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The metabolic mechanisms for imidazolidine oxidation of imidacloprid (IMI) by cytochrome P450 3A4 (CYP3A4) have been investigated using quantum mechanical/molecular mechanical (QM/MM) calculations. The binding mode of CYP3A4 with IMI is examined by molecular docking in collaboration with molecular dynamics (MD) simulations. The results show that there are six amino acid residues, involving Arg192, Phe195, Ile349, Ala285, Phe284 and Phe88, closely distributed around the IMI. The binding free energy analysis exhibits that the CYP3A4-IMI binding structure is stabilized by electrostatic interaction and van der Waals interaction. Arg192 plays a major role in the binding of CYP3A4 with IMI based on its polarity and the hydrogen bond between the H atom in Arg192 side chain and the nitryl O atom of IMI. Two possible pathways, pathway 1 and pathway 2, are evaluated. Two spin states of the Fe (III) center, quartet and doublet, are considered. The free energy calculations are done using QM/MM steered molecular dynamics (SMD) simulation at the B3LYP/6–31 + G(d):ff14SB level for two pathways. The ONIOM QM/MM single-point calculations at the B3LYP/6–311 + G(2d,2p):ff99SB//B3LYP/6–31 + G(d): ff14SB and M06-2X/6–311 + G(2d,2p):ff99SB//B3LYP/6–31 + G(d):ff14SB levels are carried out to obtain more credible energy information. The results indicate that for both pathways, the free energy barriers on the low-spin doublet state are lower than those on the high-spin quartet state. Both pathways are the stepwise processes. Pathway 1 has higher possibility to occur with the free energy barriers being lower by 10–15 kcal·mol−1 compared with pathway 2, which gives rise to trans-5′-hydroxyl-IMI as the final product. The first proton-transfer is the rate-limiting step and the calculated activation free energy is consistent with the experimental conclusion.

To investigate the constituents from the fruit dregs of Rhus chinensis.The constituents were isolated and purified by chromatography on silica gel,Sephadex LH-20,RP-C18 and Pre-TLC and recrystalization. The structures were identified on the basis of the chemical evidence,spectroscopic data.Ten compounds were obtained and elucidated as m-digalloyl acid( 1),ethyl-m-digallate( 2),apigenin( 3),kaempferol( 4),quercetin( 5),3,7-dimethoxy-5,3’,4’-trihydroxy-flavone( 6),quercitrin( 7),kaempferol-3-O-α-L-rhamnoside( 8),myricetrin( 9) and quercetin-3-O-( 4″-methoxy)-α-L-rahmnopyranosyl( 10),respectively.Compounds 1 ~ 3,6 ~ 10 are separated from the Rhus genus for the first time.

The hydrolysis of substituted amidines XN′=CH–N(Y)2 (X = alkyl, nucleoside, aryl; Y = methyl, benzyl) is studied by use of computational techniques. For each substituted system, two possible pathways, N′-Path and N-Path, are considered, in which the proton transfer to N′ and N, respectively, after the nucleophilic attack of H2O to C=N′ double bond. The geometry optimizations of the stationary states are carried out to map out the hydrolysis pathways at the density functional theory B3LYP/6-311+G(d,p) level. Single-point MP2 calculations (MP2/6-311++G(d,p)//B3LYP/6-311+G(d,p)) are performed to obtain more credible energy information. A microhydration surrounding is constructed to describe the effect of water molecules in the first hydration shell on the energy barrier from radial distribution functions, g(R). The bulk solvent effects are examined by using the conductor-like polarizable continuum model (CPCM). The calculated results indicate that the hydrolysis of N,N-disubstituted formamidines is more favored for Y = methyl than for Y = benzyl. Furthermore, for N′-substituted formamidines, the hydrolysis reactivity increases in the following order: X = aryl

To isolate and elucidate the constituents from the fruit dregs of Rhus chinensis.The constituents were isolated and purified by chromatography on silica gel,Sephadex LH-20, RP-C18 gel and recrystallization. The structures were elucidated on the basis of the chemical evidence and spectroscopic data.Ten compounds were obtained: β-sitosterol (1), morolic acid (2), (2S) -1-O-heptatriacontanoyl glycerol (3), α-monpalmitin (4), palmitic acid (5), gallic acid (6), methyl gallate (7), ethyl gallate (8), propyl gallate (9), and protocatechuic acid (10).Compounds 3, 4 and 9 are isolated from the plants of Rhus genus for the first time.

For the first time the computed mechanisms for the novel reaction of 2-naphthol with N-methyl-N-phenylhydrazine, leading to 1-amino-2-naphthol (Tang et al., J Am Chem Soc 2008, 130, 5840), have been investigated using the density functional theory. Four distinct possible pathways were evaluated: two amination mechanisms with the attack of NH(2) group respectively at the α-position C1 and β-position C3 atoms of 2-naphthol (pathways 1 and 2) as well as two rearrangement processes with displacement of the phenolic hydroxyl group followed by the benzidine-like rearrangement at the α-position C1 and β-position C3 atoms of 2-naphthol, respectively (pathways 3 and 4). Solvent effect has been tested based on the optimized geometries of the stationary points in solution at the B3LYP/PCM/6-31+G(d,p) level of theory with an averaged dielectric constant of binary solvent. Single-point energies of the optimized structures have been calculated using three hybrid density functionals, B3LYP, MPW3LYP, and B3PW91 with the 6-311++G(3df,2p) basis set. Our computed results clearly manifest that pathway 1 (α-amination) has the highest possibility to occur, with the Gibbs free energies being lower by 6 to 20 kcal/mol compared with the other three pathways, which leads to 1-amino-2-naphthol and N-methylaniline as products. It is in excellent agreement with the experimental observation.

The intense innate immunological activities occurring at the enteric mucosal surface involve interactions between intestinal epithelial cells and immune cells. Our previous studies have indicated that Peyer's patch lymphocytes may modulate intestinal epithelial barrier and ion transport function in homeostasis and host defense via cell-cell contact as well as cytokine signaling. The present study was undertaken using the established co-culture system of Caco-2 epithelial cells with lymphocytes of Peyer's patch to investigate the expression of IL-8 and IL-6 cytokines and cytokine receptors in the co-culture system after challenge with Shigella F2a-12 lipopolysaccharide (LPS). The human colonic epithelial cell line Caco-2 was co-cultured with freshly isolated lymphocytes from the murine Peyer's patch either in the mixed or separated (isolated but permeable compartments) co-culture configuration, and was challenged with Shigella F2a-12 LPS for 8 h. The level of mRNA expressions of human interleukin-8 (hIL-8), human interleukin-8 receptor (hIL-8R), mouse interleukin-8 receptor (mIL-8R), mouse interleukin-6 (mIL-6), mouse interleukin-6 receptor (mIL-6R) and human interleukin-6 receptor (hIL-6R) was examined by semi-quantitative PCR. In both co-culture groups, hIL-8 expression of Caco-2 cells was decreased, and hIL-8R expression was increased compared to the Caco-2 alone group. Upon LPS challenge, hIL-8 expression from the Caco-2 cells of both co-culture groups was higher than in the Caco-2 control group. The increased hIL-8 expression of Caco-2 cells in the separated co-culture group is correlated with a decreased hIL-8R expression and an increased mIL-8R expression. In the mixed co-culture group, the increased expression of hIL-8 was associated with the upregulated hIL-8R expression on Caco-2 cells and downregulated mIL-8R on murine Peyer's patch lymphocytes (PPL). mIL-6 expression from mouse PPL was also upregulated by LPS in mixed co-culture. However, upon the treatment with LPS, hIL-6R expression of Caco-2 cells was decreased in the mixed co-culture, but increased in separated co-culture. The data suggest that release of hIL-8 from epithelial cells may act on lymphocytes through a paracrine pathway, but it may also act on the epithelial cells themselves via an autocrine pathway. The data also suggest that the release of mIL-6 from Peyer's patch lymphocytes affects epithelial cells in a paracrine fashion.

To study the chemical components from the ethanol extract of Acori Calami Rhizoma from Hunan Province.Components were isolated and purified through various chromatographic methods and recrystallization, and identified by spectroscopic data.Ten compounds were isolated and identified as follows: heptadecanoic acid(1), monopentadecanoin(2), syringic acid(3), aurantiamide acetate(4), monononadecanoin(5),tatarine A(6),tatanan C(7),cerevisterol(8),2 ,6-dioxopiperidin-3-yl acetate(9) and palmatine(10).Compounds 1-5 and 8-10 are isolated from Acorus genus for the first time, and compounds 1-5 and 7-10 are isolated from this plant for the first time.

To isolate and elucidate the constituents from whole plant of Pholidota cantonensis.The constituents were isolated and purified by silica gel, Sephadex LH-20 and MCI gel chromatography and recrystallization. The structures were elucida- ted on the basis of the chemical evidence and spectroscopic data.Ten compounds were obtained : batatasin ll(1), orchinol(2), ephmeranthoquinone(3 ), densiflorol B (4) , 3, 5-dimethoxy-4-hydroxy-propiophenone (5) , cinnamic acid (6) , syringaresinol (7) ,24- methylenencycoartanol( 8),ergosterol peroxide(9) and β-sitosterol( 10).Compounds 6 and 9 are isolated from Pholidota genus for the first time,and compounds 4,5 and 7 are isolated from this plant for the first time.

The decomposition mechanism of 5-aza-2′-deoxycytidine (decitabine) has been investigated using the Monte Carlo simulation with free energy perturbation technique based on the local microhydration model. The irreversible deformylation process (process 2) was firstly evaluated. Four possible pathways, two stepwise (paths 1 and 3) and two concerted (paths 2 and 4) were examined. In two stepwise pathways, a tetrahedral intermediate is given by the addition of H2O to the C(1)=O(2) bond, followed by the proton shift to the N(3) atom leading to the final products. In two concerted pathways, the nucleophilic attack of H2O at the C(1) atom and the simultaneous movement of hydroxyl H to the N(3) atom induce the cleavage of the C(1)–N(3) single bond. The potential energy profiles along the minimum energy path for four pathways in the gas phase and in water were obtained. Our computed results exhibit that two stepwise mechanisms (paths 1 and 3) are more favorable than two concerted mechanisms (paths 2 and 4) when the solvent effects of bulk water are taken into account. Then, in collaboration with the previous study (Gao et al. in Theor Chem Acc 131:1108–1123, 2012), the whole decomposition processes of decitabine were discussed. Two possible pathways were considered: pathway t1 be made up of B-path 2 (in process 1) and path 1 as well as pathway t2 be composed of B-path 3 (in process 1) and path 3. The results clearly manifest that pathway t2 is more favorable than pathway t1 in the decomposition reaction of decitabine, which leads to IM-dR2 and GuaUre-dR2 as ring-opening-formylated intermediate and decomposition product, respectively. The third step is the rate-controlling step with the free energy barrier height of 29.8 kcal/mol, which is in agreement with the experimentally determined activation free energy (25.4 kcal/mol).

The decomposition mechanism of 5-Aza-2′-deoxycytidine has been studied by the use of computational techniques. Optimized structures for all of the stationary points in the gas phase were investigated at B3LYP/6-31+G(d,p) level of theory. Single-point energies were determined employing the ab initio MP2 method in conjunction with the 6-311++G(d,p) basis set. Five possible pathways, paths 1–5, were evaluated. In each pathway, the direct (A-paths 1–5) and water-assisted (B-paths 1–5) processes were considered. Meanwhile, the local microhydration model with the direct participation of three water molecules around the reaction centers was adopted to mimic the system for the water-assisted decomposition mechanisms above, where one water molecule is the nucleophilic reactant and the other two are the auxiliary molecules located on each side of the nucleophilic water. The results in the gas phase exhibit that the energy barriers of the water-assisted pathways based on the local microhydration model decrease dramatically by about 15–20 kcal/mol as compared with those of the direct pathways because of the contribution of the auxiliary water molecules. In addition, bulk solvent effects of water were determined by means of the self-consistent reaction field based on the conductor-like polarized continuum model and Monte Carlo simulation with free energy perturbation (MC-FEP) technique, respectively. Our computational results indicate that B-path 3 in the decomposition reaction of 5-azadC is the most favorable, where the calculated rate constant (1.68 × 10−3 min−1) using the MC-FEP method is within the range of the experimentally determined values [(5.89 ± 0.54) × 10−3 min−1 by UV and (1.46 ± 0.08) × 10−3 min−1 by NMR].

The active-site dynamics of human brain aspartoacylase (hASPA) complexed with its substrate (N-acetyl- l -aspartate) has been studied using a hybrid quantum mechanical/molecular mechanical (QM/MM) approach based on the self-consistent charge-density functional tight-binding (SCC-DFTB) model. The Michaelis complex, which is constructed from a recent X-ray structure of the human brain aspartoacylase with a stable tetrahedral intermediate analogue, is reproduced in 1 ns molecular dynamics simulations at 300 K. The simulation shows that the substrate is tightly held in the active site by a hydrogen bond network and the putative nucleophilic water molecule is reasonably close to the nucleophilic center. The catalysis is further modeled with the density functional theory (DFT) in a truncated active-site model at the B3LYP/6-31G(d) level of theory. The DFT calculations indicate the reaction proceeds via a water promoted pathway with Glu178 serving as the general base and general acid. Transition state stabilization for nucleophilic addition is achieved by formations of the weak coordination bond between the substrate carbonyl oxygen atom and the zinc ion as well as of the strong hydrogen bonds between the substrate carbonyl oxygen atom and Arg63.

The water-assisted hydrolysis mechanism of N,N-dimethyl-N'-(2',3'-dideoxy-3'-thiacytidine) formamidine (MFA-3TC) with three water molecules was studied by use of computational techniques. Optimized structures for all of the stationary points in the gas phase were investigated using the B3LYP/6-31+G(d,p) method. Single-point energies were determined employing the ab initio MP2 method in conjunction with the 6-311++G(d,p) basis set. Two possible pathways in the title reaction are considered, involving the attack of water molecule at first to the C(1)=N(1) double bond (path A) and the attack of water molecule at first to the C(1)-N(2) single bond (path B), respectively. A local microhydration model concerning three water molecules is adopted to mimic the system for the two reaction mechanisms above, where one water molecule is the nucleophilic reactant and the others are the auxiliary molecules. The calculated results indicate that the first steps in both pathways are the rate-limiting processes, and path A is more favorable than path B in the gas phase. In addition, bulk solvent effect is tested at the geometry optimization level by means of the conductor-like polarized continuum model (CPCM). Single-point computation was done at the MP2/6-311++G(d,p) level based on the geometries in the solution phase. Our results exhibit that the rate-limiting process in both pathways in water is the first step reaction, and path A is still favored. Two pathways are stepwise and slightly endothermic processes.

To get cell lines which express mouse CD1.1 (mCD1.1) stably and to study the stimulatory effects of mCD1.1 on lymphocytes from many tissues.The intestinal epithelial cells were isolated and their total RNA was prepared. By RT-PCR, the gene coding mCD1.1 was obtained and then cloned into the pcDNA3.1 vector through BamH I and EcoR I. The reconstructed plasmid, named pcDNA3.1-mCD1.1, was transfected into CHO cells by electroporation. The clones that grew well in the medium containing G418 were selected and their mCD1.1 expression was analyzed by RT-PCR and flow cytometry(FCM). The mCD1.1-expressing CHO cells were co-cultured with lymphocytes freshly isolated from the liver or mesenteric lymph nodes with or without LPS. The CHO cells were treated with mitomycin C to inhibit their proliferation. The lymphocyte proliferation was detected by MTT. In addition, the lymphocytes collected from the co-culture system were stained with fluorescein-labeled monoclonal antibodies against mouse NK1.1 and CD3. The double positive cells were detected by FCM.By RT-PCR, the gene coding mCD1.1 was acquired, identical to that reported by some authors with one base different from that reported by Genbank. Many clones that express mCD1.1 stably were obtained. MCD1.1-expressing CHO cells could stimulate lymphocytes to proliferate in the presence or absence of LPS and elevate the percentage of NK1.1 and CD3 double-positive cells.The mCD1.1 expressed on the membrane of CHO cells could stimulate the proliferation of NKT cells.

AIM: To investigate the effect of interaction between enteric epithelial cells and lymphocytes of Peyer’s patch on the release of nitric oxide (NO) and IL-6 in response to Shigella lipopolysaccharide (LPS). METHODS: Human colonic epithelial cells (Caco-2) were mixed cocultured with lymphocytes of Peyer’s patch from wild-type (C57 mice) and inducible NO synthase knockout mice, and challenged with Shigella F2a-12 LPS. Release of NO and mIL-6 was measured by Griess colorimetric assay and enzyme-linked immunosorbent assay (ELISA), respectively. RESULTS: In the absence of LPS challenge, NO was detected in the culture medium of Caco-2 epithelial cells but not in lymphocytes of Peyer’s patch, and the NO release was further up-regulated in both cocultures with lymphocytes from either the wild-type or iNOS knockout mice, with a significantly higher level observed in the coculture with iNOS knockout lymphocytes. After Shigella F2a-12 LPS challenge for 24-h, NO production was significantly increased in both Caco-2 alone and the coculture with lymphocytes of Peyer’s patch from the wild-type mice but not from iNOS knockout mice. LPS was found to stimulate the release of mIL-6 from lymphocytes, which was suppressed by coculture with Caco-2 epithelial cells. The LPS-induced mIL-6 production in lymphocytes from iNOS knockout mice was significantly greater than that from the wild-type mice. CONCLUSION: Lymphocytes of Peyer’s patch maintain a constitutive basal level of NO production from the enteric epithelial cell Caco-2. LPS-induced mIL-6 release from lymphocytes of Peyer’s patch is suppressed by the cocultured epithelial cells. While no changes are detectable in NO production in lymphocytes from both wild-type and iNOS knockout mice before and after LPS challenge, NO from lymphocytes appears to play an inhibitory role in epithelial NO release and their own mIL-6 release in response to LPS.

To observe the changes of lymphocyte phenotype in different lymphoid tissues of mice at various time after intranasal immunization with bivalent Shigella vaccines.BALB/c mice were randomly divided into three groups, 30 mice per group. Mice were intranasally immunized respectively with PBS, FSM-2117 or FS-5416 four times (bacterial number was sequentially 5x10(6), 1x10(7),4x10(7)and 4x10(7)CFU/mouse) with two week intervals. Lymphocytes in nasal associated lymphoid tissue (NALT), nasal passage(NP), spleen or Peyer's patch (PP) were isolated on the 7th,30th and 90th day after the last immunization. The phenotype of the lymphocytes was detected by FACS.CD3(+) T cells in NALT, NP and PP increased significantly on the 7th day after the immunization, in which most were CD4(+)T cells. B220(+) cells and CD3(+) T cells increased notably in spleens of FSM-2117 group and FS-5416 group, respectively. The same phenotypic changes still maintained in the NALT, NP and spleen on the 30th day after immunization, but only present in NALT and NP on the 90th day.Intranasal inoculation with the two bivalent Shigella vaccines can effectively induce immune responses in different mucosal sites and systematically which can durate for a long time and start to weaken from the tissues distal from nose to those proximal.

hIL-5 cDNA was amplified through reverse transcription-polymerase chain reaction from peripheral blood lymphocytes induced with PMA and calcium ionophore A23187. The hIL-5 fragment was cloned into pUC18 and its sequence was identified to be hIL-5 cDNA sequence. The fragment which encodes hIL-5 mature polypeptide was amplified and cloned into pBV220 to express hIL-5 recombinant protein in E. coli, but there was no expected recombinant protein expressed. Only one clone expressed a 10kD peptide at high level. DNA sequencing showed that this clone had an adenosine deletion at 86th codon in hIL-5 cDNA and expressed a polypeptide of 93 amino acids at high level, and hIL-5 cDNA had not yet been expressed in E.coli successfully. These results suggested that two consecutive rare codons after 86th codon in hIL-5 cDNA could block polypeptide synthesis in E. coli. Through recombinant PCR technology the rare codons after 86th codon in hIL-5 cDNA were mutated into corresponding codons preferentially used in E. coli, and the mutated hIL-5 cDNA was highly expressed in pBVhIL5-H/DH5alpha to approximately 15% TCP after thermal induction. hIL-5 recombinant protein existed as inclusion bodies in E. coli. ELISA with a cross-reacting rat anti-mIL-5 monoclonal antibody confirmed the expressed product was hIL-5 recombinant protein.

AIM: To investigate the role of Peyer’s patch lymphocytes in the regulation of enteric epithelial barrier and ion transport function in homeostasis and host defense. METHODS: Mouse Peyer’s patch lymphocytes were co-cultured with human intestinal epithelial cell line Caco-2 either in the mixed or separated (isolated but permeable compartments) culture configuration. Barrier and transport functions of the Caco-2 epithelial monolayers were measured with short-circuit current (Isc) technique. Release of cytokines was measured by enzyme-linked immunosorbent assay (ELISA) and cytokine mRNA expression was analyzed by semi-quantitative RT-PCR. Barrier and iontransport functions of both culture conditions following exposure to Shigella lipopolysaccharide (LPS) were also examined. RESULTS: The transepithelial resistance (TER) of the epithelial monolayers co-cultured with Peyer’s patch lymphocytes was maintained whereas that of the Caco-2 monolayers alone significantly decreased after eight days in culture. The forskolin-induced anion secretion, in either absence or presence of LPS, was significantly suppressed in the both co-cultures as compared with the Caco-2 cells alone. Furthermore, only the mixed co-culture condition induced the expression and release of mIL-6 from Peyer’s patch lymphocytes, which could be further enhanced by LPS. However, both co-culture conditions suppressed expression and release of epithelial hIL-8 under the unstimulated conditions, while the treatment with LPS stimulated their hIL-8 expression and release. CONCLUSION: Peyer’s patch lymphocytes may modulate intestinal epithelial barrier and ion transport function in homeostasis and host defense via cell-cell contact and cytokine signaling.