“
“With Lewis Acids as catalysts in melt system, the influence of kinds of Lewis Acids, dosages of catalysts on the behaviors of crosslinking and grafting of ethylene-propylene-diene rubber (EPDM) were investigated. The Lewis Acids, such as anhydrous AlCl(3), FeCl(3), SnCl(4), could initiate the crosslinking of EPDM and the grafting between EPDM and polystyrene (PS). The carbon-carbon double bonds

existing on EPDM chain were favorable to the formation of the initial carbocation in the presence of Lewis Acids. The carbocation initiated carbonium ion polymerization between the unsaturated bonds, or substituted for a proton from the phenyl in the presence of PS forming EPDM-g-PS copolymer. Anhydrous aluminum chloride was found to be an efficient catalyst and its initiating temperatures GSK1120212 for crosslinking or grafting were about 110 degrees C. The amounts of gel and the data of torques showed QNZ that there was a competition between the crosslinking-grafting reaction and the degradation of blending components in the presence of AlCl(3). The EPDM-g-PS copolymer served as a compatibilizer in the EPDM/PS blends and enhanced the mechanical properties. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2961-2967, 2011″
“Functionally analogous enzymes are those that catalyze similar

reactions on similar substrates but do not share common ancestry, providing a window on the different structural strategies nature has used to evolve required catalysts. Identification and use of this information to improve reaction classification and computational annotation of enzymes newly discovered in the genome

projects would benefit from systematic determination of reaction similarities. Here, we quantified similarity CBL0137 in bond changes for overall reactions and catalytic mechanisms for 95 pairs of functionally analogous enzymes (non-homologous enzymes with identical first three numbers of their EC codes) from the MACiE database. Similarity of overall reactions was computed by comparing the sets of bond changes in the transformations from substrates to products. For similarity of mechanisms, sets of bond changes occurring in each mechanistic step were compared; these similarities were then used to guide global and local alignments of mechanistic steps. Using this metric, only 44% of pairs of functionally analogous enzymes in the dataset had significantly similar overall reactions. For these enzymes, convergence to the same mechanism occurred in 33% of cases, with most pairs having at least one identical mechanistic step. Using our metric, overall reaction similarity serves as an upper bound for mechanistic similarity in functional analogs. For example, the four carbon-oxygen lyases acting on phosphates (EC 4.2.3) show neither significant overall reaction similarity nor significant mechanistic similarity. By contrast, the three carboxylic-ester hydrolases (EC 3.1.