Synthesis of zinc 3-hydroxymethyl-porphyrins possessing carbonyl groups at the 13- and/or 15-positions for models of self-aggregative chlorophylls in green photosynthetic bacteria

Zinc 3-hydroxymethyl-protopyropheophorbide-d derivatives 1, 2, and 3 possessing carbonyl group(s) at the 13/15-, 13-, and 15-positions, respectively, and 4 lacking the C=O group were prepared from naturally occurring chlorophyll-a. Zinc porphyrins 1 and 2 possessing the 13-C=O self-aggregated in an aqueous micellar solution, similarly to the self-aggregates of BChls-c/d/e in the main light-harvesting antenna systems of green photosynthetic bacteria, whereas 3 and 4 lacking the 13-C=O failed to make such well-ordered aggregates. These results indicated that both the presence of the C=O group and its situation at the 13-position were preferable for formation of the well-ordered J-aggregates.     

Exact determination of phagocytic activity of alveolar macrophages toward polymer microspheres by elimination of those attached to the macrophage membrane

A method for exact determination of phagocytic activity of alveolar macrophage (M) cells toward synthetic microspheres (MS) by optical microscopy was developed. We examined the effectiveness of the treatment of M samples with trypsin, acid or xylene to remove the polystyrene latex microspheres (PSL MS) attached to M cell membranes during their phagocytosis by M cells. We found that centrifugation, which was employed to collect M samples after incubation with MS, affected significantly the efficiency of the various treatments. Of the three treatments, xylene treatment without centrifugation was the most effective to determine the phagocytic activity of M cells, as xylene dissolved the PSL MS on the cell surface almost completely. This treatment was also effective in the case of poly(lactic-co-glycolic acid) MS (PLGA MS), which have been commonly used as an efficient vehicle for drug delivery system.     

Electron transfer of quinone self-assembled monolayers on a gold electrode

Dialkyl disulfide-linked naphthoquinone, (NQ-C_n-S)₂, and anthraquinone, (AQ-C_n-S)₂, derivatives with different spacer alkyl chains (C_n: n = 2, 6, 12) were synthesized and these quinone derivatives were self-assembled on a gold electrode. The formation of self-assembled monolayers (SAMs) of these derivatives on a gold electrode was confirmed by infrared reflection-absorption spectroscopy (IR-RAS). Electron transfer between the derivatives and the gold electrode was studied by cyclic voltammetry. On the cyclic voltammogram a reversible redox reaction between quinone (Q) and hydroquinone (QH₂) was clearly observed under an aqueous condition. The formal potentials for NQ and AQ derivatives were −0.48 and −0.58 V, respectively, that did not depend on the spacer length. The oxidation and reduction peak currents were strongly dependent on the spacer alkyl chain length. The redox behavior of quinone derivatives depended on the pH condition of the buffer solution. The pH dependence was in agreement with a theoretical value of E_1/2 (mV) = E′ − 59pH for 2H⁺/2e⁻ process in the pH range 3–11. In the range higher than pH 11, the value was estimated with E_1/2 (mV) = E′ − 30pH , which may correspond to H⁺/2e⁻ process. The tunneling barrier coefficients (β) for NQ and AQ SAMs were determined to be 0.12 and 0.73 per methylene group (CH₂), respectively. Comparison of the structures and the alkyl chain length of quinones derivatives on these electron transfers on the electrode is made.     

Formation of intermediate micellar phase between hexagonal and discontinuous cubic liquid crystals in brine/N-acylamino acid surfactant/N-acylamino acid oil system

The phase behavior in the brine/sodium N-dodecanoyl sarcosinate (Sar)/isopropyl N-dodecanoyl sarcosinate (SLIP) system has been investigated by means of phase study, static light scattering, and small-angle X-ray scattering. The liquid crystal phases, hexagonal (H(1)) and discontinuous cubic (I(1)), melt upon the addition of NaCl, which shows the similar effect to the increasing of temperature. The addition of SLIP to the brine/Sar solution at high Sar concentration induces the phase transition from H(1) to I(1) via the isotropic micellar solution (W(m2)). The micellar structure in the W(m2) phase also changes from the wormlike to the globular micelle with SLIP concentration. Adding NaCl reduces the repulsive force between the Sar head groups and simultaneously the space of the solubilized SLIP in the palisade layer, leading SLIP to shift their location further into the micelle core. As a consequence, the hexagonal symmetry breaks into the micelle solution and the liquid crystal order is destabilized entropically.     

Solubilization of oil in a mixed cationic liquid crystal

The mixing fraction of didodecyldimethylammonium bromide (DDAB) in dodecyltrimethylammonium bromide + DDAB to produce a lamellar liquid crystal (L _α) abruptly decreases upon addition of a small amount of m-xylene, whereas the mixing fraction becomes constant at high m-xylene content. Similar results were obtained in saturated hydrocarbon systems. It is considered that oil molecules in the surfactant palisade layer increases the effective cross-sectional area per surfactant head group, a_s, whereas a_s is constant if the oil molecules are solubilized in the core of the liquid crystal. The volume fraction of penetrating oil in the total solubilized oil is defined as a penetration parameter, Pe, which is calculated from small-angle X-ray scattering data. Pe is high in the m-xylene system, whereas it is low in the n-decane system. Even in the same oil system, Pe decreases dramatically with increasing solubilization. Hence, most of the oil added penetrates into a palisade layer at an early stage of oil addition. This causes a change in the mixing fraction of surfactant in the L _α phase. Thereafter the oil is solubilized in the core of the bilayer with further addition of oil. Received: 20 April 1998 Accepted: 16 July 1998     

Asymmetric synthesis of α-fluoro-α-sulfenyl-β-ketoesters using DBFOX-Ph/Ni(II) complex

Enantioselective α-sulfenylation of α-fluoro-β-ketoesters 4 with phenylsulfenyl chloride catalyzed by DBFOX-Ph/Ni(II) complex afforded the corresponding α-fluoro-α-sulfenyl-β-ketoesters 2 in moderate to good yields with excellent enantiomeric excesses up to 93% ee. α-Fluoro-α-sulfenyl-β-ketoesters can be effectively converted to tri-fluorinated α-sulfenylcarboxylates by the use of DAST, which should be useful intermediates for the synthesis of non-racemized fluorinated isosteres of pharmaceutically attractive SM₃₂. The enantioselective α-phenylsulfenylation as well as α-pentafluoro-phenylsulfenylation of non-fluorinated β-ketoesters 5 were also carried out under the same catalyst conditions affording up to 95% ee of the products 6-8.     

Phase behavior and preparation of mesoporous silica in aqueous mixtures of fluorinated surfactant and hydrophobic fluorinated polymer

The phase behavior and formation of self-assemblies in the ternary water/fluorinated surfactant (C(8)F(17)EO(10))/hydrophobic fluorinated polymer (C(3)F(6)O)(n)COOH system and the application of those assemblies in the preparation of mesostructured silica have been investigated by means of phase study, small angle X-ray scattering, and rheology. Hexagonal (H(1)), bicontinuous cubic (V(1)) with Ia3d symmetry, and polymer rich lamellar (L(alpha)(')) are observed in the ternary diagram. C(8)F(17)EO(10) molecules are dissolved in polymer rich aggregates, whereas (C(3)F(6)O)(n)COOH molecules are practically insoluble in the surfactant lamellar phase due to packing restrictions. Hence, two types of lamellar phases exist: one with surfactant rich (L(alpha)) and the other with polymer rich (L(alpha)(')) in the water/C(8)F(17)EO(10)/(C(3)F(6)O)(n)COOH system. As suggested by rheological measurements, worm-like micelles are present in C(8)F(17)EO(10) aqueous solutions but a rod-sphere transition takes place by solubilization of (C(3)F(6)O)(n)COOH. C(8)F(17)EO(10) acts as a structure directing agent for the preparation of hexagonal mesoporous silica by the precipitation method. The addition of (C(3)F(6)O)(n)COOH induces the formation of larger but disordered pores.