN2, 1) was systematically investigated. The combined HPLC and MALDI-TOF analyses show that carbene addition by photochemical reaction afforded three isomers of Th@C 3v(8)-C82Ad and four isomers of U@C 2v(9)-C82Ad (Ad = adamantylidene), presenting notably higher reactivity than their lanthanide analogs. Among these novel EMF derivatives, Th@C 3v(8)-C82Ad(I, II, III) and U@C 2v(9)-C82Ad(I, II, III) were successfully isolated and were characterized by UV-vis-NIR spectroscopy. In particular, the molecular structures of first actinide fullerene derivatives, Th@C 3v(8)-C82Ad(I) and U@C 2v(9)-C82Ad(I), were unambiguously determined by single crystal X-ray crystallography, both of which show a [6,6]-open cage structure. In addition, isomerization of Th@C 3v(8)-C82Ad(II), Th@C 3v(8)-C82Ad(III), U@C 2v(9)-C82Ad(II) and U@C 2v(9)-C82Ad(III) was observed at room temperature. Computational studies suggest that the attached carbon atoms on the cages of both Th@C 3v(8)-C82Ad(I) and U@C 2v(9)-C82Ad(I) have the largest negative charges, thus facilitating the electrophilic attack. Furthermore, it reveals that, compared to their lanthanide analogs, Th@C 3v(8)-C82 and U@C 2v(9)-C82 have much closer metal-cage distance, increased metal-to-cage charge transfer, and strong metal-cage interactions stemming from the significant contribution of extended Th-5f and U-5f orbitals to the occupied molecular orbitals, all of which give rise to their unusual high reactivity. This study provides first insights into the exceptional chemical properties of actinide endohedral fullerenes, which pave ways for the future functionalization and application of these novel EMF compounds.

Diuranium(IV) Carbide Cluster U2C2 Stabilized Inside Fullerene Cages.

Novel actinide cluster fullerenes, U2C2@Ih(7)-C80 and U2C2@D3h(5)-C78, were synthesized and fully characterized by mass spectrometry, single-crystal X-ray crystallography, UV-vis-NIR, nuclear magnetic resonance spectroscopy (NMR), X-ray absorption spectroscopy (XAS), Raman spectroscopy, IR spectroscopy, as well as density functional and multireference wave function calculations. The encapsulated U2C2 is the first example of a uranium carbide cluster featuring two U centers bridged by a C≡C unit. The U-C bond distances in these U2C2 clusters are in the range between 2.130 and 2.421 Å. While the U2C2 cluster in U2C2@C80 adopts a butterfly-shaped geometry with a U-C2-U dihedral angle of 112.7° and a U-U distance of 3.855 Å, the U-U distance in U2C2@C78 is 4.164 Å and the resulting U-C2-U dihedral angle is increased to 149.1°. The combined experimental and quantum-chemical results suggest that the formal U oxidation state is +4 in the U2C2 cluster, and each U center transfers three electrons to the C2n cage and one electron to C2. Different from the strong U═C covalent bonding reported for U2C@C80, the U-C bonds in U2C2 are less covalent and predominantly ionic. The C-C triple bond is somewhat weaker than in HCCH, and the C-C π bonds undergo donation bonding with the U centers. This work demonstrates that the combination of the unique encapsulation effect of fullerene cages and the variable oxidation states of actinide elements can lead to the stabilization of novel actinide clusters, which are not accessible by conventional synthetic methods.

Th@Td(19151)-C76: A Highly Symmetric Fullerene Cage Stabilized by a Tetravalent Actinide Metal Ion.

For the first time, Th@Td(19151)-C76, a highly symmetric C76 cage encapsulating an actinide metal ion, has been synthesized and characterized by single-crystal X-ray crystallography, mass spectrometry, UV-vis-NIR spectroscopy, and cyclic voltammetry. The single-crystal crystallographic analysis unambiguously assigned the fullerene cage as Td(19151)-C76 and confirmed Th@Td(19151)-C76 as the first IPR (isolated-pentagon rule) C76-based monometallofullerene. The crystallographic results further revealed that the optimal Th site resides over a sumanene-type hexagon, similar to that of the Th@C1(11)-C86 but different from the previously reported Th@C3v(8)-C82. In addition, electrochemical study found that Th@Td(19151)-C76 processes an unusually low first oxidation potential (0.03 V), suggesting its strong electron donating ability.