HYDROGEN PEROXIDE INDUCED RESISTANCE TO BROAD-SPECTRUM NEAR-ULTRAVIOLET LIGHT(300–400 nm) INACTIVATION IN Escherichia coli

Abstract— Strains of Escherichia coli carrying the four possible combinations of the alleles nur, nur⁺, uvrAb, and uvrA ⁺ were either untreated or pretreated with a sublethal dose of H₂0₂ prior to inactivation with NUV radiation. Pretreated cells exhibited a greater resistance to NUV than did untreated cells. Pretreatment with H₂O₂ did not induce resistance to FUV radiation. The induction of resistance to NUV inactivation by H₂O₂ pretreatment apparently leads to protection against the damage caused by NUV radiation. Although pretreatment of cells with H₂0₂ leads to resistance of such cells to inactivation by H₂O₂ and NUV, survival of H₂O₂ treated bacteriophage PI cml clr100 is not enhanced when assayed on H₂O₂ pretreated E. coli host cells.     

One-electron oxidation of the iron(II) complex of 1,10-phenanthroline-5,6-quinone A pulse radiolysis study

One-electron oxidation of the ferrous tris-PQ complex, a model for lipoxygenase, was attempted using oxidants such as •OH, N^•₃, Br^•-₂, Tl²⁺ and TlOH⁺. •OH was found to react with the complex with a bimolecular rate constant of (3.9±0.6)x10⁹dm³mol^-1s^-1, a rate which is not very dissimilar to that for the reaction with the ligand PQ. However the product of the reaction was found to be a OH-adduct rather than a cation radical. No reaction was found to occur with N^•₃ or Br^•-₂. Both Tl²⁺ and TlOH⁺ reacted with the complex to form its oxidised species with rate constants of (7.0±1)x10⁸dm³mol^-1s^-1 and (4.0±0.8)x10⁸dm³mol^-1s^-1, respectively. From a comparison of the rate constants and the transient spectra it was concluded that the centre of oxidation is the ligand rather than the metal.     

负载型Pd-Cu催化剂的制备及富氢气氛下CO优先氧化性能

分别以Al₂O₃, SiO₂和C₃N₄为载体, 通过简单浸渍法制备了3种负载型Pd-Cu催化剂(PC-Al₂O₃, PC-SiO₂, PC-C₃N₄), 考察了其在室温下富氢气氛中CO优先氧化反应性能. 采用X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 氮气物理吸附仪(N₂-physisorption)、 氢气程序升温还原(H₂-TPR)、 二氧化碳程序升温脱附(CO₂-TPD)、 X射线光电子能谱(XPS)和原位漫反射傅里叶变换红外光谱(In situ DRIFTS)等手段对其进行了表征. 结果表明, 与PC-SiO₂和PC-C₃N₄相比, PC-Al₂O₃具有更高的CO优先氧化性能. 这是由于PC-Al₂O₃上形成了大量与Pd物种具有强相互作用的Cu₂Cl(OH)₃物种; 而PC-SiO₂中仅有少量的Cu₂Cl(OH)₃, 且与Pd物种相互作用较弱; PC-C₃N₄中Cu物种则更易与C₃N₄基质配位, 由此削弱了Pd, Cu之间的相互作用. 在反应气氛下PC-Al₂O₃表面还易形成具有更强CO活化能力的Pd⁺物种, 通过与大量Cu⁺物种紧密相互作用, 在一定程度上抑制Pd⁺被过度还原为Pd⁰, 从而维持了其催化活性. 与SiO₂和C₃N₄相比, Al₂O₃更适合负载Pd-Cu用于富氢气氛下CO优先氧化反应.     

TUMOR IMAGING WITH [111niIn]MONO-DTPA-ETHYLENEGLYCOL-Ga-DEUTEROPORPHYRIN

Abstract Mono-DPTA-ethyleneglycol-Ga-deuteroporphyrin (MDEGD) was synthesized, by coordinating non-radioactive Ga in the porphyrin ring and connecting DTPA (diethylene-triamine-N,N,N,N,N,-pentaacetic acid) to its side chain. By labeling with 111_In, chemicals for scintigraphy were developed. They were applied to Syrian golden hamsters with implanted pancreatic gland cancers and C57-black mice with Lewis lung cancer to enable tumor imaging and biodistribution examination. A comparative study was also conducted with [⁶⁷Ga]citrate. In the resultant data, [¹¹¹In]MDEGD showed larger tumor/lung, tumor/kidney and tumor/blood ratio with [⁶⁷Ga]citrate. The affinity of [ⁿIn]MDEGD in inflammatory tissue was much lower than that of ⁶⁷Ga citrate. [¹¹¹In]MDEGD lost its photosensitivity.     

Regulating the Oxygen Affinity of Single Atom Catalysts by Dual-atom Design for Enhanced Oxygen Reduction Reaction Activity

This work chooses Cu/Fe single-atom catalysts(SACs) with weak/strong oxygen affinity to clarify the effect of dual-atom configuration on oxygen reduction reaction(ORR) performance based on density functional theory(DFT) calculations. The stability and ORR activity of single or dual Cu/Fe atomic sites anchored on nitrogen-doped graphene sheets(Cu-N₄-C, Cu₂-N₆-C, Fe-N₄-C, and Fe₂-N₆-C) are investigated, and the results indicate the dual-atom catalysts(Cu₂-N₆-C and Fe₂-N₆-C) are thermodynamically stable enough to avoid sintering and aggregation. Compared with single-atom active sites of Cu-N₄-C, which show weak oxygen affinity and poor ORR performance with a limiting potential of 0.58 V, the dual-Cu active sites of Cu₂-N₆-C exhibit enhanced ORR activity with a limiting potential up to 0.87 V due to strengthened oxygen affinity. Interestingly, for Fe SACs with strong oxygen affinity, the DFT results show that the dual-Fe sites stabilize the two OH^* ligands structure[Fe₂(OH)₂-N₆-C], which act as the active sites during ORR process, resulting in greatly improved ORR performance with a limiting potential of 0.90 V. This study suggests that the dual-atom design is a potential strategy to improve the ORR performance of SACs, in which the activity of the single atom active sites is limited with weak or strong oxygen affinity.     

Preparation and reactions of some sterically hindered silanols, including [tris(trimethylsilyl)methyl]silanetriol

The silanol TsiSiMe₂OH (Tsi = (Me₃Si)₃C) has been made by hydrolysis of the iodide TsiSiMe₂I in H₂O/dioxane or H₂O/Me₂SO. It has been shown to react with some acid chlorides RCOCl (R=Me, Et, CICH₂ Ph, 4-O₂NC₆H₄, and 3,5- (O₂N)₂C₆H₃) and anhydrides (RCO)₂O (R = Me, CF₃, or Ph) to give the carboxylates TsiSiMe₂OCOR, and with SO₂Cl₂ to give TsiSiMe₂OSO₂Cl. The triol TsiSi(OH)₃ has been made by treatment of TsiSiH(OH)I with H₂O/Me₂SO at 150°C or with a mixture of aqueous AgClO₄ and an organic solvent. The triol has been shown to react with RCOCl (R = Me, Et, or Ph) or (RCO)₂O (R = Ph) to give the corresponding TsiSi(OCOR)₃, with (CF₃CO)₂O to give TsiSi(OH)₂(OCOCF₃), and with a mixture of Me₃SiCl and AgClO₄ in benzene or one of Me₃Sil and (Me₃Si)NH to give TsiSi(OSiMe₃)₃. The triol is unusually stable, but decomposes at its m.p. of 285–290°C.     

Reactions of the sterically hindered organosilicon diol (Me3Si)2C(SiMe2OH)2 and some of its derivatives

The diol R₂C(SiMe₂OH)₂ (R = Me₃Si) has been shown to react with: SO₂Cl₂ to give R₂ Me₂; SOCl₂ to give R₂C(SiMe₂Cl)₂; Me₃SiI or Me₃SiCl to give R₂C(SiMe₂OSiMe₃)₂; R′COCl; (R′ = Me or CF₃) to give R₂C(SiMe₂O₂CR′)-(SiMe₂Cl); (R′CO)₂O (R′ = Me or CF₃ to give R₂C(SiMe₂O₂CR′)₂; with MeOH containing acid to give R₂C(SiMe₂OMe)₂; with neutral MeOH to give R₂C-(SiMe₂OMe)₂ and probably R₂ Me₂; MeLi to give R₂C(SiMe₂OLi)₂ (and the latter to react with PhMeSiF₂ to give R₂ Me₂). The diacetate R₂C(SiMe₂O₂CMe)₂ reacts with CsF in MeCN to give R₂C(SiMe₂F)₂; it does not react with NaN₃ or KSCN in MeCN, but the bis(trifluoroacetate) reacts with these salts with KOCN to give R₂C(SiMe₂X)₂ (X = N₃, NCS, NCO).     

ON THE PRODUCTION OF NITROXIDE RADICALS BY SINGLET OXYGEN REACTION: AN EPR STUDY

Abstract— The production of free radicals by reaction of 2,2,6,6-tetramethyl-4-piperidinol with singlet oxygen was studied by EPR spectroscopy. The rate constant of the amine was found to be equal to 8 ×10⁵ M ^-1s^-1 in ethanol and to 4 × 10⁷M^-1s^-1 in phosphate buffer (pH 8). Competition experiments were performed with singlet oxygen quenchers such as NaN₃, DABCO and the quenching rate constants were found to be consistent with the literature values. The EPR method proved to be a valuable technique to study the reaction of singlet O₂ with the sterically hindered amine without any interfering effect.     

Estimating the limiting reducing power of SmI2/H2O/amine and YbI2/H2O/amine by efficient reduction of unsaturated hydrocarbons

The mixture of samarium diiodide, amine, and water (SmI2/H2O/Et3N) is known to be a particularly powerful reductant, but until now the limiting reducing power has not been determined. A series of unsaturated hydrocarbons with varying half-wave reduction potentials (E(1/2) = -1.6 to -3.4 V, vs SCE) have been treated with SmI2/H2O/Et3N and YbI2/H2O/Et3N, respectively. All hydrocarbons with potentials of -2.8 V or more positive were readily reduced with SmI2/H2O/Et3N, whereas all hydrocarbons with potentials of -2.3 V or more positive were readily reduced using YbI2/H2O/Et3N. This defines limiting values of the chemical reducing power of SmI2/H2O/Et3N to -2.8 V and of YbI2/H2O/Et3N to -2.3 V vs SCE.     

Macroporous composite capacitive bioanode applied in microbial fuel cells

Interfacial electron transfer between electroactive biofilm and the electrode was crucial step for microbial fuel cells(MFCs).A three-dimensional multilayer porous sponge coating with nitrogen-doped carbon nanotube/polyaniline/manganese dioxide(S/N-CNT/PANI/MnO2)electrode has been developed for MFC anode.Here,the S/N-CNT/PANI/MnO2 anode can function as a biocapacitor,able to store electrons generated from the degradation of organic substrate under the open circuit state and release the accumulated electrons upon requirement.Thus,the mismatching of the production and demand of the electricity can be overcome.Comparing with the sponge/nitrogen-doped carbon nanotube(S/N-CNT)bioanode,S/N-CNT/PANI/MnO2 capacitive bioanode displays a strong interaction with the microbial biofilm,advancing the electron transfer from exoelectrogens to the bioanode.The maximum power density of MFC with S/N-CNT/PANI/MnO2 capacitive bioanode is 1019.5 mW/m^2,which is 2.2 and5.8 times as much as that of S/N-CNT/MnO2 bioanode and S/N-CNT bioanode(470.7 mW/m^2 and176.6 mW/m^2),respectively.During the chronoamperometric experiment with 60 min of charging and 20 min of discharging,the S/N-CNT/PANI/MnO2 capacitive bioanode was able to store 10743.9 C/m^2,whereas the S/N-CNT anode was only able to store 3323.4 C/m^2.With a capacitive bioanode,it is possible to use the MFC simultaneously for production and storage of electricity.     

Origins of the differences in solvation by alkanes and perfluoroalkanes Evidence from the S2-S0 spectra of jet-cooled van der Waals complexes of xanthione and azulene

The S₂-S₀ fluorescence excitation spectra ofxanthione (XT) and azulene (AZ) complexed with 1 or 2 molecules of the C₁ to C₁₀ n-alkanes and the C₁ to C₆ perfluoro-n-alkanes have been measured. The 1:1 complexes exhibit microscopic solvent shifts, Δ gn, which are larger for the alkanes than the corresponding perfluoroalkanes, despite the larger molecular polarizability of the latter. The values of Δ gn increase monotonically with carbon number of the adduct to C₁₀ in 1:1 n-alkane complexes with XT and to C₅ in 1:1 n-alkane complexes with AZ. However, Δ gn exhibits no further increase beyond C₂ in 1:1 perfluoro-n-alkane complexes with XT and beyond C₃ in 1:1 perfluoro-n-alkane complexes with AZ. The results are interpreted in terms of a model in which the n-alkanes stretch out along the long axis of the chromophore and ‘wet’ its surface whereas the perfluoro-n-alkanes with carbon numbers 3 away from the surface of the chromophore and are ‘non-wetting’.     

Preparation, crystal structure, and reactivity of bis {tris(trimethylsilyl) methyl} magnesium

Heating of the lithium magnesate [Li(THF)₂(μ-Br)₂Mg(Tsi)(THF)] (Tsi = (Me₃Si)₃C) under vacuum gives the dialkylmagnesium compound Mg(Tsi)₂, the first two-coordinate magnesium derivative to have been structurally characterized in the solid state. The compound is remarkably thermally stable, not decomposing (or melting) when heated to 350°C. It has a very low reactivity, failing to react in toluene with, for example, CO₂, Me₃SiCl, Me₂SiHCl, MeI, BCl₃ or CH₃COCl, and even with neat CH₃COCl at its boiling point. It does react, though fairly slowly, with I₂ in toluene to give TsiI, and more rapidly with Br₂ to give TsiBr, and with an excess of PhSO₂Cl in toluene at 1OO°C to give TsiCl. It decomposes quickly in the air, and reacts readily with MeOH in toluene to give TsiH without formation of detectable amounts of the intermediate TsiMgOMe, and with O₂ in toluene.     

神木半焦粉末萃取物的组成特征

依次用石油醚、CS₂、CH₂Cl₂、丙酮和甲醇在索氏萃取器中萃取了神木半焦粉末,得到了五级萃取物(E_1-5)和最终的萃余物,总萃取率为1.76%。分别用气相色谱/质谱联用仪(GC/MS)、大气压固体探针/飞行时间质谱仪(ASAP/TOF-MS)和电喷雾电离/飞行时间质谱仪(ESI/TOF-MS)分析了各级萃取物。用GC/MS分析的结果表明,在E₁中C_15-24的直链烷烃和E₂中3与4环的芳烃比较丰富,在E_3-5中含杂原子有机化合物较丰富,特别是E₄和E₅中含氧有机化合物的含量最高。与用GC/MS分析的结果相比,用ASAP/TOF-MS和ESI/TOF-MS从E_3-5中检测出更多的含杂原子有机化合物。     

Ab initio molecular orbital study of Fe2Cl6 and FeAlCl6

Ab initio molecular orbital theory was used to determine the equilibrium structure and vibrational frequencies of Fe₂Cl₆ and FeAlCl₆. The equilibrium structure the Fe₂Cl₆ dimer has D_2h symmetry with a planar arrangement of the four membered {FeCl_brFeCl_br} ring, similar to the Al₂Cl₆ dimer. The calculated bond distances and vibrational frequencies are in good agreement with experiment. The potential energy surface for the puckering of the {FeCl_brFeCl_br} ring is extremely flat. This prevents an unambiguous assignment of either D_2h or C_2v symmetry to the Fe₂Cl₆ structure in electron diffraction measurements. The FeAlCl₆ molecule is found to have a C_2v structure similar to Fe₂Cl₆ with vibrational frequencies in good agreement with experiment.     

Profiles of ethylene polymerization with zirconocene–trialkylaluminum/borane compound

Ethylene polymerization was conducted with bis(cyclopentadienyl)zirconium dichloride (1) and rac-dimethylsilylenebis(indenyl)zirconium dichloride (2) combined with trialkylaluminum (AlR₃; R=methyl (Me), ethyl (Et), isobutyl (iBu))/triphenylcarbenium tetrakis(pentafluorophenyl)borate (Ph₃CB(C₆F₅)₄) or tris(pentafluorophenyl)borane (B(C₆F₅)₃) to study the effect of cocatalysts on polymerization rate (R_p). When AlMe₃ was used, no activity or very low activity was observed with both zirconocenes regardless of the borane compounds used. The replacement of AlMe₃ to AlEt₃ or AliBu₃ with 1–AlR₃/Ph₃CB(C₆F₅)₄ caused polymerization and induction time was observed to reach the maximum R_p. Especially in the case of using AlEt₃, it took about 30 min to show the activity. When B(C₆F₅)₃ was used, AlEt₃ was not effective but AliBu₃ gave the highest activity among all the combinations of AlR₃ and the borane compounds. In the case of polymerization with 2 using Ph₃CB(C₆F₅)₄, high activity was observed with both AlEt₃ and AliBu₃ without any induction period. When B(C₆F₅)₃ was used instead of Ph₃CB(C₆F₅)₄, very low activity was observed with AlEt₃. On the other hand, high activity was observed with AliBu₃, and the maximum R_p was found at the beginning of the polymerization. The effect of AlR₃ on the formation of active species was discussed based on these results.     

BIOLUMINESCENCE FROM THE REACTION OF FMN, H2O2 AND LONG CHAIN ALDEHYDE WITH BACTERIAL LUCIFERASE

Abstract— The bioluminescent oxidation of reduced flavin mononucleotide by bacterial luciferase involves a long-lived flavoenzyme intermediate whose chromophore has been postulated to be the 4a-sub-stituted peroxy anion of reduced flavin. Reaction of long chain aldehyde with this intermediate results in light emission and formation of the corresponding acid. These experiments show that the typical aldehyde-dependent, luciferase-catalyzed bioluminescence can also be obtained starting with FMN and H₂O₂ instead of FMNH₂ and O₂. We postulate that the 4a-peroxy anion intermediate is formed directly by attack of H₂O₂ on FMN. The latter may be bound to luciferase. An enzyme bound intermediate is formed which by kinetic analysis, flavin specificity for luminescence, aldehyde dependence, and bioluminescent emission spectrum appears to be identical with the species generated by reaction of FMNH, and O₂ with luciferase. The quantum yield of the H₂O₂-_- and FMN-initiated biolumlnescence is low but can be enhanced by certain metal ions, which also stimulate a chemiluminescent reaction of oxidized flavin with H₂O₂. The peak of this chemiluminescence. however, appears to be at a shorter wavelength than that (490 nm) of the bioluminescence.     

Anion recognition with porphyrin-bottomed tetraurea receptors

Three tetraurea-appended porphyrin-derived anion receptors were synthesized and were found to efficiently encapsulate various anions with high association constants of up to 1.1×10⁸ L/mol.     

[C_2mim][Ala]丙氨酸离子液体水溶液粘滞流动的活化参数

在288.15-328.15 K温度范围内,测量了不同浓度的氨基酸离子液体[C_2mim][Ala]水溶液的密度和粘度,根据J ones-Dole方程得到了较大正值的粘度B系数并且dB/dT0。借助Feakins理论,计算了溶质对溶液粘滞流动活化自由能贡献Δμ_2~(≠0),根据Δμ_2~(≠0)随温度的线性变化,进而得到流动活化熵ΔS_2~(≠0)和活化焓ΔH_2~(≠0);在E yring液体粘度的过渡态理论基础上,提出了预测离子液体[C_2mim][Ala]水溶液粘度的半经验新方法,其预测值与相应的实验值很好的一致。     

SINGLET OXYGEN FORMATION BY SENSITIZATION OF FUROCOUMARINS COMPLEXED WITH, OR BOUND COVALENTLY TO DNA

Abstract— The formation of singlet molecular oxygen (¹O₂) by sensitization of the furocoumarins 5-methoxypsoralen (5-MOP), 8-methoxypsoralen (8-MOP) and psoralen complexed with DNA was investigated. From the results it is concluded that 5-MOP complexed with native DNA is able to generate ¹O₂, even in a larger extent than 5-MOP free in solution. Also, with 8-MOP and especially with psoralen, ¹O₂ formation by the complexed compound could be observed. The ¹O₂ formation sensitized by covalently bound furocoumarin was demonstrated with psoralen as a model compound. 4',5'-Dihydropsoralen, a model compound for the UVA light absorbing 4',5'monoadducts of furocoumarins to DNA, is also able to generate ¹O₂.     

Vesicle size and stability of biomimetic liposomes from 3'-sulfo-Lewis a (SuLea) containing glycolipids

We report on the use of a natural Lewis type saccharide ligand, 3′-sulfo-Lewis a (SuLe^a) for glycocalyx-mimetic surface modification of liposomes. Two SuLe^a-containing glycolipids, monovalent SuLe^a-lipid and trivalent SuLe^a (TSuLe^a)-lipid, were synthesized, and used with 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol to prepare unilaminar vesicles (ULVs) by a freeze–thaw and extrusion method. The effects of the glycolipid concentrations and the pore sizes of extrusion membranes on vesicle size and stability were investigated by photon correlation spectroscopy (PCS). Glycoliposomes, with 5% SuLe^a- or TSuLe^a-lipids obtained by 50 nm extrusion, had 25–30% more vesicles less than 100 nm in diameter compared with the 100 nm extrusion. TSuLe^a-liposomes always produced larger vesicle size than SuLe^a-liposomes, which we attribute to the larger TSuLe^a headgroup. Both SuLe^a- and TSuLe^a-liposomes increased their vesicle size with increasing glycolipid concentration from 5% to 15%, and demonstrated good stability at room temperature for over 1 month. Further increasing the glycolipid concentration to 20% resulted in large vesicle aggregation after 5 days for TSuLe^a-liposomes, while the SuLe^a-liposomes remained stable for 10 days. SuLe^a- and TSuLe^a-liposomes with 15% glycolipids demonstrated better stability due to the electrostatic effect from the negatively charged SuLe^a and TSuLe^a headgroups. The results indicate that the biomimetic liposomes with SuLe^a- and TSuLe^a-lipids with 5 to 15% incorporation are sufficiently stable for the potential applications in targeted drug delivery.