Mamoru Nango - Academia.edu (original) (raw)

Papers by Mamoru Nango

Chemistry Letters, Jan 5, 2008

1α-Helix hydrophobic polypeptide bearing spermine, which has similar amino acid sequences to the ... more 1α-Helix hydrophobic polypeptide bearing spermine, which has similar amino acid sequences to the hydrophobic core in the native photosynthetic light-harvesting (LH) 1-α polypeptide from Rhodospirillum (Rsp.) rubrum, was synthesized. Interestingly, an enhanced photoelectric current was observed when BChI a complexes together with the LH1-α model polypeptide were assembled onto an ITO electrode.

Journal of Photochemistry and Photobiology A: Chemistry, 2015

The primary process of photosynthesis involves the absorption of sunlight by antenna complexes an... more The primary process of photosynthesis involves the absorption of sunlight by antenna complexes and subsequent transfer of excitation energy toward the reaction center where a charge separation takes place. This process is usually performed in photosynthetic membranes. The photosynthetic apparatus from purple photosynthetic bacteria contains the reaction center (RC) and two types of antenna complexes, the core antenna light-harvesting 1 (LH1) complex and the peripheral light-harvesting 2 (LH2) complex, and is embedded in these membranes. The arrangement of these light-harvesting pigment-protein complexes in the photosynthetic membranes does have an influence on the lightharvesting performance in the primary process of photosynthesis. In this study, we have constructed hybrid artificial photosynthetic membranes by introducing both LH2 complexes (from Rhodopseudomonas acidophila) and LH1-RC core complexes (from Blastochloris viridis) to a lipid bilayer system composed of Egg PC. The architecture of the artificial photosynthetic membranes can be varied by controlling the ratio of added LH2 to LH1-RC core complexes (LH1-RC/LH2 = 1/1, 1/2, 1/5, 1/12). Previous studies using transmission electron microscopy (TEM) showed that the packing of LH1-RC in a trigonal lattice was changed to orthorhombic by increasing the ratio of LH2 to LH1-RC. We further investigated the local arrangement of the pigment-protein complexes using high-resolution atomic force microscopy and postulate some types of arrangement depending on the condition of the sample preparation. LH2 to LH1 energy transfer was studied using confocal laser fluorescence microscopy with 400 nm spatial resolutions. We found a difference in the ratio of the fluorescence intensity emitted from LH2 and LH1 depending on the local arrangement of these antenna complexes in the hybrid artificial photosynthetic membranes. The effect of the arrangement of the pigment-protein complexes on the light harvesting efficiency is discussed. 2015 Elsevier B.V. All rights reserved.

Science Access, 2001

Molecular assemblies of zinc-substituted bacteriochloropyll a (Zn-BChl a ) using light-harvesting... more Molecular assemblies of zinc-substituted bacteriochloropyll a (Zn-BChl a ) using light-harvesting ( LH ) polypeptide separately isolated from photosynthetic bacteria, R. rubrum and its model synthetic polypeptides were examined in lipid bilayers as well as in n-Octyl-b-D-glucopyranoside (OG) micelle. The key to the assemby is of constructing an artificial LH complex in lipid bilayers as well as of providing insight into structural requirements for formation of the core LH complex (LH 1). UV-vis., CD, SAXS, and DLS data indicated that the LH- a polypeptide selectively organizeds Zn-BChl a complex in OG micelle rather than BChl a complex, analogous to the LH1-type complex, depending on the temperature. Comparing the amino acid sequence in the N- and C-terminal segments of the LH- a polypeptide and its model peptides on the complex-formation with Zn-BChl a or BChl a reveals that the amino acid residues from M to F in the N-terminal segment of the LH-a polypeptide essentially account fo...

Chemical Physics, 2013

ABSTRACT In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting... more ABSTRACT In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency.

Chemical Engineering Science, 1991

Cancer, 2003

BACKGROUND. The authors previously observed that antiangiogenic scheduling of photodynamic therap... more BACKGROUND. The authors previously observed that antiangiogenic scheduling of photodynamic therapy (PDT) was effective in causing tumor regression through hemostasis. It would thus be expected that photosensitizer entrapped in polycation liposomes (PCLs) would be efficiently taken up in tumor-derived angiogenic vascular endothelial cells due to the strong electrostatic adhesion between the polycation and the plasma membrane, thus resulting in enhanced phototherapeutic efficacy.

Bulletin of the Chemical Society of Japan, 1986

Bulletin of the Chemical Society of Japan, 2009

Bulletin of the Chemical Society of Japan, 2000

ABSTRACT

Biomacromolecules, 2012

A polyhistidine (His) tag was fused to the C- or N-terminus of the light-harvesting (LH1)-α chain... more A polyhistidine (His) tag was fused to the C- or N-terminus of the light-harvesting (LH1)-α chain of the photosynthetic antenna core complex (LH1-RC) from Rhodobacter sphaeroides to allow immobilization of the complex on a solid substrate with defined orientation. His-tagged LH1-RCs were adsorbed onto a gold electrode modified with Ni-NTA. The LH1-RC with the C-terminal His-tag (C-His LH1-RC) on the modified electrode produced a photovoltaic response upon illumination. Electron transfer is unidirectional within the RC and starts when the bacteriochlorophyll a dimer in the RC is activated by light absorbed by LH1. The LH1-RC with the N-terminal His-tag (N-His LH1-RC) produced very little or no photocurrent upon illumination at any wavelength. The conductivity of the His-tagged LH1-RC was measured with point-contact current imaging atomic force microscopy, indicating that 60% of the C-His LH1-RC are correctly oriented (N-His 63%). The oriented C-His LH1-RC or N-His LH1-RC showed semiconductive behavior, that is, had the opposite orientation. These results indicate that the His-tag successfully controlled the orientation of the RC on the solid substrate, and that the RC produced photocurrent depending upon the orientation on the electrode.

Biomacromolecules, 2007

Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodospirillum rubrum and Rhodopse... more Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodospirillum rubrum and Rhodopseudomonas palustris were successfully self-assembled on an ITO electrode modified with 3-aminopropyltriethoxysilane. Near infra-red (NIR) absorption, fluorescence, and IR spectra of these LH1-RC complexes indicated that these LH1-RC complexes on the electrode were stable on the electrode. An efficient energy transfer and photocurrent responses of these LH1-RC complexes on the electrode were observed upon illumination of the LH1 complex at 880 nm.

Biomacromolecules, 2011

The construction and structural analysis of a tethered planar lipid bilayer containing bacterial ... more The construction and structural analysis of a tethered planar lipid bilayer containing bacterial photosynthetic membrane proteins, light-harvesting complex 2 (LH2), and light-harvesting core complex (LH1-RC) is described and establishes this system as an experimental platform for their functional analysis. The planar lipid bilayer containing LH2 and/or LH1-RC complexes was successfully formed on an avidin-immobilized coverglass via an avidin-biotin linkage. Atomic force microscopy (AFM) showed that a smooth continuous membrane was formed there. Lateral diffusion of these membrane proteins, observed by a fluorescence recovery after photobleaching (FRAP), is discussed in terms of the membrane architecture. Energy transfer from LH2 to LH1-RC within the tethered membrane was observed by steady-state fluorescence spectroscopy, indicating that the tethered membrane can mimic the natural situation.

Biological & Pharmaceutical Bulletin, 2011

Previously we developed dicetyl phosphate-tetraethylenepentamine-based polycation liposomes (TEPA... more Previously we developed dicetyl phosphate-tetraethylenepentamine-based polycation liposomes (TEPA-PCL) for use in small interfering RNA (siRNA) therapy. In the present study, mammalian target of rapamycin (mTOR) expression in cancer cells was silenced with mTOR-siRNA (simTOR) formulated in TEPA-PCL modified with Ala-Pro-Arg-Pro-Gly (APRPG), a peptide having affinity for vascular endothelial growth factor receptor-1 (VEGFR-1). We investigated the effects of inhibition of mTOR, focusing on the differences between cells treated with simTOR and those with rapamycin in terms of Akt (ser473) phosphorylation and antiproliferative effects. Rapamycin treatment is known to induce Akt (ser473) phosphorylation which attenuates the antiproliferative effects of rapamycin. As a result, knockdown of mTOR did not alter or only slightly reduced Akt (ser473) phosphorylation in phosphatase and tensin homolog deleted from chromosome 10 (PTEN)-null (LNCaP and MDA-MB-468 cells) and PTEN-positive (DU 145 and MDA-MB-231) cells, although rapamycin induced Akt (ser473) phosphorylation of these cells. Rapamycin suppressed the growth of PTEN-null cells, in which the rapamycin-sensitive mTOR complex 1 (mTORC1) is excessively activated. On the other hand, rapamycin did not suppress the growth of PTEN-positive cells possibly through a negative feedback mechanism via the rapamycin-insensitive mTOR complex 2 (mTORC2) signaling pathway. In contrast, simTOR significantly suppressed the growth of cancer cells regardless of the presence of PTEN, possibly through inhibition of both mTORC1 and mTORC2. These results indicate that mTOR knockdown using APRPG-TEPA-PCL/simTOR is likely to be an effective strategy for cancer siRNA therapy.

Biological and Pharmaceutical Bulletin, 2013

Novel polycation liposomes decorated with cyclic(Cys-Arg-Gly-Asp-D-Phe) peptide (cyclicRGD)-polye... more Novel polycation liposomes decorated with cyclic(Cys-Arg-Gly-Asp-D-Phe) peptide (cyclicRGD)-polyethylene glycol (PEG) (RGD-PEG-polycation liposomes (PCL)) were previously developed for cancer therapy based on RNA interference. Here, we demonstrate the in vivo delivery of small interfering RNA (siRNA) to tumors by use of RGD-PEG-PCL in B16F10 melanoma-bearing mice. Pharmacokinetic data obtained by positron emission tomography showed that cholesterol-conjugated siRNA formulated in RGD-PEG-PCL markedly accumulated in the tumors. Delivered by RGD-PEG-PCL, a therapeutic cocktail of siRNAs composed of cholesterol-conjugated siRNAs for c-myc, MDM2, and vascular endothelial growth factor (VEGF) were able to significantly inhibit the growth of B16F10 melanoma both in vitro and in vivo. These data suggest that targeted delivery of siRNAs by use of RGD-PEG-PCL has considerable potential for cancer treatment.

Bioconjugate Chemistry, 2010

Synthetic cationic lipids are promising transfection agents for gene therapy. We report here that... more Synthetic cationic lipids are promising transfection agents for gene therapy. We report here that polyamine conjugates of dialkyl phosphates, combined with natural lipids and assembled in the form of liposomes (polycationic liposome: PCL), possess high transfection activity in the COS-1 cell line. Furthermore, we describe the functional morphology of the PCL/DNA complexes as revealed by atomic force microscopy (AFM). The conjugates were synthesized from dialkyl phosphates (with alkyl chain lengths of 12, 14, or 16 carbons) by reaction with the polyamine molecules, spermidine, spermine, or polyethylenimine (PEI(1800)). [Dewa, T., et al. Bioconjugate Chem. 2004, 15, 824]. The PCL composed of the spermidine and C16 conjugate combined with phospholipid and cholesterol (conjugate/phospholipid/cholesterol = 1/1/1 as a molar ratio) exhibited 3.6 times higher activity than that of a popular commercial product. Systematic tests revealed clear correlations of the transgene activity with physical properties of the polyamine, in particular, that longer alkyl chains and the lower molecular weight polyamines (spermidine, spermine) favor high efficacy at the higher nitrogen/phosphate ratio = 24 (N/P, stoichiometric ratio of nitrogen in the conjugate to phosphate in DNA). The low molecular weight polyamine-based PCLs, which formed 150-400 nm particles with plasmid DNA (lipoplexes), exhibited approximately 3-fold higher gene transfer activity than micellar aggregates (lacking phospholipid and cholesterol) of the corresponding conjugate. In contrast, the PEI-based PCL formed large aggregates (approximately 1 microm), that, like the micellar aggregate form, had low activity. Activity of the low molecular weight polyamine-based PCLs increased linearly with the N/P of the lipoplex up to N/P = 24. Formation of lipoplexes was examined by agarose gel electrophoresis, dynamic light scattering (DLS), and AFM. At the lower N/P = 5, large aggregates of complex (approximately 1 microm), in which DNA molecules were loosely packed, were observed. At higher N/P, lipoplexes were converted into smaller particles (150-400 nm) having a lamellar structure, in which DNA molecules were tightly packed. Such morphological features of the lipoplex correlate with the dependence of transfection on the N/P in that the lamellar structures gave superior transfection. AFM also indicated that the lipoplexes disassembled significantly, releasing DNA, when the lipoplexes were exposed to acidic conditions (pH 4). The significance for transfection activity of the metamorphosis of bilayer lipoplexes is discussed relative to that of the less active micellar aggregate form, which is unresponsive to pH change.

Bioconjugate Chemistry, 2004

To develop a novel nonviral gene carrier, three types of polyamine-dialkyl phosphates conjugates ... more To develop a novel nonviral gene carrier, three types of polyamine-dialkyl phosphates conjugates were synthesized via an unprecedented synthetic intermediate, dimerized dicetyl phosphate (DCP) anhydride, and the transfection efficiency and the complexation properties of the conjugate-DNA were evaluated. Condensation of DCP by 1,3,5-triisopropylbenzenesulfonyl chloride, TPSCl, gives the dimerized anhydride, which is stable enough to isolate by column chromatography in approximately 90% yield. The anhydride is reactive with various amines, i.e., spermidine, spermine, and polyethylenimine (PEI(1800)), providing corresponding polyamine-DCP conjugates via phosphoramidate linkage. The polyamine-DCP conjugates exhibited moderate transfection efficacy evaluated by beta-galactosidase assay. The conjugate-DNA complex was observed by using an atomic force microscope (AFM), revealing that the PEI(1800)-DCP conjugate, which showed the most efficient transfection, enables the formation of the more compact complex with DNA.

Bioconjugate Chemistry, 2011

Biochemistry, 1995

To ascertain the minimal structural requirements for formation of the subunit and core lightharve... more To ascertain the minimal structural requirements for formation of the subunit and core lightharvesting complex (LHl), the aand /3-polypeptides of the LH1 from three purple photosynthetic bacteria were enzymatically or chemically truncated or modified. These polypeptides were then used in reconstitution experiments with bacteriochlorophyll a (BChla), and the formation of subunit and LH1 complexes was evaluated using absorbance and circular dichroism spectroscopies. Truncation or modification outside of the conserved core sequence region of the polypeptides had no effect on subunit or LH1 formation. However, the extent of formation and stability of the subunit and LH1 decreased as the polypeptide was shortened inside the core region within the N-terminal domain. This behavior was suggested to be due to the loss of potential ion-pairing and/or hydrogen-bonding interactions between the polypeptides. While the spectroscopic properties of the subunit complexes generated using truncated polypeptides were analogous to those obtained using native polypeptides, in some cases the resulting LHl complex absorption was blue-shifted relative to the control. Thus, truncation within the N-terminal domain may have long-range effects on the immediate BChla binding environment, since the putative BChla binding site resides near the C-terminal end of the polypeptides. It was also demonstrated that the His located within the membrane-spanning domain on the N-terminal end of the /3-polypeptide is not participating in ligation of the BChla in the reconstituted subunit and therefore probably not in LH1.

Biochemistry, 2005

A series of cysteine-bearing hydrophobic polypeptides analogous to a light-harvesting one betapol... more A series of cysteine-bearing hydrophobic polypeptides analogous to a light-harvesting one betapolypeptide (LH1beta) from the LH1 complex from the purple photosynthetic bacterium, Rhodobacter sphaeroides, was synthesized using an Escherichia coli expression system. The cysteine was placed in the C- or N-terminal regions of the polypeptide to investigate the influence of steric confinement and orientation of the polypeptides via disulfide linkages as they were self-assembled with zinc-substituted bacteriochlorophyll a ([Zn]-BChl a). The polypeptides were expressed as water-soluble fusion proteins with maltose-binding protein (MBP). The fusion proteins formed a subunit-type complex with the [Zn]-BChl a in an n-octyl-beta-d-glucopyranoside (OG) micellar solution regardless of the cross-links or the cleavage of the cysteines, judging from absorption, CD, and fluorescence spectra. Following treatment with trypsin, the polypeptides were detached from the MBP portion. Such trypsin-digested polypeptides formed a subunit-type LH complex at 25 degrees C, which also showed that the disulfide linkage was not crucial for the subunit formation. When a polypeptide having cysteine on the C-terminus was assembled at 4 degrees C, the Qy absorption band was remarkably red-shifted to approximately 836 nm, suggesting that the cleavage of the large MBP portion liberates the polypeptides to form the progressive type of complex similar to LH1-type complex. The trypsin-treated polypeptides bearing cysteines in both terminal regions, which are randomly cross-linked, did not form the LH1-type complex under oxidative conditions but did form the complex under reductive conditions. This observation suggests that the polypeptide orientation strongly influences the LH1-type complex formation. The progressive assembly from the subunit to the holo-LH1-type complex following cleavage of MBP portion in a lipid bilayer is also briefly discussed.