Hiroyuki Noji

We present a novel device employing one million femtoliter droplets immobilized on a substrate for the quantitative detection of extremely low concentrations of biomolecules in a sample. Surface-modified polystyrene beads carrying either zero or a single biomolecule-reporter enzyme complex are efficiently isolated into femtoliter droplets formed on hydrophilic-in-hydrophobic surfaces. Using a conventional micropipette, this is achieved by sequential injection first with an aqueous solution conta

adenosine 5′-(β,γ-imino)- triphosphate piconewtons dicyclohexylcarbodiimide ATP synthase, a major ATP supplier in the cell, is a rotary machine found next to the bacterial flagella motor in the biological world. This enzyme is composed of two motors, F0 and F1, connected by a common rotor shaft to exchange the energy of proton translocation and ATP synthesis/hydrolysis through mechanical rotation. Rotation of the isolated F1 motor driven by ATP hydrolysis was directly observed with an optical mi

The enzyme assay in a femtoliter chamber array is a simple and efficient method for concentrating the reaction product; it greatly improves the detection sensitivity down to the single-molecule level. However, in previous methods, controlling the initiation and termination of the reaction in each chamber is difficult once enclosed. Furthermore, the recovery of the enzyme and product is also difficult. To overcome these drawbacks, we developed a femtoliter droplet array in which the individual dr

The epsilon subunit of bacterial FoF1-ATP synthase (FoF1), a rotary motor protein, is known to inhibit the ATP hydrolysis reaction of this enzyme. The inhibitory effect is modulated by the conformation of the C-terminal alpha-helices of epsilon, and the "extended" but not "hairpin-folded" state is responsible for inhibition. Although the inhibition of ATP hydrolysis by the C-terminal domain of epsilon has been extensively studied, the effect on ATP synthesis is not fully understood. In this stud