Improvement of targeted gene delivery to human cancer cells by a novel trifunctional crosslinker.

A facile method for the construction of an immunoconjugate which displays targeting ligands, such as antibody fragments, with a high density is reported. For this purpose, we synthesized a novel trifunctional crosslinking reagent. By the use of this reagent, ligands targeting the specific cell can be displayed on the surface of the drug carrier with a high density.

Crystallographic snapshots of an entire reaction cycle for a retaining xylanase from Streptomyces olivaceoviridis E-86.

Retaining glycosyl hydrolases, which catalyse both glycosylation and deglycosylation in a concerted manner, are the most abundant hydrolases. To date, their visualization has tended to be focused on glycosylation because glycosylation reactions can be visualized by inactivating deglycosylation step and/or using substrate analogues to isolate covalent intermediates. Furthermore, during structural analyses of glycosyl hydrolases with hydrolytic reaction products by the conventional soaking method, mutarotation of an anomeric carbon in the reaction products promptly and certainly occurs.

Chemistry-based RNA technologies: demonstration of usefulness of libraries of ribozymes and short hairpin RNAs (shRNAs).

Mechanism of action of hammerhead ribozymes has been investigated and their intracellular activities have been improved. Based on the improved ribozymes and more recently discovered natural RNAi, we have created libraries of both ribozymes and short hairpin RNAs (shRNAs). The introduction of a library of active ribozymes or shRNAs into cells, and the subsequent screening for phenotypic changes, allows the rapid identification of gene function.

Theoretical study about remarkable stability of guanine tetramer.

The cyclic guanine tetramer (G-quartet) formation was theoretically studied. Total hydrogen bond energy in a G-quartet was large (-70.89 kcal/mol).

Lewis acidity/basicity of pi-electron systems: theoretical study of a molecular interaction between a pi system and a Lewis acid/base.

Molecular interactions between pi systems having different pi-electron character (benzene, hexafluorobenzene, and borazine), and a Lewis acid/base (borane and ammonia) were theoretically studied. An attractive interaction between benzene, the electron-rich pi system, and borane was observed. On the other hand, repulsive interactions between benzene and ammonia was observed when the lone pair of nitrogen points toward the benzene ring.

Specific 3'-terminal modification of DNA with a novel nucleoside analogue that allows a covalent linkage of a nuclear localization signal and enhancement of DNA stability.

We report a straightforward method for the site-specific modification of long double-stranded DNA by using a maleimide adduct of deoxycytidine. This novel nucleoside analogue was efficiently incorporated at the 3'-termini of DNA by terminal deoxynucleotidyl transferase (TdT). Thiol-containing compounds can be covalently linked to the maleimide moieties.

A new, but old, nucleoside analog: the first synthesis of 1-deaza-2'-deoxyguanosine and its properties as a nucleoside and as oligodeoxynucleotides.

The first synthesis of 5-amino-3-(2'-deoxy-beta-D-ribofuranosyl)imidazo[4,5-b]pyridin-7-one (1-deaza-2'-deoxyguanosine) is described. The compound was converted from the known AICA-deoxyriboside. The tautomeric structure of the base moiety was determined by theoretical calculation to be a hydroxyl form.

2-Pyridone and 3-oxo-1,2,6-thiadiazine-1,1-dioxide derivatives: a new class of hydrogen bond equivalents of uracil.

Hydrogen bond complex stability between adenine (A) and hydrogen bond equivalents of uracil: 2-pyridone derivatives (U(X2O)X) and 3-oxo-1,2,6-thiadiazine-1,1-dioxide derivatives (U(SO2)X) was studied, and as the result, the hydrogen bond energy of U(X2O)X-A and a complex of UX(SO2)X-A, was about 1.5 kcal/mol more stable than that of the corresponding adenine-uracil derivatives complex, respectively. The energy difference between the imide tautomer and enol tautomer was smaller than those of uracil derivatives.

Synthesis of a novel histidine analogue and its efficient incorporation into a protein in vivo.

Proteins containing unnatural amino acids have immense potential in biotechnology and medicine. We prepared several histidine analogues including a novel histidine analogue, beta-(1,2,3-triazol-4-yl)-DL-alanine. These histidine analogues were assayed for translational activity in histidine-auxotrophic Escherichia coli strain UTH780.

Theoretical study of substitution effect of the hydrogen bond stability of 9-methylguanine derivatives and 1-methylcytosine.

The substitution effect on hydrogen bond stability of the Watson-Crick type base pair between 1-methylcytosine (C) and substitution-introduced 9-methylguanine derivatives (Gx) was studied by an ab initio molecular orbital theory. Introduction of an electron-withdrawing group on the 8-position or on the exo-cyclic amino moiety enforced the base pair stability.