[en] Originally, it was thought that X-rays did not influence implantable cardiac pacemakers. In general radiological technologists did not take proper care of these devises at the time of X-Ray examinations. However, 11 cases in which pacemakers malfunctioned (for example partial electrical reset) during CT examinations have been reported in recent years. At the time, we tended to attribute such problems to the peculiarities of multi-detector CT (MDCT). However, on logical grounds this explanation seemed weak. To better explain the problem, we attempted various tests in which pacemakers were exposed to CT and X-ray photography equipment. We analyzed some electrocardiogram (ECG) results to clarify the matter and took measurements to examine these problems. (author)

[en] It is well known that polyamines induce a folding transition from an elongated coil to a compact globule state for giant DNA larger than several tens of kbp (kilo base pairs). Here, we studied the interaction between compact DNA molecules in the presence of linear and branched-chain isomers of polyamines. We compared the stability of the assembly among plural number of compact DNA molecules generated by laser trapping. As a result, the assembly of compact DNAs with a linear-chain polyamine is stable even after the laser is switched off. On the other hand, the assembly of DNAs with a branched-chain polyamine disperses into individual compact DNAs when the laser is switched off. Thus, compact DNAs with linear- and branched-chain polyamines attract and repel each other, respectively. This difference in the effects of linear and branched polyamines is discussed in terms of the steric interaction between negatively charged double-strand DNA and cationic polyamines.

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[en] Highlights: • Biogenic triamine and tetraamine efficiently activated the ∆P5 ribozyme. • Spermine (tetraamine) modestly inhibited the full-length Tetrahymena ribozyme. • Polyamines are promising small molecule modulators to activate and possibly inhibit the core catalytic ability of group I ribozymes. Group I intron ribozymes share common core elements that form a three-dimensional structure responsible for their catalytic activity. This core structure is unstable without assistance from additional factors that stabilize its tertiary structure. We examined biogenic triamine and tetraamine and also their fragments for their abilities to stabilize a structurally unstable group I ribozyme, ΔP5 ribozyme, derived from the Tetrahymena group I intron ribozyme by deleting its large activator module. Biogenic triamine (spermidine) and tetraamine (spermine) efficiently activated the ΔP5 ribozyme under conditions where the ribozyme was virtually inactive. These observations suggested that polyamines are promising small molecule modulators to activate and possibly inhibit the core catalytic ability of group I ribozymes.

[en] Highlights: • Three stereoisomers of a pentamine showed distinct effects on a group I ribozyme. Among cationic molecules that can modulate ribozyme activities, polyamines act as both activator and inhibitor of ribozyme reactions partly due to their structural flexibility. Restriction of structural flexibility of polyamines may allow them to emphasize particular modulation effects. We examined eight stereoisomers of a synthetic pentamine bearing three cyclopentane rings. In the reaction of a structurally unstable group I ribozyme, three stereoisomers exhibited distinct effects as inhibitor, an additive with a neutral effect, and also as an activator.

[en] TiO₂ nanoparticles were modified with a porphyrin derivative, 5-[4-benzoic acid]-10,15,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (H₂P-COOH), and fluorescein derivatives, 9-[2-(3-carboxy-9,10-diphenyl)anthryl]-2,7-difluoro-6-hydroxy-3H-xanthen -3-one (DPAX-COOH) and 2',7'-difluorofluorescein (FL-COOH). The dye-modified TiO₂ nanoparticles were deposited on nanostructured OTE/SnO₂ (OTE: optically transparent electrodes) together with nanoclusters of fullerene (C₆₀) from acetonitrile/toluene (3:1, v/v) using an electrophoretic deposition technique. The dye-modified TiO₂ composite electrodes [OTE/SnO₂/(dye+C₆₀)_n] have broad as well as high absorbance properties in the visible region, exhibiting the photo response under visible light excitation using I₃^-/I^- redox couple. The incident photon to photocurrent efficiency (IPCE) for these electrodes increases in order: OTE/SnO₂/(H₂P)_n< OTE/SnO₂/(H₂P-COO-TiO₂)_n< OTE/SnO₂/(H₂P-COO-TiO₂+C₆₀). The IPCE value can be further improved by replacing H₂P-COOH with a fluorescein derivative containing an electron donor moiety: DPAX-COOH (DPA: diphenylanthracene). The maximum IPCE value (42%) is obtained for OTE/SnO₂/(DPAX-COO-TiO₂+C₆₀)_n under the bias of 0.2V vs. SCE. the bias of 0.2V vs. SCE.