Immobilization of π-conjugated molecules on Au using dendrimer-based templates

Hideo Tokuhisa,Emiko Koyama,Abdelhak Belaissaoui,Hiroshi Suga,Takao Ishida,Yasushiro Nishioka,Masatoshi Kanesato 한국물리학회 2006 Current Applied Physics Vol.6 No.4

In this paper, we demonstrate immobilization of two kinds of p-conjugated molecules on Au using dendrimer-based templates; one is a p-phenylene ethynylene derivative and the other is a 4,40-bis(phenylethynyl)-2,20-bipyridine derivative. Both molecules were bound to benzyl-ether dendrons through an alkali-labile, ester linkage to give two different generation dendrimers. The removal of the dendrons from the self-assembled monolayers of the dendrimers left the isolated p-conjugated-molecules as well as small collections of the molecules on the surfaces, which was confirmed by surface Fourier transform infrared (FT-IR) spectroscopy and scanning tunneling microscopy (STM). Insertion of the dendrimer into n-dodecanethiol monolayer instead of the direct adsorption on a bare gold gave only the isolated, single molecules on the surface after the dendrons were removed.

Highly Stable Au Nanoparticles with Tunable Spacing and Their Potential Application in Surface Plasmon Resonance Biosensors

Gao, Shuyan,Koshizaki, Naoto,Tokuhisa, Hideo,Koyama, Emiko,Sasaki, Takeshi,Kim, Jae-Kwan,Ryu, Joonghyun,Kim, Deok-Soo,Shimizu, Yoshiki WILEY-VCH Verlag 2010 Advanced Functional Materials Vol.20 No.1

<P>Colloidal Au-amplified surface plasmon resonance (SPR), like traditional SPR, is typically used to detect binding events on a thin noble metal film. The two major concerns in developing colloidal Au-amplified SPR lie in 1) the instability, manifested as a change in morphology following immersion in organic solvents and aqueous solutions, and 2) the uncontrollable interparticle distance, determining probe spacing and inducing steric hindrance between neighboring probe molecules. This may introduce uncertainties into such detecting techniques, degrade the sensitivity, and become the barricade hampering colloidal Au-based transducers from applications in sensing. In this paper, colloidal Au-amplified SPR transducers are produced by using ultrathin Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite films via a radio frequency magnetron co-sputtering method. Deposited Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite films exhibit superior stability, and average interparticle distances between Au nanoparticles with similar average sizes can be tuned by changing surface coverage. These characteristics are ascribed to the spacer function and rim confinement of dielectric Al<SUB>2</SUB>O<SUB>3</SUB> and highlight their advantages for application in optimal nanoparticle-amplified SPR, especially when the probe size is smaller than the target molecule size. This importance is demonstrated here for the binding of protein (streptavidin) targets to the probe (biotin) surface. In this case, the dielectric matrix Al<SUB>2</SUB>O<SUB>3</SUB> is a main contributor, behaving as a spacer, tuning the concentration of Au nanoparticles, and manipulating the average interparticle distance, and thus guaranteeing an appropriate number of biotin molecules and expected near-field coupling to obtain optimal sensing performance.</P> <B>Graphic Abstract</B> <P>An innovative colloidal Au-amplified surface plasmon resonance (SPR) transducer is achieved by a using remarkably stable and space-tunable Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite film. This study indicates that the Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite film is very promising; it simultaneously overcomes the instability and uncontrollable interparticle distance, which are the current bottlenecks hampering the application of SPR sensors. <img src='wiley_img/1616301X-2010-20-1-ADFM200901232-content.gif' alt='wiley_img/1616301X-2010-20-1-ADFM200901232-content'> </P>

Differences in the Amino Acid Sequences of CPD Photolyases of UV-sensitive and UV-resistant Rice Cultivars

Teranishi, Mika,Hidema, Jun,Fujino, Takana,Hirouchi, Tokuhisa,Yamamoto, Kazuo,Kumagai, Tadashi Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2

There is a difference in the inhibitory effects to supplemental UVB (wavelengths 280 to 320 nm) among Japanese rice (Oryza sativa L.), the cultivar Norin I is less resistant while the cultivar Sasanishiki is resistant. UVB induces photodamage in DNA. Cyclobutane pyrimidine dimer (CPD) is a major UV-induced DNA lesion. Photorepair, which is mediated by photolyase, is the major pathway in plants for repairing CPD. We have analyzed CPD induction and repair in Sasanishiki and its close relative Norin I using alkaline agarose gel electrophoresis. Norin I is deficient in CPD photoreactivation and excision, thus UV sensitivity correlates with deficient dimer repair [I]. The photorepair deficiency in Norin I results from a functionally altered photolyase with a photoflash analysis [2]. In this paper, we examined the UVB-sensitivity of several other UV-sensitive and -resistant cultivars and found that the CPD photolyase activity was deficient in UV-sensitive ones. It was also evident that there was a variation in the deduced amino acid sequences of CPD photolyases of the UV-sensitive and -resistant cultivars, whereas each deduced amino acid sequence of the UV-sensitive cultivars and of the UV-resistant ones was the same. These results suggest that the difference in the CPD photolyases of UV-sensitive and -resistant rice might be due to the structural alteration of CPD photolyase.

Downregulation of bcl - xL Is Relevant to UV - induced Apoptosis in Fibroblasts

(Yuki Nakagawa),(Seiji Okada),(Masahiko Hatano),(Masaaki Ebara),(Hiromitsu Saisho),(Takeshi Tokuhisa) 생화학분자생물학회 2002 BMB Reports Vol.35 No.5

Exposure to ultraviolet light (UV) induces apoptosis in mammalian cells. The caspase group of proteases is required for the apoptosis. This pathway is initiated by a release of cytochrome c from the mitochondria into the cytosol. Several Bcl-2 family proteins can regulate the release of cytochrome c by stabilizing the mitochondrial membrane. Here we show that expression of the endogenous bcl-xL was strongly downregulated in NIH3T3 cells within 2 h after UV-C irradiation, and that of bax was upregulated from 8 h after irradiation. Apoptosis was induced in more than 50% of the NIH3T3 cells 48 h after irradiation. Constitutive overexpression of bcl-xL in NIH3T3 cells protected the UV-induced apoptosis by preventing the loss of mitochondrial membrane potential and the activation of caspase 9. These results suggest that downregulation of Bcl-xL is relevant to UV-induced apoptosis of fibroblasts.

Downregulation of bcl-xL Is Relevant to UV-induced Apoptosis in Fibroblasts

Nakagawa, Yuki,Okada, Seiji,Hatano, Masahiko,Ebara, Masaaki,Saisho, Hiromitsu,Tokuhisa, Takeshi Korean Society for Biochemistry and Molecular Biol 2002 Journal of biochemistry and molecular biology Vol.35 No.5

Exposure to ultraviolet light (UV) induces apoptosis in mammalian cells, The caspase group of proteases is required for the appotosis. This pathway is initiated by a release of cytochrome c from the mitochondria into the cytosol. Several Bcl-2 family proteins can regulate the release of cytochrome c by stabilizing the mitochondrial membrane. Here we show that expression of the endogenous bcl-xL was strongly downregulated in NIH3T3 cells within 2 h after UV-C irradiation, and that of bax was upregulated from 8 h after irradiation. Apoptosis was induced in more than 50% of the NIH3T3 cells 48 h after irradiation. Constitutive overexpression of bcl-xL in NIH3T3 cells protected the UV-induced apoptosis by preventing the loss of mitochondrial membrane potential and the activation of caspase 9. There results suggest that downregulation of Bcl-xL is relevant to UV-induced apoptosis of tibroblasts.

Au/SiO₂ nanocomposite film substrates with a high number density of Au nanoparticles for molecular conductance measurement

Kim, Dae-Gun,Koyama, Emiko,Kikkawa, Yoshihiro,Kirihara, Kazuhiro,Naitoh, Yasuhisa,Kim, Deok-Soo,Tokuhisa, Hideo,Kanesato, Masatoshi,Koshizaki, Naoto IOP Pub 2007 Nanotechnology Vol.18 No.20

<P>Au/SiO<SUB>2</SUB> nanocomposite films consisting of an extremely high number density of Au nanoparticles dispersed in a SiO<SUB>2</SUB> matrix a few nanometres thick were deposited by a co-sputtering method, and employed for molecular conductance measurement by immobilizing and bridging conjugated biphenyl molecules on dispersed Au nanoparticles. The number density of Au nanoparticles in the insulating SiO<SUB>2</SUB> matrix was approximately 14 000 µm<SUP>−2</SUP>, and the average interparticle distance from their neighbours was about 8 nm. The current increased considerably up to the range of nanoamperes after the immobilization of the conjugated biphenyl molecules, 10<SUP>5</SUP> times larger than without molecules before immobilization. Although the Au nanoparticles can be connected to only 30% of all combinations of neighbouring Au nanoparticles by biphenyl molecules 2.4 nm long from the topological analysis, the biphenyl molecules can bridge most of the Au nanoparticles, and their bridging continuity is over 100 nm in length. Thus the measured current is suggested to come from the continuously bridged molecules between the Au nanoparticles. Furthermore the <I>I</I>–<I>V</I> data of the whole Au/SiO<SUB>2</SUB> nanocomposite film immobilized with conjugated molecules are confirmed to be in a reasonable range in comparison with the scanning tunnelling spectroscopy data of similar conjugated molecules.</P>