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MotA and MotB form the stator of the proton-driven bacterial flagellar motor, which conducts protons and couples proton flow with motor rotation. Asp-33 of Salmonella enterica serovar Typhimurium MotB, which is a putative proton-binding site, is critical for torque generation. However, the mechanism of energy coupling remains unknown. Here, we carried out genetic and motility analysis of a slowly motile motB(D33E) mutant and its pseudorevertants. We first confirmed that the poor motility of the motB(D33E) mutant is due to neither protein instability, mislocalization, nor impaired interaction with MotA. We isolated 17 pseudorevertants and identified the suppressor mutations in the transmembrane helices TM2 and TM3 of MotA and in TM and the periplasmic domain of MotB. The stall torque produced by the motB(D33E) mutant motor was about half of the wild-type level, while those for the pseudorevertants were recovered nearly to the wild-type levels. However, the high-speed rotations of the motors under low-load conditions were still significantly impaired, suggesting that the rate of proton translocation is still severely limited at high speed. These results suggest that the second-site mutations recover a torque generation step involving stator-rotor interactions coupled with protonation/deprotonation of Glu-33 but not maximum proton conductivity.

Research has been conducted on the optically active propargylic alcohols. The reaction of the alpha-carbanion derived from 2-(trimethylsilyl)vinyl sulfoxides with aldehydes has been investigated and the results indicate that it produces diastereomeric product mixture.

New and excellent carbonyl-face selective reactions of 2-formyl- and 2-acylnaphthalenes bearing the bulky (2,3,6-triisopropylphenyl)sulfinyl group, which can be performed without isolation of the disastereomeric rotamers are described. The removal of the sulfinyl group from the products would provide a convenient and efficient method for preparation of the optically active 2-naphthylalkanols.

Results reveal that p-tolyl alpha-lithio-beta-(trimethylsilyl)ethyl sulfoxide is a powerful chiral vinyl anion that is useful in the preparation of new chiral centers. Further, the p-tolyl alpha-lithio-beta-(trimethylsilyl)ethyl sulfoxide reacts with alpha,beta-unsaturated esters to form optically pure homoallylic carboxylates.

Research has been conducted on the reactions of alpha-sulfinyl carbanions with electrophiles. High stereoselectivity of the syn products of the reaction is discussed.

The bacterial flagellar motor accommodates ten stator units around the rotor to produce large torque at high load. But when external load is low, some previous studies showed that a single stator unit can spin the rotor at the maximum speed, suggesting that the maximum speed does not depend on the number of active stator units, whereas others reported that the speed is also dependent on the stator number. To clarify these two controversial observations, much more precise measurements of motor rotation would be required at external load as close to zero as possible. Here, we constructed a Salmonella filament‐less mutant that produces a rigid, straight, twice longer hook to efficiently label a 60 nm gold particle and analyzed flagellar motor dynamics at low load close to zero. The maximum motor speed was about 400 Hz. Large speed fluctuations and long pausing events were frequently observed, and they were suppressed by either over‐expression of the MotAB stator complex or increase in the external load, suggesting that the number of active stator units in the motor largely fluctuates near zero load. We conclude that the lifetime of the active stator unit becomes much shorter when the motor operates near zero load. [ABSTRACT FROM AUTHOR]

The enantioselective reaction of alpha-seleno carbanions derived from bis(phenylseleno)acetal and bis-(2-pyridylseleno)acetal in the presence of bis(oxazoline)s with various electrophiles gave products with high enantioselectivity. Mechanistic investigation reveals that the enantiodetermination of the reactions at -78 degree Celsius depends on dynamic thermodynamic resolution.

The study conducted to examine the enantioselective reaction of various alpha-lithiated dithioacetals with aldehydes or a ketone in the presence of bis(oxaline)s, is presented. With various aldehydes, an enantioselective reaction of a variety of lithiated dithioacetals is reported.

A peripherally substituted or unsubstituted phthalocyanines, having variety of metals is described by using a convenient synthesis. A novel synthesis of phthalocyanines directly from phtalimides and phthalic anhydride, by the action of hexamethyldisilazane (HMDS) under mild conditions, is reported.

Research has been conducted on p-tolyl 2-(trimethylsilyl)ethyl sulfoxide's alpha-carbanion. The reaction of this carbanion with esters and the following reduction with diisobutylaluminum hydride which produces highly stereoselective alpha-(trimethylsilyl)methyl-beta-ketosulfoxide is described.