Akimasa Iwado

Effect of molecular charges on renal uptake of 111In-DTPA-conjugated peptides

The effect of molecular charges on renal accumulation of 111In-DTPA-labeled low molecular weight (LMW) peptides was investigated using 111In-DTPA-octreotide derivatives as models to design radiolabeled peptides that are taken up less by renal cells. The N-terminal D-phenylalanine (Phe) of 111In-DTPA-D-Phe(1)-octreotide was replaced with L-aspartic acid (Asp), L-lysine (Lys), L-methionine (Met) or L-Phe. Cellulose acetate electrophoresis indicated that both 111In-DTPA-L-Phe(1)-octreotide and 111In-DTPA-L-Met(1)-octreotide showed similar net charges, whereas 111In-DTPA-L-alphaLys(1)-octreotide and 111In-DTPA-L-Asp(1)-octreotide had more positive and negative charges, respectively, at pH values similar to those in blood and glomerular filtrate. When injected into mice, significant differences were observed in the renal radioactivity levels. 111In-DTPA-L-alphaLys(1)-octreotide showed the highest radioactivity levels from 10 min to 6 h postinjection, whereas the lowest radioactivity levels were observed with 111In-DTPA-L-Asp(1)-octreotide at all the postinjection intervals. These findings indicated that the replacement of only one amino acid in 111In-DTPA-D-Phe(1)-octreotide significantly altered net molecular charges of the resulting peptides and that the net charges of the 111In-DTPA-octreotide derivatives significantly affected their renal uptake. Thus, an increase of negative charges in peptide molecules may constitute a strategy for designing 111In-DTPA-conjugated LMW peptides with low renal radioactivity levels.

Design, synthesis, and biological evaluation of a novel series of quercetin diacylglucosides as potent anti-MRSA and anti-VRE agents.

A series of novel quercetin diacylglucosides were designed and first synthesized by Steglich esterification on the basis of MRSA strains inhibiting natural compound A. The in vitro inhibition of different multi-drug resistant bacterial strains and Escherichia coli DNA gyrase B was investigated. In the series, compound 10h was up to 128-fold more potent against vancomycin-resistant enterococci and more effective than A, which represents a promising new candidate as a potent anti-MRSA and anti-VRE agent.

Significance of 111In-DTPA chelate in renal radioactivity levels of 111In-DTPA-conjugated peptides

Metabolic studies of (111)In-DTPA-labeled polypeptides and peptides showed that the radiolabeled (poly)peptides generated (111)In-DTPA-adducts of amino acid that possess long residence times in the lysosomal compartment of the tissues where (poly)peptides accumulated. However, a recent study suggested that metal-chelate-methionine (Met) might possess in vivo behaviors different from metal-chelate adducts of other amino acids. In this study, to elucidate whether some biological characteristics of Met may accelerate the renal elimination rate of (111)In-DTPA-adduct of Met into urine, (111)In-DTPA-Met(1)-octreotide was synthesized and the renal handling of (111)In-DTPA-Met was investigated using (111)In-DTPA-L-Phe(1)-octreotide (Phe represents phenylalanine), which was reported previously, as a reference. Both (111)In-DTPA-conjugated octreotide analogs were stable against 3-h incubation in murine serum at 37 degrees C. Both (111)In-DTPA-octreotide analogs also showed rapid clearance of the radioactivity from the blood and similar accumulation of the radioactivity in the kidney. No significant differences were observed in the renal radioactivity levels from 10 min to 24 h postinjection between the two. Metabolic studies indicated that (111)In-DTPA-Met(1)-octreotide and (111)In-DTPA-L-Phe(1)-octreotide generated (111)In-DTPA-adducts of Met and Phe, respectively, as the final radiometabolites at similar rates. These findings suggested that the long residence times of the radioactivity in tissues after administration of (111)In-DTPA-labeled peptides and polypeptides would be attributed to inherent characteristics of (111)In-DTPA chelate.

Gas chromatography—mass spectrometry of polyamines as their N-ethyloxycarbonyl derivatives and identification of sym-homospermidine and sym-norspermine in mosses and ferns

Abstract The N-ethyloxycarbonyl derivatives of eleven naturally occurring polyamines were investigated by combined gas chromatography—mass spectrometry using electron impact ionization. The mass spectra exhibited molecular ions of low but detectable intensity. The spectral data were used to identify the polyamines in some mosses and ferns, and the results showed that in addition to the well known polyamines sym-homospermidine was present in both of these plants and sym-norspermine exclusively in mosses.

Peroxidase-like catalytic activity of Mn- and Fe-tetrakis(4-carboxyphenyl) porphines bound to aminopropyl-glass bead in oxidative reaction of heterocyclic amines

Fe- or Mn-tetrakis(4-carboxyphenyl)porphine (Fe- and Mn-TCPP) bound to aminopropyl-glass bead (Fe- and Mn-TCPP(g)s) was examined for the peroxidase (POD)-like function in order to develop a solid catalyst which can exhibit POD-like activity without adsorbing heterocyclic amines (HCAs). Mn-TCPP in aqueous solution had only a slight POD-like catalytic activity on HCAs (IQ and MeIQ). As for Fe-TCPP, it was impossible to examine the POD-like activity since it reacted with hydrogen peroxide in a liquid reaction system. However, both Fe- and Mn-TCPP when immobilized on aminopropyl-glass bead via peptide bond (Fe- and Mn-TCPP(g)s), catalyzed the oxidative reaction of mutagenic HCAs with hydrogen peroxide. The catalytic activity of Fe- and Mn-TCPP(g)s was investigated in more detail using as a substrate IQ and MeIQ which were oxidized more rapidly among the tested HCAs. Consequently, the optimal conditions for the oxidative reaction catalyzed by Fe- and Mn-TCPP(g)s were determined. In addition, ESI-mass and absorption spectra of oxidation products of IQ and MeIQ showed that they are dimers. Thus, it was demonstrated that a solid catalyst with POD-like activity can be obtained by immobilizing Fe- and Mn-TCPPs on aminopropyl-glass beads.

Uricase-like catalytic activity of ion-exchange resins modified with metalloporphyrins.

The uricase-like catalytic activity of the ion-exchange resins modified with metalloporphyrins has been investigated through the oxidation of uric acid. The anion-exchange resins modified with Mn(3+)-tetrakis(sulfophenyl)porphine and the cation-exchange resin modified with Mn(3+)-tetrakis(1-methylpyridinium-4-yl)porphine exhibited the highest uricase-like activity among the modified resins tested. The fact that these resins accelerated the oxidation of uric acid even after ten cycles of use indicates that the modified resins act as catalysts in the reaction catalysed by uricase. Some of the modified resins may be effectively used for the determination of uric acid in place of uricase.

π-Electron interaction of PAHs with anion-exchange silica gels modified with anionic metal-porphine and -phthalocyanine derivatives as HPLC stationary phase for preparative column in organic solvents

To develop easy-to-prepare stationary phases for HPLC, we investigated anion-exchange silica gels, Nucleosil 5SB (Nuc), modified with metal-porphines and -phthalocyanines (M-P). The modified silica gels (M-P(N)) were evaluated for the availability as a stationary phase of HPLC for the separation of pi-electron-rich polyaromatic hydrocarbons (PAHs) in polar and non-polar eluents. Separation ability of silica gels modified with Cu-phthalocyanine derivative (Cu-PCS(N)) was comparable to that of the silica gels binding Cu-PCS through sulfonamide bonds; however, the latter requires troublesome procedures for the preparation. The PAHs tested interact with Cu-PCS(N) in non-polar organic eluents through their pi-electrons similarly as in the case of the PYE column((R)), in which interaction with PAHs was reported to be only the pi-pi-electron interaction.

Peroxidase-like activity on organic hydroperoxides of ion-exchange resins modified with metal-porphine analogues and analytical application for determination of linoleate hydroperoxide

The ion-exchange resins modified with metal-porphyrins and -phthalocyanines (M-P(r)) have been found to exhibit a peroxidase (POD)-like activity on organic peroxides in a reaction wherein a quinoid dye is formed from phenol and 4-aminoantipyrine. Among them, Mn- and Co-P(r) exhibited stronger activity than hemoglobin and Fe-P(r), and hence were expected to be practically useful as a solid catalyst for the determination of linoleate hydroperoxide (LOOH). In addition, a resin modified with Co(3+)-phthalocyanine tetrasulfonate (Co-PCS(r)) lacks POD-like activity on hydrogen peroxide in contrast with Mn-P(r). We, therefore, concluded that Co-PCS(r) is superior to both Mn-P(r) and hemoglobin as a solid catalyst on organic hydroperoxides, and developed a new method for the determination of LOOH.

A catalytic activity of glass beads, silica gels and anion-exchange resins modified with metal-porphines in oxidative reactions of ascorbic acid

Abstract An anion-exchange resin was modified with metal-tetrakis(4-sulfophenyl)porphine (M-TSPP) by ion-exchange reaction and physical adsorption, and silica gels and glass beads were modified by using the acid chloride of metal-tetrakis(4-carboxyphenyl)porphine (M-TCPP) through the peptide bond. The supports modified with Co3+-porphine were proved to accelerate the following redox reaction(s), of which the former is also catalyzed by ascorbate-oxidase (AsA): 2 Ascorbate ( AsA ) + O 2 → ASO x or supports modified with M - porphine 2 Dehydroascorbate ( DhAsA ) + 2 H 2 O Ascorbate ( AsA ) + O 2 → supports modified with M - porphine Dehydroascorbate ( DhAsA ) + H 2 O 2 Formation of DhAsA and hydrogen peroxide was confirmed by means of mass spectroscopy and colored reaction, respectively. The supports modified with Co3+-porphine would be useful in practice as solid catalysts for the determination of AsA and for the removal of AsA which interferes with the determination of vital materials in clinical assays.

Flow injection analysis of ascorbic acid using carriers modified with metal-porphine as oxidative solid catalyses.

To investigate one of practical applications of the supports modified with metal-porphines as artificial solid-catalysts, columns into which the supports were packed were supplied to catalytic columns for a flow injection analysis (FIA) system for determination of ascorbic acid (AsA) by the following reactions: AsA+O(2)-->dehydoroAsA+H(2)O(2),H(2)O(2)+chromogen-->2H(2)O+Dye. Among the columns tested, the column containing silica gels modified with Co-tetrakis(carboxyphenyl)porphine catalyzed most rapidly the oxidation reaction of AsA that is accompanied by the formation of hydrogen peroxide. The resulting hydrogen peroxide was determined by FIA system equipped with the column containing glass beads modified with Mn-tetrakis(carboxyphenyl)porphine, which gave a linear calibration curve and large peak-areas of the range corresponding to AsA concentration between 0.2 and 10 micromol/ml. The results indicated that some supports modified with metal-porphine would be applicable to the FIA for AsA as the solid catalyses which function as if the immobilized enzymes.