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The Möbius rule predicts that a planar four-membered metallacycle can be aromatic with four mobile electrons, but such a simple ring has escaped recognition because it usually favors Hückel anti-aromaticity. Here, we report that a quasi-square four-membered actinide compound (Pa2B2) is doubly Möbius aromatic. Chemical bonding analyses reveal that this diboron protactinium molecule has four delocalized π electrons in addition to four delocalized σ electrons, satisfying the 4n Möbius rule for both σ and π components. Energetically, the block-localized wavefunction method, which is the simplest variant of ab initio valence bond theory, shows that the delocalization energy for the π and σ electrons reaches up to 65.0 and 72.3 kcal/mol, respectively, while the extra cyclic resonance energy (ECRE) amounts to 45 kcal/mol. The large positive ECRE values strongly confirm the unprecedented double Möbius aromaticity in Pa2B2. We anticipate that this new type of aromatic molecule can enrich the concept of Möbius aromaticity and open a new avenue for actinide compounds.

The chemical bond between a transition metal and a methyl group (M–CH3) is typically defined as a single covalent bond, which is of fundamental significance and general interest in understanding the structural properties and reactivity of transition metal alkyl compounds. Herein, we demonstrate that the M–CH3bonding involves varying σ and π components and thus should be best described in terms of the partial double M═CH3bond. The often-neglected π bonding stems from an occupied π-symmetric orbital of the methyl group comprising all three C–H σ bonds (but one C–H′ contributes more than the other two) and a vacant low-lying metal d(π) orbital, and is associated with the intramolecular C–H′···M agostic effect (i.e., an acute M–C–H′ angle and a short H′···M distance), whose origin is still controversial. We quantify the geometric and energetic impacts of the π interaction involved in the M–CH3bond by explicitly computing the intramolecular πCH′→ dMinteraction with the ab initio valence bond (VB) theory. Our computations of the ligand-free [TiCH3]3+and a series of metallocene catalysts provide a direct proof for the presence of the π bonding in M–CH3bonds, which is the cause for the agostic effect. The partial double M═CH3bonding model is not only validated by a range of bonding analyses including VB self-consistent field (VBSCF)-based energy decomposition and quantum theory of atoms in molecules (QTAIM) but also authenticated by the specific activity of double M═CH3bonds in the C–H activation and olefin insertion. More importantly, the σ bond gradually switches from a classical covalent bond to a novel charge-shift bond with the π bonding becoming increasingly significant. We anticipate that the recognition of the π interaction between electrophilic metal centers and C–H bonds can benefit the understanding of the nature of metal–carbon bonds in transition metal ethyl, alkyl, and carbene compounds.

Pentatrichomonas hominis, a flagellated parasitic protozoan, predominantly infects the mammalian digestive tract, often causing symptoms such as abdominal pain and diarrhea. However, studies investigating its pathogenicity are limited, and the mechanisms underlying P. hominis-induced diarrhea remain unclear. Establishing an in vitrocell model for P. hominisinfection is imperative. This study investigated the interaction between P. hominisand IPEC-J2 cells and its impact on parasite growth, adhesion, morphology, and cell viability. Co-cultivation of P. hominiswith IPEC-J2 cells resulted in exponential growth of the parasite, with peak densities reaching approximately 4.8 × 105cells/mL and 1.2 × 106cells/mL at 48 h for initial inoculation concentrations of 104cells/mL and 105cells/mL, respectively. The adhesion rate of P. hoministo IPEC-J2 cells reached a maximum of 93.82% and 86.57% at 24 h for initial inoculation concentrations of 104cells/mL and 105cells/mL, respectively. Morphological changes in IPEC-J2 cells co-cultivated with P. hominiswere observed, manifesting as elongated and irregular shapes. The viability of IPEC-J2 cells exhibited a decreasing trend with increasing P. hominisconcentration and co-cultivation time. Additionally, the mRNA expression levels of IL-6, IL-8, and TNF-α were upregulated, whereas those of CAT and CuZn-SOD were downregulated. These findings provide quantitative evidence that P. hominiscan promote its growth by adhering to IPEC-J2 cells, inducing morphological changes, reducing cell viability, and triggering inflammatory responses. Further in vivostudies are warranted to confirm these results and enhance our understanding of P. hominisinfection.

The peculiar Au···H hydrogen bonding has garnered significant interests, but its existence and nature remain an open question in gold chemistry. In this paper, we established and authenticated the first intramolecular Au···H–O hydrogen bonding in gold(I) complexes. Our computational results based on an ab initio valence bond (VB) method, namely the block-localized wave function (BLW) method, clarified that this Au···H–O hydrogen bonding is a new type of resonance-assisted hydrogen bond (RAHB). In this RAHB, π conjugation in the hydrogen bond donor has the capability to modulate the Au···H–O hydrogen bonding. In contrast to conventional RAHBs, however, the Au···H–O hydrogen bonding is antielectrostatic and is dominated by the charge transfer interaction including cooperative σ electron donation from the d orbital of the metal center to the antibonding orbital of the hydroxyl group and π conjugation from the hydroxyl group to adjacent π deficient or strong π electron withdrawing groups. This novel theoretical perspective not only confirms the existence and reveals the nature of intramolecular Au···H hydrogen bonding but also provides a promising strategy to rationally design strong gold hydrogen bonds.

The accurate prediction of SO2, NOxand PM emissions in the iron ore sintering process could adjust the desulfurization and denitrification operation in time. The study presented an integrated prediction model for SO2, NOxand PM in sintering flue gas. Gradient boosting decision tree, recurrent neural network, gated recurrent unit were chosen as sub-models to predict SO2, NOxand PM by comparing different regression prediction models, which were then combined to form an integrated prediction model (MMEP). The box plots, empirical mode decomposition algorithm, Pearson correlation coefficient and maximum information coefficient to select independent variables for the predictive model. The MMEP model had an overall accuracy greater than 0.82, as verified by production data, which could provide guidance for on-site sintering production.

The concept of resonance-assisted hydrogen bond (RAHB) has been widely accepted, and its impact on structures and energetics can be best studied computationally using the block-localized wave function (BLW) method, which is a variant of ab initio valence bond (VB) theory and able to derive strictly electron-localized structures self-consistently. In this work, we use the BLW method to examine a few molecules that result from the merging of two malonaldehyde molecules. As each of these molecules contains two hydrogen bonds, these intramolecular hydrogen bonds may be cooperative or anticooperative, depended on their relative orientations, and compared with the hydrogen bond in malonaldehyde. Apart from quantitatively confirming the concept of RAHB, the comparison of the computations with and without π resonance shows that both σ-framework and π-resonance contribute to the nonadditivity in these RAHB systems with multiple hydrogen bonds.

The secondary electrostatic interaction (SEI) has been regarded as the fundamental cause for the relative strengths of multiple hydrogen bonds for decades, though recent studies challenged its validation. Here, we used our developed block-localized wave function (BLW) method, which is a variant of ab initio valence bond (VB) theory and can self-consistently derive the wave function for a strictly electron-localized state, to study a series of exemplary multiply hydrogen-bonded complexes and critically examine the role of SEI in the binding. Our computations show that the multiple hydrogen bond in self-assembled complexes is a kind of resonance-assisted hydrogen bond (RAHB) in nature, and the π resonance which moves electron density from the hydrogen bond donor to the acceptor is the true origin of the different hydrogen bond strengths. By quenching the π resonance effect, the hydrogen bond strengths become nearly identical for various neutral doubly, triply, and quadruply hydrogen-bonded dimers where in general the SEI model works. In other words, the SEI plays only a minor role in multiply hydrogen-bonded complexes, and the π resonance, which changes not only electron densities but also molecular polarities (dipole moments), is the major force.

To determine the prevalence of Cryptosporidium in dairy cattle in Guangdong Province, South China, 1440 fecal samples were collected from 10 farms and screened for Cryptosporidium with PCR. The overall prevalence of Cryptosporidium was 4.38% (63/1440), and the infection rates in preweaned calves, postweaned calves, heifers and adults were 6.4% (19/297), 6.19% (33/533), 1.48% (4/271) and 2.06% (7/339), respectively. Three Cryptosporidium species, Cryptosporidium andersoni (n = 33), Cryptosporidium bovis (n = 22) and Cryptosporidium ryanae (n = 8) were detected by DNA sequence analysis of the 63 positive samples, and C. andersoni was identified as the most common species on the dairy cattle farms. In preweaned calves, C. bovis was the most prevalent species (9/19, 47.4%). In contrast, C. andersoni was the predominant species (19/33, 57.6%) in postweaned calves and the only species found in heifers and adults. The zoonotic species Cryptosporidium parvum was not detected in this study. Twenty-four C. andersoni isolates were successfully classified into three multilocus sequence typing (MLST) subtypes. MLST subtype A4,A4,A4,A1 was the predominant subtype, and MLST subtype A2,A5,A2,A1, previously found in sheep, was detected in cattle for the first time. A linkage disequilibrium analysis showed that the C. andersoni isolates had a clonal genetic population structure. However, further molecular studies are required to better understand the epidemiology of Cryptosporidium in Guangdong. [ABSTRACT FROM AUTHOR]

Both computations and experiments have confirmed that amides have stronger self-associations than imides. While this intriguing phenomenon is usually explained in the term of secondary electrostatic repulsion from the additional spectator carbonyl groups in imides, recently it was proposed that the π resonance effect from the spectator carbonyl which alters the balance between the acidity of the hydrogen-bond (H-bond) donor and the basicity of the H-bond acceptor is the major cause. In this work, we examined the roles of π resonance and the secondary electrostatic interaction in the formation of amide and imide dimers by deactivating the π conjugation from the spectator carbonyl and flipping the spectator carbonyl using the block-localized wave function method which is the simplest variant of valence bond theory. Energetic, geometrical, and spectral results show that three major forces, namely the σ induction effect (IE), π resonance effect (RE), and secondary electrostatic interaction (SEI), contribute to the different binding energies in the dimers of amides and imides. Whereas IE favors stronger binding among imides, both RE and SEI diminish the self-association of imides. Obviously, the negative force from RE and SEI exceeds the positive force from IE. Relatively, SEI plays a little bigger role than RE.

Most recently, Wiberg and Rablen examined a few substituted methanes and identified the polar effect, which is associated with the atomic charge at the central carbon, as a possible factor for bond energy changes while the exact role of the hyperconjugation effect is unsettled. In this work, we revisited a series of substituted methanes CH4-nXn(n= 0–4, X= F, Cl, CN, OCH3) by explicitly computing the intramolecular electron delocalization energies using the simplest variant of ab initio valence bond (VB) theory, namely the block-localized wave function (BLW) method. This BLW method is designated to derive electron-localized states where intramolecular electron delocalization is “turned off”. Computations show that the deactivation of the intramolecular electron delocalization in these molecules only slightly increases the charge (i.e., reduces the atomic population) at the central carbon in all systems. This seems consistent with the polar effect therein as proposed by Wiberg and Rablen. But apart from the stabilizing polar effect, there should be steric (including both Pauli and electrostatic) repulsion among the substituent groups. This is evidenced by the stretched C–X bonds in CX4compared with the same bonds in H3CX (X = Cl, CN) when the specific nX′→ σCH/CX*orbital interactions are “turned off”, though there is indeed notable polar effect in fluoromethanes considering fluorine is the most electronegative atom. By focusing on one C–X′ bond, we show that its involved orbital interactions enhance the bond strength from H3C–F′ (by 11.6 kcal/mol) to F3C–F′ (by 18.7 kcal/mol) but weaken from H3C–CN′ (by 11.6 kcal/mol) to (CN)3C–CN′ (by 9.3 kcal/mol).

Avian coccidiosis is the most serious parasitic disease in the poultry industry. Therefore, the aim of the current study was to explore the effects of B. subtilisand live coccidiosis vaccine alone or in combination on the production performance and anticoccidiosis, as well as the dynamic changes of intestinal microbial community. Nine hundred ninty Mahuang chickens were randomized into 4 preimmune groups including control group, coccidiosis vaccine immunization group; B. subtilisadministration group and a group that was administrated a combination of live coccidiosis vaccine and B. subtilisgroup. Intestinal mucosal scraps collected from all these experimental groups at the age of 8 d and 15 d for microbial community 16S rRNA gene sequencing. At the age of 25 d, 30 broilers from each preimmune group were randomly assigned to a subgroup infected with Eimeriaspp.and renamed as CI, V-CI BS-CI, and VBS-CI group. The production performance was monitored at the age of 25 d, 35 d, 45 d, and 55 d for the rest broilers from each pre-immune group. Otherwise, in the Eimeriaspp.challenge stage, intestinal mucosal scraps collected for microbial community sequencing, while duodenum, jejunum, and cecum collected for pathological examination after sacrifice at the age of 32 d. In addition, the oocysts per gram of feces (OPG) and intestinal lesion score of broilers after Eimeriaspp.challenge were also counted. Overall, the probiotics and coccidiosis vaccine resulted in the significantly improvement of the production performance. Otherwise, the intestinal lesion score and OPG after Eimeriaspp. infection was significantly decreased in the VBS-CI group (P< 0.05). Moreover, these protective effects may also be closely related to genus such as Romboutsia, Blautia, and Butyricococcus, as well as microbiota functions like the quorum sensing pathway. According to these results, a combination of B. subtilisand coccidiosis vaccines can improve performance and provide additional protection against Eimeriaspp.infection.