Molecular beams and model catalysis: activity and selectivity of specific reaction centers on supported nanoparticles.

Reaction kinetics on nanometer-scale particles are different from those on extended surfaces of bulk materials. This fact has been utilized for a long time to empirically maximize the performance of heterogeneous catalysts, but the understanding of the underlying effects is poor at the microscopic level. Modern molecular beam-based methods, however, allow us to derive very detailed kinetic information on catalytically active surfaces. In combination with structurally highly controlled model catalysts, microscopic insights into the activity and selectivity of specific reaction centers on catalyst nanoparticles can be obtained. This combined approach is illustrated through simple model reactions.     

真空下X2 (X=Cl、Br)与AgOCN气-固反应机理

在真空条件下完成了X2 (X=Cl、Br)与AgOCN间的气-固异相反应，利用紫外光电子能谱（PES）仪，探测与确定反应产物是XNCO (X=Cl、Br)，并推断其可能为一过渡态反应，生成中间络合物，新键产生与旧键断裂同时进行.     

微量元素对人体健康的影响

阐述了微量元素的生理作用以及对人体健康的影响和微量元素平衡的重要性，对临床医学及日常生活有一定的参考价值。     

氧同位素交换及其在多相催化氧化反应研究中的应用

简单介绍了氧同位素交换技术及其在多相催化氧化反应机理研究中的应用     

On the stereochemistry of the Horner—Emmons reaction between 3-functionally substituted 2-methyl-2-propenylphosphonates and aliphatic aldehydes

The reaction of diethyl 3-ethoxycarbonyl-2-methyl-2-propenylphosphonate (1a) with 3-methylbutanal (2) in heterogeneous MOH (solid)-benzene systems in the presence of 5–10 mol.% of benzyltriethylammonium chloride (BTEAC) gives the reaction product (3) with a higher, for M=K, or lower, for M=Li, ratio of 2E,4E and 2Z,4E-stereoisomers than that observed in the absence of BTEAC. Tetrabutylammonium bromide (TBAB) as a catalyst of the reaction1a + 2 3 in the system KOH (solid)-wet benzene leads to a higher [2E,4E-3][2Z,4E-3] ratio than BTEAC; this ratio grows from 4456 without TBAB to 8020 at 100 mol.% of TBAB. In the latter case the stereochemical outcome of the reaction is similar to that obtained when tetrabutylammonium hydroxide in dry benzene is used as the deprotonating agent. The corresponding diisopropyl phosphonate (1b) and 3,7-dimethyloctanal (4a) interact in the system KOH (solid)-wet benzene-TBAB to give hydroprene (5) containing 88 % of the 2E,4E-isomer (5a) while in the case of 1 equiv. of [(n-Bu₄)N]OH in dry benzene the content of5a is 92 %. Diisopropyl 3-isopropoxycarbonyl-2-methyl-2-propenylphosphonate (1c) and 7-methoxy-3,7-dimethyloctanal (4b) under either of these conditions afford methoprene (6) containing 93 % of the 2E,4E-isomer.Part 6, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1094–1098, June, 1993.     

Comparative DSC study of human and bovine serum albumin

The thermal denaturation process of bovine and human both fatty acid containing and fatty acid free albumins in aqueous solution was studied by use of differential scanning calorimetry. Human serum albumins were found to be more stable than their bovine counterparts. Fatty acid free albumins were characterized as generally less stable, more susceptible to aggregation, their unfolding endothermic transition was less cooperative and with the smaller degree of reversibility. Deconvolution analysis with using a non-two-state model with two component transitions showed essential differences in the thermodynamic parameters between all studied albumins, particularly regarding the high-temperature component transition.     

High-level expression of soluble human β-defensin-2 fused with green fluorescent protein in Escherichia coli cell-free system

Human β-defensin-2 (hBD2), a small cationic peptide, exhibits a broad range of antimicrobial activity and does not acquire any microbial resistance. To produce this uneasily detectable, degradable, and toxic polypeptide efficiently, an alternative approach based on the Escherichia coli cell-free biosynthesis system was proposed. The approach implies that a polypeptide of interest is synthesized as a fusion protein linked to a green fluorescent protein (GFP) through a cleavable spacer. With batch-mode operation, a significant amount of hBD2 fused with GFP (0.25 mg/mL) can be expressed in this cell-free system. The productivity of the fusion protein can be improved up to 1.2 mg/mL by employing a continuous-exchange cell-free system. Furthermore, the GFP moiety provides directly visible and quantitative monitoring of the polypeptide synthesis, and the product is soluble and stable. This work will be helpful in allowing the rapid and visible expression of other similar defensins using an in vitro cell-free system.     

Selective alterations of the antibody response to HIV-1

HIV infection leads to progressive alterations of humoral immune functions, including B-cell hyperplasia, hypergammaglobulinemia, elevated autoantibody titers, a poor response to neoantigens and mitogens, polyclonal B-cell activation, monoclonal gammopathies, and a significant deterioration of the antigen-specific humoral response. There is also an important isotypic imbalance of the antibody (Ab) response in the systemic compartment and a profound modification of mucosal immune functions. These abnormalities may contribute to disease progression and development of opportunistic infections, despite the presence of serum-neutralizing anti-HIV Abs. Equally important are the abnormal selection mechanisms of the Ab repertoire that seem to be responsible for B-cell clonal deletions. The V_H3 gene family, which encodes for approx 50% of immunoglobulins expressed by peripheral B-cells from normal adults, is underrepresented in human monoclonal antibodies to HIV-1 and in the peripheral B-cells of AIDS patients. These abnormalities, together with features of germinal center alteration, could be responsible for the clonal elimination of a subset of B-cells, and could contribute to HIV pathogenesis.     

The use of Nafion-H® as an efficient catalyst for the direct conversion of primary and secondary trimethylsilyl ethers to their corresponding ethers under mild and heterogeneous conditions

Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence Nafion-H® with good to excellent yields under mild and heterogeneous conditions.     

Novel metathesis catalysts based on ruthenium 1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidenes: synthesis, structure, immobilization, and catalytic activity

The synthesis of novel ruthenium-based metathesis catalysts containing the saturated 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene ligand, that is, [RuCl2(NHC)[=CH-2-(2-PrO)-5-NO(2)-C6H3]] (1) and [Ru(CF3COO)2(NHC)[=CH-2-(2-PrO)-5-NO2-C6H3]] (2) (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) is described. Both catalysts are highly active in ring-closing metathesis (RCM) and ring-opening cross-metathesis (ROCM). Compound 1 shows moderate activity in enyne metathesis. Compound 2 is not applicable to enyne metathesis since it shows high activity in the cyclopolymerization of diethyl dipropargylmalonate (DEDPM). Poly(DEDPM) prepared by the action of 2 consists of 95% five-membered rings, that is, poly(cyclopent-1-enevinylene)s, and 5 % of six-membered rings, that is, poly(cyclohex-1-ene-3-methylidene)s. The polymerization proceeds in a nonliving manner and results in polyenes with broad polydispersities (1.9< or =PDI< or =2.3). Supported analogues of 2 were prepared by immobilization on hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization (ROMP). Catalyst loadings of 1 and 2.5%, respectively, were obtained. Both supported versions of 2 showed excellent reactivity. With 0.24-2% of the supported catalysts, yields in RCM and ROCM were in the range of 76-100%. Leaching of ruthenium was low and resulted in Ru contaminations of the products of less than 0.000014% (0.14 ppm).