Apigenin and Ampicillin as Combined Strategy to Treat Severe Streptococcus suis Infection

As an important zoonotic pathogen, Streptococcus suis (S. suis) can cause a variety of diseases both in human and animals, especially Streptococcal toxic shock-like syndrome (STSLS), which commonly appears in severe S. suis infection. STSLS is often accompanied by excessive production of inflammatory cytokines, which is the main cause of host death. Therefore, it is urgent to find a new strategy to relieve the damage caused by STSLS. In this study, we found, for the first time, that apigenin, as a flavonoid compound, could combine with ampicillin to treat severe S. suis infection. Studies found that apigenin did not affect the growth of S. suis and the secretion of suilysin (SLY), but it could significantly inhibit the hemolytic activity of SLY by directly binding to SLY and destroying its secondary structure. In cell assays, apigenin was found to have no significant toxic effects on effective concentrations, and have a good protective effect on S. suis-infected cells. More importantly, compared with the survival rate of S. suis-infected mice treated with only ampicillin, the survival rate of apigenin combined with an ampicillin-treated group significantly increased to 80%. In conclusion, all results indicate that apigenin in combination with conventional antibiotics can be a potential strategy for treating severe S. suis infection.     

Effect of Syringopicroside Extracted from Syringa oblata Lindl on the Biofilm Formation of Streptococcus suis

Syringopicroside is a natural drug with antibacterial activity, which is the main ingredient of Syringa oblata Lindl (S. oblata). In order to further develop the application of S. oblata and evaluate the ability of syringopicroside against Streptococcus suis (S. suis), this investigation first applied an ultrasonic-assisted method to extract syringopicroside, and then response surface methodology (RSM) was performed to get the optimum condition. Based on RSM analysis, a second-order polynomial equation about the syringopicroside yield and four variables, including ultrasonic power, time, temperature, and liquid-to-solid ratio, was purposed. Through RSM prediction and model verification experiments, the optimum conditions were determined, as follows: ultrasonic time was 63 min, temperature was 60 °C, a liquid-to-solid ratio was set to 63 mL/g, and ultrasonic power was 835 W. Under this condition, a high syringopicroside yield was obtained (3.07 ± 0.13 mg/g), which was not significantly different with a predicated value. After separation and purification by HPD 500 microporous resin, then mass spectrum was applied to identify the main ingredient in aqueous extract. A minimal inhibitory concentration (MIC) assay revealed the value against S. suis of syringopicroside was 2.56 µg/µL and syringopicroside with sub-inhibitory concentrations that could effectively inhibit biofilm formation of S. suis. Besides, scanning electron microscopy analysis indicated syringopicroside could destroy the multi-layered aggregation structure of S. suis. Finally, molecular docking analysis confirmed that syringopicroside was combined with Orfy protein of S. suis through hydrogen bonds, hydrophobic interaction, and π-π stacking.     

Dietary Supplementation with Bovine Lactoferrampin–Lactoferricin Produced by Pichia pastoris Fed-batch Fermentation Affects Intestinal Microflora in Weaned Piglets

This work is aimed at investigating the effects of recombinant bovine lactoferrampin?Clactoferricin (LFA-LFC) instead of chlortetracycline on intestinal microflora in weaned piglets. The high cost of peptide production from either native digestion or chemical synthesis limits the clinical application of antimicrobial peptides. The expression of recombinant peptides in yeast may be an effective alternative. In the current study, recombinant LFA-LFC was produced via fed-batch fermentation in recombinant strain Pichia pastoris (KM71) XS10. Uniform design U6(6⁴) was used to optimize the fermentation conditions. The target peptide purified via cation-exchange and size-exclusion chromatography was added into the dietary of weaned piglets. After 21?days, the Lactobacilli, Bifidobacteria, and Enterobacteria in the chyme of the gut were quantified using real-time polymerase chain reaction. The results showed that approximately 82?mg of LFA-LFC was secreted into 1?L of medium under optimized conditions. Moreover, purified peptide showed strong antimicrobial activities against all the tested microorganisms. Compared with the control group, the LFA-LFC group increased the amount of Lactobacilli and Bifidobacteria (P?<?0.05) in the chyme of the stomach, duodenum, jejunum, ileum, colon, and caecum. These results show that dietary supplementation with LFA-LFC can affect intestinal microflora in weaned piglets.     

The Ability of Nuclease-Resistant RNA Aptamer against Streptococcus suis Serotype 2, Strain P1/7 to Reduce Biofilm Formation In Vitro

Streptococcus suis, a Gram-positive bacterium, is an important swine and human pathogen, with serotype 2 being the most prevalent strain found worldwide. Deafness, meningitis, and death (in severe cases) are observed in S. suis-infected cases. Development of the ligands that can bind to S. suis with high affinity and specificity could be beneficial for the diagnosis and treatment of S. suis infection. Herein, the nuclease-resistant RNA aptamers based on 2′-fluoropyrimidine modification against S. suis serotype 2, strain P1/7, were established using the cell- Systematic Evolution of Ligands by Exponential enrichment (SELEX) technique. One of the aptamers, R8-su12, could bind to the S. suis target strain as well as other S. suis serotypes, i.e., 1, 1/2, 9, and 14, but not to other bacteria tested, i.e., S. pneumoniae ATCC 49619, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853. Moreover, the R8-su12 RNA aptamer was also capable of inhibiting the biofilm formation of the S. suis target strain, making it potentially useful for the study of biofilm formation and the treatment of S. suis infection in humans and pigs in the future.     

Fast liquid chromatography/tandem mass spectrometry (highly selective selected reaction monitoring) for the determination of toltrazuril and its metabolites in food

In this work a fast liquid chromatography (LC)–tandem mass spectrometry (MS/MS) method was developed for the analysis of toltrazuril, a coccidiostatic drug, and its metabolites in meat food products. The applicability of atmospheric pressure chemical ionization (APCI) and heated electrospray ionization in both positive and negative modes was studied. APCI in negative mode provided the best results and the base peak originated from the loss of CF₃ (toltrazuril and toltrazuril sulfone) and CHF₃• (toltrazuril sulfoxide) was used as the precursor ion in MS/MS. A fast LC separation on a C₁₈ Fused-Core™ column was used together with the APCI-MS/MS method developed using enhanced mass resolution mode (highly selective selected reaction monitoring, H-SRM) to improve the sensitivity and selectivity for the analysis of these compounds in food samples. A simple sample treatment based on an extraction with acetonitrile and a cleanup with a C₁₈ cartridge was used. The LC-MS/MS (H-SRM) method showed good precision (relative standard deviation lower than 10%), accuracy, and linearity and allowed the determination of these compounds in food samples down to the parts per billion level (limits of detection between 0.5 and 5 μg kg^-1).     

Deposition of chromium species on Sr-doped LaMnO3 cathodes in solid oxide fuel cells

The system of chromia-forming alloy/Sr-doped LaMnO₃ (LSM) electrode/3 mol%Y₂O₃–ZrO₂ (TZ3Y) electrolyte has been investigated at 900°C in air under cathodic polarization conditions. Deposition of chromium species was found to occur preferentially at the TZ3Y electrolyte surface, forming a deposit ring around the edge of the LSM electrode coating. The width of the ring was about 60 μm for an LSM electrode polarized for about 50 h. Overpotential (η) increases with polarization time. In contrast to η, electrode interface resistance (R_E) measured under open circuit conditions decreases initially after passing the current and remains almost constant with polarization. The results indicate that the deposition process of chromium species may not be dominated by electrochemical reduction processes in competition with O₂ reduction at an early stage of polarization.     

Flavone-Rich Fractions and Extracts from Oroxylum indicum and Their Antibacterial Activities against Clinically Isolated Zoonotic Bacteria and Free Radical Scavenging Effects

Oroxylum indicum extracts from the seeds collected from Lampang and Pattani provinces in Thailand, and young fruits and flowers exhibited in vitro display antioxidant and antibacterial activities against clinically isolated zoonotic bacteria including Staphylococcus intermedius, Streptococcus suis, Pseudomonas aeruginosa, β-hemolytic Escherichia coli and Staphylococcus aureus. The orange crystals and yellow precipitates were obtained from the preparation processes of the seed extracts. The orange-red crystals from the seeds collected from Lampang province exhibited strong in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging effects (EC₅₀ value = 25.99 ± 3.30 μg/mL) and antibacterial effects on S. intermedius and β-hemolytic E. coli while the yellow precipitate from the same source exhibited only antioxidant activity. Quantitative analysis of phytochemicals in O. indicum samples by spectrophotometric and HPLC techniques showed that they contained different amounts of total phenolic, total flavonoid and three major flavones; baicalin, baicalein and chrysin contents. Young fruit extract, which contained low amounts of flavone contents, still promoted antibacterial effects against the tested bacteria with IC₅₀ values lower than 1 mg/mL and MIC values between 4 to 10 mg/mL in S. intermedius, S. aureus and S suis while higher IC₅₀ and MIC values against P. aeruginosa and β-hemolytic E. coli were found. From scanning electron microscopy, the extract of the young fruit of O. indicum promoted morphological changes in the bacterial cells by disrupting the bacterial cell walls, inducing leakage of the cellular content, and generating the abnormal accumulation of cells. The mechanism of action of the extract for this antibacterial effect may be the disruption of the cell membrane and abnormal cell aggregations. Regression analysis of the results suggests the correlation between total phenolic and total flavonoid contents and antioxidant and antibacterial effects. Baicalin was found to have a high correlation with an inhibitory effect against β-hemolytic E. coli while three unidentified peaks, which could be flavones, showed high correlations with an inhibitory effect against S. intermedius, S. suis, P. aeruginosa and S. aureus.     

Is C4 bent?

Cheung and Graham have recently obtained high resolution ESR spectra of the C₄ molecule which show splittings of the perpendicular lines into separatex andy components [1]. Their interpretation of these new spectra is that triplet C₄ is not linear, but is slightly bent. This is contrary to numerous ab initio calculations. Using larger basis sets than have previously been employed for C₄, triple-zeta plus two sets of (d) polarization functions, denoted TZ (2d), and triple-zeta plus two sets ofd functions and one set off functions, denoted TZ (2df), the structure of this molecule has been reinvestigated via ab initio calculations which include electron correlation to second order in the many-body perturbation theory (MP2). Linear, several forms of alinear, and rhombic C₄ were studied. Within the levels of theory used here, triplet C₄ is found not to be bent, but rather is linear. The inclusion off functions in the basis set lowers the energy of rhombic C₄ over that of the linear isomer by about 10 kJ/mol.     

Simultaneous identification and validated quantification of 11 oral hypoglycaemic drugs in plasma by electrospray ionisation liquid chromatography-mass spectrometry

The detection of diabetic metabolism disorders raises problems in forensic practice and sudden death with a subsequent negative autopsy finding is a common problem. In the case of an unclear hypoglycaemia, the detection of oral antidiabetics allows the differentiation of hypoglycaemia due to oral antidiabetics from that due to other reasons (insulin-induced, insulinoma). The development of an electrospray ionisation (ESI) liquid chromatography?Ctandem mass spectrometry (LC-MS/MS) procedure for the simultaneous identification and quantification of oral antidiabetics of the sulfonylurea, the glinide, the thiazolidinedione and the gliptin types in human plasma is desired. The following analytes were included: glimepiride, glibenclamide, gliquidone, glibornuride, glisoxepide, glipizide and gliclazide (sulfonylurea type), nateglinide and repaglinide (glinide type), rosiglitazone and pioglitazone (thiazolidinedione type) and the dipeptidyl peptidase inhibitors vildagliptin, sitagliptin and saxagliptin. After a liquid?Cliquid extraction with tert-butyl methyl ether at two pHs, the oral antidiabetics were separated with fast gradient elution over a C₈ column. Identification of the oral antidiabetics was achieved by two specific ion transitions of each analyte in multiple reaction monitoring mode. Quantification was performed by referring the most intense ion transition peak areas to peak areas of the ion transitions of deuterated oral antidiabetics (hydroxytolbutamide-d ₉ for the sulfonylureas, repaglinide-ethyl-d ₅ for the glinides, pioglitazone-d ₄ for the thiazolidinediones and vildagliptin-d ₃ for the gliptins). The assay was validated according to international guidelines. The LC-MS/MS assay allows the simultaneous identification of 14 oral antidiabetics and quantification of 11 oral antidiabetics in plasma in the ESI mode in a single run. Linearity is shown up to overdose concentrations. The limits of detection with a signal-noise-ratio greater than 3 were below 1?ng/ml for all analytes. Recoveries ranged from 78 to 105%; for vildagliptin and saxagliptin recoveries were worse (45%) owing to their hydrophilic character. Intraday and interday precision and accuracy were below 20% for 11 drugs at three concentrations. For the gliptins, several validation parameters were out of range and, therefore, quantitatively this method is inappropriate.     

CuO/Ti0.5Zr0.5O2催化剂对NO+CO反应的催化作用

环境治理是当今社会面临的一大主要问题。目前,城市空气污染日趋严重,特别是工厂和汽车排放的大量未燃烧的烃类、CO、NOx是主要的空气污染物。其中,氮氧化物(NOx)排放状况尤其严重,它的排放会给环境和人们生活带来严重危害,因此,如何有效地消除NOx已成为目前环境保护中一个非常     

Bioguided Fractionation of Local Plants against Matrix Metalloproteinase9 and Its Cytotoxicity against Breast Cancer Cell Models: In Silico and In Vitro Study (Part II)

In our previous work, the partitions (1 mg/mL) of Ageratum conyzoides (AC) aerial parts and Ixora coccinea (IC) leaves showed inhibitions of 94% and 96%, respectively, whereas their fractions showed IC₅₀ 43 and 116 µg/mL, respectively, toward Matrix Metalloproteinase9 (MMP9), an enzyme that catalyzes a proteolysis of extracellular matrix. In this present study, we performed IC₅₀ determinations for AC n-hexane, IC n-hexane, and IC ethylacetate partitions, followed by the cytotoxicity study of individual partitions against MDA-MB-231, 4T1, T47D, MCF7, and Vero cell lines. Successive fractionations from AC n-hexane and IC ethylacetate partitions led to the isolation of two compounds, oxytetracycline (OTC) and dioctyl phthalate (DOP). The result showed that AC n-hexane, IC n-hexane, and IC ethylacetate partitions inhibit MMP9 with their respective IC₅₀ as follows: 246.1 µg/mL, 5.66 µg/mL, and 2.75 × 10⁻² µg/mL. Toward MDA-MB-231, 4T1, T47D, and MCF7, AC n-hexane demonstrated IC₅₀ 2.05, 265, 109.70, and 2.11 µg/mL, respectively, whereas IC ethylacetate showed IC₅₀ 1.92, 57.5, 371.5, and 2.01 µg/mL, respectively. The inhibitions toward MMP9 by OTC were indicated by its IC₅₀ 18.69 µM, whereas DOP was inactive. A molecular docking study suggested that OTC prefers to bind to PEX9 rather than its catalytic domain. Against 4T1, OTC showed inhibition with IC₅₀ 414.20 µM. In conclusion, this study furtherly supports the previous finding that AC and IC are two herbals with potential to be developed as triple-negative anti-breast cancer agents.     

The production and characterisation of an antibody to detect the coccidiostat toltrazuril and its metabolite ponazuril

The production of an antibody to detect toltrazuril or its metabolite ponazuril is complicated due to structural constraints of conjugating these coccidiostats to a carrier protein. Therefore a search was carried out for a compound that shared a common substructure to use as an antigen mimic. The chosen compound, trifluoraminoether, was conjugated to two carrier proteins (HSA and BTG) and used in the immunisation of six rabbits. Two immunogen doses (1 mg and 0.1 mg) were also used. All six rabbits produced an immunological response to the hapten regardless of the carrier protein or immunogen dose used. The most sensitive polyclonal antibody produced, designated R609, was subsequently characterised. This antiserum exhibited an IC50 of 18 ng ml(-1) using a competitive ELISA format. Cross reactivity studies show that this serum is specific for toltrazuril and its metabolites (toltrazuril sulfoxide and toltrazuril sulfone) but does not cross-react with other coccidiostats such as halofuginone, nitroimidazoles or nicarbazin. This is the first reported production of an antibody capable of specifically binding toltrazuril and ponazuril.     

Surface and Catalytic Properties of TiO2–ZrO2 Mixed Oxides

This paper reviews acid–base bifunctional catalysis and surface properties (morphology, composition, specific area, acidity/basicity, site density) on TiO₂–ZrO₂ (abbreviated as TZ) mixed oxides. The phase change from crystalline single oxides (TiO₂ and ZrO₂) to amorphous TZ mixed oxide results in decreasing grain size and site density, increasing surface area, acid/base amount and strength, and better activity/selectivity. Different acid–base bifunctional mechanisms (concerted, go-together, stepwise) were proposed to interpret the reaction behavior of various reactions (esterification, dehydration, dehydrogenation, isomerization, dehydrocyclization) over the acid–base bifunctional TZ catalysts.     

Carboranes Tuning the Phosphorescence of Iridium Tetrazolate Complexes

New iridium tetrazolate complexes containing o‐, m‐, or p‐carboranyl substitution in different positions of a phenylpyridine ligand have been prepared. The carborane isomers and the effect of their substitution position in the tuning of optical properties have been examined. The neutral complexes with the carboranyl substituent on the phenyl ring in meta position relative to the metal exhibit redshifted emission bands in contrast to blueshifts for those with carboranyl in para position. All cationic complexes display evidently blueshifted dual‐peak emission compared with the carborane‐free complex (c‐ TZ ) with a broad single‐peak emission. Introduction of carborane leads to a blueshift over 70 nm relative to c‐ TZ . Carboranes also significantly improve phosphorescence efficiency (Φ_P) and lifetime (τ), that is, Φ_P=0.64 versus 0.21 (c‐ TZ ) and τ=880 ns versus 241 ns (c‐ TZ ). The unique hydrophilic nido‐carborane‐based Ir^III complex nido‐o‐ 1 shows the largest phosphorescence efficiency (abs Φ_P=0.57) among known water‐soluble iridium complexes, long emission lifetime (τ=4.38 μs), as well as varying emission efficiency and lifetime with O₂ content in aqueous solution. Therefore, nido‐o‐ 1 has been used as an excellent oxygen‐sensitive phosphor for intracellular O₂ sensing and hypoxia imaging.     

Applications of isothermal titration calorimetry to measure enzyme kinetics and activity in complex solutions

The application of isothermal titration calorimetry (ITC) was tested towards measurements of enzyme kinetics in complex solutions containing high concentrations of proteins. Such investigations are important, due to the increasing interest in biochemical reactions in physiological relevant media as well as the application of enzymes in industrial processes. In contrast to spectral methods, measurements performed with ITC, are independent of the optical properties of solutions, making it possible to measure enzyme kinetics in concentrated solutions of macromolecules. In this study the kinetic properties of hexokinase was investigated in concentrated protein solutions (BSA). It was found, that the quality of the measured kinetic data was independent of protein concentration in the investigated range (0-250 mg BSA ml⁻¹). All results could be accounted for by Michaelis-Menten's approach and both k_cat and K_M decreased with increasing protein concentrations. The decrease in K_M with increasing protein concentration was ascribed to an increase in the ratio of activity coefficients between the native enzyme and the enzyme-substrate complex. The decrease in k_cat with increasing protein concentrations indicates that crowding by BSA effect the conformational changes/rehydration that accompanies catalysis and/or diffusion of product from the enzyme-product complex. The methodology is discussed together with an analysis of the experimental results.     

Electrochemical Determination of Tartrazine in Foods by Voltammetry with a Screen-printed Carbon/Chitosan-MnO2 Microcomposite Electrode

This paper presents a new application for a screen-printed carbon electrode (SPCE) modified with chitosan (Cs) and manganese oxide (II). This new electrode (Cs-Mn_OX/SPCE) was applied in the detection of tartrazine (TZ) by linear scan voltammetry (LSV). The anodic peak current for TZ increased by nearly 500 % compared with Cs/SPCE and unmodified SPCE. The surface of the electrode was characterized by cyclic voltammetry. The detection limit was 0.06 μmol/L. The relative standard deviations (RSDs) were between 1.0 and 6.0 % (n=15). The accuracy of the new method was evaluated with real samples spiked with known quantities of TZ.     

Assessment of the Activity of Decoquinate and Its Quinoline-O-Carbamate Derivatives against Toxoplasma gondii In Vitro and in Pregnant Mice Infected with T. gondii Oocysts

The quinolone decoquinate (DCQ) is widely used in veterinary practice for the treatment of bacterial and parasitic infections, most notably, coccidiosis in poultry and in ruminants. We have investigated the effects of treatment of Toxoplasma gondii in infected human foreskin fibroblasts (HFF) with DCQ. This induced distinct alterations in the parasite mitochondrion within 24 h, which persisted even after long-term (500 nM, 52 days) treatment, although there was no parasiticidal effect. Based on the low half-maximal effective concentration (IC₅₀) of 1.1 nM and the high selectivity index of >5000, the efficacy of oral treatment of pregnant mice experimentally infected with T. gondii oocysts with DCQ at 10 mg/kg/day for 5 days was assessed. However, the treatment had detrimental effects, induced higher neonatal mortality than T. gondii infection alone, and did not prevent vertical transmission. Thus, three quinoline-O-carbamate derivatives of DCQ, anticipated to have better physicochemical properties than DCQ, were assessed in vitro. One such compound, RMB060, displayed an exceedingly low IC₅₀ of 0.07 nM, when applied concomitantly with the infection of host cells and had no impact on HFF viability at 10 µM. As was the case for DCQ, RMB060 treatment resulted in the alteration of the mitochondrial matrix and loss of cristae, but the changes became apparent at just 6 h after the commencement of treatment. After 48 h, RMB060 induced the expression of the bradyzoite antigen BAG1, but TEM did not reveal any other features reminiscent of bradyzoites. The exposure of infected cultures to 300 nM RMB060 for 52 days did not result in the complete killing of all tachyzoites, although mitochondria remained ultrastructurally damaged and there was a slower proliferation rate. The treatment of mice infected with T. gondii oocysts with RMB060 did reduce parasite burden in non-pregnant mice and dams, but vertical transmission to pups could not be prevented.     

Evaluation of behaviour of linear monoamines CH3-(CH2)n−1-NH2 (n=1-6) in ion chromatography

This paper reports the results on a study of ion chromatography (IC) behaviour on strong cationic exchange column of CH₃-(CH₂)_n−1-NH₂ (n=1-6) type linear monoamines. The eluents were mixtures of HCl-NaCl, HNO₃-NaNO₃, HClO₄-NaClO₄, H₂SO₄-Na₂SO₄, HClO₄-NaClO₄-CH₃CN. Amines were revealed with an amperometric detector. The influence of different counter-ions on retention factors, k′, is discussed. Relationships between k′ and pE (E=sum of Na⁺ and H⁺ concentrations), and length of alkylic chain, and sensitivity coefficient S, are reported and discussed. The addition of acetonitrile (ACN) in the eluent was also taken into account. Suitable considerations are derived from these data. An example of monoamines separation is given.     

Physiology-Based Pharmacokinetic Study on 18β-Glycyrrhetic Acid Mono-Glucuronide (GAMG) Prior to Glycyrrhizin in Rats

To understand that 18β-Glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG) showed better pharmacological activity and drug-like properties than 18β-Glycyrrhizin (GL); a rapid and sensitive HPLC-MS/MS method was established for the simultaneous determination of GAMG and its metabolite 18β-Glycyrrhetinic acid (GA) in rat plasma and tissues after oral administration of GAMG or GL. This analytical method was validated by linearity, LLOQ, specificity, recovery rate, matrix effect, etc. After oral administration, GAMG exhibited excellent C_max (2377.57 ng/mL), T_max (5 min) and AUC_0-T (6625.54 mg/L*h), which was much higher than the C_max (346.03 ng/mL), T_max (2.00 h) and AUC_0-T (459.32 mg/L*h) of GL. Moreover, GAMG had wider and higher tissue distribution in the kidney, spleen, live, lung, brain, etc. These results indicated that oral GAMG can be rapidly and efficiently absorbed and be widely distributed in tissues to exert stronger and multiple pharmacological activities. This provided a physiological basis for guiding the pharmacodynamic study and clinical applications of GAMG.     

Quantum chemical study of the arylacyl azide complexes with Lewis acids and their Curtius rearrangement to isocyanates

The structures of donor-acceptor complexes of syn-benzoyl azide, its 2-methyl- and 2,6-dimethyl-substituted derivatives with BF₃, AlCl₃, and SbCl₅, and the corresponding transition states of the rearrangement into isocyanates were studied by the PBE/TZ2P method in the framework of the density functional theory (DFT). The complexes are formed at the oxygen and nitrogen atoms of the acyl azide group and have the composition 1: 1 or 1: 2 depending on the Lewis acid (L) structure. The complexes at the oxygen atom are more stable; the most stable complexes are formed by the reactions of acyl azides with AlCl₃. Complex formation with Lewis acids decreases the activation energy of the transformation of acyl azides into isocyanates owing to the +M effect and stabilization of the Ar-C(O-L^(1?))=N(1)-N(2)⁽¹⁺⁾≡N(3) mesomeric form. The activation energy decreases with an increase in the number of ortho-methyl substituents in benzoyl azide due to the +I effect of the phenyl group. The turn of the phenyl ring at almost 90° with respect to the CON₃ group is needed for the rearrangement to occur, and the energy necessary for this process is ～8 kcal mol^?1.