Fluorescent lanthanide chelates for biological systems

Certain lanthanide chelate complexes are known to emit strong fluorescence with very distinct physical properties that are different from those of organic fluorescent compounds: the fluorescence of lanthanide complexes is long-lived with the half decay-time of several hundreds microseconds to 2 ms. The complexes are excited by UV light and emit fluorescence in the visible region. The emission profile is very sharp and the wavelength is specific to each metal, for instance, Eu³⁺ complexes emit at 615 nm and Tb³⁺ at 545 nm regardless of the ligand. These properties show that the complexes can be excellent fluorescence labels for proteins and DNAs and, when time-resolved fluorometry is employed, provide highly sensitive detection methods in biotechnology. Among many labels we have developed, BHHCT-Eu³⁺ and BPTA-Tb³⁺ are suitable for immunoassay, DNA hybridization assay, and DNA chip technology. Homogeneous DNA hybridization assay systems using fluorescence resonance energy transfer and fluorescence intercalators will be introduced.     

Molecularly Imprinted Nanogels Acquire Stealth In Situ by Cloaking Themselves with Native Dysopsonic Proteins

Protein corona formation was regulated on the surface in vivo by molecular imprinting to enable polymeric nanogels to acquire stealth upon intravenous administration. Albumin, the most abundant protein in blood, was selected as a distinct protein component of protein corona for preparing molecularly imprinted nanogels (MIP-NGs) to form an albumin-rich protein corona. Intravital fluorescence resonance energy transfer imaging of rhodamine-labeled albumin and fluorescein-conjugated MIP-NGs showed that albumin was captured by MIP-NGs immediately after injection, forming an albumin-rich protein corona. MIP-NGs circulated in the blood longer than those of non-albumin-imprinted nanogels, with almost no retention in liver tissue. MIP-NGs also passively accumulated in tumor tissue. These data suggest that this strategy, based on regulation of the protein corona in vivo, may significantly influence the development of drug nanocarriers for cancer therapy.     

Characterization of 4-(2,3-diphenylcyclopropenylidene)cyclohexa-2,5-dienone. Highly polarized 6,7-diphenyl[3.6]q́uinaren-3-one

The title quinarenone 2 has a pronounced contribution of the dipolar resonance structure to the ground state, and the three-membered ring of $\text{2}$ is more diatropic than that of diphenylcyclopropenone. The quinarenone 2 exists in equilibrium with its oligomer in solution. The excited state properties of 2 have also been described.     

Geometrical isomorism of ethyl N-(pyrimidinyl) aminomethylenceyanoacetates

The geometrical isomers of ethyl N-(Pyrimidinyl)a minomethylenecy anoacetates were isolated and their structures and interconversions are discussed.     

Electrochemical determination of superoxide anions generated from a single neutrophil

The oxidation current of superoxide anions generated from a single neutrophil stimulated with Immunoglobulin G or phorbol myristate acetate has been determined with a carbon fibre microelectrode. Superoxide generation by a stimulated porcine or human neutrophil is initiated 1 min after the stimulation, reaches a maximum around 5 min later, and ends within 20 min. The current—time profiles thus determined agreed well to the time-course curves of superoxide generation obtained from conventional techniques using macroscopic numbers of cells. A sampled dc voltammogram of superoxide anions having a redox potential at around −0.3 V vs. Ag/AgCl was obtained using carbon fibre microelectrode.     

Precise investigation of the axial ligand substitution mechanism on a hydrogenphosphato-bridged lantern-type platinum(III) binuclear complex in acidic aqueous solution

Detailed equilibrium and kinetic studies on axial water ligand substitution reactions of the "lantern-type" platinum(III) binuclear complex, [Pt(2)(mu-HPO(4))(4)(H(2)O)(2)](2)(-), with halide and pseudo-halide ions (X(-) = Cl(-), Br(-), and SCN(-)) were carried out in acidic aqueous solution at 25 degrees C with I = 1.0 M. The diaqua Pt(III) dimer complex is in acid dissociation equilibrium in aqueous solution with -log K(h1) = 2.69 +/- 0.04. The consecutive formation constants of the aquahalo complex () and the dihalo complex () were determined spectrophotometrically to be log = 2.36 +/- 0.01 and log = 1.47 +/- 0.01 for the reaction with Cl(-) and log = 2.90 +/- 0.04 and log = 2.28 +/- 0.01 for the reaction with Br(-), respectively. In the kinetic measurements carried out under the pseudo-first-order conditions with a large excess concentration of halide ion compared to that of Pt(III) dimer (C(X)()- > C(Pt)), all of the reactions proceeded via a one-step first-order reaction, which is a contrast to the consecutive two-step reaction for the amidato-bridged platinum(III) binuclear complexes. The conditional first-order rate constant (k(obs)) depended on C(X)()- as well as the acidity of the solution. From kinetic analyses, the rate-limiting step was determined to be the first substitution process that forms the monohalo species, which is in rapid equilibrium with the dihalo complex. The reaction with 4-penten-1-ol was also kinetically investigated to examine the reactivity of the lantern complex with olefin compounds.     

Functional masking of carbonyl group by 1-methyl-1H-imidazol-2-YL moiety

Easily obtained 1-methyl-2-(1′-hydroxyalkyl)-1H-imidazoles (4) were found to be a new type of masked form for carbonyl group which could survive under various severe conditions. The corresponding carbonyl compounds (3) were easily reproduced by quarternization of the imidazole (4) with CH₃I followed by aqueous basic treatment. 2-Acyl-1H-imidazoles (5) were convertible to aldehydes or ketones (3) by using the present methodology.     

Ferrocene-containing polymers. XIII. Polymeric compounds possessing carboxyphenyl side groups

As an extension of earlier work on the condensation of ferrocene with aldehydes, the polycondensation of ferrocene with p- and o-carboxybenzaldehyde is described. While, in the former case, regular polycondensation occurs giving rise to a polymer composed of ferrocenylene and 4-carboxybenzal units, a deviation from this route is observed in the o-carboxybenzaldehyde case, where a polymer containing both carboxybenzal and 3,3-phthalide bridging units between the ferrocenylene groups is formed instead. This unexpected behavior can be accounted for by a hydride abstraction mechanism. In support of the polymer structure proposed, 3-ferrocenylphthalide and 3,3-diferrocenylphthalide are isolated as intermediates or by-products. In both polymer series, number-average molecular weights up to 3000 (unsubfractionated) are measured. The polymers are soluble in a number of organic solvents and can be cured with epoxides.     

Induction of Cell Killing, Mutation and umu Gene Expression by 6-Mercaptopurine or 2-Thiouracil with UVA Irradiation

Abstract— When Escherichia coli cells were irradiated by UVA in the presence of 6-mercaptopurine (6-MP) or 2-thiouracil (S²Ura), two kinds of repair-deficient strains of recA ⁻ and uvrA ⁻ were killed more efficiently than the parental wild-type strain having normal repair capacities. In addition, these agents with UVA exposure greatly induced the incidence of mutations in the uvrA ⁻ strain as compared with the wild-type strain but not the uvrA ⁻ strain. Furthermore, the induction of expression of umuDC genes was investigated in two Salmonella typhimurium strains, TA1S35 and TA1538, carrying a pSK1002 plasmid. In these systems, it is easy to measure β-galactosidase activities for the induced activities of SOS responses. These agents with UVA exposure also induced expression of the umuDC genes. These results suggest that 6-MP and S²Ura with UVA induce DNA damage which is repairable by the excision repair mechanism.