Synthesis and EPR studies of 2-N-tert-butylaminoxylpurine derivatives

[Structure: see text] 2'-Deoxyribofuranosylpurine derivatives bearing an N-tert-butylaminoxyl group (1a and 2a) were synthesized via oxidation of the corresponding N-tert-butylhydroxylamines (1b and 2b), which were synthesized by lithiation of 8-TIPS-6-chloropurine (3) at the 2-position and the following reaction with 2-methyl-2-nitrosopropane. Treatment of 1b and 2b with 1 equiv of NaIO4 resulted in efficient formation of 1a and 2a, which were isolated as purple and red solids, respectively. The EPR spectra of 1a showed pH dependency due to structural change of purine moiety.     

Architectural formation of a conjugated bimetallic Pd(II) complex via oxidative complexation and a tetracyclic Pd(II) complex via self-assembling complexation

The conjugated homobimetallic palladium(II) complex [(L1)Pd(qd)Pd(L1)] (qd = quinonediimine) was obtained in a one-pot reaction by the in-situ oxidative complexation of 1,4-phenylenediamine with the palladium(II) complex [(L1)Pd(MeCN)] (H2L1 = N,N'-bis(2-phenylethyl)-2,6-pyridinedicarboxamide) while in the absence of an additional ligand [(L1)Pd(MeCN)] was converted to the amide-bridged macrocyclic tetramer [Pd(L1)]4.     

Enhancement of the mutagenicity of Trp-P-1, Trp-P-2 and benzo[a]pyrene by bupleuri radix extract

Boiling-water extract of Korean-Saiko (Bupleuri Radix, from South Korea, Bupleurum falcatum L.) enhanced the mutagenic activity of Trp-P-1, Trp-P-2 and benzo[a]pyrene with S9mix. The boiling-water extract was fractionated with ether and then n-BuOH. Both the ether and the n-BuOH fractions also enhanced mutagenicity of Trp-P-1, respectively. The n-BuOH fraction was separated into seven fractions by silica gel chromatography and the chloroform eluate had the strongest enhancing effect on the mutagenic activity of Trp-P-1 with S9mix. The chloroform eluate fraction was further separated into five spots by thin-layer chromatography. Two of the spots had the strongest enhancing effect on the mutagenic activity of Trp-P-1. Since saikosaponin is a well known component in Bupleuri Radix, the effects of its existence were tested and saikosaponins a and c were found. The enhancement activity of saikosaponin a was very weak. The effective components are now being studied.     

Manipulation of globular DNA molecules for sizing and separation

Handling large DNA molecules, such as chromosomal DNA, has become necessary due to recent developments in genome science. However, large DNA molecules are fragile and easily broken by shear stress accompanying flow in solution. This fragility causes difficulties in the preparation and handling of large DNA molecules. This study demonstrates the transition of DNA from a coiled to a globular form, which is highly condensed. This state suppresses DNA fragmentation due to shear stress in solution. The transition enables large DNA molecules to undergo mechanical manipulation. We confirmed that the fluorescence intensity of stained globular DNA increases with increasing length, suggesting that the resistance of globular DNA to shear stress is the factor that allows analysis of large DNA by flow cytometry.     

Production and application of pulsed slow positron beam using an electron linac

Slow positron beam is quite useful for non-destructive material research. At the Electrotechnical Laboratory (ETL), an intense slow positron beam line has been constructed by exploiting an electron linac in order to carry out various experiments on material analysis. The beam line can generate pulsed positron beams of variable energy and variable pulse period. Various capabilities of the intense pulsed positron beam is presented, based on the experience at the ETL, and the prospect for the future is discussed.     

Completely monotone sequences and universally prestarlike functions

We introduce universally convex, starlike and prestarlike functions in the slit domain ℂ [1, ∞), and show that there exists a very close link to completely monotone sequences and Pick functions. S. R. and L. S. received partial support from FONDECYT (grants 1070269 and 7080064) and DGIP-UTFSM (grant 240954). S. R. acknowledges partial support also from the German-Israeli Foundation (grant G-809-234.6/2003) and a JSPS Grant-in-Aid for Scientific Research (A), 17204010. T. S. was partially supported by JSPS Grant-in-Aid for Scientific Research (B), 17340039.