Synergism in binary mixtures of Thermobifida fusca cellulases Cel6B,Cel9A,and Cel5A on BMCC and Avicel

In an earlier binding study conducted in our laboratory using Thermobifida fusca cellulases Cel6B, Cel9A, and Cel5A (formally Thermomonospora fusca E₃, E₄, and E₅), it was observed that binding capacities for these three cellulases were 18–30 times higher on BMCC than on Avicel. These results stimulated an interest in how the difference in accessibility between the two cellulosic substrates would affect synergism observed with cellulase mixtures. To explore the impact of substrate, accessibility on the extent of conversion and synergism, three binary T. fusca cellulase mixtures were tested over a range of cellulase ratios and total molar cellulase concentrations on Avicel and BMCC. Higher extents of conversion were observed for BMCC due to the higher enzyme to substrate ratio resulting from the higher binding The processive endoglucanase, Cel9A, had four times the extent of conversion of the end endocellulase Cel5A, while the exocellulase Cel6B had three times the extent of conversion of Cel5A. Approximately 500 nmol/g of the cel9A+Cel6B mixture was needed to obtain 80% conversion, while the Cel6B+Cel5A and Cel9A+Cel5A mixtures required 1500 and 1250 nmol/g, respectively, to obtain 80% conversion. Thus, it appears that the more accessible structure of BMCC, as reflected by its binding capacity, results in relative higher processive activity.     

氢化物发生—分光光度法测定染发剂中的微量铅

本文提出了用铁氰化钾将铅氧化至高价,再用氢化物发生-分光光度法测定铅的一种新方法。该法灵敏度高,简便快速,用于分析染发剂中的铅,取得了较好的效果。     

一种分离抗凝血酶Ⅲ的高效亲和色谱填料的制备及表征

以聚甲基丙烯酸环氧丙酯微球 ( PGMA)为基质 ,利用还原氨化方法将肝素键合在其表面上 ,得到一种以肝素为配基的高效亲和色谱填料 ,该填料对抗凝血酶 的亲和容量为 1 .2 mg/g,对抗凝血酶 和人血清白蛋白的回收率分别为 96.9%和 94 .4 % .利用前沿色谱法测定了肝素与抗凝血酶 之间的表观解离常数为 1 .96× 1 0 - 5mol/L.利用该填料可直接从人血浆中分离出抗凝血酶     

Oxidation of organophosphorus compounds—IV : Kinetics and mechanism of the oxidation of diarylphosphine oxides by t-butyl hydroperoxide,hydrogen peroxide and p-nitroperoxybenzoic acid in alkaline media

The influence of OH⁻ concentration, in the solvent medium dioxane-water 40:60 at 25·0, on the oxidation rates of diphenylphosphine oxide (DPPO) by t-BuOOH, H₂O₂ and p-nitroperoxybenzoic acid, and of bis-p-tolylphosphine oxide by t-BuOOH has been investigated. For the oxidation of the phosphorus substrates by the hydroperoxides above, the rate law found (R = k₂″[Ar₂PHO] [ROO⁻]) differs from the rate law confirmed to hold for the oxidation of DPPO by peroxyacids in alkaline media, i.e.: R = (k₂″ + k₃[OH−])[Ar₂PHO] [RCO₃⁻]. This is interpreted on the basis of one common reaction mechanism involving formation of an intermediate of similar structure, wherein a change in the rate controlling step is likely to occur on passing from p-O₂N·C₆H₄CO₃⁻ to t-BuOO⁻. In the same solvent medium, pK_a′ values for t-BuOOH and H₂O₂ have been estimated.     

Mechanism of silver-promoted ligand metathesis in square-planar complexes of d(8) Ions. Kinetics of formation and molecular structures of a trinuclear intermediate [(Me)(N-N)Pt(mu-Cl)Ag(mu-Cl)Pt(N-N)(Me)](+) and its dinuclear evolution product [(Me)(N-N)Pt(mu-Cl)Pt(N-N)(Me)](+) (N-N = ArN=C(Me)C(Me)=NAr,Ar = 2,6-(i-Pr)(2)C(6)H(3))

The silver-assisted ligand metathesis reaction involving a platinum(II) complex of formula [PtClMe(N,N-chelate)] with acetonitrile has been investigated. By using a suitably hindered N,N-chelate, an otherwise hardly detectable trinuclear species has been isolated and characterized through X-ray diffractometry. The trinuclear cation consists of two nearly orthogonal [PtCl(Me)(N,N-chelate)] square-planar units entrapping an Ag(+) cation through the chloride ligands that, acting as bidentate, form a linear AgCl(2) unit with two nonequivalent Ag-Cl bonds. The residual acidity of the silver cation is satisfied by one secondary Ag-Pt interaction [Ag-Pt(1) = 2.82 A] in which the platinum atom acts as a donor. Kinetic studies have demonstrated that the silver assistance operates both through a simple associative step and through a pathway in which the above trinuclear complex is an active intermediate. In a noncoordinating solvent the latter species evolves with AgCl loss and formation of a dinuclear Pt,Pt complex showing a rare single chloride bridge.     

New phosphite-oxazoline ligands for efficient Pd-catalyzed substitution reactions

We have designed and synthesized a new family of readily available highly modular phosphite-oxazoline ligands for the Pd-catalyzed asymmetric allylic substitution reactions. The introduction of a pi-acceptor flexible bulky biphenyl phosphite moiety in the ligand design is highly adventitious in the product outcome. Thus, this ligand series affords excellent reaction rates (TOF's up to >2400 mol.(mol.h)-1) and enantioselectivities (ee's up to >99%) and, at the same time, shows a broad scope for different substrate types.     

Asymmetric Synthesis of α-Substituted-γ-butyrolactone Empolying Prolinol Type of Auxiliaries

Eleven (S)-(-)-bishydrocarbyl-(l-alkanoylpyrrolidin-2_yl)_methanol derivatives of three types were synthesized from L-proline.asymmtncally selective alkylation products were obtained oy LDA treatment and alkylation using methyl 2-bromoethyl ether, and three types of chiral α-Substituted-γ-butyrolactones were obtained by hydrolyzing the alkylation products, with %e.e. beijing up to 89 percent.     

2,4,6-三硝基苯酚改性锆铝复合氧化物固定相分离富勒烯的色谱性能研究

制备了用于分离C60和C70的2，4，6－三硝基苯酚改性锆铝复合氧化物高效液相色谱固定相，考察了流动相中甲苯的含量、柱温及流速对C60和C70分离的影响，同时比较了酸腐蚀前后锆铝复合氧化物基质对分离的影响，结果表明，2，4，6－三硝基苯酚改性酸腐蚀后锆铝复合氧化物填料对富勒烯表现出较强的分离能力，具有作为富勒烯制备分离的潜力。     

Investigative proteomics: identification of an unknown plant virus from infected plants using mass spectrometry

We describe the identification of a previously uncharacterized plant virus that is capable of infecting Nicotiana spp. and Arabidopsis thaliana. Protein extracts were first prepared from leaf tissue of uninfected tobacco plants, and the proteins were visualized with two-dimensional electrophoresis (2-DE). Matching gels were then run using protein extracts of a tobacco plant infected with tobacco mosaic virus (TMV). After visual comparison, the proteins spots that were differentially expressed in infected plant tissues were cut from the gels and analyzed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Tandem mass spectrometry data of individual peptides was searched with SEQUEST. Using this approach we demonstrated a successful proof-of-concept experiment by identifying TMV proteins present in the total protein extract. The same procedure was then applied to tobacco plants infected with a laboratory viral isolate of unknown identity. Several of the differentially expressed protein spots were identified as proteins of potato virus X (PVX), thus successfully identifying the causative agent of the uncharacterized viral infection. We believe this demonstrates that HPLC-MS/MS can be used to successfully characterize unknown viruses in infected plants.