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Illumination of PSII core preparations can cause the production of H2O2 at rates which approach 60 mumol of H2O2 (mg of Chl.h)-1. The rate of peroxide production is maximal at pH 7.2 at low sucrose concentrations and at concentrations of Cl- (1.5-3.0 mM) that limit the rate of the oxidation of water to O2. The rate of H2O2 production increased with pH from(More)
In tobacco seedlings (Nicotiana tabacum L.), glucose from supplied uridine diphosphate-[U-(14)C]glucose was first incorporated into steryl glycosides and later into acylated steryl glycosides. However, when [(14)C]cholesterol was used as substrate, the acylated steryl glycosides became labeled earlier than the steryl glycosides. With [(14)C]cholesteryl(More)
The Mg(2+) cofactor of the F(1)F(0) ATP synthase is required for the asymmetry of the catalytic sites that leads to the differences in affinity for nucleotides. Vanadyl (V(IV)=O)(2+) is a functional surrogate for Mg(2+) in the F(1)-ATPase. The (51)V-hyperfine parameters derived from EPR spectra of VO(2+) bound to specific sites on the enzyme provide a(More)
Although single-molecule experiments have provided mechanistic insight for several molecular motors, these approaches have proved difficult for membrane bound molecular motors like the F₀F₁-ATP synthase, in which proton transport across a membrane is used to synthesize ATP. Resolution of smaller steps in F₀ has been particularly hampered by signal-to-noise(More)
A novel method for detecting F(1)-ATPase rotation in a manner sufficiently sensitive to achieve acquisition rates with a time resolution of 2.5 micros (equivalent to 400,000 fps) is reported. This is sufficient for resolving the rate at which the gamma-subunit travels from one dwell state to another (transition time). Rotation is detected via a gold nanorod(More)
F1-ATPase, the catalytic complex of the ATP synthase, is a molecular motor that can consume ATP to drive rotation of the γ-subunit inside the ring of three αβ-subunit heterodimers in 120° power strokes. To elucidate the mechanism of ATPase-powered rotation, we determined the angular velocity as a function of rotational position from single-molecule data(More)
Increases in the power stroke and dwell durations of single molecules of Escherichia coli F(1)-ATPase were measured in response to viscous loads applied to the motor and inhibition of ATP hydrolysis. The load was varied using different sizes of gold nanorods attached to the rotating gamma subunit and/or by increasing the viscosity of the medium using(More)
We report the construction of a novel biosensing nanodevice to detect single, sequence-specific target DNA molecules. Nanodevice assembly occurs through the association of an immobilized F1-ATPase molecular motor and a functionalized gold nanorod via a single 3',5'-dibiotinylated DNA molecule. Target-dependent 3',5'-dibiotinylated DNA bridges form by(More)
Removal of the ability to form a salt bridge or hydrogen bonds between the beta subunit catch loop (beta Y297-D305) and the gamma subunit of Escherichia coli F1Fo-ATP synthase significantly altered the ability of the enzyme to hydrolyze ATP and the bacteria to grow via oxidative phosphorylation. Residues beta T304, beta D305, beta D302, gamma Q269, and(More)