间规1,2—聚丁二烯合成的实验室研究

报道了使用Ｃｏ－Ａｌ－Ｐ－Ｈ２Ｏ催化体系实验室合成间规１，２－取丁二烯的研究结果，详细讨论了催化组分的加料顺序，老化条件及聚合工艺条件对聚合反应的影响，在此基础上得到最佳工艺条件，进行了模试放大，所得聚合物的基本性能与ＪＳＲ ＲＢ８２０相近。     

Nitric oxide synthase in neuroepithelial brain tumors

Immunohistochemical investigation of NO-synthase in brain astrocytic tumors revealed intense reaction in many tumor cells as well as direct correlation in the intensity of reaction and the degree of tumor anaplasia. Grade I astrocytomas did not show immunoreactivity in contrast to high anaplastic tumors where many cells had positive reaction with a different degree of intensity. Positive immunoreaction was shown in many giant cells. Small cell glioblastomas and oligodendrogliomas were immunonegative. There was a direct correlation between NO-synthase expression and glial fibrillar acidic protein.     

Protein structure alignment by incremental combinatorial extension (CE) of the optimal path

A new algorithm is reported which builds an alignment between two protein structures. The algorithm involves a combinatorial extension (CE) of an alignment path defined by aligned fragment pairs (AFPs) rather than the more conventional techniques using dynamic programming and Monte Carlo optimization. AFPs, as the name suggests, are pairs of fragments, one from each protein, which confer structure similarity. AFPs are based on local geometry, rather than global features such as orientation of secondary structures and overall topology. Combinations of AFPs that represent possible continuous alignment paths are selectively extended or discarded thereby leading to a single optimal alignment. The algorithm is fast and accurate in finding an optimal structure alignment and hence suitable for database scanning and detailed analysis of large protein families. The method has been tested and compared with results from Dali and VAST using a representative sample of similar structures. Several new structural similarities not detected by these other methods are reported. Specific one-on-one alignments and searches against all structures as found in the Protein Data Bank (PDB) can be performed via the Web at http://cl.sdsc.edu/ce.html.      

Adsorption of haematoporphyrins on the planar bilayer membrane

Adsorption of haematoporphyrin derivatives with different hydrophobicities of peripheral groups on a planar bilayer lipid membrane (BLM) was studied in the dark and upon illumination by the visible light. Haematoporphyrin molecules were shown to adsorb on the BLM as anions. The adsorption changed the boundary potential at the membrane/water interface, in particular, it altered the potential in the diffuse part of the double layer outside the membrane and increased an additional unscreenable potential drop inside it. Illumination decreased the value of the negative potential drop due probably to the appearance of a positive charge in the haematoporphyrin macrocycle. The adsorption of haematoporphyrins affected the BLM conductivity induced by different ionophores, which can be explained by changes in membrane structure. Haematoporphyrin derivatives with higher hydrophobicities adsorbed deeper inside the membrane, caused greater changes in its structure and displayed a stronger photodynamic effect.     

Power conditioner control and protection for distributed generators and storage

This paper describes an integrated control and protection scheme for the power conditioner used by the medium rating grid-connected distributed generators and storage devices. The proposed control scheme consists of two loops: a steady-state loop that achieves optimum harmonic output by selective elimination of low-order harmonics and a transient loop based on space vector methods that enhances the transient response of the generator and provides overcurrent protection and fault rejection. The paper presents simulation studies of a grid-connected storage device equipped with a controller based on the proposed scheme. The results of these studies demonstrate the robustness of the controller to varying line conditions and disturbances.     

The theta rhythm of the infant EEG and the development of the mechanisms of voluntary control of attention in the 2nd half of the first year of life

The neurophysiological basis of attention control was studied in infants at the second half-year of life, i.e. in the period when the capability for voluntary control over behavior fundamentally improves. EEG was recorded in 60 infants aed 8-11 months in three experimental conditions: 1) attention to an object in the visual field (externally controlled attention, or the baseline state), 2) anticipation of a person in the peek-a-boo game (internally controlled attention), 3) attention to the reappeared person in the peek-a-boo game (control condition). The spectral analysis of the EEG data revealed a sharp increase in the EEG theta (3.6-6.0 Hz) during internally controlled attention as compared to the baseline and control conditions. The theta1 (3.6-4.8 Hz) increase was maximal in the frontal derivations. The reactivity of the frontal theta1 during internally controlled attention discriminated infants with different abilities to maintain this type of attention. The reactivity of the theta2 (5.2-6.0 Hz) was maximal in the right temporal derivation (T6) and did not depend on stability of the anticipatory attention. The findings point to different functional significance of the theta1 and theta2 rhythms in infants. It is suggested that synchronization of the frontal theta1 rhythm in infants reflects the activity of the anterior attention system which realizes the executive attention control. The ability to maintain anticipatory attention increased with age, whereas the frontal theta1 synchronization decreased and totally disappeared at the age of 11 months. At the age of 8 months there was a positive correlation between the frontal theta1 synchronization and behavioral index of stability of the internally controlled attention. On the contrary, this correlation was negative at the age of 9 and 10 months. It is suggested that the age-dependent dynamics of the relationship between the frontal theta1 reactivity and attention reflects a leap in maturation of the anterior attention system resulting in its more economic and efficient functioning.     

Effects of mutations in the starch-binding domain of Bacillus macerans cyclodextrin glycosyltransferase

Cyclodextrin glycosyltransferase (CGTase) is an industrially important enzyme that produces cyclodextrins (CD) from starch by intramolecular transglycosylation. CGTase consists of five globular domains labeled A through E. To better understand the role of domain E in CGTase catalysis, we have constructed several mutants of Bacillus macerans CGTase. Removing the entire E domain resulted in an inactive enzyme. Adding six amino acids between domains D and E caused a decrease in activity and thermostability. Replacing domain E with the similar starch-binding domain from Aspergillus awamori glucoamylase I caused a drastic decrease in activity, indicating the necessity of correct alignment of bound substrate. Substituting tyrosine residue 634 (Tyr634) with phenylalanine had very little effect on activity or thermostability. Substituting Tyr634 with glycine resulted in a 25% increase of specific cyclization and starch-hydrolyzing activities compared with that of the wild-type enzyme. The latter mutant was less thermostable. The results of this study indicate that domain E is important for the stability and integrity of B. macerans CGTase.