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S Iijima

Publications and source records attributed to S Iijima.

At least 19 recordsLinked to original sources
PubMed2006

Changes in the fluorescence spectrum of individual single-wall carbon nanotubes induced by light-assisted oxidation with hydroperoxide.

Through fluorescence-spectrum measurements, we investigated the effects of light-assisted oxidation with H2O2 (LAOx) on single-wall carbon nanotubes (SWNTs) that were individually dispersed in an aqueous solution of surfactant. The intensities of the fluorescence spectra were decreased remarkably by the LAOx when the light's wavelength was 400-500 nm and a little when 600-700 nm. The spectrum intensity did not recover even when the pH was restored to an original value of 6.5. The spectra changed little when the LAOx wavelength was 500-600 nm or the light was not irradiated. In addition, the effect of LAOx on SWNTs was related to the diameters of SWNTs. We inferred that these phenomena reflected that H2O2 was dissociated by absorbing the fluorescence light emitted from optically excited SWNTs, which, in turn, accelerated the burning out of SWNTs.

Journal Article↗
PubMed2005

Isolating single-wall carbon nanohorns as small aggregates through a dispersion method.

An approach to isolating small aggregates of single-wall carbon nanohorns (SWNHs) is presented. SWNHs are ultrasonically treated in an aqueous solution of surfactant, resulting in dispersion of SWNH aggregates. Subsequent centrifuging enables the separation of small aggregates from larger aggregates or agglomerations and removal of graphitic particles (GG balls), the main impurity. The SWNHs obtained in this way were purified and formed small aggregates, thus exhibiting characteristics superior to those of SWNHs before treatment. We believe that the ability to isolate small SWNH aggregates in an aqueous solution should contribute to their application in the fields of biological sensing and drug delivery systems.

Journal Article↗
PubMed2005

Dissociation of electrolytes in a nano-aqueous system within single-wall carbon nanotubes.

Research on material incorporation within single-wall carbon nanotubes (SWNTs) through aqueous solutions of various electrolytes is performed for the purpose of providing a foundation for future application of SWNTs to, for example, drug delivery systems. We have determined that the optical spectra of SWNTs were significantly affected when SWNTs that had opened holes or removed caps were treated through immersion in an aqueous solution of electrolytes, followed by drying at room temperature; however, the spectra of SWNTs without opened holes or removed caps were not subjected to such treatment. We infer that when the sucked solutions remained inside the tubes, even after drying (the nano-aqueous system), the electrolyte was dissociated into ions, which was likely to change the electronic states of SWNTs. On the other hand, when the SWNTs were well-dried under vacuum, no remarkable changes in their optical spectra were observed.

Letter↗
PubMed2004

Fe-sapphire and C-Fe-sapphire interactions and their effect on the growth of single-walled carbon nanotubes by chemical vapor deposition.

We previously reported that the quantity of single-walled carbon nanotubes grown on Fe-coated sapphire by chemical vapor deposition depended on the crystallographic faces of sapphires. In this report, we show that the interaction of Fe, sapphire, and carbon depended on the sapphire faces. We deduce that the quantity of Fe available to catalyze the growth of single-walled carbon nanotubes was suppressed by the formation of Fe-Al alloys and whether the Fe-Al alloys were formed on Fe-coated sapphire or not depended on the sapphire-surface structure.

Aluminum↗
PubMed2003

Chemically doped double-walled carbon nanotubes: cylindrical molecular capacitors.

A double-walled carbon nanotube is used to study the radial charge distribution on the positive inner electrode of a cylindrical molecular capacitor. The outer electrode is a shell of bromine anions. Resonant Raman scattering from phonons on each carbon shell reveals the radial charge distribution. A self-consistent tight-binding model confirms the observed molecular Faraday cage effect, i.e., most of the charge resides on the outer wall, even when this wall was originally semiconducting and the inner wall was metallic.

Journal Article↗
PubMed2003

Direct imaging of Sc2@C84 molecules encapsulated inside single-wall carbon nanotubes by high resolution electron microscopy with atomic sensitivity.

Intramolecular structure of the scandium dimetallofullerene (Sc(2)@C(84)) has been clearly revealed by high resolution transmission electron microscopy with the single-atom sensitivity. Direct observation of two Sc atoms inside each fullerene molecule has led to a successful determination of the molecular symmetry among the three possible structural isomers for the Sc(2)@C(84). The present work introduces a new electron microscopic approach to investigate individual molecular structures and demonstrates the possibility for determining the molecular isomer on a single-molecular basis.

Journal Article↗
PubMed2002

Linking chiral indices and transport properties of double-walled carbon nanotubes.

We performed in situ transport measurements in a transmission-electron microscope (TEM) on individual double-walled carbon nanotubes (DWNT). Using selected-area electron diffraction, the chiral indices of the two tubes constituting the DWNTs were determined through careful comparison with theory. We discuss the case of a DWNT whose two tubes have a gap at half filling and show a finite density of delocalized state at the Fermi level. The exact determination of chiral indices should be reachable in any transport-measurement experiment with samples that allow TEM characterization.

Journal Article↗
PubMed2002

Distribution and partial characterisation of IgG Fc binding protein in various mucin producing cells and body fluids.

BACKGROUND AND AIMS: Mucus released from goblet cells is important in intestinal mucosal defence, and mucin glycoproteins are thought to be major components of mucus. Recently, we identified and cloned another component of human colonic mucus, IgG Fc binding protein (Fc gamma BP). Fc gamma BP is immunologically distinct from known Fc gamma receptors and its structure contains repeated cysteine rich unit sequences resembling those present in mucins. In this work, we assessed the tissue distribution of Fc gamma BP, its binding activity in various body fluids, and its ability to inhibit complement mediated haemolysis. METHODS: Immunohistochemical localisation of Fc gamma BP, using monoclonal antibodies against Fc gamma BP (K9 or K17) and labelled IgG, was conducted in various mucin producing tissues: colon, small intestine, stomach, gall bladder, cystic duct, choledochus, bronchus, submandibular gland, conjunctiva, and cervix uteri. The binding activity of Fc gamma BP in mucus extracted from colon, gastric juice, bile, nasal discharges, saliva, sputum, and tears was also examined by immunodotblot and immunoprecipitation using these monoclonal antibodies. Inhibition of complement mediated haemolysis by Fc gamma BP was investigated using sheep red blood cells (SRBC) and anti-SRBC IgG. RESULTS: The immunohistochemical study revealed that mucin secreting cells in the colon, small intestine, gall bladder, cystic duct, choledochus, bronchus, submandibular gland, and cervix uteri contained Fc gamma BP, and immunodotblot and immunoprecipitation analysis using IgG and monoclonal antibodies demonstrated that the fluids secreted by these cells were capable of binding IgG. Mucin producing cells of the conjunctiva did not express Fc gamma BP molecules or bind to IgG. The surface mucus cells in the stomach were variably positive for Fc gamma BP. Perhaps because of proteolytic degradation, Fc gamma BP in gut lavage fluid did not have IgG binding activity, although this activity was present in the mucus covering the colon. Fc gamma BP suppressed complement mediated haemolysis of SRBC. CONCLUSIONS: Fc gamma BP is widely expressed on mucosal surfaces and in external secretions. It is functionally intact in several fluids. These findings lend support to the concept that Fc gamma BP is an important component of mucosal immunological defences.

Animals↗
PubMed2001

Type-specific separation of animal cells in aqueous two-phase systems using antibody conjugates with temperature-sensitive polymers.

A new type of aqueous two-phase system (ATPS) has been developed in which a temperature-sensitive polymer, poly-N-isopropylacrylamide [poly (NIPAM)] was used as a ligand carrier for the specific separation of animal cells. Monoclonal antibodies were modified with itaconic anhydride and copolymerized with N-isopropylacrylamide, and the ligand-conjugated carriers were added to the polyethylene glycol 8000-dextran T500 aqueous two-phase systems. The antibody-polymer conjugates were partitioned to the top phase in the absence or presence of 0.15 M NaCl. When ligand-conjugated carriers were used, more than 80% of the cells were specifically partitioned to the top phase in the presence of NaCl up to 0.1 M. The cells were partitioned almost completely to the bottom phase at 0.1 M NaCl or above, when no antibody-conjugate was added in the ATPS. As a model system, CD34-positive human acute myeloid leukemia cells (KG-1) were specifically separated from human T lymphoma cells (Jurkat) by applying anti-CD34 conjugated with poly-N-isopropylacrylamide in the aqueous two-phase system. By the temperature-induced precipitation of the polymer, about 90% of the antibody-polymer conjugates were recovered from the top phase, which gave approximately 75% cell separating efficiency in the next cycle of reuse.

Acrylamides↗
PubMed2001

Production of transgenic quails with high frequency of germ-line transmission using VSV-G pseudotyped retroviral vector.

We report here the production of transgenic quails using a replication-defective pantropic retroviral vector based on Moloney murine leukemia virus (MoMLV) pseudotyped with vesicular stomatitis virus G protein (VSV-G). The retroviral vector was injected into laid quail embryos at the blastodermal stage, and the embryos were incubated to hatch to produce G(0) transgenic quails. Among 134 embryos subjected to viral injection, 37 hatched. The viral vector sequence was detected in the tissues of all G(0) quails. The germ-line transmission efficiency of G(0) quails mated with nontransgenic quails was more than 80% on average. Southern blot analysis revealed that the G(1) transgenic progeny had one to three copies of the transgene. The expression of vector-encoded neomycin-resistance gene under the control of the Rous sarcoma virus (RSV) promoter was observed in several tissues including heart and muscle of both G(1) and G(2) transgenic offspring. Due to the high frequency of germ-line transmission, this method may markedly facilitate the production of transgenic avian.

Animals↗
PubMed2001

Novel polygonized single-wall carbon nanotube bundles.

We have synthesized novel crystalline ropes of "polygonized" single-wall carbon nanotubes (SWCNTs). The tubes exhibit rounded-hexagonal cross sections in contrast to the earlier observations of nearly circular tubes. To investigate the structural characteristics of the lattice of SWCNTs we have performed extensive molecular-dynamics simulations. We find several metastable structures of the lattice characterized by different tube cross sections, hexagonal, rounded-hexagonal, and circular, and increasing cell volume. The competition between different tube shapes as a function of tube diameter is analyzed and compared to experiments.

Journal Article↗
PubMed2001

Construction of tumor-specific cells expressing a membrane-anchored single-chain Fv of anti-ErbB-2 antibody.

Cells expressing a membrane-anchored single-chain fragment variable (scFv) domain against a tumor-specific antibody were fabricated. These cells were able to bind to cells of a human colon cancer line (BM314) expressing the erbB-2 proto-oncogene. A plasmid, pMFverbB, was first constructed in which the anti-ErbB-2 scFv gene was cloned in-frame between a signal peptide sequence and the platelet-derived growth factor receptor (PDGFR) transmembrane domain gene to express scFv on the cell surface. An African green monkey cell line, COS-1, was stably transfected with pMFverbB. Immunofluorescence assay experiments and microscopic observation showed that the cells expressing scFv bound to the human tumor cells overexpressing the ErbB-2 protein as well as to cells of a mouse fibroblast line (NIH-3T3) transfected with the erbB-2 gene. The cells expressing scFv could take up magnetite cationic liposomes as a model of particle-type drug and retained the ability to target ErbB-2-expressing cells. The fabricated cells have the potential to serve as drug carriers in drug targeting applications.

3T3 Cells↗
PubMed2001

Cholecystokinin-8 (CCK-8) has no effect on heart rate in rats lacking CCK-A receptors.

Heart rate responses to i.v. administration of cholecystokinin-8 (CCK-8) were investigated in Otsuka Long-Evans Tokushima Fatty (OLETF) rats lacking CCK-A receptors and control Long-Evans Tokushima Otsuka (LETO) rats. The heart rate decreased after i.v. administration of 3 nmol.kg(-)(1) of CCK-8 in LETO rats, but not in OLETF rats. Bradycardia in the LETO rats disappeared after treatment with MK-329, but not after treatment with L-365,260. The expression of CCK-A receptor precursor mRNA was found exclusively in the atrium in LETO rats. These results suggest that CCK-8 decreases heart rate via CCK-A receptors located in the atrium of the rats.

Animals↗
PubMed2001

Chemoradiotherapy followed by surgery for thoracic esophageal cancer potentially or actually involving adjacent organs.

The objective of this study was to evaluate the therapeutic usefulness of chemoradiotherapy (CRT) followed by surgery in patients with clinically T4 (cT4) esophageal cancer involving adjacent organs such as the trachea, main bronchi, and large vessels. Thirty-seven patients with cT4 squamous cell carcinoma of the thoracic esophagus were enrolled in this study. The CRT regimen comprised cisplatin (70 mg/m2) on day 1, 5-fluorouracil (700 mg/m2) on days 1-4 and external irradiation (200 cGy/day, total 30 Gy) on either days 8-26 (sequential schedule, n=15) or days 1-19 (concurrent schedule, n022). Two courses of CRT were given. The results of CRT were complete response in nine patients, partial response in 19, no change in three (minor response in two), and progressive disease in six patients. The median response duration in all responders was 172 days (range: 56-2469, n=19). After CRT, 13 patients received surgery. In 12 of these patients, tumors were completely resected. Histopathologic examination of the resected specimen revealed a discrepancy between clinical response and histopathologic effect. The median duration of survival and the 1-, 2- and 5-year survival rates were 304 days (84-3155), 45%, 35% and 23% in all patients, respectively, 866 days (190-3155), 83%, 83% and 57% in the 13 patients whose tumors were resected, and 187 days (84--2630), 25%, 5% and 5% in the 24 patients whose tumors were not resected. Grade 3 toxicity, especially hematological reactions, was noted in 13.5% (5/37) of the patients. There was one toxicity-related death (sepsis). A good outcome may be obtained with CRT, followed by surgery when feasible. However, CRT can cause toxic reactions, and close monitoring of patients is required.

Aged↗
PubMed2001

Protamine-modified DDAB lipid vesicles promote gene transfer in the presence of serum.

Cationic lipid vesicle-mediated gene transfer has become common for in vitro gene delivery. However, the transfection efficiency is often impaired by serum. DDAB (dimethyldioctadecyl ammonium bromide) lipid vesicle-mediated gene transfer, which we previously reported, has the same problem. To overcome this obstacle, we here report a novel transfection vehicle using protamine-modified DDAB lipid vesicles. While free protamine was simply added to the DNA/lipid complex in the previous study, in the present method the protamine is chemically conjugated to stearic acid and incorporated into DDAB lipid vesicles. Gene transfer was not significantly inhibited in 10% serum-containing medium by this method for the transfection of cultured cells. Protamine-modified DDAB lipid vesicles also enhanced virus transduction efficiency in the presence of serum using a replication-defective retroviral vector. Furthermore, the vesicles allowed efficient gene transfer for avian embryos in vivo. These results indicate that the method is useful for the production of transgenic animals and gene therapy.

3T3 Cells↗