Soft metal-mediated base pairing with novel synthetic nucleosides possessing an O,S-donor ligand

Metal-mediated base pairing with artificial ligand-bearing nucleosides allows site-selective metal incorporation inside DNA duplexes. In particular, this strategy has provided a general way of discrete, heterogeneous metal arrays in a programmable manner. To increase the kind of metallo-building blocks, we have newly synthesized two artificial nucleosides which have an O, S-donor ligand as the nucleobase moiety, mercaptopyridone ( M) and hydroxypyridinethione ( S). These nucleosides were found to efficiently form metal-mediated base pairs with soft transition metal ions such as Pd (2+) and Pt (2+).     

Controlled growth for synthesizing a compact mordenite membrane

Controlling the growth of zeolite crystals on a porous alumina support is essential for preparing a compact zeolite membarne. First, mordenite seed crystals applied on a nonporous -alumina disk were grown and morphological change of mordenite crystals were observed in the course of growth. Then, mordenite membranes were synthesized on a porous -alumina tube under the same conditions employed in the study using the alumina disks. We found that seed crystal growth was widely controllable by changing water content in reaction solution, which resulted in better control of the morphology of mordenite crystals for synthesizing a thin compact mordenite membrane. Separation properties for mordenite membranes were studied in water–hydrogen binary system at 473 K with 10 kPa of water partial pressure, where no capillary condensation was expected in non-zeolitic pores. Separation factor for a mordenite membrane with a few defects was poor; however, a defect-free mordenite membrane prepared under a suitable condition highly separated steam from hydrogen.     

New nucleotide pairs for stable DNA triplexes stabilized by stacking interaction

New nucleotide pairs applicable to formation of DNA triplexes were developed. We designed oligonucleotides incorporating 5-aryl deoxycytidine derivatives (dC5Ars) and cyclic deoxycytidine derivatives, dCPPP and dCPPI, having an expanded aromatic area, as the second strand. As pairing partners, two types of abasic residues (C3: propylene linker, phi: abasic base) were chosen. It was concluded that, when the 5-aryl-modified cytosine bases paired with the abasic sites in TFOs in a space-fitting manner, the stability of the resulting triplexes significantly increased. The recognition of C3 toward dC5Ars was selective because of the stacking interactions between their aromatic part and the nucleobases flanking the abasic site. These results indicate the potential utility of new nucleotide triplets for DNA triplex formation, which might expand the variety of structures and sequences and might be useful for biorelated fields such as DNA nanotechnologies.     

Synthesis of branched oligonucleotides with three different sequences using an oxidatively removable tritylthio group

We synthesized a three-way branched oligodeoxynucleotide (ODN) 30-mer using a new branch unit with acid-labile DMTr and oxidatively cleavable TrS groups as orthogonal protecting groups. The branched ODN was successfully synthesized using 5-[3,5-bis(trifluoromethyl)phenyl]-1H-tetrazole and (2R,8aS)-(+)-(camphorylsulfonyl)oxaziridine as the activator of phosphoramidite units and the oxidizing reagent, respectively. We also found that the TrS group was orthogonal to the Lev, TBDMS, and Fmoc groups. These results indicate the possibility of the synthesis of more complex four- and five-way branched ODNs by the combined use of DMTr, TrS, Lev, TBDMS, and Fmoc groups.     

Separation of carrier free95mTc from niobium targets irradiated with alpha-particles

A^95mTc tracer with an excellent quality was prepared by a simple sublimation method after α-bombardment of niobium metal. Technetium-95m produced by the⁹³Nb(α,2n)^95mTc reaction was separated from the niobium targets in a quartz tube by heating at 1100°C in an oxygen gas flow. Technetium-95m sublimed as an oxide was deposited on the inner wall of the quartz tube outside an electric furnace, and then collected as a pertechnetate solution by washing with water. The ICP-MS analysis of the^95mTc solution revealed its excellent quality, compared to a^95mTc solution prepared from the same targets through a wet chemical separation method and a commercial^95mTc solution. With this tracer, the precision of ICP-MS analysis of⁹⁹Tc in environmental samples are highly improved.     

Production of positron emitters and application of their labeled compounds to plant studies

The positron emitters¹¹C,¹³N and¹⁸F and their labeled compounds have been produced for studies on plants using a newly developed positron emitting tracer imaging system. Although this system covers, at present, a limited area in a plant, the distribution of the positron emitter fed into the plant can be visualized dynamically. Further development of positron-emitter-labeled compounds is expected to elucidate the physiological function of plants in vivo.     

Selective formation of thecis isomer of the nitridotechnetium(V) complex with 2,2′:6′,2″-terpyridine

The reaction of [TcNCl₂(PPh₃)₂] with 2,2′:6′,2″-terpyridine producedcis-[TcNCl₂(terpy)] selectively. The resulting complexes were characterized by¹H NMR and IR spectroscopy. The geometries of thecis andtrans isomers were estimated by theoretical calculations following a density functional method. Thecis isomer is likely more stable than thetrans one with respect to thetrans influence of the nitrido ligand. Furthermore, the behavior of nitridotechnetium complexes in polar solvents was compared to Os-analogues.     

Structural assignment of n3-acylated uridine derivatives by means of 13c nmr spectroscopy

Diisopropylethylamine was effective as a base for acylation of 2′,3′,5′-tri-O-acetyluridine with various acid chlorides. The ¹³C NMR spectra of the products and related compounds showed clearly that the acyl groups intoduced to the uracil moiety are attached to the N³-nitrogen.     

A heme degradation enzyme, HutZ, from Vibrio cholerae

HutZ, one of the crucial proteins of the iron uptake system in Vibrio cholerae, was purified, which binds to heme at a stoichiometry of 1 : 1. In the presence of ascorbic acid, the HutZ-bound heme degrades via the same intermediates observed in heme oxygenase, suggesting that HutZ works as a heme degradation enzyme.