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At least 1,729 records · Page 96Linked to original sources
PubMed2005

Metal-oxide-Semiconductor capacitors fabricated by layer-by-layer nanoassembly and microfabrication.

Metal oxide semiconductor (MOS) capacitors were fabricated by electrostatic layer-by-layer self-assembly (LbL-SA) combined with a modified lift-off technique. The MOS capacitors were built on both n-type and p-type silicon substrates. The numbers of silicon dioxide (SiO2) nanoparticle layers were varied to characterize the electrical performance of MOS capacitors. Unlike the conventional process, LbL-SA allows us to deposit the thin films for a semiconductor device with a lower temperature, lower cost, and shorter processing time. The stability of the silica insulation layers was also investigated. Atomic force microscopy (AFM) served to monitor the film quality of the self-assembled thin films.

Metals↗
PubMed2004

Characteristics of monolayer behavior and multilayer film structures of comb polymers having different kinds of fluorocarbon side-chains.

With comb polymers with different kinds of fluorocarbon side-chains, significant effects of spreading solvents on the monolayers at the air/water interface and the molecular arrangement in the deposited films could be found by the use of trifluoroacetic acid and its mixed solvents with n-hexane, depending on the atoms, fluorine or hydrogen, substituted at the end of the fluorocarbon side-chains. These facts are probably due to intralayer hydrogen bonding cooperating with the carbonyl groups of the long-chain esters. The deposited films of solid substrates were characterized by polarized near-edge X-ray absorption fine structure (NEXAFS) spectroscopy as well as in-plane X-ray diffraction and scanning electron and atomic force microscopy.

Acrylic Resins↗
PubMed2006

Properties of mixed lipid monolayers assembled on hydrophobic surfaces through vesicle adsorption.

Supported lipid films are becoming increasingly important tools for the study of membrane protein function because of the availability of high-sensitivity surface analytical and patterning techniques. In this study, we have characterized the physical chemical properties of lipid films assembled on hydrophobic surfaces through the spontaneous adsorption of large unilamellar lipid vesicles composed of dioleoylphosphatidylglycerol (DOPG) and dioleoylphosphatidylcholine (DOPC). The density of the lipid films was measured with surface plasmon resonance spectroscopy as the lipid composition of the vesicles and ionic concentration were varied. As expected, monolayer films were formed, but the density of the monolayers was found to be weakly dependent on the lipid composition of the vesicles and strongly dependent on the ionic concentration of the solution in contact with the monolayer. Atomic force microscopy (AFM) images of the lipid films indicate that they are composed of a homogeneous monolayer. Surface force measurements were used to determine the surface charge and DOPG density of the monolayers. The DOPG content of the films was found to be weakly dependent on the DOPG composition of the vesicles and strongly dependent on the salt concentration of the environment. A model has been developed to describe the behavior of the lipid composition of the films in terms of the hydrophobic, electrostatic, and steric forces acting on the lipid monolayer on the hydrophobic surface.

Adsorption↗
PubMed2005

Single molecular imaging and spectroscopy of conjugated polyelectrolytes decorated on stretched aligned DNA.

DNA is the prototype template for building nanoelectronic devices by self-assembly. The electronic functions are made possible by coordinating electronic polymer chains to DNA. This paper demonstrates two methods for fabrication of aligned and ordered DNA nanowires complexed with conjugated polyelectrolytes (CPEs). The complex can be formed either in solution prior to stretching or after stretching of the bare DNA on a surface. Molecular combing was used to stretch the complexes on surface energy patterned surfaces, and PMMA for the bare DNA. Single molecular spectroscopy, in fluorescence, and microscopy, in atomic force microscopy, give evidence for coordination of the short CPE chains to the aligned DNA.

DNA↗
PubMed2004

Monitoring the formation of biosilica catalysed by histidine-tagged silicatein.

Surface bound silicatein retains its biocatalytic activity, which was demonstrated by monitoring the immobilisation of silicatein using a histidine-tag chelating anchor and the subsequent biosilicification of SiO(2) on surfaces by surface plasmon resonance spectroscopy, atomic force microscopy and scanning electron microscopy.

Catalysis↗
PubMed2005

Gene cloning, functional expression and secretion of the S-layer protein SgsE from Geobacillus stearothermophilus NRS 2004/3a in Lactococcus lactis.

The ~93-kDa surface layer protein SgsE of Geobacillus stearothermophilus NRS 2004/3a forms a regular crystalline array providing a nanopatterned matrix for the future display of biologically relevant molecules. Lactococcus lactis NZ9000 was established as a safe expression host for the controlled targeted production of SgsE based on the broad host-range plasmid pNZ124Sph, into which the nisA promoter was introduced. SgsE devoid of its signal peptide-encoding sequence was cloned into the new vector and purified from the cytoplasm at a yield of 220 mg l- of expression culture. Secretion constructs were based on the signal peptide of the Lactobacillus brevis SlpA protein or the L. lactis Usp45 protein, allowing isolation of 95 mg of secreted rSgsE l-1. N-terminal sequencing confirmed correct processing of SgsE in L. lactis NZ9000. The ability of rSgsE to self-assemble in suspension and to recrystallize on solid supports was demonstrated by electron and atomic force microscopy.

Bacterial Proteins↗
PubMed2006

AFM force spectroscopy of the fibrinogen adsorption process onto dental implants.

Protein binding to implants is governed by the physicochemical properties of the biomaterial surface. The adhesion of a protein onto a solid surface is nonspecific. The aim of this study was to assess the adsorption process of fibrinogen at two different dental implants. The first biomaterial has a sand-blasted titanium surface, whereas the second one is covered by a calcium phosphate coating. After scanning electron microscopy and atomic force microscopy characterization of the implant surfaces, force spectroscopy has been used to determine the unbinding force of fibrinogen adsorbed at the two different substrates. Force-measurement findings indicate that the detachment force of fibrinogen adsorbed onto both surfaces varies as a function of the interaction time. The mean strength of the unbinding forces increases with the interaction time (100 and 1,000 ms, respectively). However, experimental data suggest that fibrinogen fixes to the two studied biomaterials by different mechanisms. Moreover, it appears that, after an interaction time of 1,000 ms, the detachment force of the adsorbed protein is quite larger for the titanium surface than for the calcium phosphate coating.

Adsorption↗
PubMed2005

The contribution of microscopy to the study of Alzheimer's disease, amyloid plaques and Abeta fibrillogenesis.

A broad survey is presented in this chapter, dealing with the impact that microscopy has made to the study of Alzheimer's disease, amyloid plaques and amyloid-beta fibrillogenesis. This includes classical light microscopy and the modem immunolabelling and confocal microscopies, together with the contribution of transmission electron microscopy and atomic force microscopy. Whilst usefully standing alone, the individual microscopies often contribute most effectively when they are integrated with cellular, biophysical and molecular approaches.

Alzheimer Disease↗
PubMed2006

Thin casein films as prepared by spin-coating: influence of film thickness and of pH.

Casein films were successfully prepared with the spin-coating technique of aqueous casein solutions on base-treated glass surfaces. The film structure is investigated in real space with optical microscopy and atomic force microscopy and for the first time in reciprocal space with grazing incidence small-angle X-ray scattering (GISAXS). The size of the substructures detected in the film increases with pH from 170 nm (pH 5.1) up to 490 nm (pH 9.4). Dynamic light scattering experiments reveal that the average diameters of casein micelles in solution exhibit the same quantitative increase. This result suggests that the substructures detected in the bulklike films with GISAXS reflect intact casein micelles. However, with thin homogeneous casein films, the micelle size diminishes with decreasing film thickness. This indicates that the moderate pressures introduced by spin-coating force the micelles to rearrange into a more compact structure.

Caseins↗
PubMed2004

Adhesion forces measured at the level of a terminal plate of the fly's seta.

The attachment pads of fly legs are covered with setae, each ending in small terminal plates coated with secretory fluid. A cluster of these terminal plates contacting a substrate surface generates strong attractive forces that hold the insect on smooth surfaces. Previous research assumed that cohesive forces and molecular adhesion were involved in the fly attachment mechanism. The main elements that contribute to the overall attachment force, however, remained unknown. Multiple local force-volume measurements were performed on individual terminal plates by using atomic force microscopy. It was shown that the geometry of a single terminal plate had a higher border and considerably lower centre. Local adhesion was approximately twice as strong in the centre of the plate as on its border. Adhesion of fly footprints on a glass surface, recorded within 20 min after preparation, was similar to adhesion in the centre of a single attachment pad. Adhesion strongly decreased with decreasing volume of footprint fluid, indicating that the layer of pad secretion covering the terminal plates is crucial for the generation of a strong attractive force. Our data provide the first direct evidence that, in addition to Van der Waals and Coulomb forces, attractive capillary forces, mediated by pad secretion, are a critical factor in the fly's attachment mechanism.

Adhesiveness↗
PubMed2003

Electrophoretic mobility of Bacillus subtilis knockout mutants with and without flagella.

Mutants of Bacillus subtilis 168 strain were obtained by inactivation of a specific gene by homologous recombination with the plasmid pMutinT3. The cell surface properties of these strains were characterized by measuring the electrophoretic mobility of the cells as a function of pH and ionic strength. The surface properties were different for the strains possessing flagella on their cells and strain FlgB, having no flagellum, due to knockout of the corresponding gene. The cell surface properties of the strains possessing flagella become similar to those of strain FlgB after acid treatment. It was confirmed that the acid treatment degraded the flagella without causing any apparent structural change on the cell surface via observations made using atomic force microscopy, transmission electron microscopy, and scanning electron microscopy. These results indicate that the flagella are a key factor influencing cell surface properties.

Bacillus subtilis↗
PubMed2005

Oriented carbon nanostructures containing nitrogen obtained by ion beam assisted deposition.

In this paper, we report the deposition of graphite multilayer containing nitrogen covering nanometric nickel particles. In-situ photoelectron emission spectroscopy (XPS) reveals the presence of nitrogen in the carbon layer covering the nickel particles. The field emission properties of the structures are reported. Atomic force microscopy displays regular domelike structures. Raman spectroscopy shows the characteristic frequencies associated with graphite and disordered structures. High-resolution transmission electron microscopy confirms the presence of multiwall well-organized graphite layers covering the nickel particles. Disorder increases on increasing nitrogen content. The samples were prepared in-situ by depositing first a few atomic layers of nickel and subsequent islands formation by thermal annealing. Then, an argon ion beam bombards an ultrapure carbon target and simultaneously the growing film is assisted with a second low-energy nitrogen ion beam (ion beam assisted deposition).

Argon↗
PubMed2005

Nanowell-array surfaces prepared by argon plasma etching through a nanopore alumina mask.

A method for preparing a glass surface containing an ordered array of nanowells is described. These nanowell arrays are prepared via a plasma-etch method using a nanopore alumina film as the etch mask. A replica of the pore structure of the alumina mask is etched into the glass. We demonstrate that chemical information in the form of negatively charged latex nanoparticles can be selectively stored within these nanowells and not indiscriminately deposited on the surface surrounding the nanowells. To accomplish this, the chemistry of the glass surfaces within these nanowells (walls and bottoms) must be different from the chemistry of the surface surrounding the nanowells. Two different procedures were developed to make the inside vs. surrounding surface chemistries different. Atomic force microscopy (AFM) was used to image the nanowells and, via friction-force measurements, to prove that the inner nanowell surfaces can be made chemically different from the surface surrounding the nanowells.

Aluminum Oxide↗
PubMedDate not supplied

Controlled delivery of paclitaxel from stent coatings using poly(hydroxystyrene-b-isobutylene-b-hydroxystyrene) and its acetylated derivative.

A poly(styrene-b-isobutylene-b-styrene) (SIBS) triblock polymer is employed as the polymer drug carrier for the TAXUS Express2 Paclitaxel-Eluting Coronary Stent system (Boston Scientific Corp.). It has been shown that the release of paclitaxel (PTx) from SIBS can be modulated by modification of either drug-loading ratio or altering the triblock morphology by blending. In the present work, results toward achieving release modulation of PTx by chemical modification of the styrenic portion (using hydroxystyrene or its acetylated version) of the SIBS polymer system are reported. The synthesis of the precursor poly[(p-tert-butyldimethylsilyloxystyrene)]-b-isobutylene-b-[(p-tert-butyldimethylsilyloxystyrene] triblock copolymers was accomplished by living sequential block copolymerization of isobutylene (IB) and p-(tert-butyldimethylsiloxy)styrene (TBDMS) utilizing the capping-tuning technique in a one-pot procedure in methylcyclohexane/CH3Cl at -80 degrees C. This procedure involved the living cationic polymerization of IB with the 5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene/TiCl4 initiating system and capping of living difunctional polyisobutylene (PIB) chain ends with 1,1-ditolylethylene (DTE) followed by addition of titanium(IV) isopropoxide (Ti(OIp)4) to lower the Lewis acidity before the introduction of TBDMS. Deprotection of the product with tetrabutylammonium fluoride yielded poly(hydroxystyrene-b-isobutylene-b-hydroxystyrene), which was quantitatively acetylated to obtain the acetylated derivative. The hydroxystyrene and acetoxystyrene triblock copolymers have acceptable mechanical properties for use as drug delivery coatings for coronary stent applications. It was concluded that the hydrophilic nature of the endblocks and polarity effects on the drug/polymer miscibility lead to enhanced release of PTx from these polymers. The drug-polymer miscibility was confirmed by differential scanning calorimetry and atomic force microscopy evaluations.

Absorption↗
PubMed2006

Study of a pingyangmycin delivery system: Zein/Zein-SAIB in situ gels.

Venous malformations (VM) are common vascular abnormality, and their management remains difficult. Pingyangmycin hydrochloride (PYM) is a useful sclerosant to treat venous malformations. This study was aimed to evaluate the effect of a new drug delivery system, PYM-loaded Zein/Zein-sucrose acetate isobutyrate (SAIB) in situ gels, in gelling and extending the local release of PYM. It was demonstrated that in vitro and in vivo release of PYM from the in situ gels could be extended up to 7 and 4 days, respectively. SAIB could significantly cut down the initial burst of PYM from the in situ gels (P<0.05). The possible gel forming and drug release mechanisms were described according to the morphology analysis by atomic force microscopy (AFM), optical microscopy and SEM. The gel forming efficacy and the viscosity of in situ gel solutions were satisfying.

Animals↗
PubMed2005

Comparison of resistance to protein adsorption and stability of thin films derived from alpha-hepta-(ethylene glycol) methyl omega-undecenyl ether on HSi(111) and HSi(100) surfaces.

Oligo(ethylene glycol)-terminated thin films were prepared by photo-induced hydrosilylation of alpha-hepta-(ethylene glycol) methyl omega-undecenyl ether (EG(7)) on hydrogen-terminated silicon (111) and (100) surfaces. Their resistance to protein adsorption, and stabilities (from hours to days) under a wide variety of conditions, such as air, water, biological buffer, acid, and base, were investigated using contact-angle goniometry and ellipsometry techniques. Results indicated higher stability of the films chemisorbed on Si(111) than on Si(100). Furthermore, micron-sized patterns were fabricated on the films via AFM anodization lithography. Using atomic force microscopy (AFM) and fluorescence microscopy, we demonstrated that various proteins including fibrinogen, avidin, and bovine serum albumin (BSA) predominately adsorbed onto the patterns, but not the rest of the film surfaces.

Adsorption↗
PubMed2005

Self-assembled, mesoporous polymeric networks for patterned protein arrays.

A facile, self-assembly approach to the fabrication of a robust, mesoporous, biocompatible polymeric network for the spatial organization of proteins is described. Surface-deposited poly(styrene) (PS) beads that assemble into a two-dimensional (2-D) hexagonal array are used to template cross-linked poly(vinyl alcohol) (PVA), yielding an inverse opal structure. The porous, water insoluble network is used to entrain a model, soluble protein, green fluorescent protein (GFP). The polymeric network is characterized by atomic force microscopy (AFM) and optical microscopy, and the spatial localization of the incorporated GFP is determined by fluorescence microscopy. The results demonstrate that this system may constitute a versatile platform for the lateral organization of biomolecules.

Green Fluorescent Proteins↗
PubMed2005

Myomesin is a molecular spring with adaptable elasticity.

The M-band is a transverse structure in the center of the sarcomere, which is thought to stabilize the thick filament lattice. It was shown recently that the constitutive vertebrate M-band component myomesin can form antiparallel dimers, which might cross-link the neighboring thick filaments. Myomesin consists mainly of immunoglobulin-like (Ig) and fibronectin type III (Fn) domains, while several muscle types express the EH-myomesin splice isoform, generated by the inclusion of the unique EH-segment of about 100 amino acid residues (aa) in the center of the molecule. Here we use atomic force microscopy (AFM), transmission electron microscopy (TEM) and circular dichroism (CD) spectroscopy for the biophysical characterization of myomesin. The AFM identifies the "mechanical fingerprints" of the modules constituting the myomesin molecule. Stretching of homomeric polyproteins, constructed of Ig and Fn domains of human myomesin, produces a typical saw-tooth pattern in the force-extension curve. The domains readily refold after relaxation. In contrast, stretching of a heterogeneous polyprotein, containing several repeats of the My6-EH fragment reveals a long initial plateau corresponding to the sum of EH-segment contour lengths, followed by several My6 unfolding peaks. According to this, the EH-segment is characterized as an entropic chain with a persistence length of about 0.3nm. In TEM pictures, the EH-domain appears as a gap in the molecule, indicating a random coil conformation similar to the PEVK region of titin. CD spectroscopy measurements support this result, demonstrating a mostly non-folded conformation for the EH-segment. We suggest that similarly to titin, myomesin is a molecular spring, whose elasticity is modulated by alternative splicing. The Ig and Fn domains might function as reversible "shock absorbers" by sequential unfolding in the case of extremely high or long sustained stretching forces. These complex visco-elastic properties of myomesin might be crucial for the stability of the sarcomere.

Circular Dichroism↗