Non-IRC Mechanism of Bimolecular Reactions with Submerged Barriers: A Case Study of Si+ + H2O Reaction.

Chemical reactions with submerged barriers may feature interesting dynamic behaviors that are distinct from those with substantial barriers or those entirely dominated by capture. The Si+ + H2O reaction is a prototypical example, involving even two submerged saddle points along the reaction path: one for the direct dissociation of H (H-dissociation SP) and another for H migration from the O-side to the Si-side (H-migration SP). We investigated the intricacies of this process by employing quasi-classical trajectory calculations on an accurate, full-dimensional ab initio potential energy surface. Through careful trajectory analysis, an interesting nonintrinsic reaction coordinate mechanism was found to play an important role in producing SiOH+ and H. This new pathway is featured as that the H atoms do not form HSiOH+ complexes along the minimum-energy path but directly dissociate into the products after passing through the H-migration SP. Furthermore, based on artificially scaled potential energy surfaces (PESs), the impact of barrier height on the reaction is also explored. This work provides new insights into the dynamics of the Si+ + H2O reaction and enriches our understanding of reactions with submerged barriers.

Role of keystone drives polycyclic aromatic hydrocarbons degradation and humification especially combined with aged contaminated soil in co-composting.

Accumulation of persistent organic pollutants polycyclic aromatic hydrocarbons (PAHs) in soil has become a global problem. Composting is considered one of the more economical methods of soil remediation and is important for the resourceful use of wastes. Agroforestry waste is produced in huge amounts and is utilized at low rates, hence there is an urgent need to manage it. Here, leaf (LVS) or rice straw (SVS) was co-composting with aged contaminated soil to investigate bacteria interaction to PAHs degradation and humus formation. The degradation rate of high molecular weight PAHs (HMW-PAHs) in LVS and SVS reached 58.9% and 52.5%, and the low molecular weight PAHs (LMW-PAHs) were 77.5% and 65%. Meanwhile, the humus increased by 44.8% and 60.5% in LVS and SVS at the end of co-composting. The topological characteristics and community assembly of the bacterial community showed that LVS had higher complexity and more keystones than SVS, suggesting that LVS might more beneficial for the degradation of PAHs. The stability of the co-occurrence network and stochastic processes (dispersal limitation) dominated community assembly made SVS beneficial for humus formation. Mantel test and structural equation models indicated that the transformation of organic matter was important for PAHs degradation and humus formation. Degradation of HMW-PAHs led to bacterial succession, which affected the formation of precursors and ultimately increased the humus content. This study provided potential technology support for improving the quality of agroforestry organic waste composting and degrading PAHs in aged contaminated soil.

Guest-Facilitated Heteroleptic Assembly of Helical Anionocages Enables Reversible Chirality Modulation.

We report a novel strategy for reversible modulation of the supramolecular chirality based on guest-facilitated heteroleptic assembly of helical anionocages. Two triple-stranded helical anionocages including a chiral cage 1 (A2 L1 3 ) and a crown ether functionalized achiral cage 2 (A2 L2 3 ) were synthesized by anion coordination of bis-monourea-based ligands and PhPO3 2- . Both cages exhibited favorable binding with tetraethylammonium TEA+ and cobaltocenium Cob+ (endo-guest, bound in the cavity). Additionally, cage 2 could reversibly release and recapture the guests through binding the exo-guest potassium ions (K+ ) in the crown ethers and subsequent removal of the K+ by [2,2,2]-cryptand. The circular dichroism (CD) spectrum of cage 1 was not significantly affected by guest encapsulation or mixing with the "empty" cage 2. However, in the presence of both cage 2 and an endo-guest/exo-guest, the Cotton effects were reversed at 391 nm and significantly enhanced at 310 nm. This observation was attributed to the guest-facilitated formation of heteroleptic cages that enabled effective chirality transfer from the chiral to the achiral ligands. The CD changes induced by K+ could be fully reversed by removing it with [2,2,2]-cryptand. Sequential addition and removal of K+ allowed reversible modulation of the chirality for at least 10 cycles without significant attenuation.

Isolation of Fluorescent 2π-Aromatic 1,3-Disiladiboretenes.

Herein, we reported the isolation of 2π-aromatic disiladiboretenes (L2Si2B2Ph2) [L = ArC(NtBu)2, Ar = Ph (1), Mes (2)], which have been synthesized from the straightforward reduction of silylene-borane adducts (LSiX → BX2Ph) [X = Cl, Br] with potassium graphite (KC8). X-ray diffraction analysis of 1 and 2 revealed that the Si2B2 units are completely planar, and DFT calculations suggested delocalization of 2π-electrons over the Si2B2 rings. Moreover, their photophysical properties and reactivity toward sulfur were also investigated in detail.

Enhancing reactivity of SiO+ ions by controlled excitation to extreme rotational states.

Optical pumping of molecules provides unique opportunities for control of chemical reactions at a wide range of rotational energies. This work reports a chemical reaction with extreme rotational excitation of a reactant and its kinetic characterization. We investigate the chemical reactivity for the hydrogen abstraction reaction SiO+ + H2 → SiOH+ + H in an ion trap. The SiO+ cations are prepared in a narrow rotational state distribution, including super-rotor states with rotational quantum number (j) as high as 170, using a broad-band optical pumping method. We show that the super-rotor states of SiO+ substantially enhance the reaction rate, a trend reproduced by complementary theoretical studies. We reveal the mechanism for the rotational enhancement of the reactivity to be a strong coupling of the SiO+ rotational mode with the reaction coordinate at the transition state on the dominant dynamical pathway.

ON-OFF Fluorescent Cyanine Dye Based on a Benzothiophenyl Rotor Enables Selective Illumination of G-Quadruplexes in Mitochondria.

Conventional cyanine dyes exist as "always-on" fluorescent probes leading to inevitable background signals which often limit their performance and scope of applications. To develop specific fluorescent probes with high sensitivity and robust OFF/ON switching for targeting G4s, we introduced aromatic heterocycles through conjugation with polymethine chains to construct a rotor-π system. Here, a universal strategy is presented to synthesize pentamethine cyanines with different aromatic heterocycle substituents on the meso-polymethine chain. In these probes, SN-Cy5-S is self-quenched in aqueous solution due to H-aggregation. The structure indicates that SN-Cy5-S with a flexible meso-benzothiophenyl rotor conjugated to the cyanine backbone matches adaptively with G-tetrad planes, enhancing π-π stacking and resulting in triggered fluorescence. This allows recognition of G-quadruplexes due to the synergy of disaggregation-induced emission (DIE) and inhibited twisted intramolecular charge-transfer effects. This combination leads to a robust lighting-up fluorescence response for c-myc G4 with superior fluorescence enhancement (98-fold), allowing for a low detection limit of 1.51 nM, which is much more sensitive than the previously reported DIE-based G4 probes (22-83.5 nM). In addition, the superior imaging properties and rapid internalization time (5 min) in mitochondria allow SN-Cy5-S to also have a high potential for mitochondrially targeting anti-cancer therapy.

Stereoselective Assembly of Hydrogen-Bonded Anionic Cages Dictated by Organophosphate-Based Chiral Nodes.

Inspired by the signal transduction function of organophosphates in biological systems, bioactive organophosphates were utilized for the first time as chiral nodes to dictate the stereoselective assembly of hydrogen-bonded anionic cages. Phosphonomycin (antibiotics), tenofovir (antivirals), adenosine monophosphate (natural product, AMP) and clindamycin phosphate (antibiotics) were assembled with an achiral bis-monourea ligand, thereby leading to the stereoselective formation of quadruple or triple helicates. The extent of the stereoselectivity could be enhanced by either lowering the temperature or adding stronger-binding cations as templates. With the chiral anionic cages as the host, some enantioselectivity was achieved when binding chiral quaternary ammonium cations.

Chiral adaptive recognition with sequence specificity of aromatic dipeptides in aqueous solution by an achiral cage.

Sequence-specific recognition of peptides and proteins by synthetic compounds or systems remains a huge challenge in biocompatible media. Here, we report the chiral adaptive recognition (CAR) with sequence specificity of aromatic dipeptides in a purely aqueous solution using an achiral tetraphenylethene-based octacationic cage (1) as both a molecular receptor and chiroptical sensor. 1 can selectively bind and dimerize aromatic dipeptides to form 1 : 2 host-guest complexes with high binding affinity (>1010 M-2), especially up to ∼1014 M-2 for TrpTrp. Given the dynamic rotational conformation of TPE units, achiral 1 can exhibit chiral adaptive responses with mirror-symmetrical circular dichroism (CD) and circularly polarized luminescence (CPL) spectra to enantiomeric dipeptides via supramolecular chirality transfer in the host-guest complexes. Furthermore, this CAR with sequence specificity of 1 can be applied for molecular recognition of TrpTrp- or PhePhe-containing tetrapeptides, polypeptides (e.g., amyloid ß-peptide1-20 and somatostatin), and proteins (e.g., human insulin) with characteristic CD responses.

A novel CRISPR/Cas14a-based electrochemical biosensor for ultrasensitive detection of Burkholderia pseudomallei with PtPd@PCN-224 nanoenzymes for signal amplification.

In this work, PtPd nanoparticles functionalized porphyrin metal-organic framework nanoenzymes (PtPd@PCN-224 nanoenzymes) are exploited as signal amplification tags to fabricate a rapid and ultrasensitive sensitive CRISPR/Cas14a-based electrochemical biosensor for Burkholderia pseudomallei (B. pseudomallei) specific DNA sequences detection. The prepared PtPd@PCN-224 nanoenzymes not only catalyze the reduction peak current of H2O2 to obtain a strong electrochemical signal output, but also provide massive active sites for the assembly of nucleic acids by Zr-O-P bonds. Besides, the designed target-activated CRISPR/Cas14a is able to recognize the target DNA sequences and further trigger the trans-cleavage of ssDNA for signal amplification. Benefiting from the target-activated CRISPR/Cas14a and PtPd@PCN-224 nanoenzymes, the developed electrochemical biosensor for B. pseudomallei DNA detection exhibits high sensitivity with detection of limit down to 12.8 aM and excellent specificity for distinguishing non-targeted bacteria. Moreover, the CRISPR/Cas14a-based electrochemical detection platform can also apply for other pathogenic bacteria diagnostic by well-designing sgRNA for target sequence recognition, possessing high flexibility and versatility in clinical diagnosis.

Less is More: A Shortcut for Anionocages Design Based on (RPO3 2- )-Monourea Coordination.

Anionocages have been developed as a unique family of hydrogen bonded cages. However, strategies for constructing anionocages are mainly limited to that based on (PO4 3- )-bisurea coordination, neither the ligands nor the anions lack the simplicity and diversity of the maturely developed analogues based on metal coordination (i.e. metallocage). We report herein a more simple strategy for anionocages design based on (RPO3 2- )-monourea coordination, utilizing monourea rather than bisurea as the hydrogen binding donor, and RPO3 2- rather than PO4 3- as the acceptor. Two fluorescent, quadruple helicate anionocages were constructed by a bis-monourea ligand, and dianions PhOPO3 2- (H1 ) or HOPO3 2- (H1A ), respectively, which were capable of encapsulating a series of cation guests. As revealed by molecular modeling, H1 features remarkable guest-adaptive cavity breathing without change of the quadruple helicate topology, which allowed the encapsulation of different sized guests in an "induced fit" manner.

A novel lytic phage potentially effective for phage therapy against Burkholderia pseudomallei in the tropics.

BACKGROUND: Burkholderia pseudomallei is a tropical pathogen that causes melioidosis. Its intrinsic drug-resistance is a leading cause of treatment failure, and the few available antibiotics require prolonged use to be effective. This study aimed to assess the clinical potential of B. pseudomallei phages isolated from Hainan, China. METHODS: Burkholderia pseudomallei strain (HNBP001) was used as the isolation host, and phages were recovered from domestic environmental sources, which were submitted to the host range determination, lytic property assays, and stability tests. The best candidate was examined via the transmission electron microscope for classification. With its genome sequenced and analyzed, its protective efficacy against B. pseudomallei infection in A549 cells and Caenorhabditis elegans was evaluated, in which cell viability and survival rates were compared using the one-way ANOVA method and the log-rank test. RESULTS: A phage able to lyse 24/25 clinical isolates was recovered. It was classified in the Podoviridae family and was found to be amenable to propagation. Under the optimal multiplicity of infection (MOI) of 0.1, an eclipse period of around 20 min and a high titer (1012 PFU/ml) produced within 1 h were demonstrated. This phage was found stabile at a wide range of temperatures (24, 37, 40, 50, and 60 °C) and pH values (3-12). After being designated as vB_BpP_HN01, it was fully sequenced, and the 71,398 bp linear genome, containing 93 open reading frames and a tRNA-Asn, displayed a low sequence similarity with known viruses. Additionally, protective effects of applications of vB_BpP_HN01 (MOI = 0.1 and MOI = 1) alone or in combination with antibiotics were found to improve viability of infected cells (70.6 ± 6.8%, 85.8 ± 5.7%, 91.9 ± 1.8%, and 96.8 ± 1.8%, respectively). A significantly reduced mortality (10%) and a decreased pathogen load were demonstrated in infected C. elegans following the addition of this phage. CONCLUSIONS: As the first B. pseudomallei phage was isolated in Hainan, China, phage vB_BpP_HN01 was characterized by promising lytic property, stability, and efficiency of bacterial elimination during the in vitro/vivo experiments. Therefore, we can conclude that it is a potential alternative agent for combating melioidosis.

Berberine Ameliorates Insulin Resistance by Inhibiting IKK/NF-κB, JNK, and IRS-1/AKT Signaling Pathway in Liver of Gestational Diabetes Mellitus Rats.

Introduction: Berberine is derived from rhizoma coptidis, a well-known Traditional Chinese herbal Medicine that has been found to be effective in the treatment of type 2 diabetes mellitus in recent years. The aim of the present study was to investigate the effects of berberine on a gestational diabetes mellitus (GDM) rat model and the related mechanisms. Methods: GDM was induced in Sprague-Dawley rats using a high-fat diet before and during pregnancy. Berberine (100 mg/kg/day) was administered from the 7th to 20th day of pregnancy. Insulin resistance (IR), glucose tolerance, and maternal, fetal, and placental weight were determined. Liver histopathological analysis, as well as analysis of C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), inhibitor kappa B kinaseß (IKKß), nuclear factor kappa-B (NF-κB), c-Jun N-terminal kinase (JNK), insulin receptor substrate-1 (IRS-1), and protein kinase B (AKT), was performed at the end of pregnancy. Results: Treatment of GDM rats with berberine markedly decreased IR, the number of dead and absorptive fetuses, maternal body weight gain, and fetal and placental weight compared with GDM without berberine. Furthermore, berberine decreased CRP and TNF-α levels, IKKß expression, NF-κB P65 nuclear translocation, and changed the phosphorylation of JNK, IRS-1, and AKT in the liver of GDM rats. Conclusions: Berberine improved IR and maternal-fetal outcomes of GDM rats, possibly through modulation of IKK/NF-κB, JNK, and IRS-1/AKT signaling pathways in the liver. Therefore, berberine may be a potential GDM treatment.

An α-diiminato germylene family: syntheses, structures, and reactivity towards C-C coupled digermylene and digermylene oxide.

The synthesis and reactivity of a rigid α-diiminate ligand supported chlorogermylene 2 were demonstrated. The reaction of 2 with hydride donor K[BH(sBu)3] yielded a hydride addition product, a five-membered 6π-aromatic germylene 3. A nonaromatic germylene 4 was produced by dehydrochlorination of 2 with KN(SitBuMe2)2. Halide abstraction with AlCl3 from 2 afforded a cationic germylene 5, and the reduction of 2 with potassium led to a C-C coupled digermylene 6via a radical coupling pathway. Hydrolysis of 2 in the presence of NHC ((tBu-NCH)2C:) gave digermylene oxide 7. DFT investigations of central GeII-rings in molecules 3-5 provided the details of frontier molecular orbitals. The energy level of the lone pair on the Ge atom in 3 is slightly higher than that in 4, indicating that 3 is the stronger σ-donor than 4. Digermylene 6 and its diastereoisomer 6a feature trans-bent and gauche-bent configurations along their axially chiral C-C bonds, respectively. The conformational and cis-trans isomerism was observed by the isolation of crystal structures 7 and 7a because of intramolecular steric hindrance.

The Clinical Value of Lipid Abnormalities in Early Stage Cervical Cancer.

Background: To describe the characteristics of plasma lipid proliferation in cervical cancer and further evaluate the prognostic significance of lipid levels in cervical cancer. Methods: We retrospectively reviewed 1713 patients with cervical cancer in our hospital. The preoperative plasma lipid profile, including cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL), of 1713 cervical cancer patients was compared with that of 10,397 healthy women. Then, we evaluated the impact of lipids on overall survival (OS) and recurrence-free survival (RFS) in cervical cancer using univariate and multivariate Cox models. Results: While plasma TC, TG, and LDL were significantly higher, HDL was lower in patients with cervical cancer than in healthy women. TG was identified as an independent predictor for RFS and OS among patients with cervical cancer. Further stratified by age, patients with higher TGs showed a significantly worse RFS and OS than those with lower TGs among patients ≥50 years old but not among those <50 years old. Conclusion: Cervical cancer was associated with a disordered lipid profile. Hypertriglyceridemia was an independent poor prognostic indicator for cervical cancer, especially for elderly patients. Strengthening lipid management may be beneficial for improving postoperative OS and RFS in patients with cervical cancer.

Mode-specific dynamics in multichannel reaction NH+ + H2.

The vibrational- and rotational-mode specificity of the multichannel NH+ + H2 reaction is studied on a recently constructed ab initio-based global potential energy surface using an initial state selected quasi-classical trajectory method, and the trajectories are analyzed using an isometric feature mapping and k-means approach. All excitation modes promote two reactions (R1: NH'+ + H2 → NH+ + HH' and R4: NH'+ + H2 → NH2+ + H') where both NH and HH bonds are broken, but reduce the reactivity of the proton-transfer reaction R2 (NH'+ + H2 → N + H'H2+) at low collision energies. For the hydrogen-transfer reaction R3 (NH'+ + H2 → HNH'+ + H), the rotational excitation of NH+ enhances the reactivity remarkably, while its vibrational excitation has an inhibiting effect on the reaction. The trajectory analyses show that the vibrational and rotational excitations of NH+ make R3 tend to go over a submerged saddle point instead of extracting hydrogen atoms directly. On the other hand, the motions of the H2 reactant facilitate the enhancement of the reactivity but they do not affect the mechanism of R3. In addition, the results suggest that the coupling of the isometric feature mapping and the k-means approach in the trajectory analysis is an appropriate tool for reaction-dynamics studies.

Anionic oxoborane and thioxoborane molecules supported by a 1,2-bis(imino)acenaphthene ligand.

The isolable anionic oxoborane 3 and thioxoborane 4 have been assembled using a 1,2-bis(imino)acenaphthene ligand (Dip-BIAN). Structural characterization and DFT calculations confirmed that two compounds contain terminal doubly bonded B[double bond, length as m-dash]E (E = O, S) groups, respectively, in which only the B[double bond, length as m-dash]O group is associated with imidazolium via a hydrogen bond.

Isomer-specific kinetics of the C+ + H2O reaction at the temperature of interstellar clouds.

The reaction C+ + H2O → HCO+/HOC+ + H is one of the most important astrophysical sources of HOC+ ions, considered a marker for interstellar molecular clouds exposed to intense ultraviolet or x-ray radiation. Despite much study, there is no consensus on rate constants for formation of the formyl ion isomers in this reaction. This is largely due to difficulties in laboratory study of ion-molecule reactions under relevant conditions. Here, we use a novel experimental platform combining a cryogenic buffer-gas beam with an integrated, laser-cooled ion trap and high-resolution time-of-flight mass spectrometer to probe this reaction at the temperature of cold interstellar clouds. We report a reaction rate constant of k = 7.7(6) × 10-9 cm3 s-1 and a branching ratio of formation η = HOC+/HCO+ = 2.1(4). Theoretical calculations suggest that this branching ratio is due to the predominant formation of HOC+ followed by isomerization of products with internal energy over the isomerization barrier.

Crown Ether Functionalized Potassium-Responsive Anionocages for Cascaded Guest Delivery.

In many critical biological processes, host-guest chemistry of protein receptors is regulated by effector molecules to realize cascaded delivery of messenger molecules between different targets. Mimicking these natural processes with artificial receptors remains a challenge. Herein, we report a cascaded guest delivery between two anionocages (anion-coordination-driven cages), in a reversible manner, wherein binding of K+ ions by a crown ether functionalized, heteroleptic A2 L3 (A=anion, L=ligand) anionocage triggers the release and delivery of a TEA+ (tetraethylammonium) guest to another A2 L3 anionocage that is a weaker and less K+ -sensitive receptor. Elimination of the K+ with [2,2,2]-cryptand enables recapture of the TEA+ by the crown ether functionalized anionocage and thus realizes a reversed guest delivery. Moreover, integrative self-sorting of anionocages is firstly reported, leading to heteroleptic cages with enhanced guest binding affinities.

Ligand symmetry significantly affects spin crossover behaviour in isomeric [Fe(pybox)2]2+ complexes.

The understanding of the correlation between the spin-state behaviour and the structural features in transition-metal complexes is of pronounced importance to the design of spin crossover compounds with high performance. However, the study of the influence of ligand symmetry on the spin crossover properties is still limited due to the shortage of suitable structural systems. Herein we report the magneto-structural correlations of three mononuclear Fe(ii) isomers with respect to their ligand symmetry. In this work, two phenyl-substituted meso and optically pure pybox ligands were employed to construct meso (1), optically pure (2), and racemic (3) ligand types of [Fe(pybox)2]2+ complexes. Their magnetic susceptibilities were measured via temperature-dependent paramagnetic 1H NMR spectroscopy. We fitted the midpoint temperatures of the transition (T1/2) of 260 K for 1(ClO4), 247 K for 2(ClO4), and 281 K for 3(ClO4). The influence of structural symmetry on spin crossover was rationalized through density functional theory calculations. The optimized structures of [Fe(pybox)2]2+ complex cations show that the geometric distortion of the central FeN6 coordination sphere is mainly caused by the steric congestions between adjacent phenyl substituents. In these compounds, there is a distinct correlation that more steric congestions produce larger coordination distortion and favor the electron configuration in the high-spin state, which reflects in the increase of T1/2. Additionally, the influence of the counter anion and lattice solvent on the meso series compounds was inspected. It is revealed that multiple factors dominate the spin-state behaviour in the solid state. This work provides deep insight into the effect of ligand symmetry on the spin transition behaviour in spin crossover compounds. It demonstrates that molecular symmetry should be considered in the design of spin crossover compounds.

Fine-Tuning the Spring-Like Motion of an Anion-Based Triple Helicate by Tetraalkylammonium Guests.

Supramolecular springs are a class of molecular devices that may provide implications to the macroscopic spring behavior from the molecular level. Helical structures are suitable molecular springs because the specific twisting of the helical strands can cause spring-like (extension-contraction) movement along the axis upon external stimuli. Herein we report an anion-based triple-helicate spring, which can undergo reversible contraction-extension motion through introduction and removal of tetraalkylammonium cations, including TMA+ and analogous irregular tetrahedral cations bearing different alkyl chains, while the relative orientation of the two phosphate ions changes to facilitate guest inclusion. Notably, the degree of contraction (shortening of the helical pitch) can be fine-tuned by varying the shape and size of guest cation. However, with the larger cations (TEA+ , TPA+ and TBA+ ), the meso-helicate configuration is obtained, which interconverts with the helicate by addition/removal of TMA+ ion.