Electron transfer with myoglobin in free and strongly confined regimes: disclosing diverse mechanistic role of the Fe-coordinated water by temperature- and pressure-assisted voltammetric studies

The naturally occurring electron-transfer (ET) event for myoglobin (Mb) can be mimicked through its functionalization at diversely modified metal platforms to allow for the electron exchange either in freely diffusing or immobilized regimes. In this work, horse muscle Mb was involved in the electron exchange with Au electrodes modified by dissimilar, thin or thick alkanethiol SAMs, terminated either by unicomponent (–OH) or 1 : 1 mixed (–OH/–COOH) functional (externally exposed) entities, respectively. The systematic, temperature- and pressure-supported cyclic voltammetry studies perfectly confirmed certainty of two kinds of ET patterns for Mb, embodying: (a) different operational kinetic regimes (including protein’s freely diffusing and strongly confined motifs) and (b) different intrinsic physical mechanisms (including dynamically controlled and non-adiabatic modes). Our analysis of obtained and published data for Mb and the reference redox-active protein, cytochrome c, specified further the central mechanistic role of the Fe-(heme-)coordinated water whose displacement is directly coupled to ET, and can be, in turn, controlled by the conformational organization and intrinsic fluctuational mobility of the Mb macromolecule.     

Directing Role of Cage Structure for Crystallization of Zeolites

The directing mechanisms of liquid directing agents of zeolite Y and zeolite L were studied by means of light transmission, ultracentrifugation, NMR, XRD and “cross-exchange” experiments. It was discovered that not only microcfystals of zeolites, but also cage structures of zeolites play the directing role for crystallization of zeolites.     

The antioxidant role of α-tocopherol in polymers. I. The nature of transformation products of α-tocopherol formed during melt processing of LDPE

The antioxidant role of α-tocopherol (vitamin E) in low-density polyethylene (LDPE), and the nature of its transformation products formed during extrusion of the polymer are investigated. The melt stabilizing effectiveness of α-tocopherol was found to be very high, higher than that of the commercial hindered phenol antioxidants, Irganox 1076 and 1010, after single and multiple extrusion. The high antioxidant activity of α-tocopherol as a melt stabilizer is due, at least in part, to its transformation products. The importance of the processing history and the parent antioxidant concentration on the transformation products is discussed. Transformation products of α-tocopherol were analyzed after each of the four extrusion passes of the polymer. These were fractionated, analyzed, and characterized by HPLC and spectroscopy, respectively. The main products formed are diastereoisomers of dimers and trimers, as well as aldehydes; the relative concentration of each was shown to depend on processing severity (number of extrusion passes) and the initial concentration of α-tocopherol. The dihydroxydimer was found to be formed at a high concentration relative to the other products and proportional with the initial concentration of tocopherol. Based on both the identity and distribution of transformation products, a mechanism is proposed for the melt stabilization effect of α-tocopherol in LDPE. © 1994 John Wiley & Sons, Inc.     

Pt-Ga/HZSM-5催化剂上丙烷芳构化

考察了Ｐｔ／ＨＺＳＭ－５，Ｇａ／ＨＺＳＭ－５和Ｐｔ－Ｇａ／ＨＺＳＭ－５上的丙烷芳构化反应，其中Ｐｔ－Ｇａ／ＨＺＳＭ－５双组份催化剂上有较高的丙烷反应活性和芳烃选择性，用程序升温还原（ＴＰＲ）和Ｈ２化学吸附法表征催化剂，发现Ｐｔ与Ｇａ的协同相互作用促进了Ｇａ＾３＋的还原，使其峰温向低温移动的７０℃，且双组分催化剂中Ｐｔ的Ｈ２吸附性能大大降低，使催化剂表成乙烯加氢能力降低，从而提高了产物芳烃的选择性，     

Surface fine structure of hydrodesulfurization catalysts. New aspects of promoting effects of Co and Ni

By using the highpressure DRIFT, EXAFS, and TPDDRIFT methods, it is shown that the wellknown effects concerning Co–Mo/Al₂O₃ (i.e., promoting effect of Co or Ni, activating effect of catalyst presulfiding, and inhibiting effect of H₂S) are closely connected to each other. Some direct evidence of the interactions between Mo and Co on sulfided Co–Mo/Al₂O₃ is also shown.     

On the role of water in molecular recognition and self-assembly

The conventional concept of hydrophobic interaction is generalized to include any kind of solvent-induced effects on the binding of two or more solutes in aqueous solutions. Specifically, we focus on the role of hydrogen-bonding between the solutes and solvent molecules. A qualitative examination of the solute-solvent hydrogen-bonding effect on molecular recognition, self-assembly, and stabilization of biopolymers shows that these effects might be quite large and possible more important than direct interactions between solute particles.     

Initial steps in the reductive condensation of trichloromethylarenes with hydroxylamine and hydrazines in pyridine

Data concerning the initial steps in the reductive condensation of trichloromethylarenes with hydroxylamine or hydrazines in pyridine have been obtained. High yields of the products of the reductive condensation obtained even at equimolar ratios of trichloromethylarene with hydroxylamine or hydrazine as well as the formation of unusual products,i.e., 4-pyridylhydrazones of substituted benzaldehydes, have been interpreted as the result of the participation of pyridine in the reaction as a reductive agent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1928–1931, November, 1993     

Synthesis and Crystal Structure of 3-Phenyi- 6-（4-methylphenyi）-1,2,4-triazolo[4,3-b]-1,2,4-triazine

1 INTRODUCTION The fused heterocycles bearing 1,2,4-triazine have attracted considerable attention in recent years owing to their biological and pharmaceutical activi- ties[1～3]. The 1,2,4-triazine core is a versatile synthe- tic platform to access a wide range of condensed heterocyclic ring systems via inter- and intramolecu- lar Diels-Alder reaction with a vast array of dieno- philes[4～6]. IBD (iodobenzene diacetate) is commer- cially available and used as benign non-metallic oxidant…     

并流淤浆混合法制备铜基甲醇合成催化剂及助剂Al2O3的作用研究

采用并流淤浆混合法制备了一系列具有不同铜锌铝比的铜基甲醇合成催化剂CuO/ZnO/Al2O3，测试了其催化性能(甲醇收率和CO转化率)及物相结构，并对该制备方法进行评价。Cu∶Zn∶Al摩尔比为4∶5∶1 的铜基催化剂显示了最好的催化活性。通过对催化剂前驱物煅烧过程进行DTA分析及对前驱物进行XRD分析表明， 催化剂前驱物的物相与Al2O3的量有关。当Al2O3的量较低时，前驱物的物相以(Cu0.3 Zn0.7)5(CO3)2(OH)6为主；当Al2O3的量较高时，前驱物中物相(Cu0.3Zn0.7)5(CO3)2(OH)6的量下降，而物相Cu2CO3(OH)2的量增加。物相(Cu0.3 Zn0.7)5(CO3)2(OH)6对终态催化剂的活性是十分有利的 。     

Temperature-dependent behavior of immobilized alkaline phosphatase. I. Role of working conditions and pH during coupling

Alkaline phosphatase from hog intestine was immobilized to controlled-pore glass under various conditions. The specific activity of the enzyme was not diminished by immobilization. The influence of temperature and pH on the behavior and the stability of the immobilized enzyme preparations is discussed and compared to that of the native enzyme.