CCl4 Solution Research Articles

Vibrational population dynamics of methyl formate in CCl4 solution

The vibrational relaxation of the CO stretching mode of HCO2CH3 in CCl4 solution was measured using femtosecond infrared spectroscopy. Time-resolved spectra after excitation of the CO stretching mode revealed a new absorption other than that of the excited CO mode. Transient signals for the fundamental band and the absorption of the excited CO mode showed nonexponential kinetics having a subpicosecond component. A three-state kinetic scheme showed that the excited CO mode decayed via the v1 state of the CO mode. The subpicosecond decay component might be due to fast equilibration of the excited state with the adjacent 2nd excited state of the OCH3 stretching mode. Or it might be caused by solvent memory effects, which may cause unusually rapid nonexponential absorption decay. As demonstrated herein, time-resolved infrared spectra with high spectral resolution and sensitivity can provide detailed relaxation pathways of vibrational energy.

Effect of Gallic Acid on Regression of Murine CCL4-Induced Hepatic Cirrhosis

Hepatic cirrhosis can be induced by chronic exposure to reactive oxygen species (ROS). However, phenolic compounds, such as gallic acid (GA), appear to inhibit ROS-induced oxidative stress. We aimed to investigate the effects of GA on murine hepatic fibrogenesis. The effects of GA were evaluated on the regression of liver cirrhosis that was induced by chronic intraperitoneal CCl4 administration (20% v/v) in C57 mice for a period of 10 weeks. The animals were treated intraperitoneally and distributed in three groups, as follows: SHAM group – 8 weeks with Olive oil (CCL4 solution vehicle); C group – 8 weeks with CCL4 solution, and then 2 more weeks with deionized water (Gallic Acid solution vehicle); and C + GA group – 8 weeks with CCL4 solution, and then 2 more weeks with Gallic Acid solution (100 mg/Kg/day) on alternated days. The cirrhosis and inflammation-related factors were estimated using histological, western blotting and PCR-RT analysis. There was a significant decrease in the collagen deposition, as indicated by Sirius red staining, in the C + GA group compared to the C group (p<0.05). This improvement was accompanied by a reduction in the number of α-SMA-positive cells observed in these animals (p<0.05). The expression of the Procollagen α1(I), TGFβ1 and TIMP1 genes was also diminished by GA administration compared to the control (p<0.001). Additionally, proteomic studies revealed reduced p65 NFκB and p38 MAPK protein levels in the C + GA group. These findings reveal the effect of GA on the regression of cirrhosis. The mechanisms of this process might involve the anti-inflammatory activity of GA, which represses the TGFβ1, p65 NFκB, and p38 MAPK-mediated signaling pathways.

Discrimination of Axial and Central Stereogenic Elements in Chiral Bis(oxazolines) Based on Atropisomeric 3,3'-Bithiophene Scaffolds Through Chiroptical Spectroscopies.

Two diastereoisomeric pairs of bis-oxazolines, provided with a stereogenic center at carbon 4 and based on the 3,3'-bithiophene atropisomeric scaffold, were synthesized and structurally characterized. They differ in the substituents at positions 2 and 5 of the thiophene rings, which are functionalized with methyl (1) or phenyl (2) groups, respectively. In vibrational circular dichroism (VCD) spectra, recorded in CCl4 solutions, it is possible to distinctly recognize the characteristic features of axial and central stereogenic elements. In tandem with Density Functional Theory (DFT) calculations, the absolute configuration (AC) of the diastereoisomers was safely established. In this case, VCD was shown to be superior to ECD (electronic circular dichroism) in the assignment of AC. The normal modes, evaluated from DFT calculations, show that the VCD signals in correspondence with the stereogenic axis of the bithiophene unit are different for 1 and 2. The VCD spectra of a molecular analog of 1, the (S)-2,2',5,5'-tetramethyl-4,4'-bis-(diphenylphosphino)-3,3'-bithiophene oxide (3), characterized by the same 3,3'-bithiophene scaffold, but devoid of stereogenic centers, exhibits signals similar to those observed in the case of diastereoisomer (aS,R,R)-1a, associated with almost identical normal modes. Chirality 28:686-695, 2016. © 2016 Wiley Periodicals, Inc.

The conformational analysis of push-pull enaminones using FTIR and NMR spectroscopy, and quantum chemical calculations. VI. β−N−Methyl-aminovinyl trifluoromethyl ketone and α−methyl−β−N−methylaminovinyl trifluoromethyl ketone

X-Ray analysis, NMR and IR Fourier spectra of two enaminoketones 4-(N-methylamino)-1,1,1-trifluorobut-3-en-2-one F3CCOCHCHNH(CH3) (1) 4-(N-methylamino)-1,1,1-trifluoro-3-methylbut-3-en-2-one F3CCOC(CH3)CHNH(CH3) (2) were studied in solid state and solutions. It was shown that the substitution of proton at α-position of vinyl moiety with methyl group changes significantly electronic and spatial structure of enaminoketone. In solid state enaminoketone 1 is found to be exclusively as Z-s-Z-ap isomer with intramolecular hydrogen bond. At the same time molecules of enaminoketone 2 have E-s-E-ap stereoisomeric structure forming dimers due to intermolecular NH⋯OC hydrogen bonds. Exposure of Ar-matrix isolated 1 to UV-radiation results in appearance of various E forms with free methylamino- and hydroxy groups. The same effect was observed for 2 in solutions in CCl4 under addition of polar HMPA or DMSO during spontaneous E ⇌ Z isomerization. For enaminoketone 1 under similar conditions we observed reverse process of Z ⇌ E isomerization, E stereoisomeric forms with hydroxy group being trace quantity only.Study of solvent influence on FTIR spectra revealed that introduction of methyl group as substituent at α-position of vinyl moiety increases electron population of CO double bond. Consequently, in contrast with enaminoketone 1 where the main contribution to the ν˜ (CO) band shift to lower wavenumbers in all three stereoisomeric structures makes solvent polarity/polarizability term (π*), influence of solvent's hydrogen bond acceptor (HBA) basicity (β) on ν˜ (CO) band shift of 2 predominates in the E-s-Z-ap and Z-s-Z-ap isomers. Similarly to enaminoketone 1, negative shift of the ν˜ (CC) band to lower wavenumbers occurs due to hydrogen bond formation between π system of vinyl moiety and hydrogen bond donor solvents in all stereoisomeric forms of enaminoketone 2.

Spectroscopic and Computational Study of Acetic Acid and Its Cyclic Dimer in the Near-Infrared Region.

Anharmonic vibrational analysis of near-infrared (NIR) spectra of acetic acid was carried out by anharmonic quantum chemical calculation in a wide concentration range of its CCl4 solution. By predicting vibrational spectra of acetic acid for the first time over a wide NIR region, it was possible to elucidate the influence of the formation of acetic acid cyclic dimer on its NIR spectrum. Quantum chemical simulations were based on coupled cluster and density functional theory quantum methods. Additionally, Møller-Plesset perturbation theory was employed for the additional calculation of hydrogen bonding stabilization energies. An anharmonic vibrational analysis was performed with the use of generalized second-order vibrational perturbation theory (GVPT2). A hybrid approach was assumed, in which monomeric species was treated by CCSD(T)/aug-cc-pVDZ (harmonic approximation) and B3LYP/SNSD (anharmonic approximation) methods. For the cyclic dimer, B3LYP and B2PLYP single and double hybrid functionals, paired with an SNSD basis set, were employed. DFT calculations were augmented with additional empirical dispersion correction. It was found that quantum chemically calculated vibrational modes in the NIR region are in a good agreement with experimental data. The results of anharmonic vibrational analysis were supported by a harmonic shift analysis, for elucidating the very strong anharmonic coupling observed between stretching modes of hydrogen bonded bridge in the cyclic dimer. However, the calculated wavenumbers for combination modes of double hydrogen bonded bridge in the cyclic dimer, which are very sensitive to the formation of hydrogen bonding, were found to be underestimated by quantum chemical methods. Therefore, by band fitting, the wavenumbers and shape parameters for these bands were found, and the modeled spectra were adjusted accordingly. A high accuracy of simulated spectra was achieved, and a detailed analysis of the experimental NIR spectra of acetic acid was possible, with successful identification of numerous experimental bands, including those which originate from concentration effects. It was also found that the main spectral features observed in the NIR spectra of carboxylic acid upon the formation of hydrogen bond should be accounted for combination modes of the stretching and bending vibrations of double hydrogen-bonded bridge in the cyclic dimers of acetic acid.

Nonlinear thermal lens signal of the (Δυ = 6) C–H vibrational overtone of C6H6 in liquid solutions of n-C6H14 and CCl4

The thermal lens technique is applied to vibrational overtone spectroscopy of solutions of benzene. The pump and probe thermal lens technique has been found to be very sensitive for detecting samples of low concentration in transparent solvents. The C–H fifth vibrational (Δυ = 6) overtone spectrum of benzene is detected at room temperature for compositions per volume in the range (1 to 1 × 10−4) using CCl4 and n-C6H14 as solvents. By detecting the absorption band in a 100-ppm solution, the peak absorption of the signal is approximately (2.2 ± 0.3) × 10−7 cm−1. The parameters that determine the magnitude of the thermal lens signal such as the pump laser power and the thermodynamic properties of the solvent and solute are discussed. A plot of normalized integrated intensity as a function of composition of benzene in solution reveals a nonlinear behavior. The nonlinearity cannot be explained assuming solvent enhancement at low concentrations. A two-color absorption model that includes the simultaneous absorption of the pump and probe lasers explains the enhanced magnitude and the nonlinear behavior of the thermal lens signal for solutions of composition below 0.01.

Effects of pirfenidone on hepatic fibrosis in mice induced by carbon tetrachloride

To investigate the effects of pirfenidone on CCl4-induced liver fibrosis in mice. After 8-week feeding, 40 healthy male SPF ICR mice were randomly divided into 4 groups:liver fibrosis group (CCL4 group), low doses of Pirfenidone group (PFD-L group), high doses of Pirfenidone group (PFD-H group) and control group. The mice in CCL4 group, low doses of Pirfenidone group (PFD-L group), high doses of Pirfenidone group (PFD-H group) were injected intraperitoneally with 0.4 ml 10% CCL4 solution dissolved in soybean oil. Then the PFD-L and PFD-H groups were treated with 120 mg and 240 mg PFD via gastric gavage, respectively. Control group was injected with same volume of saline. Alanine aminotransferase(ALT), aspartate aminotransferase(AST), alkaline phosphatase(ALP) in serum were tested with automatic biochemistry analyzer and the pathologic changes of liver tissue were examined by HE staining. Furthermore, we identi-fied hyaluronic acids(HA), laminin(LN), collagentype IV(IV-C) in serum using radioimmunoassay and the expression of smooth muscle acti-nalpha(α-SMA) related gene in liver was tested by real-time fluorescence quantitative PCR. Compared with control group, hepatic lobules in CCL4 mice were damaged significantly, collagenous fiber was deposited obviously, and counterfeit hepatic lobules formed. The serum levels of ALT, AST, ALP were increased obviously (P<0.05) with the enhancement of HA, LN, IV-C in serum (P<0.05) and the ex-pression of α-SMA related gene (P<0.05). Compared to CCL4-treated mice, the serum levels of ALT, AST, ALP in PFD-L and PFD-H groups were decreased, HA, LN, IV-C in PFD-L and PFD-H mice went down obviously,and the expression of α-SMA related gene was con-trolled (P<0.05). From pathological observation, we found the degree of liver fibrosis in PFD-L mice was reduced and collagenous fiber was decreased, only a little counterfeit hepatic lobule could be found. Cell arrangement in PFD-H mice recovered, the structural of hepatic lobules disordered and no obvious counterfeit hepatic lobules were found. Therefore, the recovery of PFD-H group was better than PFD-L group. Pirfenidone has a protective role in improving the outcome of the liver fibrosis and it may become a new direction of early intervention in liver fibrosis.

A spectroscopic and theoretical study in the near-infrared region of low concentration aliphatic alcohols.

The near-infrared (NIR) spectra of low-concentration (5 × 10(-3) M) solutions in CCl4 of basic aliphatic alcohols, methanol, ethanol, and 1-propanol were, for the first time, calculated by second-order vibrational perturbation theory computations and were compared with the corresponding experimental data. Density functional theory (DFT) using single hybrid (B3LYP) and double hybrid (B2PLYP) density functionals and their derivatives with additional empirical dispersion correction (B3LYP-D3 and B2PLYP-D, respectively) and second order Møller-Plesset perturbation theory were used in combination with selected basis sets including fairly new basis sets from the "spectroscopic" SNS family, double-ζ SNSD and triple-ζ SNST basis sets. Each time, anharmonic vibrational modes and intensities were calculated by using second-order vibrational perturbation theory. The effect of solvent cavity on the calculated results was included by the application of a self-consistent reaction field with a polarized continuum model. Ethanol and 1-propanol have conformational isomerism; following a conformational analysis, theoretical spectra of all isomers were calculated and their final predicted NIR spectra were obtained as Boltzmann-averaged spectra of resolved conformers. For ethanol and 1-propanol, the observed broadening of the overtone band of the OH stretching mode was well reflected by the differences in the position of the relevant band among conformational isomers of these alcohols; the effect of solvent on broadening was also discussed. Detailed band assignments in the experimental NIR spectra of the studied alcohols were proposed based on the calculation of potential energy distributions. The final accuracy of the predicted NIR spectra for each of the theoretical methods was estimated based on the errors in calculated frequencies of overtones and combination bands.

肝硬化大鼠全肝血流阻断对血清相关炎性因子表达的影响

目的：研究肝硬化大鼠全肝血流阻断后血清中易导致多器官功能损伤的相关炎性因子表达的情况。方法：选用雄性SD大鼠80只，体重160~200 g，30%CCl4油溶液灌胃及饮用5%乙醇水制成肝硬化模型，随机分4组，每组20只。采用阻断肝门、肝上上腔静脉及肝下下腔静脉15 min (A2组)、30 min (A3组)、45 min (A4组)制作肝硬化大鼠全肝血流阻断模型，并以假手术组(A1组)作为对照。按阻断时间活杀取材，采用肝下下腔静脉取血，监测血清中TNF-α、NF-KB及IL-21的表达。多个样本均数比较采用单因素方差分析，两组间比较采用t检验。结果：全肝血流阻断各组与A1组相比血清中TNF-α，NF-KB，IL-21浓度明显升高(P < 0.05)，且随时间增加，表达呈逐渐增强趋势。结论：肝硬化大鼠全肝血流阻断后，血清中相关炎性因子的表达浓度是升高的，随阻断时间的延长，因子的浓度呈上升趋势，而不同炎性因子之间存在影响，在器官功能损伤中发挥作用。 Objective: To research the expression of inflammatory cytokines which easily lead to multiple organ damage in liver cirrhosis rats serum under the condition of the whole liver blood flow blocking. Methods: Eights male SD rats weight 160 - 200 g were selected. The liver cirrhosis rats model was established by 30% CCl4 solution to fill the stomach and 5% alcohol to feed. Eighty SD rats were randomly divided into four groups, with 20 rats in each group. By blocking porta hepatis, liver up and inferior vena cava for 15 min (A2 group ), 30 min (A3group), 45 min (A4 group) production of cirrhosis rats whole liver blood flow blocking model, and the sham operation group (A1 group) as control. Twenty rats in each group were sacrificed at 15, 30, 45 min, respectively after modeling. According to the blocking time, they were killed lively, to monitor the expression of TNF-α, NF-KB and IL-21 in the serum from the inferior vena cava. All data were analyzed by using the analysis of variance or t test. Results: Cirrhosis rats whole liver blood flow blocking model compared with those in group A1, levels of TNF-α, NF-KB and IL-21 were significantly increased (p < 0.05), and the expression of inflammatory cytokines trend to grow by time. Conclusion: The expression of inflammatory cytokines which easily lead to multiple organ damage in liver cirrhosis rats serum under the condition of the whole liver blood flow blocking was increased. The concentration of inflammatory cytokines increases with the extension of blocking time. There is a mutual influence among different inflammatory cytokines which play a role in the injury of organ function.

Self association of α-tocopherol in solutions. Infrared absorption and theoretical study

The IR spectra of α-tocopherol (α-T) solutions in CCl4 at different concentrations (0.0009–0.5 M) and temperatures from 15 to 50 °C were recorded. The formation of relatively weak and broad red-shifted band arising with increasing of α-T concentration was observed. The band was attributed to the formation of α-T H-bonded oligomers. The resolution of the complex band and DFT calculation of oligomers molecular structure, energy and IR spectra were performed. As a result the experimental IR spectra, equilibrium constants, the most probable structures of oligomers and H-bond energies were found.

Effect of Acid–Base Interactions on Conformation of Adsorbed Polymer Chains

Sum frequency generation spectroscopy (SFG) and attenuated-total-reflection IR (ATR-IR) were used to investigate polymer adsorption on solid surfaces in CCl4 (neutral), CHCl3 (acidic), and acetone (basic) solvents. Fowkes showed that the adsorbed amount of the polymer from acidic and basic solvents is less than that from a neutral solvent (Ind. Eng. Chem. Prod. Res. Dev. 1978, 17, 3-7). Here, we show that besides the differences in adsorbed amount, chains adsorbed from an acidic solvent adopted a flat conformation with a much smaller ratio of segments of loops and tails to trains compared to those adsorbed from a neutral solvent. Sapphire (Al2O3) surfaces were saturated by train segments at 1.3 × 10-5 volume fraction for both CCl4 and CHCl3 solutions, with a large fraction of the surface sites occupied by the PMMA segments, which was different from what was expected based on Fowkes' experiment. In contrast, PMMA segments were not able to replace acetone molecules from the surface in a time period of 2 h. Surface interaction parameters alone were unable to predict the differences in conformation of chains adsorbed from acidic or neutral solvents.

Spectroscopic and theoretical studies of some 4′-substituted-phenyl 2-(ethanesulfonyl)acetates. Structure of 4′-nitrophenyl 2-(ethanesulfonyl)acetate

Abstract An analysis of carbonyl bands in the infrared spectra of some 2-ethylsulfonyl 4′-substituted phenylacetates bearing substituents NO2 (1), H (2) and OMe (3), supported by B3LYP/6-31G(d,p) and SM5.42R at PM3 level calculations, along with natural bond orbital analysis (NBO) and X-ray diffraction (for 1) was performed. Theoretical data indicated the existence of two stable gauche conformations (g 1 and g 2). The g 1 conformer is the most stable, least polar and has the lowest νCO frequency. The more intense, lower frequency carbonyl doublet component found in CCl4 solution is assigned to the g 1 conformer. As the solvent dielectric constant increases (going from CCl4 to MeCN) the higher frequency νCO doublet increases in intensity. This behaviour is reproduced by the solvation free energy calculations, supporting the conformer assignments. NBO calculations indicate that the most important orbital interaction is LPO9 → π*C7=O8 for both conformers, which corresponds to [C=O ↔ C+–O-] conjugation. This stabilises the g 1 conformer to a greater extent and is responsible for the lower νCO frequency. The sum of the selected NBO delocalisation energies for 1–3 indicates that the g 1 conformer is more stable. It is concluded that the calculated greater stability of the g 1 conformer is due to a balance of attractive electrostatic and orbital interactions along with relevant hydrogen bonds. The X-ray crystal structure analysis of 1 shows the presence of two crystallographic independent but almost superimposable molecules each which adopt a cis geometry. The molecules are consolidated into the three-dimensional crystal packing by C–H…O interactions as well as by nitro- N–O…π(phenyl) contacts.

Patho- and morphogenesis of microcirculation disturbances in toxic hepatitis in immature rats.

Background. Chronic exogenous intoxication leads to the development of typical pathological processes. In this case the structural and functional disturbanses of the liver frequently occur. Objective: to investigate the pathogenic and morphogenetic violations of blood and lymph circulation at chronic toxic hepatitis in immature rats. Methods. Experiment was conducted on white laboratory immature rats. The chronic toxic hepatitis was modelled by intragastric administration of 20% oil solution of CCl4 and 5% solution of ethanol during six weeks twice a week. Liver tissue was stained by hematoxylin and eosin and by Van Gieson for histological studies. Results. The liver is an important lymph producer in both normal and pathological conditions. At chronic toxic hepatitis in immature rats violation of lymph circulation leads to the dilation of lymph capillaries of the portal tracts and liver capsule, presence of anastomoses between superficial and deep lymphatic vessels, formation of new lymph vessels under the liver capsule, appearance of splits, lacunae, capillaries with a wide lumen, deformating the liver lobule. Connective tissue proliferation takes place on the background of lymphostasis. Сonclusion. The accumulation of fluid in the space of Disse can lead to capillarisation of sinusoids with formation of blood and lymphatic capillaries with the central direction of the fluid flow.

Effect of solvent on proton location and dynamic behavior in short intramolecular hydrogen bonds studied by molecular dynamics simulations and NMR experiments

Hydrogen phthalate anion has a short strong O–H–O hydrogen bond (H-bond). According to previous experimental studies, the H-bond is asymmetric and two tautomers are interconverted in aqueous solutions. In the present study, the effects of polar solvents on the H-bond in a zwitterionic hydrogen phthalate derivative 1 were investigated by quantum mechanics/molecular mechanics molecular dynamics (MD) simulations. The analyses of the trajectories for the methanol solution showed that the H-bonding proton tends to be located closer to the carboxylate group that forms fewer intermolecular H-bonds, than to the other carboxylate group and that the intramolecular proton transfer in 1 is triggered by the breakage and/or formation of an intermolecular H-bond. The enol form of dibenzoylmethane (2) also has a short H-bond, and the OH bond is reported to be rather long (>1.1Å) in the crystal. In the present study, the effects of the solvent on the H-bond in 2 were investigated by molecular orbital (MO) calculations, MD simulations and nuclear magnetic resonance (NMR) spectroscopy. Density functional theory (DFT) calculations for 2 in vacuum indicated that the barrier height for the intramolecular proton transfer is almost the same as the zero-point energy of the vibrational ground state, resulting in broad distribution of the proton density along the H-bond, owing to the nuclear quantum effect. The OH distances were determined in CCl4, acetonitrile, and dimethylsulfoxide solutions from the magnetic dipolar interactions between the 17O and 1H nuclei monitoring the nuclear magnetic relaxation times of 1H. The experimental results indicated that the H-bond geometry of 2 is influenced by the interactions with dimethylsulfoxide, suggesting the formation of a bifurcated H-bond, which was supported by the DFT calculations. The MD simulations for the methanol solution of 2 showed that the asymmetry of the OH distance is correlated with the asymmetry in the electrostatic field of the solvent, although the correlation is weaker than that for the methanol solution of 1. The lower sensitivity of 2 to the solvent is attributed to the smaller number of oxygen atoms and the less negative electrostatic potential at the proton-accepting sites. The present study indicates that the specific interactions with protic solvents or strong H-bond-accepting solvents affect the geometry and dynamic behavior of short intramolecular H-bonds.

Populations of Ethanol Conformers in Liquid CCl4 and CS2 by Raman Spectra in OH Stretching Region

Combining Raman spectroscopy with density functional theory, the populations of the trans- and gauche- ethanol conformers are investigated in carbon tetrachloride (CCl4) and carbon disulfide (CS2). The spectral contributions of two ethanol conformers are identified in OH stretching region. The energy difference between both conformers is estimated with the aid of the calculated Raman cross sections. It can be seen that the trans- ethanol is more stable in CCl4 and CS2 solutions. The spectra are also obtained at different temperatures, and it is found the van't Hoff analysis is invalid in these solutions. By taking accounts of the Boltzmann distribution and theoretical Raman cross section, the energy difference is found to be increased with temperature, which shows the weak intermolecular interactions can enhance the population of trans- ethanol.

N-trimetylsilyl carboxamides RC(O)NHSiMe3 (R = Me, CF3, Ph): X-ray, DFT and FTIR study

The X-ray single-crystal structures of N-trimetylsilyl acetamide CH3CONHSiMe3 (1), N-trimethylsilyl trifluoroacetamide CF3CONHSiMe3 (2) and N-trimethylsilyl benzamide PhCONHSiMe3 (3) have been determined. Quantum chemical calculations (B3LYP/6-311+G**, NBO analysis) were performed for gas phase optimized structures, proton affinities and N–H bond dissociation energies of amides 1–3 and their isostructural carbon analogs 4–6. The effect of silicon atom on structural features and intermolecular electron interactions was determined. Types of self-associates which can be formed by amides 1–3 in CCl4 solution were studies by infrared spectroscopy.

Conformational properties of chiral tobacco alkaloids by DFT calculations and vibrational circular dichroism: (−)-S-anabasine

A thorough DFT and MM study of the conformational landscape, molecular and electronic structures of (−)-S-anabasine is reported aimed to reveal the mechanism controlling its conformational preference. Although the conformational flexibility and diversity of this system is quite extensive, only two structures are populated both in gas-phase and solution (CCl4 and DMSO). NBO-aided electronic structure analyses performed for the eight conformers representing minima in the potential energy surface of (−)-S-anabasine indicate that both steric and electrostatic factors are determinant in the conformational distribution of the sample in gas phase. Nonetheless, hyperconjugative effects are the key force tipping the balance in the conformational equilibrium between the two main rotamers. Increasing the polarity of the medium (using the IEF-PCM formalism) barely affect the conformational energy profile, although a slight increase in the theoretical population of those structures more affected by electrostatic interactions is predicted. The validity of the theoretical models and calculated conformers populations are endorsed by the accurate reproduction of the IR and VCD spectra (recorded in pure liquid and in CCl4 solution) of the sample (that have been firstly recorded and assigned in the present work) which are consistent with the occurrence of a 2:1 conformational ratio.

Evaluation methods of angiogenesis in experimental liver fibrosis

To investigate the methods for assessing angiogenesis in experimental liver fibrosis. Male C57BL/6 mice were randomly divided into a normal (unmodeled) group and a liver fibrosis model group.The model was established by a 4-week course of 10% CCl4 solution (in olive oil) intraperitoneal injection. Liver vasculature was observed by magnetic resonance (MR),computed tomography (CT),synchrotron radiation X-ray,and von Willibrand factor(vWF) immunofluorescence staining. Liver inflammation and fibrosis were observed by staining with hematoxylin-eosin and Sirius red.The t-test and Pearson's correlation analysis were used for statistical analyses. Compared with the normal group,the model group had more robust inflammation and fibrosis in liver tissue.The liver tissue in the modeled mice showed significant deceases in MR signal intensity on T2WI before and after enhancement (386.67+/-69.04 vs.492.67+/-112.50,t =-2.456, P=0.026).The liver tissue in the modeled mice also showed significantly decreased enhancement CT values (P < 0.01).Synchrotron radiation X-ray imaging showed that the small vessels in the liver tissues of the modeled mice were significantly increased compared to that in the normal mice (P < 0.01).The MR T2W enhanced signal value (439.67+/-104.80, Pearson's r=0.714, P=0.009) and microvascular relative length (676.53+/-122.75, Pearson's r=0.791, P=0.002) were positive correlated with microvessel density (MVD) (14.50+/-5.95),as shown by detection of labeled vWF.The before and after CT enhancement difference (132.60+/-57.02, Pearson's r=-0.612, P=0.034) was negatively correlated with MVD. s MR,CT and synchrotron radiation X-ray imaging can be used for assessing angiogenesis in liver fibrosis,and the findings from each are correlated with the traditional MVD detection method. The two-dimensional imaging of synchrotron radiation X-ray is more intuitive,and has been confirmed as an effective evaluation method for liver angiogenesis.

UV-light induced conformational changes of 2-pyridinecarboxylic acid in low-temperature argon matrices

Conformational changes of 2-pyridinecarboxylic acid (2-picolinic acid) upon UV irradiation have been investigated by low-temperature matrix-isolation infrared spectroscopy. Only one conformer having an intramolecular hydrogen bond of COOH⋯N in the pyridine ring is found to exist in argon matrices after deposition before UV irradiation, in contrast to a reported feature in the CCl4 solution. The hydrogen bond is broken by UV irradiation, resulting in two less stable conformers; one increases immediately at the early irradiation stage while the other increases slowly during the prolonged irradiation time. The conformations around the OCOH and CCOOH bonds of the photoproducts are identified by assignments of the IR bands measured in an argon matrix with an aid of the density-functional-theory calculation. The proposed photoreaction pathways of the conformational changes based on this observation are supported by a kinetic analysis of the IR absorbance changes with the reactants and the photoproducts against the irradiation time.

Hepatoprotective Effect of the Aqueous Extract of Simarouba amara Aublet (Simaroubaceae) Stem Bark against Carbon Tetrachloride (CCl4)-Induced Hepatic Damage in Rats

Simarouba amara stem bark decoction has been traditionally used in Brazil to treat malaria, inflammation, fever, abdominal pain, diarrhea, wounds and as a tonic. In this study, we investigate the hepatoprotective effects of the aqueous extract of S. amara stem bark (SAAE) on CCl4-induced hepatic damage in rats. SAAE was evaluated by high performance liquid chromatography. The animals were divided into six groups (n = 6/group). Groups I (vehicle—corn oil), II (control-CCl4), III, IV, V and VI were pretreated during 10 consecutive days, once a day p.o, with Legalon® 50 mg/kg b.w, SAAE at doses 100, 250 and 500 mg/kg b.w, respectively. The hepatotoxicity was induced on 11th day with 2 mL/kg of 20% CCl4 solution. 24 h after injury, the blood samples were collected and their livers were removed to biochemical and immunohistochemical analyzes. The SAAE decreased the levels of liver markers and lipid peroxidation in all doses and increased the catalase levels at doses 250 and 500 mg/kg. Immunohistochemical results suggested hepatocyte proliferation in all doses. These results may be related to catechins present in SAAE. Thus, SAAE prevented the oxidative damage at the same time that increased regenerative and reparative capacities of the liver.