Ryo Murakami

A-102395, a New Inhibitor of Bacterial Translocase I, Produced by Amycolatopsis sp. SANK 60206

Bacterial phospho-N-acetylmuramyl-pentapeptide translocase (translocase I: EC 2.7.8.13) is a key enzyme in peptidoglycan biosynthesis, and a known target of antibiotics. Here we report a new nucleoside inhibitor for translocase I, A-102395, isolated from the culture broth of the strain Amycolatopsis sp. SANK 60206. A-102395 is a new derivative of capuramycin that has the benzene with a uniquely substituted chain instead of an aminocaprolactam. A-102395 is a potent inhibitor of bacterial translocase I with IC50 value of 11 nM, but possesses no antimicrobial activity against various strains tested.

A-94964, a novel inhibitor of bacterial translocase I, produced by Streptomyces sp. SANK 60404. I. Taxonomy, isolation and biological activity.

Bacterial phospho-N-acetylmuramyl-pentapeptide translocase (translocase I: EC 2.7.8.13) is a key enzyme in peptidoglycan biosynthesis, and a known target of antibiotics. Here we report a novel nucleoside inhibitor against translocase I, A-94964, isolated from the culture broth of the strain Streptomyces sp. SANK 60404. A-94964 inhibited bacterial translocase I with IC50 value of 1.1 μg/ml, and showed antimicrobial activities against Staphylococcus aureus and Enterococcus faecalis with MIC of 100 and 50 μg/ml, respectively. A-94964 did not show cytotoxicity against mammalian cell lines.

Ammocidins B, C and D, new cytotoxic 20-membered macrolides from Saccharothrix sp. AJ9571

Ammocidins B, C and D were isolated from the culture broth of Saccharothrix sp. AJ9571, an ammocidin A-producing strain. Their structures were determined by a detailed spectroscopic analysis and by a comparison of their NMR data with those of ammocidin A. Ammocidins A and B showed potent anti-proliferative activities against human cancer cell lines.

Mechanical diagnosis of human erythrocytes by ultra-high speed manipulation unraveled critical time window for global cytoskeletal remodeling

Large deformability of erythrocytes in microvasculature is a prerequisite to realize smooth circulation. We develop a novel tool for the three-step “Catch-Load-Launch” manipulation of a human erythrocyte based on an ultra-high speed position control by a microfluidic “robotic pump”. Quantification of the erythrocyte shape recovery as a function of loading time uncovered the critical time window for the transition between fast and slow recoveries. The comparison with erythrocytes under depletion of adenosine triphosphate revealed that the cytoskeletal remodeling over a whole cell occurs in 3 orders of magnitude longer timescale than the local dissociation-reassociation of a single spectrin node. Finally, we modeled septic conditions by incubating erythrocytes with endotoxin, and found that the exposure to endotoxin results in a significant delay in the characteristic transition time for cytoskeletal remodeling. The high speed manipulation of erythrocytes with a robotic pump technique allows for high throughput mechanical diagnosis of blood-related diseases.

Ion-Specific Modulation of Interfacial Interaction Potentials between Solid Substrates and Cell-Sized Particles Mediated via Zwitterionic, Super-Hydrophilic Poly(sulfobetaine) Brushes

Zwitterionic polymer brushes draw increasing attention not only because of their superhydrophilic, self-cleaning capability but also due to their excellent antifouling capacity. We investigated the ion-specific modulation of the interfacial interaction potential via densely packed, uniform poly(sulfobetaine) brushes. The vertical Brownian motion of a cell-sized latex particle was monitored by microinterferometry, yielding the effective interfacial interaction potentials V(Δh) and the autocorrelation function of height fluctuation. The potential curvature V″(Δh) exhibited a monotonic increase according to the increase in monovalent salt concentrations, implying the sharpening of the potential confinement. An opposite tendency was observed in CaCl2 solutions, suggesting that the ion specific modulation cannot be explained by the classical Hofmeister series. When the particle fluctuation was monitored in the presence of free sulfobetaine molecules, the increase in [sulfobetaine] resulted in a distinct increase in hydrodynamic friction. This was never observed in all the other salt solutions, suggesting the interference of zwitterionic pairing of sulfobetaine side chains by the intercalation of sulfobetaine molecules into the brush layer. Furthermore, poly(sulfobetaine) brushes exhibited a very low V″(Δh) and hydrodynamic friction to human erythrocytes, which seems to explain the excellent blood repellency of zwitterionic polymer materials.

Catch, load and launch toward on-chip active cell evaluation

An automatic system for evaluating single cell viscoelasticity is proposed and tested in this paper. The system includes three main operations, and they are the operations of catch, load and launch. In the catch operation, the system is capable of capturing a target cell by high-speed vision and high-frequency flow control. The captured cell is pushed into a narrow constriction for the load operation. Different durations of loading time are applied to cells for evaluating cell viscoelasticity. Finally, the cell is launched out from the constriction, and the recovery response of the cell is monitored for cell characterization. Human red blood cells are experimentally tested by the proposed system. The experimental results show that the system successfully perform the evaluation, and the viscoelastic characteristics of the cells are discussed.

SMK-17, a MEK1/2-specific inhibitor, selectively induces apoptosis in β-catenin-mutated tumors

Although clinical studies have evaluated several MEK1/2 inhibitors, it is unlikely that MEK1/2 inhibitors will be studied clinically. BRAF mutations have been proposed as a responder marker of MEK1/2 inhibitors in a preclinical study. However, current clinical approaches focusing on BRAF mutations have shown only moderate sensitivity of MEK1/2 inhibitors. This has led to insufficient support for their promoted clinical adoption. Further characterization of tumors sensitive to MEK inhibitors holds great promise for optimizing drug therapy for patients with these tumors. Here, we report that β-catenin mutations accelerate apoptosis induced by MEK1/2 inhibitor. SMK-17, a selective MEK1/2 inhibitor, induced apoptosis in tumor cell lines harboring β-catenin mutations at its effective concentration. To confirm that β-catenin mutations and mutant β-catenin-mediated TCF7L2 (also known as TCF4) transcriptional activity is a predictive marker of MEK inhibitors, we evaluated the effects of dominant-negative TCF7L2 and of active, mutated β-catenin on apoptosis induced by MEK inhibitor. Indeed, dominant-negative TCF7L2 reduced apoptosis induced by MEK inhibitor, whereas active, mutated β-catenin accelerated it. Our findings show that β-catenin mutations are an important responder biomarker for MEK1/2 inhibitors.

Wireless Full-Duplex Medium Access Control for Enhancing Energy Efficiency

Recent years have witnessed a proliferation of battery-powered mobile devices, e.g., smartphones, tablets, sensors, and laptops, leading to a significant demand for high capacity wireless communication with high energy efficiency. Among the technologies capable of such efficiency is full-duplex wireless communication, based on the simultaneous uplink and downlink data transmission with limited frequency resources. Previous studies on full-duplex wireless mostly focused on doubling the network capacity, whereas in this paper we discuss how full-duplex wireless can also increase the energy efficiency. We propose low-power communication by wireless full-duplexing (LPFD), taking advantage of the fact that in full-duplex the duration of communication is half that of half-duplex communication. In LPFD, by using the sleep state in which the transceiver in the wireless communication terminal is turned off, the power consumption of the wireless communication terminal is reduced, and the energy efficiency is improved.

An Energy Efficient MAC for Wireless Full Duplex Networks

Full-duplex (FD) wireless communication is a key technology for enhancing the capacity of next- generation wireless networks. Previous studies have investigated FD wireless communication medium access control (MAC) schemes to double the existing network capacity. However, energy consumption and power saving mode (PSM) in wireless FD infrastructure networks have not been discussed extensively. Current implementations of 802.11 wireless infrastructure local area networks (WLANs) support PSM to extend the battery life of energy-limited mobile devices. In this paper, we propose a MAC protocol that supports PSM for wireless FD networks (FDPSM). FDPSM enables PSM for both half- duplex(HD)-capable clients and FD-capable clients in FD WLANs with FD-enabled access points (APs) by supporting not only bidirectional FD communication but also two- directional FD communication. In addition, FDPSM does not require any change in frame designs from the IEEE 802.11 standard. Simulation results show that the proposed method achieves a higher bit per energy than conventional FD communication. Thus, the proposed method facilitates energy-efficient wireless communication. Moreover, the request to send/clear to send (RTS/CTS) mechanism enhances the bit per energy. Specifically, the bit per energy achieved by FDPSM with RTS/CTS (FDPSM+) is approximately 10 times higher than that achieved by FDPSM when the data rate is 54 [Mbps] and the number of clients is 10.

“Cell Pinball”: What is the physics?

During the deformability test of Red Blood Cell (RBC) by utilizing a micro fluidic channel, we found an interesting phenomenon where some RBCs behave just like elastic pinball with the motion in the perpendicular direction with respect to the main flow line, while most of RBCs simply move along the main flow line. This phenomenon is called “Cell Pinball”. Through visualization, we found that the RBC being in Cell Pinball mode rotates around the perpendicular axis to the flow line and the rotating direction has one-to-one relationship with the moving direction without any exceptions. We also found that the rotating axis exists slightly behind the center of gravity with respect to the flow direction. This geometrical configuration makes an unstable condition for the cell under the fluid force, which eventually produces the motion perpendicular to the main flow line.