J-KEM's Vacuum Regulator
NO Mercury 100% Stainless steel ^ "*"
Regulate any piece of equipment to ± 1 torr using a high vacuum pump
^ *
Recover > 98% of any solvent from rotary evaporators.
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'Rotary' catalysis of ATP imaged Researchers in Japan have imaged the ro tation of the catalytic domain of ATP syn thase, the enzyme that synthesizes aden osine triphosphate. In doing so, they have validated previous suggestions that the enzyme operates via "rotary" cataly sis [Nature, 386, 299 (1997)]. The domain contains a hexamer of al ternating a- and β-subunits that surround a single γ-subunit. Indirect evidence sup ported the notion that, during catalysis, the γ-subunit rotates within a stationary hexamer to interact sequentially with cata lytic sites on the β-subunits. ATP synthase comprises a transmem brane, proton-conducting domain (FQ) con-
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J-KEM's Digital Vacuum Regulator is ideally suited for use with rotary evaporators or other laboratory equipment. Place the regulator between the vacuum pump and the evaporator for bumpless removal of solvent.
Digital Temperature Control Actin filament attached to the y-subun'rt of immobilized ATP synthase catalytic domain rotates counterclockwise in the presence of ATP. Reprinted by permission from Nature, Vol. 386, 1997.
± 0.1 ° C regulation of any volume or piece of equipment. 1
DUAL Temperature Controller
Control 2 reactions at different temperatures with 1 controller Specializing in custom and safety controllers
Data Acquisition System Collect Data on 96 separate channels 24-Bit accuracy (0.1 PPM resolution)
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nected to a catalytic domain (Fj). In the presence of a proton gradient, the Fj do main catalyzes ATP synthesis. Isolated F1 do mains, however, hydrolyze ATP. Thus, the isolated domains have served as model sys tems for studying the enzyme's catalytic mechanism. The Japanese team, led by Masasuke Yoshida at Tokyo Institute of Technology, Yokohama, engineered Ft domains con taining β-subunits with decapeptide histidine "tails." They anchored them to a glass plate coated with a reagent that binds histidine. The γ-subunits were engineered to at tach afluorescentlylabeled actin filament. Using fluorescence microscopy, the re searchers watched the filaments rotate counterclockwise in the presence of ATP, powered by the ATP hydrolysis reaction. In an accompanying commentary, Steven M. Block, a professor of molecular biology at Princeton University, says the achievement "adds to a burgeoning array of motility assays that are revolutionizing the study of macromolecular machines." Mairin Brennan
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MARCH 31, 1997 C&EN 27
