Suppression of chemical mutagen-induced SOS response by allylbenzen from Asiasarum heterotropoides in the Salmonella typhimurium TA1535/PSK1002 umu test

A methanol extract from Asiasarum heterotropoides showed a suppressive effect of the SOS-including activity on the mutagen 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with chloroform, butanol, and water. The chloroform fraction showed a suppressive effect. Suppressive compounds in the chloroform fraction were isolated by silica gel column chromatography and identified as methyleugenol (1), elemicin (2), and gamma-asaron (3) by GC/MS, IR, and 1H- and 13C-NMR spectroscopy. These compounds suppressed the MeIQ-induced SOS response in the umu test. Gene expression was suppressed 52.2, 61.8, and 71.6% at a concentration of 0.1 mM, respectively. The ID50 values (50% inhibition dose) of these compounds were 0.080, 0.028, and 0.013 mM, respectively. On the other hand, Compounds 1-3 showed weak suppressive effect of the SOS-inducing activity on activated MeIQ. These results indicate that the inhibition of the SOS-inducing activity on MeIQ, which was caused by Compound 1-3 was due to the inhibition of metabolic activity by S9.     

Suppressive components in rice husk against mutagens-induced SOS response using Salmonella typhimurium TA1535/pSK1002 umu test

The EtOAc extract from rice (Oriza sativa cv. Hinohikari) husk showed a suppressive effect on umu gene expression of the SOS response in Salmonella typhimurium TA1535/pSK1002 against the mutagen, Trp-P-1, which requires liver metabolizing enzyme. To obtain the suppressive compound, the EtOAc extract was fractionated by SiO(2) column chromatography using umu test as a bioassay guide. Suppressive compound was isolated and identified as momilactone A (1) by EIMS, IR, (1)H- and (13)C-NMR spectroscopy. Compound 1 inhibited of the SOS-inducing activity of Trp-P-1 in the umu test. Gene expression was suppressed by 32.6% at less than 0.60 mM. Compound 1 was assayed with activated Trp-P-1. The suppressive effect of Compound 1 was decreased compared with that of Trp-P-1. Furthermore, 1 was assayed with another mutagens, such as MeIQ, activated MeIQ, furylfuramide (AF-2), MNNG, and UV-irradiation. Compound 1 showed greater suppressive effect on AF-2-inducing SOS response than other mutagens.     

Suppressive effect of the SOS-inducing activity of chemical mutagen by citric acid esters from Prunus mume Sieb. Et Zucc. using the Salmonella typhimurium TA1535/pSK1002 umu test

A methanol extract from Prunus mume Sieb. Et Zucc. showed a suppressive effect of the SOS-inducing activity on the mutagen 3-amino-1,4-dimethyl-SH-pyrido[4,3-b]indole(Trp-P-1) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with hexane, dichloromethane, ethyl acetate, butanol and water. The dichloromethane and ethyl acetate fractions showed suppressive effect. Suppressive compounds were isolated by silica gel column chromatography and identified as trimethyl citrate (1) and dimethyl citrate (2) by GC-MS, IR and 1H and 13C-NMR spectroscopy. Compounds 1 and 2 suppressed 51 and 39% of the SOS-inducing activity at a concentration of 2.0 micromol/mL.     

Antioxidant effects of hydroxybenzalacetones on peroxynitrite-induced lipid peroxidation in red blood cell membrane ghost and SOS response in Salmonella typhimurium TA4107/pSK1002

Antioxidant activity of a series of hydroxybenzalacetones was determined against peroxynitrite-induced lipid peroxidation in red blood cell membrane and SOS response through DNA damage in bacterial cells. Hydroxybenzalacetone derivatives with hydroxy, methoxy, ethoxy or methyl substitution were analyzed and found to be more effective than the water-soluble vitamin E analogue Trolox. The inhibitory effect against lipid peroxidation correlated well to that against the SOS response, which is dependent on decomposition of peroxynitrite by hydroxybenzalacetones outside of the cell membrane. The antioxidant activity was shown to correlate well with the electric parameter sigma+. Electron-donating substituents with more negative sigma+ values increased the potencies. The result suggests that hydroxybenzalacetones with more electron-donating substituents will protect tissue more effectively against oxidative stress.     

Conformational studies of the robust 2-Cys peroxiredoxin Salmonella typhimurium AhpC by solution phase hydrogen/deuterium (H/D) exchange monitored by electrospray ionization mass spectrometry

This is the first comprehensive HX-MS study of a "robust" 2-Cys peroxiredoxin (Prx), namely Salmonella typhimurium AhpC (StAhpC). Prx proteins control intracellular peroxide levels and are abundant antioxidant proteins in eukaryotes, archaea and bacteria. Crystal structural analyses and structure/activity studies of several bacterial and mammalian 2-Cys Prxs have revealed that the activity of 2-Cys Prxs is regulated by redox-dependent oligmerization and a sensitivity of the active site cysteine residue to overoxidation. The propensity to overoxidation is linked to the conformational flexibility of the peroxidatic active site loop. The HX-MS results emphasize the modulation of the conformational motility of the active site loop by disulfide formation. To obtain information on the conformational impact of decamer formation on the active site loop motility, mutants with Thr77 substituted by Ile, a decamer-disrupting mutation or by Val, a decamer-stabilizing mutation, were studied. For the isoleucine mutant, enhanced mobility was observed for regions encompassing the α4 helix located in the dimer-dimer interface and regions surrounding the peroxidatic loop. In contrast, the T77V mutation resulted in an increase in conformational stability in most regions of the protein except for the active site loop and the region encompassing the resolving cysteine.     

Suppression of the Charge Density Wave State in Two-Dimensional 1T-TiSe2 by Atmospheric Oxidation

Two-dimensional (2D) metallic transition-metal dichalcogenides (TMDCs), such as 1T-TiSe₂, have recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T-TiSe₂ undergoes rapid oxidation under ambient conditions, significantly affecting its CDW phase-transition behavior. We comprehensively investigate the oxidation process of 2D TiSe₂ by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique selenium-assisting oxidation mechanism. Our findings facilitate a better understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers, and thus open a way to further explore the functionality of these materials toward devices.     

Cloning of the histidine transport genes from Salmonella typhimurium and characterization of an analogous transport system in Escherichia coli

The genes for the well-characterized high-affinity histidine transport system of S typhimurium have been cloned in lambda gt4. Genetic and physiological analyses of the analogous transport system of E coli were undertaken in order that available lambda vectors, recombinant DNA techniques, and a genetic selection for transport function might be used to isolate the Salmonella genes. The presence of the transport genes on a 12.4 Kb cloned DNA fragment has been confirmed 1) genetically, by complementation studies; 2) physiologically, by the rates of histidine uptake by bacteria containing this DNA; and 3) by demonstrating that the cloned DNA codes for the previously identified transport proteins J and P. The isolated fragment carries the entire transport operon, the argT gene and the ubiX locus, but neither the purF gene nor the ack/pta loci.     

A Plausible Mechanism for the Mutagenic Activity (Salmonella typhimurium TA100) of MX Compounds: A Formation of CG-CG+-CG Radical Cation by One-electron Reduction

Abstract

Combining our previous QSAR work with recent high-level quantum mechanical calculations, a plausible mechanism for the mutagenic activity of halogenated furanones (so called MX compounds) in Salmonella typhimurium TA100 tester strain is proposed. The mechanism involves one-electron reduction as a key step and it seems reasonable to suggest that the mutagenicity of these direct-acting compounds may be a purely thermodynamic phenomenon, rather than the result of site-specific binding or adduct formation. Overall, the proposed model is consistent with the most experimental findings.     

A one-pot stereoselective synthesis of trans-1-aryl-2-aminotetralins from 2-arylethyl styrenes

An efficient stereoselective synthesis of trans-1-aryl-2-aminotetralins has been achieved via Cu(OTf)₂ catalyzed one-pot aziridination and regioselective intramolecular arylation of in situ generated aziridines from 2-arylethyl styrenes and PhINSO₂(4-NO₂C₆H₄) [PhINNs]. Reaction of a mixture of E/Z-styrenes (?85:15) provided trans-N-protected-1-aryl-2-aminotetralins with high diastereoselectivity (dr > 95:5), which are important synthons for many artificial pharmaceuticals.     

Suppression of Photoinduced BBO Defects Generation on TiO2(110) by Water (cited: 1)

We have investigated creation of variable concentrations of defects on TiO₂(110)-(1×1) sur-face by 266 nm laser using temperature programmed desorption technique. Oxygen-vacancy defects can be easily induced by ultraviolet light, the defects concentration has a linear dependence on power density higher than 50 mW/cm² for 90 s irradiation. No observa-tion of O₂ molecule and Ti atom desorption suggests that UV induced defects creation on TiO₂(110)-(1×1) is an effective and gentle method. With pre-dosage of thin films of water,the rate of defects creation on TiO₂(110)-(1×1) is slower at least by two orders of magnitude than bare TiO₂(110)-(1×1) surface. Further investigations show that water can be moreeasily desorbed by UV light, and thus desorption of bridging oxygen is depressed.     

A simple and efficient synthesis of 2-substituted benzothiazoles catalyzed by H_2O_2/HC1

A simple and efficient procedure for the synthesis of substituted benzothiazoles through condensation of 2-aminothiophenol with aromatic aldehydes in the presence of H₂O₂/HCl system in ethanol at room temperature is described. The target compounds have been characterized by ¹H NMR, ¹³C NMR, IR and MS. Short reaction time, easy and quick isolation of the products, and excellent yields are the main advantages of this procedure.     

Suppression of the Charge Density Wave State in Two‐Dimensional 1T‐TiSe2 by Atmospheric Oxidation

Two‐dimensional (2D) metallic transition‐metal dichalcogenides (TMDCs), such as 1T ‐TiSe₂, have recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T ‐TiSe₂ undergoes rapid oxidation under ambient conditions, significantly affecting its CDW phase‐transition behavior. We comprehensively investigate the oxidation process of 2D TiSe₂ by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique selenium‐assisting oxidation mechanism. Our findings facilitate a better understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers, and thus open a way to further explore the functionality of these materials toward devices.     

Recombinant Human Annexin A5 Alleviated Traumatic-Brain-Injury Induced Intestinal Injury by Regulating the Nrf2/HO-1/HMGB1 Pathway

Aims: Annexin A5 (ANXA5) exhibited potent antithrombotic, antiapoptotic, and anti-inflammatory properties in a previous study. The role of ANXA5 in traumatic brain injury (TBI)-induced intestinal injury is not fully known. Main methods: Recombinant human ANXA5 (50 µg/kg) or vehicle (PBS) was administered to mice via the tail vein 30 min after TBI. Mouse intestine tissue was gathered for hematoxylin and eosin staining 0.5 d, 1 d, 2 d, and 7 d after modeling. Intestinal Western blotting, immunofluorescence, TdT-mediated dUTP nick-end labeling staining, and enzyme-linked immunosorbent assays were performed 2 days after TBI. A series of kits were used to assess lipid peroxide indicators such as malonaldehyde, superoxide dismutase activity, and catalase activity. Key findings: ANXA5 treatment improved the TBI-induced intestinal mucosa injury at different timepoints and significantly increased the body weight. It significantly reduced apoptosis and matrix metalloproteinase-9 and inhibited the degradation of tight-junction-associated protein in the small intestine. ANXA5 treatment improved intestinal inflammation by regulating inflammation-associated factors. It also mitigated the lipid peroxidation products 4-HNE, 8-OHDG, and malonaldehyde, and enhanced the activity of the antioxidant enzymes, superoxide dismutase and catalase. Lastly, ANXA5 significantly enhanced nuclear factor E2-related factor 2 (Nrf2) and hemeoxygenase-1, and decreased high mobility group box 1 (HMGB1). Significance: Collectively, the results suggest that ANXA5 inhibits TBI-induced intestinal injury by restraining oxidative stress and inflammatory responses. The mechanisms involved sparking the Nrf2/hemeoxygenase-1-induced antioxidant system and suppressing the HMGB1 pathway. ANXA5 may be an attractive therapeutic candidate for protecting against TBI-induced intestinal injury.     

Synthesis of C2-functionalized pyrimidines from 3,4-dihydropyrimidin-2(1H)-ones by the Mitsunobu coupling reaction

The Biginelli 3,4-dihydropyrimidin-2(1H)-one was converted to various C2-multifunctionalized pyrimidines via the dehydrogenation and Mitsunobu reaction using amines, alcohols, phenols and carboxylic acids as nucleophiles. A possible mechanism was also proposed to rationalize the formation of products.     

Stark shift of the A2Pi(1/2) state in 174YbF

We have measured the Stark shift of the A2Pi(1/2)-X2Sigma+ transition in YbF. We use a molecular beam triple resonance method, with two laser transitions acting as pump and probe, assisted by an rf transition that tags a single hyperfine transition of the X state. After subtracting the known ground state Stark shift, we obtain a value of 70.3(1.5) Hz/(V/cm)2 for the static electric polarizability of the state A2Pi(1/2) (J=1/2),f by fitting our data to a purely quadratic Stark shift in the interval 0-5 kV/cm. A more exact analysis that does not assume a perfectly quadratic Stark effect yields the value mu(e)=2.48(3) D for the electric dipole moment of the A2Pi(1/2)(v=0) state.     

A further test of the shape and anisotropy of the F---H2 interaction potential

A recently proposed anisotropic potential model for the interaction of a fluorine atom with a hydrogen molecule treated as a rigid rotor analysed by carrying out exact quantum calculations of elastic and rotationally inelastic differential cross sections for comparison with previoully reported F---H₂ and newly measured F---D₂ state selected measurements. The sensitivity of the cross sections to changes of the potential anisotropy and to isotopic substitution is examined. The results provide specific indications on the features of the best potential energy surface in terms of its average ‘size’ and its most likely anisotropy responsible for inelastic rotational excitations occuring at collision energies of about 85 meV.     

A facile synthesis of structurally novel 1-aryl-2-arylamino-4-alkyl/phenyl-5-aroyl-1H-imidazoles from amidinothioureas

We report here a convenient and efficient two-step synthesis of 1-aryl-2-arylamino-4-alkyl/phenyl-5-aroyl-1H-imidazoles from easily available amidinothioureas. Guanylation of amidinothioureas 1 using mercury(II) chloride as a thiophile yielded amidinoguanidines 2, which reacted with various phenacyl bromides under mild conditions to afford the corresponding diversely functionalized imidazoles 3 in moderate to good yields.     

Partition of rose bengal anion from aqueous medium into a lipophilic environment in the cell envelope of Salmonella typhimurium: implications for cell-type targeting in photodynamic therapy

Photodynamic therapy employs photosensitizers for the selective destruction of tumor tissue while sparing the surrounding healthy tissue. Photosensitization may also be applied to the selective eradication of microorganisms. Photosensitized inactivation requires that the sensitizer bind to the target and therefore the factors that determine photosensitizer binding are critical to photosensitization selectivity. This paper reports the determination of some features of the binding site of the potent photosensitizer, Rose Bengal, in Salmonella bacteria and describes some of the factors that affect this binding. The shift in the wavelength of maximum fluorescence and experiments with the fluorescence quencher TNBS indicate that Rose Bengal is located in a non-aqueous compartment such as the outer membrane. The dye does not seem to significantly accumulate inside the cell, but rather to accumulate in the outer membrane. Time-dependent changes in sensitizer localization in two strains of Salmonella typhimurium that differ in cell wall formation, LT-2 and TA1975, correspond to their differences in susceptibility to photosensitized killing. Therefore these results provide clues to the factors that determine photosensitization selectivity. Understanding this phenomenon is essential for the efficient design of selective photosensitizers and for optimizing antitumor and antiviral photodynamic therapy.