Comparison of the architecture around the active site of soybean ␤-amylase and Bacillus cereus ␤-amylase showed that the hydrogen bond networks (Glu 380 -(Lys 295 -Met 51 ) and Glu 380 -Asn 340 -Glu 178 ) in soybean ␤-amylase around the base catalytic residue, Glu 380 , seem to contribute to the lower pH optimum of soybean ␤-amylase. To convert the pH optimum of soybean ␤-amylase (pH 5.4) to that of the bacterial type enzyme (pH 6.7), three mutants of soybean ␤-amylase, M51T, E178Y, and N340T, were constructed such that the hydrogen bond networks were removed by site-directed mutagenesis. The kinetic analysis showed that the pH optimum of all mutants shifted dramatically to a neutral pH (range, from 5.4 to 6.0 -6.6). The K m values of the mutants were almost the same as that of soybean ␤-amylase except in the case of M51T, while the V max values of all mutants were low compared with that of soybean ␤-amylase. The crystal structure analysis of the wild typemaltose and mutant-maltose complexes showed that the direct hydrogen bond between Glu 380 and Asn 340 was completely disrupted in the mutants M51T, E178Y, and N340T. In the case of M51T, the hydrogen bond between Glu 380 and Lys 295 was also disrupted. These results indicated that the reduced pK a value of Glu 380 is stabilized by the hydrogen bond network and is responsible for the lower pH optimum of soybean ␤-amylase compared with that of the bacterial ␤-amylase.

Consecutive thermal and metal‐catalyzed dehydro‐Diels–Alder (DDA) reactions of sulfur‐tethered tetraynes, possessing a 1,3‐diyne moiety, proceeded efficiently, and axial chirality was achieved for the resulting dibenzothiophenyl moieties. Chiral‐rhodium catalysis realized a highly enantioselective synthesis, and transformations into bis(benzocarbazole) derivatives were also achieved.

Since the 2000s, large fluctuations in commodity prices have become a concern among policymakers regarding price stability. This paper investigates the effects of commodity price shocks on headline inflation with a monthly panel consisting of 144 countries. We find that the effects of commodity price shocks on inflation virtually disappear within about one year after the shock. While the effect on the level of consumer prices varies across countries, this transitory effect is fairly robust, suggesting a low risk of a persistent second-round effect on inflation. Employing the smooth transition autoregressive models that use past inflation as the transition variable, we also explore the possibility that the effect of commodity price shocks could be persistent, depending on inflation regimes. In this specification, commodity price shocks may not have transitory effects when a country's currency is pegged to the U.S. dollar. However, the effect remains transitory in countries with exchange-rate flexibility.

Silicon-tethered tetraynes with a 1,3-diyne moiety underwent consecutive hexadehydro- and tetradehydro-Diels–Alder reactions to give fused polycyclic aromatic compounds.

No abstract