Hidenari Inoue

DNA binding of iron(II) mixed-ligand complexes containing 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline

Absorption spectroscopy and circular dichroism (CD) have been used to characterize the DNA binding of [Fe(phen)3]2+, [Fe(phen)2(DIP)]2+ and [Fe(phen)(DIP)2]2+ where phen and DIP stand for 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline, respectively. Both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ bind weakly to calf thymus DNA (CT-DNA) in an electrostatic mode, while [Fe(phen)(DIP)2]2+ binds more strongly to CT-DNA, possibly in an intercalation mode. The hypochromicity, red shift and Kb increase in the order [Fe(phen)3]2+ < [Fe(phen)2(DIP)]2+ < [Fe(phen)(DIP)2]2+ in accordance with the increase in size and hydrophobicity of the iron(II) complexes. The thermodynamic parameters obtained suggest that the DNA binding of both [Fe(phen)3]2+ and [Fe(phen)2(DIP)]2+ is entropically driven, while that of [Fe(phen)(DIP)2]2+ is enthalpically driven. A strong CD spectrum in the UV and visible region develops upon addition of CT-DNA into the racemate solution of each iron(II) complex (Pfeiffer effect). This has revealed that a shift in diastereomeric inversion equilibrium takes place in the solution to yield an excess of one of the DNA-complex diastereomers. The striking resemblance of the CD spectral profiles to those of the pure delta-enantiomer indicates that the delta-enantiomer of the iron(II) complexes is preferentially bound to CT-DNA. The mechanism of the development of Pfeiffer CD is proposed on the basis of kinetic studies on the DNA binding of the racemic iron(II) complexes.

CATIONIC PORPHYRINS BEARING DIAZOLIUM RINGS : SYNTHESIS AND THEIR INTERACTION WITH CALF THYMUS DNA

Two novel cationic porphyrins bearing five-membered rings at the meso-positions, meso-tetrakis(1,3-dimethylimidazolium-2-yl)porphyrin (H2TDMImP) and meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrin (H2TDMPzP), have been synthesized. These two compounds interact with calf thymus DNA (CTDNA) in different binding modes from that of mesotetrakis(N-methylpyridinium-4-yl)porphyrin (H2TMPyP). H2TDMImP outside binds to the minor groove of CTDNA while H2TDMPzP intercalates into CTDNA. These two novel cationic porphyrins strongly bind to CTDNA even at high ionic strength and the binding constant of H2TDMPzP to CTDNA is comparable to that of H2TMPyP. The binding of H2TDMImP to CTDNA is enthalpically driven. The favorable free energy changes in binding of H2TDMPzP to CTDNA come from the large negative enthalpy changes accompanied by small positive entropy changes.

Fibre-optic potassium ion sensors based on a neutral ionophore and a novel lipophilic anionic dye

Abstract A novel lipophilic anionic dye, N -2,4-dinitro-6-octyloxyphenyl-2′,4′-dinitro-6′-trifluoromethylphenylamine (LAD), was synthesized. On deprotonation at neutral Ph it forms anions and brings about a change in the absorption spectrum in the visible region. This anionic dye was incorporated into a poly(vinyl chloride) matrix membrane with dibenzo-18-crown-6 (DB18C6) or valinomycin, which are K + -selective neutral ionophores. An optical K + sensor was prepared using the polymeric membrane set 1 mm apart from the tip of a bifurcated optical fibre with a cylindrical plastic support. This sensor could detect a wide range of K + concentrations (10 −6 −1 M K + for the DB18C6-based sensor, 10 −8 −10 −2 M K + for the valinomycin-based sensor) at Ph 7.0 by measuring the absorbance change at 513 nm. The factors that influence the response sensitivity of the sensor are discussed theoretically.

DNA binding of iron(II) complexes with 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline: salt effect, ligand substituent effect, base pair specificity and binding strength

The DNA binding of iron(II) mixed-ligand complexes containing 1,10-phenanthroline(phen) and 4,7-diphenyl-1,10-phenanthroline(dip), [Fe(phen)(3)](2+), [Fe(phen)(2)(dip)](2+) and [Fe(phen)(dip)(2)](2+) has been characterized by spectrophotometric titration and melting temperature measurements. The salt concentration dependence of the binding constant has allowed us to dissect the DNA-binding constant and free energy change of each iron(II) complex into the nonelectrostatic and polyelectrolyte contributions. A comparison of the nonelectrostatic components in the binding free energy changes among iron(II) complexes has made it possible to rigorously evaluate the contribution of the ligand substituents to the DNA-binding event. The peripheral substitution of phen by two phenyl groups increases the nonelectrostatic binding constant of the iron(II) complex more than 20 times, which is equivalent to approximately 7.5 kJ mol(-1) of more favorable contribution to the DNA binding. In general, the iron(II) complexes studied have higher affinity towards the more facile A-T sequence than the G-C sequence. This preferential binding may be attributed to the steric effect induced by the ancillary part of the ligands in the course of DNA binding. The binding of disubstituted iron(II) complex to DNA is quite strong as reflected in the modest increase in the denaturation temperature (T(m)) of double helical DNA upon the interaction with the iron(II) complex.

Spectroscopic properties of chlorophylls and their derivatives. Influence of molecular structure on the electronic state

Abstract The spectroscopic properties of chlorophylls (MgChl a and H 2 Chl a ), metallochlorophyll a and b (MgChl a and b , M  Ni, Cu and Zn), zinc(II) pyromethylpheophoribide a (ZnPMP a ) and zinc(II) chlorin e 6 trimethyl ester (ZnChl e 6 TME) were studied by circular dichroism (CD), magnetic circular dichroism (MCD), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The electronic absorption spectra were assigned in terms of the spectral analysis of CD and MCD. The absorption maximum of the Q y band varied linearly with the electronegativity of the central metal M and the energy level of the macrocyclic π orbitals in MChl a . The semiempirical MO calculation demonstrated that the deviation of H 2 Chl a from the general trend is induced by rising of the energy levels of next HOMO and second next HOMO in H 2 Chl a . A comparison of the UVVIS and MCD spectral data in zinc(II) chlorophylls revealed that the substituents on the pyrrole β position and the ring V govern the position of the Q and B bands. The spectroscopic behavior was explained on the basis of the energy level of the macrocyclic π orbitals calculated by the conventional MO method.

IRON(II) AND NICKEL(II) MIXED-LIGAND COMPLEXES CONTAINING 1,10-PHENANTHROLINE AND 4,7-DIPHENYL-1,10-PHENANTHROLINE

Two types of mixed-ligand complexes, i.e. [M(phen)2 (dip)]2+ and [M(phen)(dip)2]2+ (M = iron(II) and nickel(II); phen = 1,10-phenanthroline and dip = 4,7-diphenyl-1,10-phenanthroline) have been prepared from their related tris-complexes, [M(phen)3]2+ by ligand substitution, and isolated by semi-preparative HPLC. Elemental and chromatographic analyses confirm the purity of the isolated complexes while u.v./vis and i.r. spectra were used to identify and characterize them. 1H-n.m.r. and room temperature Mössbauer spectra of the iron(III) complexes were also measured and the results are discussed. In addition, our preliminary results on hypochromicity in the MLCT band and circular dihroism (CD) emerging in the u.v./vis region upon addition of CT(calf thymus)-DNA to the racemic complexes indicated that the iron(II) mixed-ligand complexes interact with CT-DNA.

Determination of copper(II) chlorophyllin by reversed-phase high-performance liquid chromatography

Abstract Copper(II) chlorophyllin, consisting of copper(II) pheophorbide a , copper(II) chlorin e 6 , copper(II) rhodin g 7 and copper (II) chlorin e 4 , was prepared and separated by semi-preparative high-performance liquid chromatography (HPLC). The components of copper(II) chlorophyllin were determined on a reversed-phase Inertsil ODS-2 column using a mobile phase of methanol-water (97:3, v/v) containing 1% (v/v) of acetic acid. Linear calibration plots were obtained for copper(II) chlorophyllin in the concentration range of 0–30 μg cm −3 with photometric detection at 407 or 423 nm. The detection limits of copper(II) pheophorbide a , copper(II) chlorin e 6 , copper(II) rhodin g 7 and copper(II) chlorin e 4 were 3.5, 1.5, 3.3 and 1.4 ng cm −3 with relative standard deviations ( n = 10) of 1.8, 1.6, 5.2 and 3.6%, respectively. The reversed-phase HPLC method proposed here was demonstrated to be useful for the determination of the components of sodium copper(II) chlorophyllin

Synthesis and Magnetic Property of Stable Organic Radicals Bearing Imidazole Ring

Abstract Three imidazole derivatives with stable radical groups at 2-position were prepared and their magnetic property were characterized. The effect of NH hydrogen bonding site was also discussed.

Role of molecular strain on the solid-state synthesis of coordination compounds from iron(II) chloride tetrahydrate and 1,10-phenanthroline under mechanical stress

Abstract A powdered crystalline mixture of iron(II) chloride tetrahydrate (FeCl 2 ·4H 2 O) and 1,10-phenanthroline (phen) was subjected to mechanical stressing in Ar by a planetary ball-mill. By milling for 3h, the mixture turned completely non-crystalline. New IR absorption bands appeared simultaneously at 358cm −1 due to FeN(phen) stretching and at 207cm −1 due to NFeN(phen) bending for [Fe(phen) 3 ] 2+ . Only a doublet peak due to [Fe(phen) 3 ]Cl 2 · n H 2 O was detected in the Mossbauer spectrum. All these results indicate consistently the formation of [Fe(phen) 3 ]Cl 2 · n H 2 O by milling with an almost quantitative yield. Disproportionation of the hydrated water molecules was observed after milling FeCl 2 ·4H 2 O alone for 3h. The molecular strain triggers a solid-state exchange reaction between H 2 O and phen at the contact point of two dissimilar solid particles under mechanical stressing, and promotes formation of [Fe(phen) 3 ]Cl 2 · n H 2 O in the solid state.

Measurement of tire tread in urban air by pyrolysis-gas chromatography with flame photometric detection

Abstract The concentration of tire tread in suspended particulate matter (SPM) was measured by a new method based on benzothiazole generated by pyrolysis of vulcanization accelerator. The variation of production yields of benzothiazole was examined for 24 kinds of tire treads currently used in Japan Pyrolysis was carried out at 670°C using a Curie-point pyrolyzer. The vertical profile and diurnal pattern of tire tread were investigated with 4-h samples continuously collected for 24 h at a heavy traffic density area in Tokyo. The diurnal percentage of tire tread in SPM at the sampling site of 86 m height showed two peaks following the trend of traffic density throughout the day. The concentration of tire tread collected at the 86 m level was about 30% of that at the 0 m level during the daytime. The seasonal variation of concentration of tire tread in SPM was measured at the sampling site located 20 km SW of Tokyo. The weight percentage of tire tread in SPM varied between 1.3 and 3% in winter with NE-NW wind and varied between 0.5 and 1.5% in spring with SE-SW wind.