A molecular level mechanism ofn-butane oxidation to maleic anhydride over vanadyl pyrophosphate

A molecular level mechanism is proposed for the highly selective 14-e^– oxidative transformation ofn-butane to maleic anhydride on the surface of vanadyl pyrophosphate. The mechanism suggests that the dimeric active sites assume at any given time, one of four possible interconvertible states which differ from each other in the number of available oxygen atoms and the formal oxidation states of the individual vanadium atoms. The relative ratios of active sites in each of the four possible states are dictated by the reaction conditions, the redox properties of the reacting gases and the structure of the vanadyl pyrophosphate active surface. A crucial feature of the mechanism is a pseudo-ozonide surface species formed by the interaction of a chemisorbed dioxygen molecule and an adjacent metal-oxo group. This unusual species is responsible for the initial activation of then-butane, which occurs when the chemisorbed dioxygen abstracts an H-atom from the alkane and the adjacent metal-oxo group reacts with the incipient alkyl radical to form an alkoxy group. The proposed mechanism is entirely consistent with literature reports describing the behaviour of (VO)₂P₂O₇ in flow, pulse and TAP reactors.     

Bioactive IL7-diphtheria fusion toxin secreted by mammalian cells

A number of targeted cytotoxic agents have been developed that selectively kill malignant or otherwise pathological cells. These engineered proteins consist of a potent cytotoxic element connected to a ligand domain that binds to specific molecules on the surface of the target cell. Several of these agents have shown promise in clinical trials and one is currently administered to patients. A significant technical obstacle that has impeded the development of some of these toxins is the difficulty of preparing certain recombinant proteins in properly folded forms. These fusion proteins have generally been produced in bacteria requiring them to be denatured and renatured in vitro. For some proteins this is an efficient process whereas for others it is not. We describe here a system to produce fusion toxins rapidly and efficiently by engineering mammalian cells to secrete them as properly folded molecules which can be purified in native form from cell culture medium. We have used this system to produce highly active preparations of DAB(389)-IL7, a molecule consisting of the catalytic and transmembrane domains of diphtheria toxin fused to interleukin 7. This system is generalizable and can be used to produce and evaluate rapidly fusion toxins incorporating novel or uncharacterized ligands.     

Sub-ambient cold-start emissions reduction using SwRI® PO x catalyst technology

This paper describes the application of SwRI’s cold-start PO _x catalyst technology to reduce cold-start hydrocarbon emissions from a US Tier 2 vehicle at −7 °C. A reduction in −7 °C (20 °F) cold-start hydrocarbons will help US Tier 2 vehicles meet the proposed EPA NMOG standards. Improvements in cold temperature hydrocarbon emissions would also be beneficial in many parts of Europe during the winter months. In this work, a total hydrocarbon reduction of 19% was realized at 24 °C, in line with previous results, but only up to 3% at −7 °C. Insufficient oxygen in the engine-out exhaust gas at −7 °C was determined to be the reason why the PO _x catalyst failed to significantly reduce HC emissions. Addition of supplemental oxygen to the exhaust during the cold-start, to simulate an adjustment in the engine calibration to less rich operation, resulted in a total hydrocarbon reduction of 18% with the PO _x catalysts in place, but no benefit when the PO _x catalysts were removed. Hence, the PO _x catalyst approach can be used to good effect, even under sub-ambient cold-start conditions.     

在线红外检测仪在头孢噻肟酸合成中的应用

利用在线红外检测仪ReactIRTM4000在线监测以7-氨基头孢烷酸(7-ACA)与2-甲氧亚氨基-2-(2-氨基-4-噻唑基)-硫代乙酸苯并噻唑酯(MEAM)为原料,用二甲基乙酰胺(DMA)作催化剂,一步合成头孢噻肟酸的实验过程,主要考察了反应时间对反应的影响。在最佳反应条件下(催化剂用量、反应物用量、结晶pH已经优化)头孢噻肟酸的合成摩尔收率超过98%。     

硝基-3-氧-3，4-二氢-2H-[1，4]苯并噁嗪-6-羧酸的合成

以4-羟基-3-硝基苯甲酸为原料,经酯化、醚化、还原合环、硝化、水解等5步反应,合成了两个未见文献报导的化合物7-硝基-3-氧-3,4-二氢-2H-[1,4]苯并噁嗪-6-羧酸和8-硝基-3-氧-3,4-二氢-2H-[1,4]苯并嗪-6-羧酸,其结构经IR、LC/MS、1HNMR和元素分析确证。     

6,7-二氢-6-甲基-3-甲硫基吡喃[4,3-c]吡唑-4-(2H)-酮衍生物的合成及生物活性

6-甲基-5,6-二氢吡喃-2,4-二酮和二硫化碳、碘甲烷缩合得到5,6-二氢吡喃-2,4-二酮的二硫缩醛化合物,然后和取代肼反应得到1位取代和2位取代6,7-二氢-6-甲基-3-甲硫基吡喃[4,3-c]吡唑-4-(2H)-酮衍生物。其化学结构通过单晶X衍射、1HNMR、13CNMR、元素分析证实。生物活性测试结果初步表明,该类化合物表现出一定的杀菌和对前列腺癌细胞PC3的抑制活性。     

Hydrothermal synthesis of flaky crystallized La2Ti2O7 for producing hydrogen from photocatalytic water splitting

Flaky monoclinic La₂Ti₂O₇ was prepared via a hydrothermal method based on the reaction of Ti(SO₄)₂ and La(NO₃)₃. Relative to the solid-state reaction sample, the flaky La₂Ti₂O₇ showed higher surface areas, much smaller crystal size and more efficient light absorption. All these factors led to the higher photoactivity to produce H₂ from water splitting under UV irradiation.     

Nanocomposite route to the stabilization of porous ϑ-alumina

Stabilization of -alumina phase by silica was studied in nanocomposite (diphasic) alumina-silica gels by XRD and BET surface areas measurements. Five wt.% of silica (22 nm particles) increased the crystallization temperature of to -alumina by about 100°C from boehmite (10 nm particles) derived alumina. Stabilization of -alumina was caused by the formation of intimate contact (Al-O-Si) between components by diffusion of silica into the defect alumina structure.Also with the Department of Agronomy.     

Allelopathic Effects of Volatile Monoterpenoids Produced by <Emphasis Type="Italic">Salvia leucophylla</Emphasis>: Inhibition of Cell Proliferation and DNA Synthesis in the Root Apical Meristem of <Emphasis Type="Italic">Brassica campestris</Emphasis> Seedlings

Salvia leucophylla, a shrub observed in coastal south California, produces several volatile monoterpenoids (camphor, 1,8-cineole, -pinene, -pinene, and camphene) that potentially act as allelochemicals. The effects of these were examined using Brassica campestris as the test plant. Camphor, 1,8-cineole, and -pinene inhibited germination of B. campestris seeds at high concentrations, whereas -pinene and camphene did not. Root growth was inhibited by all five monoterpenoids in a dose-dependent manner, but hypocotyl growth was largely unaffected. The monoterpenoids did not alter the sizes of matured cells in either hypocotyls or roots, indicating that cell expansion is relatively insensitive to these compounds. They did not decrease the mitotic index in the shoot apical region, but specifically lowered mitotic index in the root apical meristem. Moreover, morphological and biochemical analyses on the incorporation of 5-bromo-2-deoxyuridine into DNA demonstrated that the monoterpenoids inhibit both cell-nuclear and organelle DNA synthesis in the root apical meristem. These results suggest that the monoterpenoids produced by S. leucophylla could interfere with the growth of other plants in its vicinity through inhibition of cell proliferation in the root apical meristem.     

Prediction of DNA-binding regulatory proteins in bacteriophage T7

The high-resolution structure of several specific DNA-bindingproteins have been determined, and they display a common structuralmotif which mediates their binding to DNA. This motif consistsof two -helices connected by a sharp turn, and its amino acidsequence has several distinguishing features. A computer searchof the proteins coded by the genome of bacteriophage T7 hasbeen performed in an attempt to identify those proteins thatpotentially contain this motif. Eight proteins were found tohave regions similar to that of the motif. Of these, three arerelatively small, have no known function and are good candidatesfor being DNA-binding regulatory proteins. The methods describeduse commonly available computer programs and databases, andare therefore easy to implement.