OXIDATION-REDUCTION REACTIONS OF P700 AND CYTOCHROME f IN FRACTION 1 PARTICLES PREPARED FROM SPINACH CHLOROPLASTS BY FRENCH PRESS TREATMENT

Abstract— –Fraction-1 particles were prepared by passing spinach chloroplasts three times through the French pressure cell and centrifuging in a sucrose gradient. With the electron donor DAD (diaminodurol or 2,3,5,6-tetramethyl-p-phenylenediamine) and ascorbate, a light-induced difference spectrum revealed the oxidation of both cytochrome f and P700 upon illumination of these particles. The oxidation of cytochrome f was completed in less than 0.5 msec. P700 and cytochrome f thus seem to be tightly bound to each other in these particles. Addition of Triton X-100 abolished the fast oxidation of cytochrome f but not that of P700. Artificial electron donors such as DAD, DCIP (2,6-dichlorophenol indophenol), and PMS (N-methylphenazonium methosulfate) were good electron donors for photoreaction 1 in these particles, while neither plastocyanin, Porphyra cytochrome 553, nor Euglena cytochrome-552 reduced P700 efficiently. However, after treatment of fraction 1 particles with Triton X-100 reduced DAD, DCIP and PMS were no longer efficient electron donors, while plastocyanin and the algal cytochromes were highly active in reducing P700. Mammalian cytochrome c was not a good electron donor either before or after Triton treatment. Measurements of the effectiveness of P700 reduction as a function of concentration in Triton-treated particles showed plastocyanin to be about four times more active than Porphyra or Euglena cytochromes which in turn were about fourteen times more active than mammalian cytochrome c. Recent studies by Murata and Brown have shown that plastocyanin is not required for the reduction of NADP in these particles with DCIP and isoascorbate as electron donors. The present investigation and that of Murata and Brown indicate that disintegration of chloroplasts with the French pressure cell and centrifugation in a sucrose gradient is the best method to separate system-1 particles having an electron-transport system in almost the native state as in chloroplasts.     

CELLULAR BINDING OF HEMATOPORPHYRIN DERIVATIVE IN HUMAN BLADDER CANCER CELL LINES: KK-47

Abstract— The fluorescence lifetime and degree of fluorescence polarization of hematoporphyrin derivative (HpD) have been investigated using different solutions: organic and micellar solutions. Ham's F12 medium, and KK-47 cell suspension. The lifetime and polarization degree in organic and micellar solutions did not change with increasing incubation time, but the polarization degree in the cell suspensions temporarily increased at the initial incubation time and then decreased 4 h after incubation. The lifetime in the cell suspensions exhibited a bi-phasic exponential decay. The results obtained suggested that mainly dimeric HpD may bind weakly to the cell membrane, and then slowly be distributed throughout the cytoplasm. The polarity and viscosity of the intracellular loci containing HpD were evaluated from the fluorescence polarizations of HpD in MeOH-H₂O mixtures and ethylene glycol(EG)-MeOH mixtures. The dielectric constant and viscosity of the loci containing HpD were 35 and 11 cp, respectively. Accordingly, the intracellular location of HpD were considered relatively hydrophilic loci of the cells.     

Cell adhesion molecules nectins and associating proteins: Implications for physiology and pathology

Nectins have recently been identified as new cell adhesion molecules (CAMs) consisting of four members. They show immunoglobulin-like structures and exclusively localize at adherens junctions (AJs) between two neighboring cells. During the formation of cell–cell junctions, nectins function in cooperation with or independently of cadherins, major CAMs at AJs. Similar to cadherins, which are linked to the actin cytoskeleton by binding to catenins, nectins also bind to afadin through their C-terminal region and are linked to the actin cytoskeleton. In addition to nectins, there are nectin-like molecules (Necls), which resemble nectins in their structures and consist of five members. Nectins and Necls are involved in the formation of various kinds of cell–cell adhesion, and also play key roles in diverse cellular functions including cell movement, proliferation, survival, and differentiation. Thus, nectins and Necls are crucial for physiology and pathology of multicellular organisms.     

SURFACE GRAFTING OF POLYESTERS ONTO ORGANIC PIGMENTS AND THEIR DISPERSIBILITY IN ORGANIC SOLVENT

To modify the dispersibility of an organic pigment, such as quinacridone and anthraquinone, in organic solvents, the surface grafting of polyesters onto organic pigments by the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides initiated by potassium carboxylate (COOK) groups introduced onto these surfaces was investigated. The organic pigment having COOK groups was prepared by the following two methods: (a) the reaction of potassium carbonate with surface acyl chloride groups, which were introduced by the treatment of surface amino groups with adipoyl dich bride, and (b) the graft polymerization of potassium acrylate initiated by azo groups introduced onto the surface. The anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was initiated by COOK groups introduced onto the organic pigment surfaces to give the corresponding polyester-grafted organic pigments. The dispersibility of organic pigments in organic solvent was remarkably improved by the grafting of polyesters onto the surface.     

Structure and bonding of the (C6H6)+ 2 radical

To elucidate the relative stability of various structures of the benzene dimer cation radical, (C₆H₆)⁺ ₂ in its ground and low-lying excited states, ab initio complete active space self-consistent field (CASSCF), multi-reference singly and doubly excited configuration interaction (MRSDCI), and multi-reference coupled pair approximation (MRCPA) calculations were performed. Full optimization was performed at the CASSCF level for various structures of the dimer cation, followed by MRSDCI and MRCPA calculations. It was found that the global minimum of the cation is at a slipped C_2h sandwich structure but there are some other sandwich structures with almost the same stability, being within about kcal mol^?1. T-shape structures are less stable than the sandwich structures, by more than 5 kcal mol^?1 by MRCPA calculations. Low lying electronic excited states in various structures are also discussed.     

A NEW METHOD OF DETERMINING INTRACELLULAR FREE Ca2+CONCENTRATION USING Quin2-FLUORESCENCE

We determined intracellular free Ca2+ concentration by fluorescence spectroscopy and the time-resolved measurements of 2-[(2-amino-5-methylphenoxy) methyl]-6-methoxy-8-aminoquinoline-N,N,N',N'-tetraacetic acid, tetrapotassium salt (Quin2) incorporated in suspended mouse leukemia L1210 cells. The paper reports the following two points. (1) Various fluorescence spectrum patterns in cell suspensions dissolved with Quin2 acetoxy methylester were compared with those of the complex in buffer solution containing esterase. (2) The fluorescence lifetime of Quin2 bound to Ca2+ was approx. 4.5-11 times longer (10 +/- 1 ns) than that (1.5 +/- 0.5 ns) of Quin2. The fraction of the long lifetime component was plotted against the concentration of CaCl2 in buffer solution. From the results obtained, it was found that approx. 35 nM Ca2+ was contained in each L1210 cell.     

Theoretical study of low lying electronic states of GdO

Low lying electronic states of GdO have been investigated by complete active space SCF (CASSCF) and multireference singly and doubly excited configuration interaction (MRSDCI) calculations using the model core potential (MCP) method. The 4f electrons of Gd were included explicitly in the valence space. Relativistic effects were incorporated in the MCP and basis sets for Gd at the level of Cowan and Griffin's quasirelativistic Hartree—Fock method. The ⁹Σ^? state (f⁷σ) was the ground state, and excited states, ⁹Δ, ⁹Π, 2⁹Σ^?, ⁷Σ^?, ⁷Δ, ⁷Π, and 2⁷E^?, lay between 0 ～ 22 300 cm^?1. The energy separations for these states agreed well with available experimental values. Calculated GdO bond lengths and vibrational frequencies for these states are in the ranges of 1.81–1.85 Å and of 800–880 cm^?1, respectively. Mulliken population analysis showed that the gross population of the 4f orbitals was 7.1 e for all these states, and that the 4f electrons were strongly localized on Gd atom. The effective charge distribution was approximated to be Gd⁺O^?. The σ and π bonding orbitals were mainly formed by Gd 5d and O 2p orbitals.