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1.
Biotechnol Bioeng ; 108(1): 222-5, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20812258

RESUMO

Introduction of membrane-impermeant substances into living cells is the key method to understand contemporary cellular processes by investigating cellular responses and phenotypes. Here, we performed gold ion beam exposure into live cells by using the focused ion beam implantation method, which was originally developed to precisely control semiconductor device performances. We evaluated the viability of the gold-irradiated cells by measuring the concentration of adenosine triphosphate (ATP), which is an intracellular energy source produced in the mitochondrial membrane. The viability of the irradiated cells was found to be 20% higher than that of the unirradiated control cells. The atoms might promote the energy generating processes within the mitochondrion. Our results suggest that the viability of living cells can be modulated by accurately controlling the dopant atom numbers. Our technique may be considered as a potential tool in life and medical sciences to quantitatively elucidate the dose-dependent effects of dopants.


Assuntos
Ouro/metabolismo , Íons/metabolismo , Mioblastos/efeitos dos fármacos , Mioblastos/fisiologia , Trifosfato de Adenosina/análise , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Camundongos , Mioblastos/química
2.
J Biol Chem ; 285(30): 23159-64, 2010 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-20511221

RESUMO

It has been widely believed that an asymmetric GroEL-GroES complex (termed the bullet-shaped complex) is formed solely throughout the chaperonin reaction cycle, whereas we have recently revealed that a symmetric GroEL-(GroES)(2) complex (the football-shaped complex) can form in the presence of denatured proteins. However, the dynamics of the GroEL-GroES interaction, including the football-shaped complex, is unclear. We investigated the decay process of the football-shaped complex at a single-molecule level. Because submicromolar concentrations of fluorescent GroES are required in solution to form saturated amounts of the football-shaped complex, single-molecule fluorescence imaging was carried out using zero-mode waveguides. The single-molecule study revealed two insights into the GroEL-GroES reaction. First, the first GroES to interact with GroEL does not always dissociate from the football-shaped complex prior to the dissociation of a second GroES. Second, there are two cycles, the "football cycle " and the "bullet cycle," in the chaperonin reaction, and the lifetimes of the football-shaped and the bullet-shaped complexes were determined to be 3-5 s and about 6 s, respectively. These findings shed new light on the molecular mechanism of protein folding mediated by the GroEL-GroES chaperonin system.


Assuntos
Chaperonina 10/química , Chaperonina 10/metabolismo , Chaperonina 60/química , Chaperonina 60/metabolismo , Imagem Molecular/métodos , Animais , Bovinos , Ligação Proteica , Dobramento de Proteína
3.
Langmuir ; 26(12): 9950-5, 2010 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-20429542

RESUMO

A large-scale molecular dynamics simulation was carried out in order to investigate the adsorption mechanism of ribosomal protein L2 (RPL2) onto a silica surface at various pH values. RPL2 is a constituent protein of the 50S large ribosomal subunit, and a recent experimental report showed that it adsorbs strongly to silica surfaces and that it can be used to immobilize proteins on silica surfaces. The simulation results show that RPL2, especially domains 1 (residues 1-60) and 3 (residues 203-273), adsorbed more tightly to the silica surface above pH 7. We found that a major driving force for the adsorption of RPL2 onto the silica surface is the electrostatic interaction and that the structural flexibility of domains 1 and 3 may further contribute to the high affinity.


Assuntos
Proteínas Imobilizadas/química , Simulação de Dinâmica Molecular , Proteínas Ribossômicas/química , Dióxido de Silício/química , Adsorção , Concentração de Íons de Hidrogênio , Maleabilidade , Eletricidade Estática
4.
J Biomed Biotechnol ; 2010: 290516, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-21318151

RESUMO

The exact molecular mechanism by which epigallocatechin gallate (EGCG) suppresses human pancreatic cancer cell proliferation is unclear. We show here that EGCG-treated pancreatic cancer cells AsPC-1 and BxPC-3 decrease cell adhesion ability on micro-pattern dots, accompanied by dephosphorylations of both focal adhesion kinase (FAK) and insulin-like growth factor-1 receptor (IGF-1R) whereas retained the activations of mitogen-activated protein kinase and mammalian target of rapamycin. The growth of AsPC-1 and BxPC-3 cells can be significantly suppressed by EGCG treatment alone in a dose-dependent manner. At a dose of 100 µM which completely abolishes activations of FAK and IGF-1R, EGCG suppresses more than 50% of cell proliferation without evidence of apoptosis analyzed by PARP cleavage. Finally, the MEK1/2 inhibitor U0126 enhances growth-suppressive effect of EGCG. Our data suggests that blocking FAK and IGF-1R by EGCG could prove valuable for targeted therapy, which can be used in combination with other therapies, for pancreatic cancer.


Assuntos
Antineoplásicos/farmacologia , Catequina/análogos & derivados , Quinase 1 de Adesão Focal/antagonistas & inibidores , Neoplasias Pancreáticas/metabolismo , Receptor IGF Tipo 1/antagonistas & inibidores , Chá , Antineoplásicos/uso terapêutico , Antioxidantes/metabolismo , Antioxidantes/farmacologia , Apoptose/fisiologia , Catequina/metabolismo , Catequina/farmacologia , Catequina/uso terapêutico , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ativação Enzimática/efeitos dos fármacos , Humanos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Neoplasias Pancreáticas/tratamento farmacológico
5.
Sensors (Basel) ; 10(11): 9687-97, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-22163434

RESUMO

We propose a novel sensor system for monitoring the structural health of a building. The system optically measures the relative-story displacement during earthquakes for detecting any deformations of building elements. The sensor unit is composed of three position sensitive detectors (PSDs) and lenses capable of measuring the relative-story displacement precisely, even if the PSD unit was inclined in response to the seismic vibration. For verification, laboratory tests were carried out using an Xθ-stage and a shaking table. The static experiment verified that the sensor could measure the local inclination angle as well as the lateral displacement. The dynamic experiment revealed that the accuracy of the sensor was 150 µm in the relative-displacement measurement and 100 µrad in the inclination angle measurement. These results indicate that the proposed sensor system has sufficient accuracy for the measurement of relative-story displacement in response to the seismic vibration.


Assuntos
Desenho de Equipamento , Sistemas Microeletromecânicos/instrumentação
6.
Rev Sci Instrum ; 79(7): 073707, 2008 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-18681708

RESUMO

An ion beam alignment system has been developed in order to realize real-time scanning tunneling microscope (STM) observation of "dopant-ion" irradiation that has been difficult due to the low emission intensity of the liquid-metal-ion-source (LMIS) containing dopant atoms. The alignment system is installed in our original ion gun and STM combined system (IG/STM) which is used for in situ STM observation during ion irradiation. By using an absorbed electron image unit and a dummy sample, ion beam alignment operation is drastically simplified and accurized. We demonstrate that sequential STM images during phosphorus-ion irradiation are successfully obtained for sample surfaces of Si(111)-7x7 at room temperature and a high temperature of 500 degrees C. The LMIS-IG/STM equipped with the developed ion beam alignment system would be a powerful tool for microscopic investigation of the dynamic processes of ion irradiation.

7.
Anal Chem ; 80(15): 6018-22, 2008 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-18563914

RESUMO

Real-time imaging of single-molecule fluorescence with a zero-mode waveguide (ZMW) was achieved. With modification of the ZMW geometry, the signal-to-background ratio is twice that obtainable with a conventional ZMW. The improved signal-to-background ratio makes it possible to visualize individual binding-release events between chaperonin GroEL and cochaperonin GroES at a concentration of 5 microM. Two rate constants representing two-timer kinetics in the release of GroES from GroEL were measured with the ZMW, and the measurements agreed well with those made with a total internal reflection fluorescence microscopy. These results indicate that the novel ZMW makes feasible the direct observation of protein-protein interaction at an intracellular concentration in real time.


Assuntos
Microscopia de Fluorescência/métodos , Nanotecnologia/instrumentação , Mapeamento de Interação de Proteínas/métodos , Chaperonina 10 , Chaperonina 60 , Desenho de Equipamento , Nanotecnologia/métodos
8.
J Biol Chem ; 283(35): 23931-9, 2008 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-18583344

RESUMO

To elucidate the exact role of the C-terminal region of GroEL in its functional cycle, the C-terminal 20-amino acid truncated mutant of GroEL was constructed. The steady-state ATPase rate and duration of GroES binding showed that the functional cycle of the truncated GroEL is extended by approximately 2 s in comparison with that of the wild type, without interfering with the basic functions of GroEL. We have proposed a model for the functional cycle of GroEL, which consists of two rate-limiting steps of approximately 3- and approximately 5-s duration (Ueno, T., Taguchi, H., Tadakuma, H., Yoshida, M., and Funatsu, T. (2004) Mol. Cell 14, 423-434 g). According to the model, detailed kinetic studies were performed. We found that a 20-residue truncation of the C terminus extends the time until inorganic phosphate is generated and the time for arresting protein folding in the central cavity, i.e. the lifetime of the first rate-limiting step in the functional cycle, to an approximately 5-s duration. These results suggest that the integrity of the C-terminal region facilitates the transition from the first to the second rate-limiting state.


Assuntos
Adenosina Trifosfatases/química , Chaperonina 60/química , Proteínas de Escherichia coli/química , Escherichia coli/enzimologia , Modelos Químicos , Dobramento de Proteína , Adenosina Trifosfatases/genética , Sequência de Aminoácidos , Animais , Chaperonina 60/genética , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Cinética , Estrutura Terciária de Proteína/genética , Deleção de Sequência , Fatores de Tempo
9.
J Chem Phys ; 128(16): 164710, 2008 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-18447482

RESUMO

The bonding network of an alkylsilane self-assembled monolayer (SAM)SiO(2) substrate interface is investigated by means of canonical Monte Carlo (MC) simulations. SAMSiO(2) systems with different interfacial bonding topologies are sampled by the Metropolis MC method, and the AMBER potential with a newly developed organosilicon parameters are used to obtain an optimized structure with a given bonding topology. The underlying substrates are modeled as hydroxy-terminated (100) or (111) cristobalites. The SAMSiO(2) interface is characterized by a polysiloxane bonding network which comprises anchoring bonds and cross-linking bonds, namely, molecule-substrate and molecule-molecule Si-O-Si bonds, respectively. We show that at thermal equilibrium, the ratio of the number of anchoring bonds to cross-linking bonds decreases as a total Si-O-Si bond density increases, and that nevertheless, number of anchoring bonds always dominate over that of cross-linking bonds. Moreover we show that the total Si-O-Si bond density strongly affects the lateral ordering of the alkylsilane molecules, and that increase in the Si-O-Si bond density disorders the molecular packing. Our results imply that a lab-to-lab variation in the experimentally prepared SAMs can be attributed to different Si-O-Si bond densities at the SAMSiO(2) interface.

10.
Front Biosci ; 12: 4773-8, 2007 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-17485412

RESUMO

The combination of electron beam lithography and gold nanoparticle-based detection method is subject to a novel high-resolution approach to detecting DNA nanoarrays. In this work, gold nanoparticle-based detection of DNA hybridization on nanostructured arrays is presented. The nanostructured arrays were created by electron beam lithography of a self-assembled monolayer. Amine groups, which are active moieties and are used for attachment of DNA, were introduced to the nanostructures, and the amine-modified structures were characterized by scanning Maxwell-stress microscopy (SMM) for seeing the modification process. The DNA probe covalently immobilized within the nanostructures was hybridized with a biotinylated target DNA. Streptavidin-gold conjugate was then bound to the biotin, thereby assembling inside the nanostructured arrays. The sequence-specific hybridization was imaged by atomic force microscopy (AFM). On the other hand, the activity of the DNA molecules within the nanostructured arrays was verified by fluorescence microscopy using streptavidin-Cy 5 conjugate instead of streptavidin-gold nanoparticles conjugate. On the basis of fluorescent detection, an alternative method has been developed for detection of DNA nanostructures, which will benefit the development of DNA chips.


Assuntos
Ouro/química , Nanopartículas Metálicas , Análise de Sequência com Séries de Oligonucleotídeos , DNA/química , Microscopia de Força Atômica , Hibridização de Ácido Nucleico
11.
J Nanosci Nanotechnol ; 7(2): 410-7, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17450772

RESUMO

We report on a flexible method of producing antibody (IgG) nanopatterns by combining electron beam (EB) lithography and a perfluorodecyltriethoxysilane (FDTES) self-assembled monolayer (SAM). Using EB lithography of the FDTES SAM, we easily fabricated IgG patterns with feature sizes on the order of 100 nm. The patterned IgG retained its ability to interact specifically with an anti-LgG. The influence of different concentrations of the IgG and anti-IgG on the resulting fluorescent IgG arrays was investigated. These IgG nanopatterns appeared to be remarkably well controlled and showed almost no detectable nonspecific binding of proteins on a hydrophobic SAM under a suitable incubation condition, characterized by atomic force microscopy, and epi-fluorescence microscopy. The technique enables the realization of high-throughput protein nanoscale arrays with high specificity.


Assuntos
Anticorpos/química , Nanoestruturas/química , Elétrons , Técnica Indireta de Fluorescência para Anticorpo , Imunoglobulina G/química , Microscopia de Força Atômica , Microscopia de Fluorescência , Compostos de Organossilício/química , Análise Serial de Proteínas , Propriedades de Superfície
12.
Langmuir ; 22(26): 11245-50, 2006 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-17154611

RESUMO

Here, we report a novel method of micropatterning oligonucleotides via aromatic groups as linkers on partially amino-terminated diamond and the inherence on subsequent hybridization. The covalent immobilization of probe oligonucleotides and characterization of immobilized probe oligonucleotides with carboxylic compounds were investigated by X-ray photoelectron spectroscopy (XPS). To confirm the effects of linker flexibility in a low amino group on diamond for probe oligonucleotides, three kinds of dicarboxylic compound--adipic acid, terephthalic acid, and trimesic acid--were used for immobilization of probe oligonucleotides, like linkers; and these oligonucleotides were hybridized with target oligonucleotides labeled with Cy 5 on the micropatterned diamond surface. The hybridization intensities determined by epifluorescence microscopy were compared and analyzed.


Assuntos
Carbocianinas/química , Reagentes de Ligações Cruzadas/química , Diamante/química , Análise de Sequência com Séries de Oligonucleotídeos , Oligonucleotídeos/química , Hibridização de Ácido Nucleico/métodos , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Espectrometria de Fluorescência/métodos , Espectrometria por Raios X/métodos
13.
Phys Rev E Stat Nonlin Soft Matter Phys ; 74(4 Pt 1): 041919, 2006 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17155108

RESUMO

Charge detection biosensors have recently become the focal point of biosensor research, especially field-effect-transistors (FETs) that combine compactness, low cost, high input, and low output impedances, to realize simple and stable in vivo diagnostic systems. However, critical evaluation of the possibility and limitations of charge detection of label-free DNA hybridization using silicon-based ion-sensitive FETs (ISFETs) has been introduced recently. The channel surface of these devices must be covered by relatively thick insulating layers ( SiO2, Si3N4, Al2O3, or Ta2O5) to protect against the invasion of ions from solution. These thick insulating layers are not suitable for charge detection of DNA and miniaturization, as the small capacitance of thick insulating layers restricts translation of the negative DNA charge from the electrolyte to the channel surface. To overcome these difficulties, thin-gate-insulator FET sensors should be developed. Here, we report diamond solution-gate FETs (SGFETs), where the DNA-immobilized channels are exposed directly to the electrolyte solution without gate insulator. These SGFETs operate stably within the large potential window of diamond (>3.0 V). Thus, the channel surface does not need to be covered by thick insulating layers, and DNA is immobilized directly through amine sites, which is a factor of 30 more sensitive than existing Si-ISFET DNA sensors. Diamond SGFETs can rapidly detect complementary, 3-mer mismatched (10 pM) and has a potential for the detection of single-base mismatched oligonucleotide DNA, without biological degradation by cyclically repeated hybridization and denature.


Assuntos
Técnicas Biossensoriais/instrumentação , DNA/análise , DNA/genética , Eletroquímica/instrumentação , Hibridização In Situ/instrumentação , Análise de Sequência com Séries de Oligonucleotídeos/instrumentação , Transistores Eletrônicos , Técnicas Biossensoriais/métodos , Diamante/química , Eletroquímica/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Hibridização In Situ/métodos , Análise de Sequência com Séries de Oligonucleotídeos/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Soluções
14.
Phys Rev Lett ; 96(19): 196102, 2006 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-16803114

RESUMO

We propose a new oxidation rate equation for silicon supposing only a diffusion of oxidizing species but not including any rate-limiting step by interfacial reaction. It is supposed that diffusivity is suppressed in a strained oxide region near SiO(2)/Si the interface. The expression of a parabolic constant in the new equation is the same as that of the Deal-Grove model, while a linear constant makes a clear distinction with that of the model. The estimated thickness using the new expression is close to 1 nm, which compares well with the thickness of the structural transition layers.

15.
Langmuir ; 22(8): 3728-34, 2006 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-16584249

RESUMO

We report a novel method of one-step direct amination on polycrystalline diamond to produce functionalized surfaces for DNA micropatterning by photolithography. Polycrystalline diamond was exposed to UV irradiation in ammonia gas to generate amine groups directly. After patterning, optical microscopy confirmed that micropatterns covered with an Au mask were regular in size and shape. The regions outside the micropatterns were passivated with fluorine termination by C3F8 plasma, and the chemical changes on the two different surfaces--the amine groups inside the patterned regions by one-step direct amination and fluorine termination outside the patterned regions--were characterized by spatially resolved X-ray photoelectron spectroscopy (XPS). The patterned areas terminated with active amine groups were then immobilized with probe DNA via a bifunctional molecule. The sequence specificity was conducted by hybridizing fluorescently labeled target DNA to both complementary and noncomplementary probe DNA attached inside the micropatterns. The fluorescence micropatterns observed by epifluorescence microscopy corresponded to those imaged by optical microscopy. DNA hybridization and denaturation experiments on a DNA-modified diamond show that the diamond surfaces reveal superior stability. The influence of a different amination time on fluorescence intensity was compared. Different terminations as passivated layers were investigated, and as a result, fluorine termination points to the greatest signal-to-noise ratio.


Assuntos
Físico-Química/métodos , DNA/química , Silício/química , Adsorção , Técnicas Biossensoriais , Cristalização , DNA Complementar/metabolismo , Diamante , Flúor/química , Luz , Microscopia de Fluorescência/métodos , Hibridização de Ácido Nucleico , Espectrometria por Raios X/métodos , Raios Ultravioleta , Raios X
16.
Nature ; 437(7062): 1128-31, 2005 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-16237438

RESUMO

As the size of semiconductor devices continues to shrink, the normally random distribution of the individual dopant atoms within the semiconductor becomes a critical factor in determining device performance--homogeneity can no longer be assumed. Here we report the fabrication of semiconductor devices in which both the number and position of the dopant atoms are precisely controlled. To achieve this, we make use of a recently developed single-ion implantation technique, which enables us to implant dopant ions one-by-one into a fine semiconductor region until the desired number is reached. Electrical measurements of the resulting transistors reveal that device-to-device fluctuations in the threshold voltage (Vth; the turn-on voltage of the device) are less for those structures with ordered dopant arrays than for those with conventional random doping. We also find that the devices with ordered dopant arrays exhibit a shift in Vth, relative to the undoped semiconductor, that is twice that for a random dopant distribution (- 0.4 V versus -0.2 V); we attribute this to the uniformity of electrostatic potential in the conducting channel region due to the ordered distribution of dopant atoms. Our results therefore serve to highlight the improvements in device performance that can be achieved through atomic-scale control of the doping process. Furthermore, ordered dopant arrays of this type may enhance the prospects for realizing silicon-based solid-state quantum computers.

18.
Chem Commun (Camb) ; (8): 978-9, 2004 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-15069503

RESUMO

Nanometer-sized polystyrene particles were selectively deposited by interfacial tension in nanometer-sized etchpit arrays made on a silicon substrate.

19.
Chem Commun (Camb) ; (7): 786-7, 2004 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-15045063

RESUMO

Nanoscale patterns of modified oligonucleotides are produced on octadecyltrimethoxysilane self-assembled monolayers at a silicon surface by electron beam lithography. DNA structures with feature sizes of the order of 250 nm were detected by epi-fluorescence microscopy.


Assuntos
DNA/química , Microscopia Eletrônica/métodos , Nanoestruturas/química , Oligodesoxirribonucleotídeos/química , Silício/química , Microscopia de Fluorescência , Compostos de Organossilício/química , Propriedades de Superfície
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