Facile conversion of RNA aptamers to modular fluorescent sensors with tunable detection wavelengths.

A GTP aptamer was converted to a modular fluorescent GTP sensor by conjugation of RRE (Rev responsive element) RNA and successive complex formation with a fluorophore-modified Rev peptide. Structural changes associated with substrate binding in the RNA aptamer were successfully transduced into changes in fluorescence intensity because of the modular structure of ribonucleopeptides. A simple modular strategy involving conjugation of a fluorophore-modified ribonucleopeptide to the stem region of an RNA aptamer deduced from secondary structural information helps produce fluorescent sensors, which allow tuning of excitation and detection wavelengths through the replacement of the fluorophore at the N-terminal of the Rev peptide

Influence of polymer molecular weight on the properties of in situ synthesized silver–methylcellulose nanocomposite films with a CO₂ laser

We investigate the influence of polymer molecular weight on the properties of silver–methylcellulose (Ag–MC) nanocomposite films synthesized by the irradiation of a CO₂ laser. Although the reduction power of MC with a smaller molecular weight turns out to be stronger than that with a larger molecular weight in the solution phase, we do not see such a clear difference when MC is in the matrix phase. For the 30 s irradiation at the laser power of 0.8 W, the size of Ag nanoparticles (NPs) in the two types of MC matrix is similar, and it is about 30 nm. However, for the longer irradiation time at the same laser power, aggregation of Ag NPs set in, and it is more serious for the Ag–MC film with MC of larger molecular weight. We also carry out the antibacterial test with the Ag–MC films, and find that the Ag–MC film synthesized at the lower laser power and shorter irradiation time generally exhibits a stronger antibacterial effect

Latent pH-responsive ratiometric fluorescent cluster based on self-assembled photoactivated SNARF derivatives

We have developed a self-assembled fluorescent cluster comprising a seminaphthorhodafluor (SNARF) derivative protected by a photoremovable o-nitrobenzyl group. Prior to UV irradiation, a colorless and nonfluorescent cluster was spontaneously assembled in aqueous solution. After UV irradiation, the self-assembled cluster remained intact and showed a large enhancement in pH-responsive fluorescence. The unique pH responsive fluorescent cluster could be used as a dual-emissive ratiometric fluorescent pH probe not only in the test tube but also in HeLa cell cultures

Effects of lipid-lowering drugs on intermediate-density lipoprotein in uremic patients

Effects of lipid-lowering drugs on intermediate-density lipoprotein in uremic patientsBackgroundPatients with chronic renal failure often have alterations in lipoprotein profile including elevated very-low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL), and reduced high density lipoprotein (HDL) levels. Among these changes, raised IDL has been shown as an independent risk factor for atherosclerosis in hemodialysis patients. There are a limited number of studies reporting pharmacological approaches to IDL reduction in a uremic population.MethodsWe therefore summarize the effects of lipid-lowering drugs on IDL levels in patients with chronic renal failure treated by hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD).ResultsFirst, a nicotinic acid analog niceritrol was given to hemodialysis patients. The drug increased HDL-cholesterol by 11%, but the reductions in VLDL-, IDL- and LDL-cholesterol were not significant. Second, CAPD patients were treated with a fibric acid derivative clinofibrate, which was excreted mainly into bile unlike other drugs in this class. The fibrate resulted in a remarkable reduction in VLDL-triglycerides, although it did not reduce IDL-cholesterol. Finally, an HMG-CoA reductase inhibitor (statin) pravastatin was used in HD and CAPD patients. Pravastatin reduced IDL- and LDL-cholesterol to the same extent (by 31%). None of these treatments caused serious adverse effects.ConclusionsWe propose that IDL is an important target in the management of uremic dyslipidemia. To date, statins have been shown to be suitable for this purpose, although it remains to be clarified whether such an intervention reduces the risk for atherosclerotic vascular events in the uremic population

Dynamic Assembly of Cascade Enzymes by the Shape Transformation of a DNA Scaffold

Within cells, the close spatial arrangement of cascade enzymes facilitates the channeling of intermediates and enhances cascade reaction efficiency. Reconfigurable DNA nanostructures, owing to their structural controllability and precise spatial addressability, are promising tools for mimicking such processes. In this study, a 3D DNA origami scaffold, with a dynamic shape transformation from its open boat form to a closed hexagonal prism induced by toehold-mediated strand displacement, is designed to investigate the enzyme cascade reaction of xylose reductase and xylitol dehydrogenase from D-xylose metabolic pathway. Enzymes are assembled on the DNA scaffold in its open state, which is subsequently closed by the assistance of DNA sequence-specific closing keys. The enzyme cascade efficiency is much higher in the static encapsulated closed state than in the open state due not only to the enzyme proximity but also the environmental factors of 3D DNA structure. These results provide novel insights into controlling enzyme cascade reactions by inducing the shape transformation of DNA nanostructures and how environmental factors affect the action of multi-enzyme complexes in the cell

The spin correlation in top quark production: QCD corrections vs anomalous couplings

We discuss top quark production and its subsequent decay at lepton colliders including both QCD corrections and anomalous gamma / Z - t t-bar couplings. The off-diagonal spin basis for the top and anti-top quarks is shown to be useful to probe the anomalous couplings.Comment: 6 pages, LaTeX, 8 postscript figures, uses espcrc2.sty; talk presented at Loops and Legs in Quantum Field Theory, April 2000, Bastei, German