Antimicrobial activity of rhodomyrtone isolated from Rhodomyrtus tomentosa (Aiton) Hassk

Abstract

Rhodomyrtone was isolated from the leaves of Rhodomyrtus tomentosa (Aiton) Hassk grown in Vietnam using chromatographic methods. Its chemical structure was confirmed by means of spectroscopic data analysis. The pH drop measurement, enzyme activity assays and fluorescence stain were used to examine rhodomyrtone anticaries activity. It was found that rhodomyrtone suppressed acid production by Streptococcus mutans, a major cariogenic agent in human by inhibiting enzyme activities responsible for acid production and tolerance, including membrane bound enzymes F-ATPase and phosphotransferase system (PTS), as well as glycolysis enzymes glyceraldehyphosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) in cytoplasm with the IC₅₀ values of 24?μM, 19?μM, 23?μM and 28?μM, respectively. Moreover, 50?μM rhodomyrtone reduced biofilm biomass formed by S. mutans up to 59% (p?<?0.05). Fluorescent images indicated that cells on the biofilms were significantly killed. Thus, rhodomyrtone is a new and potential anticaries agent against S. mutans.     

Copper(I)-catalyzed cycloaddition of silver acetylides and azides: incorporation of volatile acetylenes into the triazole core

Silver acetylides and organic azides react under copper(I) catalysis to afford 1,4-disubstituted 1,2,3-triazoles. Mechanistic studies implicate a process involving transmetallation to copper acetylides prior to cycloaddition. This work demonstrates that silver acetylides serve as suitable precursors for entry into copper-mediated coupling reactions. This methodology allows the incorporation of volatile and difficult-to-handle acetylenes into the triazole core.     

Power allocation policy and performance analysis of secure and reliable communication in cognitive radio networks

Wireless Networks - This paper investigates the problem of secure and reliable communications for cognitive radio networks. More specifically, we consider a single input multiple output cognitive...     

Beam polarization effects on top-pair production at the ILC

Full one-loop electroweak corrections for an \(e^-e^+\rightarrow t \bar{t}\) process associated with sequential \(t\rightarrow b \mu \nu _\mu \) decay are discussed. At the one-loop level, the spin-polarization effects of the initial electron and positron beams are included in the total and differential cross sections. A narrow-width approximation is used to treat the top-quark production and decay while including full spin correlations between them. We observed that the radiative corrections due to the weak interaction have a large polarization dependence on both the total and the differential cross sections. Therefore, experimental observables that depend on angular distributions such as the forward–backward asymmetry of the top-production angle must be treated carefully including radiative corrections. We also observed that the energy distribution of bottom quarks is largely affected by the radiative corrections.     

Highest efficiency, linear X-band performance using InP DHBTs - 48%PAE at 30 dB C/IM3

InP single heterojunction bipolar transistors have previously demonstrated 5-10 dB lower third-order intermodulation products (IM3) compared to GaAs heterojunction bipolar transistors (HBTs) under low voltage (2 V) operation. This paper reports excellent single-tone and two-tone X-band operation, including high two-tone power-added efficiency (PAE), on linear InP double heterojunction bipolar transistors (DHBTs) operated at V_ce=4 V. The InP DHBT demonstrated a 30 dB carrier to third-order intermodulation product (C/IM3) output power ratio simultaneously with 48% two-tone PAE. This is the highest known efficiency of an X-band device under linear (30 dB C/IM3) operation. This is especially significant for microwave power amplifiers for satellite communication transmitters, where lower intermodulation distortion is normally accomplished by backing off in RF drive and output power, thus sacrificing PAE performance     

Sensitized Photochemical CO2 Reduction by Hetero-Pacman Compounds Linking a ReI Tricarbonyl with a Porphyrin Unit

The hetero-Pacman architecture places two different metal coordination sites in close proximity, which can support efficient energy and/or electron transfer and allow for cooperative activation of small molecules. Here, the synthesis of dyads consisting of a porphyrin unit as photosensitizer and a rhenium unit as catalytically active site, which are held together by the rigid xanthene backbone, is presented. Mononuclear [(NN)Re(CO)₃(Cl)] complexes for CO₂ reduction in which NN represents a bidentate diimine ligand (e.g., bipyridine or phenanthroline) lack light absorption in the visible region, resulting in poor photocatalysis upon illumination with visible light. To improve their visible-light absorption, we have focused on the incorporation of a strongly absorbing free base or zinc porphyrin unit. Resulting photocatalytic experiments showed a strong dependence of the catalytic performance on both the type of photosensitizer and the excitation wavelengths. Most notably, the intramolecular hetero-Pacman system containing a zinc porphyrin unit showed much better catalytic activity in the visible region (excitation wavelengths >450 nm) than the free base porphyrin version or the corresponding mononuclear rhenium compound or an intermolecular system comprised of a 1:1 mixture of the mononuclear analogues.     

A study of properties of plastics used for

Some water-ingress characteristics of 14-lead dual-in-line plastic packages have been studied at 85°C and 85% relative humidity. The materials studied were basically encapsulation-grade silicones and epoxies, some of which have had wide use by the semiconductor industry. Bulk water absorption by the silicones was much less than by epoxies and there were significant differences between two epoxies having similar basic chemistries but made by different manufacturers. The leads did not contribute to water absorption by silicone packages, but a contribution attributable to the leads was discernible in epoxy packages. An empirical correlation has been found between the measured properties of the materials and packages and available results of accelerated temperature-humidity-bias testing on live devices. A hypothesis is proposed which accounts for some of the observed differences in performance between silicone and epoxy encapsulants.     

Glyceride‐Mimetic Prodrugs Incorporating Self‐Immolative Spacers Promote Lymphatic Transport,Avoid First‐Pass Metabolism,and Enhance Oral Bioavailability

First‐pass hepatic metabolism can significantly limit oral drug bioavailability. Drug transport from the intestine through the lymphatic system, rather than the portal vein, circumvents first‐pass metabolism. However, the majority of drugs do not have the requisite physicochemical properties to facilitate lymphatic access. Herein, we describe a prodrug strategy that promotes selective transport through the intestinal lymph vessels and subsequent release of drug in the systemic circulation, thereby enhancing oral bioavailability. Using testosterone (TST) as a model high first‐pass drug, glyceride‐mimetic prodrugs incorporating self‐immolative (SI) spacers, resulted in remarkable increases (up to 90‐fold) in TST plasma exposure when compared to the current commercial product testosterone undecanoate (TU). This approach opens new opportunities for the effective development of drugs where oral delivery is limited by first‐pass metabolism and provides a new avenue to enhance drug targeting to intestinal lymphoid tissue.