Tatsuo Oida

Simple Colorimetric Inhibition Assay of Heme Crystallization for High-Throughput Screening of Antimalarial Compounds

ABSTRACT Current assays for screening new antimalarials need initiators of β-hematin formation that require laborious preparation, special devices, and substrates. In this study, based on reduction of heme absorption in β-hematin formation, we developed a simple colorimetric assay using Tween 20 as an initiator and a microplate reader for high-throughput screening of inhibitors of β-hematin formation.

Synthesis and Surface Properties of CO2H Type Gemini Surfactant Having Semifluoroalkyl Group as Hydrophobic Group

Abstract Novel CO2H type gemini surfactants having semifluoroalkyl group (Rf-(CH2)n-: Rf = C4F9, C6F13, C8F17 and n = 2, 3) as hydrophobic group were successfully synthesized and their surface properties were studied. (Perfluoroalkyl)ethylmalonic esters were synthesized by the reaction of malonic ester with Rf(CH2)2I using NaH as base in THF/DMF. (Perfluoroalkyl)propylmalonic esters were synthesized from allylmalonic ester, namely by the radical addition of Rf-I using AIBN as initiator, and reduction with Zn/AcOH. Those fluoroalkylated malonic esters were connected using Br(CH2)sBr (s = 3, 4) to give dimeric tetraesters. Then, tetraesters were hydrolyzed using KOH/EtOH followed by decarboxylation in AcOH to afford CO2H type gemini surfactants. To study their surface properties, both surface tension-concentration and surface pressure-area isotherms were measured. As expected, COOH geminis showed one order of magnitude lower critical micellar concentrations (CMC) than that of conventional 1+1 type surfactant. In the surface pressure-area measurements, as length of fluoroalkyl increased, lift-off area (AL) decreased, monolayers were clearly formed upon compression and the limited areas (A∞) for C6F13 and C8F17 were smaller than twice of that of C8F17(CH2)2COOH. Especially, COOH geminis having Rf = C8F17 and -(CH2)3- spacer showed the formation of solid phase monolayers, and the planar five membered ring-like structure was proposed.

Photolysis of polychlorinated biphenyls on octadecylsilylated silica particles

Abstract PCBs were decomposed in a quartz column packed with octadecylsilylated silica particles (ODS-silica) by external UV irradiation. The photolysis of PCBs having two to eight chlorines, including those which are the major constituents of Aroclors (PCB-180, PCB-153, PCB-118, and PCB-105) as well as coplanar PCBs, allowed the examination of the factors that affect the reactivity and product distribution. Steric congestion and molecular symmetry were found to be the major factors affecting the reactivity and the site of the reaction. Some general rules can explain the seemingly complicated decomposition pathways of various congeners. The results indicate that the dechlorination at the ortho-position which is predominant leads to products having not only higher toxic equivalency factors but also much longer life under photolysis conditions. Highly chlorinated PCBs showed tendency to lose chlorines from meta- or para-positions. The reaction pathways were not much affected by the light source, a mercury lamp with or without a pyrex filter or sunlight, in spite of the reduction in decomposition rate with a weaker light source. Continuous photolysis of highly chlorinated PCBs trapped on ODS-silica from aqueous solution was also possible.

Neutralization of toxic haem by Porphyromonas gingivalis haemoglobin receptor

Free haem is known to be toxic to organs, tissues and cells. It enhances permeability by binding to a cell membrane, which leads to cell death, and damages lipids, proteins and DNA through the generation of reactive oxygen species. Lysine- and arginine-specific gingipains (Kgp and RgpA/B) are major proteinases that play an important role in the pathogenicity of a black-pigmented periodontopathogen named Porphyromonas gingivalis. One of the adhesin domains of gingipain, HbR could bind haem as an iron nutrient source for P. gingivalis. Using erythrocyte and its membrane as a model, results from the present study demonstrate that recombinant HbR expressed in Escherichia coli could inhibit haem-induced haemolysis, probably through removing haem from the haem-membrane complex and lowering free haem toxicity by mediating dimerization of haem molecules. The ability to protect a cell membrane from haem toxicity is a new function for HbR.

Ring fragmentations of 2-alkenyl- and 2-benzyl-1,3-dithiolanes induced by bases. A novel method for the preparation of 1,1-bisalkylthio- or 1-alkylthioalk-1-enes and -alka-1,3-dienes

The reaction of 2-alkenyl- and 2-benzyl-1,3-dithiolanes with several bases and successive alkylation with alkyl halides has been investigated. In the reaction of 2-alk-1-enyl-1,3-dithiolanes with organolithium reagents and alkyl halides, deprotonation at C-2 and subsequent cycloelimination occurs to give α,β-unsaturated dithiocarboxylate anions; these readily undergo conjugate addition and/or enolation with bases followed by alkylation to afford 1,1-bisalkylthioalk-1-enes and/or 1,1-bisalkylthioalka-1,3-dienes, respectively. In contrast, when 2-alk-2-enyl-1,3-dithiolanes are submitted to an identical procedure, the reaction proceeds via ring-opening by attack of organolithium reagents at C-4 and subsequent elimination to afford 1-alkylthioalka-1,3-dienes. In the reaction of 2-benzyl-1,3-dithiolane with bases and methyl iodide in diethyl ether, β,β-bismethylthiostyrene is the major product; this is obtained via deprotonation at C-2 and subsequent cycloelimination. In contrast, in the same reaction sequence in tetrahydrofuran, base attack at C-4 gives ring-opening and 1-methylthiophenethyl vinyl sulphide and/or β-methylthiostyrene are produced preferentially. Since each of the above reaction courses is dependent both on the C-2 substituent and the reaction conditions (mainly the reaction medium) each of the products may be prepared selectively.

Novel Synthesis of Anionic Gemini Surfactants from 1, 4-Diol as a Key Block Material

In this study, a series of all-hydrocarbon anionic gemini surfactants containing COOH (adipic acid-type and suberic acid-type), SO3Na, OSO3Na, and OP=O(OH)2 functional groups was developed from 1,4-diol and 1,4-diketone as a key block material. The effect of the surfactant head groups on the surface properties was investigated by surface tension and surface pressure-area (π-A) measurements. We found that the critical micelle concentrations (CMC) of the studied geminis were smaller by one order of magnitude than those of the corresponding 1+l-type surfactants. From π-A measurements, the limiting areas of COOH-type geminis were less than twofold of the area of the corresponding 1+1-type, which indicates that the gemini structure enabled tighter packing than is possible in surfactants of the 1+l-type. In contrast, the limiting area of the OP=O(OH)2-type gemini was larger than those of the COOH-type geminis. Furthermore, the suberic acid-type gemini showed a smaller limiting area than that of adipic acid-type gemini. Therefore, we can conclude that the flexibility of the gemini at the connecting position has a significant effect on formation of the monolayer at the air/water interface.

A Novel Synthesis of Anionic Heterogemini Surfactants Containing COOH, SO3H and PO(OH)2 Headgroups from Corynomicolic Acid and its Derivatives

Abstract Anionic heterogemini surfactants with –COOH, –SO3H and –PO(OH)2 headgroups in combination were synthesized from Corynomicolic acid derivatives having R = C11H23. The –SO3H headgroup was obtained by the successive conversion of OH → OMs → SCN → SH → –SO3H. The PO(OH)2 headgroup was introduced by the conjugate-addition to E-isomer of α,β-unsaturated ester derived from Corynomycolic acid ester. Heterogemini surfactant with –SO3H and –PO(OH)2 headgroups was also synthesized from phosphonate analog of Corynomycolic acid. The stereoisomers (syn- and anti-isomers) of heterogemini surfactants were separately prepared except for heterogemini surfactants with –COOH and –PO(OH)2 headgroups. Effects of variation and stereochemistry of two anionic headgroups on their surfactant properties were also studied on the basis of surface tension measurements.

Synthesis and Monolayer Behaviors of Succinic Acid-Type Gemini Surfactants Containing Semifluoroalkyl Groups

In this work, novel succinic acid-type gemini surfactants containing semifluoroalkyl groups, dl- and meso-2,3-bis[Rf-(CH2)n]-succinic acids (Rf = C4F9, C6F13, C8F17; n = 2, 9), were successfully synthesized, and the effects of Rf, methylene chain length (n), and stereochemistry on their monolayer behaviors were studied. Critical micelle concentrations (CMC) of dl- and meso-2,3-bis[C4F9(CH2)9]-succinic acids were one order of magnitude smaller than that of the corresponding 1+1 type surfactant, C4F9(CH2)9COOH. From surface pressure-area (π-A) measurements, the lift-off areas of the geminis were found to decrease in the order C4F9 ≥ C6F13 > C8F17, regardless of methylene chain length and stereochemistry. The zero-pressure molecular areas of the geminis were twice those of the corresponding 1+1 type surfactants. Based on Gibbs compression modulus analysis, it was clarified that 2,3-bis[C8F17(CH2)n]-succinic gemini with short methylene chains (n = 2) would form more rigid monolayers than those having long methylene chains (n = 9). Unlike for 2,3-bis(alkyl)-succinic acids, the effects of stereochemistry on the monolayer behavior of semifluoroalkylated geminis were small.

Hybrid Biosurfactant: Syntheses of Hybrid Corynomycolic Acid and its Monolayer Formation

Abstract Corynomycolic acids have two hydrophilic heads (OH and COOH) and two hydrophobic tails on adjacent carbon atoms. In this work, hybrid type corynomycolic acids (syn- and anti-isomers) were synthesized via the following three steps: 1) crossed Claisen condensation of t-butyl tridecanoate with ethyl per fluorooctanoate, 2) reduction of C = O to OH, and 3) conversion of COO-t-Bu to COOH using CF3COOH. Both hydrophilic groups (OH and COOH) of hybrid corynomycolic acid would dissociate to –O– and –COO– at alkaline condition (pH = 12) while they remain unchanged at acidic condition (pH < 3). The effect of hybrid structure on the surfactant properties was investigated by the surface tension and surface pressure-area (π-A) measurements. Hybrid type corynomycolic acid gave smaller cmc and γcmc than dialkyl type one due to fluoroalkyl chain. With respect to the stereochemistry, the anti-isomer attained a smaller γcmc value than the syn-isomer. In π-A measurements, the monolayer of the syn-isomer showed a lower collapsing pressure (∼15 mN m–1) than that of the anti-isomer.

Synthesis and Monolayer Behaviors of Novel Hybrid Corynomycolic Acids Containing Semifluoroalkyl Groups.

In this work, novel hybrid-type corynomycolic acids [hybrid-OH and hybrid-COOH, with semifluoroalkyl groups (Rf-(CH2)n-: Rf = C4F9, n = 6 and Rf = C6F13, n = 3) located on the carbon atoms attached to the hydroxyl and carboxylic acid groups (C-OH and C-COOH), respectively] were successfully synthesized. The behaviors and formation of hybrid corynomycolic acid monolayers at the air-water interface were investigated by surface tension and surface pressure-area (π-A) measurements to clarify the effects of the Rf chain length, position of the semifluoroalkyl group, and surfactant molecule stereochemistry. Compared to dialkyl corynomycolic acid, both the critical micelle concentration (CMC) and the surface tension at the CMC (γCMC) of hybrid corynomycolic acids were reduced by the presence of the Rf group. With respect to the surface tension versus log concentration (γ vs. log C) isotherms, all syn-isomers of the hybrid-OH and hybrid-COOH acids showed two break points, while the anti-isomers showed only one break point. These different isotherms can be explained in terms of the steric repulsion between the two hydrophilic groups (OH and COO(-)), which depend on the stereochemistry of the surfactant. No effect of the location of the semifluoroalkyl group was observed. With respect to the formation of a monolayer film, four parameters-the lift-off area (AL), zero-pressure molecular area (A0), maximum of the Gibbs elastic modulus [EG (max)], and monolayer collapse pressure (πc)-were measured. Both AL and A0 of all hybrid corynomycolic acids were larger than the corresponding dialkyl acids due to the bulky and rigid Rf groups. Interestingly, syn- and anti-hybrids had almost identical isotherms on compression, although the values of πc of anti-hybrids were higher than those of syn-isomers. In addition, the values of EG (max) of hybrid-COOHs were slightly larger than those of the corresponding hybrid-OHs. Using the nascent soap method (agent-in-oil method), we found that anti-F4C6-OH (a hybrid corynomycolic acid) is a promising emulsifier for a ternary system comprising octane, water, and perfluoropolyether oil.