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At least 469 records · Page 26Linked to original sources
PubMed1990

[Investigation on thermal-neutron sensitivity of commercial BeO(Na) thermoluminescence dosimeter and development of thermal-neutron insensitive BeO(Na) phosphors encapsulated in quartz-capillary].

BeO(Na) TLD on the market, UD-170 L, gives thermoluminescence response equivalent to irradiation with 3.2 +/- 0.5 cGy of 60Co gamma-rays after irradiation with 10(10) thermal neutrons per cm2. Because of this neutron sensitivity, UD-170 L is not suitable for measurement of gamma-rays in gamma-neutron mixed radiation from a nuclear reactor of Kinki University when we use it for radiobiological research. To reduce this troublesome sensitivity, we replaced the glass capillary used for UD-170 L with a quartz capillary. Quartz tube encapsulated BeO(Na) showed a markedly reduced response to thermal neutrons.

Equipment Design↗
PubMed1975

The action of quartz in the presence of iron hydroxides in the human lung.

In 1932 Kettle reported that the fibrogenic action of quartz particles is inhibited when they are coated with iron. Many authors subsequently confirmed this finding. Reif et al., who studied the effect of different iron-ore mine dusts, showed that, like aluminium hydroxide, iron hydroxide has a strong effect in inhibiting the fibrogenic action due to quartz. The findings of this paper, based on an X-ray survey of a group of 7735 iron ore miners, on autopsy examinations, tissue dust analysis and physiological examinations, confirm the view that FeO(OH) is a most powerful inhibiting substance.

Adult↗
PubMed2004

Resonator filters using shear horizontal-type leaky surface acoustic wave consisting of heavy-metal electrode and quartz substrate.

The authors have succeeded in exciting a new type of leaky surface acoustic wave (LSAW) having only a shear horizontal (SH) component that has a large electromechanical coupling factor, a large reflection coefficient, and excellent temperature stability, by combining interdigital transducers (IDTs) and reflectors made of heavy-metal films such as gold (Au), tantalum (Ta), and tungsten (W) on the ST-cut 90 degrees X propagation (direction perpendicular to the X-axis) quartz substrate. This LSAW does not have a propagation decay. The square of the electromechanical coupling factor is 2.1-2.7 times larger than, the reflection coefficient is 30 times larger than, and the temperature characteristic is the same as those of a Rayleigh wave on an ST-cut X propagation quartz substrate. The authors applied this SH LSAW to resonators and resonator filters. As a result, we succeeded in developing the low loss and very small-sized resonators and resonator filters (1/5-1/4 of conventional device sizes) with IDTs with a small number of finger pairs and very small reflectors, for the first time.

Journal Article↗
PubMedDate not supplied

Intensity of quartz-tungsten-halogen light polymerization units used in dental offices in Brazil.

PURPOSE: To determine the intensity of quartz-tungsten-halogen light polymerization units in dental offices in El Salvador, Brazil. MATERIALS AND METHODS: A team of researchers visited 100 offices in 2003. The team measured light intensity with a radiometer. The age and make of the units and the availability of light meters were recorded. RESULTS: One hundred twenty quartz-tungsten-halogen units were tested. Intensity ranged from 10 to 1,000 mW/cm2, with mean of 255.8 mW/cm2. Almost half (48%) of the units had values equal to or less than 200 mW/cm2. Their age ranged from 1 to 21 years. None of the offices had light meters. CONCLUSIONS: Clinicians should periodically monitor light intensity and carry out maintenance on their light polymerization units.

Composite Resins↗
PubMed1994

[Fluorescence monitoring of solid-phase peptide synthesis using a quartz reactor-cuvette].

The quartz reactor-cuvette for fluorescent monitoring of the solid phase peptide synthesis consists of a 10 mm diameter quartz tube jacketed in a 14 x 14 mm orthogonal holder and equipped with chemically inert adapters. This allows to use the reactor with almost any standard fluorimeter. Details of the construction are presented. Fluorescence spectra of Fmoc-group, both in solution and on the solid support, are given; effects of concentration quenching of the fluorescence are studied.

Amino Acid Sequence↗
PubMed1996

Quantitative assessment of apatite formation via a biomimetic method using quartz crystal microbalance.

Quantitative assessment of hydroxyapatite formation on a gold surface via the biomimetic method, composed of a nucleation step in a simulated body fluid (SBF) containing glass powders and a subsequent apatite growth step in glass powder-free SBF, was made using a quartz crystal microbalance (QCM) technique. The frequency change of the QCM linearly increased with increasing soaking time, and largely depended on the nucleation period. The growth rates, defined as daily increase in thickness, increased monotonicly with an increasing nucleation period of up to 96 h, thereafter being constant at 2.0 microns/day. The growth rate of the apatite layer increased with increasing temperature of the SBF: 0.9, 2.0, and 3.8 microns/day at 25, 37, and 50 degrees C, respectively. The Arrhenius-type activation energy for the growth of apatite was 47.3 kJ/mol. The QCM method was found to be a very powerful tool for quantitative, in situ measurement of precipitation and growth of apatite in real time.

Apatites↗
PubMed2001

Direct monitoring kinetic studies of DNA polymerase reactions on a DNA-immobilized quartz-crystal microbalance.

Catalytic reactions of DNA polymerase I from E. coli (Klenow fragment, KF) were monitored directly with a template/primer (40/25- or 75/25-mer)-immobilized 27-MHz quartz-crystal microbalance (QCM). The 27-MHz QCM is a very sensitive mass-measuring device in aqueous solution, as the frequency decreases linearly with increasing mass on the QCM electrode at the nanogram level. Three steps in polymerase reactions which include 1) binding of DNA polymerase to the primer on the QCM (mass increase); 2) elongation of complementary nucleotides along the template (mass increase); and 3) release of the enzyme from the completely polymerized DNA (mass decrease), could be monitored continuously from the time dependencies of QCM frequency changes. The binding constant (Ka) of KF to the template/primer DNA was 10(8)M(-1) (k(on) = 10(5)M(-1)s(-1) and k(off)= 10(-3)s(-1)), and decreased to 10(6)M(-1) (k'on = 10(4)M(-1)s(-1) and k'off = 10(-2)s(-1)) for completely polymerized DNA. This is due to the 10-fold decrease in binding rate constant (k(on)) and 10-fold increase in dissociation rate constant (k(off)) for completed DNA strands. Ka values depended slightly on the template and primer sequences. The kinetic parameters in the elongation process (k(cat) and Km) depended only slightly on the DNA sequences. The repair process during the elongation catalyzed by KF could also be monitored in real time as QCM frequency changes.

Base Pair Mismatch↗
PubMed2004

Quartz crystal microbalance-based measurements of shear-induced senescence in human embryonic kidney cells.

Fluid shear and other mechanical forces play an important role in the normal biophysical, biochemical, and gene regulatory responses of vertebrate tissue that are reflected in the expression of normal cell differentiation, growth, and function. Despite some promising work reported on the application of the quartz crystal microbalance (QCM) to both prokaryote and eukaryote cells over the last decade, QCM has yet to be successfully applied to cells in culture under conditions of flow-induced shear. In this study, high sensitivity QCM in conjunction with fluid modelling was used to monitor the onset of senescence in immortalised human embryonic kidney cells under laminar shear stresses of between 0.04 and 335 dyne/cm(2). The feasibility of this approach as a means of quantification and characterisation of cell physiological response and adhesion are explored and discussed.

Cell Culture Techniques↗
PubMed2004

Kinetic study of phosphorylation-dependent complex formation between the kinase-inducible domain (KID) of CREB and the KIX domain of CBP on a quartz crystal microbalance.

We report quantitative analysis of peptide-peptide interactions on a 27 MHz quartz crystal microbalance (QCM) in aqueous solution. The KID (kinase-inducible domain) of transcription factor CREB (cyclic AMP response element binding protein) is known to interact with the KIX domain of coactivator CBP (CREB binding protein), facilitated by phosphorylation at Ser-133 of the KID. The KIX domain peptide (86 aa) was immobilized on the QCM gold electrode surface by means of a poly(ethylene glycol) spacer. Binding of the KID peptide (46 aa) to the KIX peptide was detected by frequency decreases (mass increases) of the QCM. Both maximum binding amount (Deltammax) and association constants (Ka) obtained from the QCM measurements increased as a result of phosphorylation of Ser-133 of the KID peptide. The Ka values for KIX peptide to the phosphorylated (pKID) and unphosphorylated KID peptides were (93+/-2) x 10(3) and (5+/-1) x 10(3) M(-1), respectively. This difference was explained by the dissociation rate constant (k(-1)) of the pKID being 20 times smaller than that of the KID, while association rate constants (k1) were independent of phosphorylation.

Amino Acid Sequence↗
PubMed2006

Integrated isotachophoretic preconcentration with zone electrophoresis separation on a quartz microchip for UV detection of flavonoids.

A quartz microchip integrated isotachophoretic (ITP) preconcentration with zone electrophoresis (ZE) separation was fabricated using a novel multi-point pressure method featured in normal temperature and lower pressure during bonding process. ITP followed by subsequential ZE of two flavonoids, quercetin and isorhamnetin on the microchip was performed consecutively on the homemade microfluidic workstation with UV detection, resulting in a decreased detectable concentration of 32-fold, compared to the ZE mode only, and their detection limits decreased down to 0.2 microg/mL and 1.2 microg/mL, respectively.

Electrophoresis, Microchip↗
PubMed1987

Fluorescence lifetime measurements using total internal reflection fluorimetry: evidence for a conformational change in albumin adsorbed to quartz.

We have modified the total internal reflectance fluorimetry (TIRF) method to determine, indirectly, quantum fluorescence yield and thus infer structural changes of adsorbed plasma proteins. We employed a frequency multiplied Nd:YAG pulse laser to excite tryptophan residues of bovine serum albumin (BSA), measuring the resulting fluorescence lifetimes. BSA adsorbed on quartz was investigated at normal pH and under acidic (pH 3.8) conditions at which albumin shape change has been established in bulk solution. Albumin adsorbed at pH 7.2 has a slightly lower lifetime than the bulk solution value, reflecting a population of both native and isomerized forms. Gently washing the adsorbate surface significantly reduces fluorescence lifetime, suggesting retention of more tenacious, conformationally altered molecules. Vigorous washing further reduces fluorescence lifetimes to values close to those obtained in bulk under acidic conditions. Similar alterations in fluorescence lifetimes were observed for heat-denatured albumin. These results support the hypothesis that adsorbed albumin exists in the form of a two-layer deposit, each with a possibly different structure. A loosely held layer, consisting of BSA microaggregates and including partially unfolded molecules, exists on the undisturbed surface and is partially removed by gentle washing. Vigorous washing removes all but the most tightly held protein, which exists in a possibly further unfolded configuration. The decrease in fluorescence lifetime of adsorbed BSA implies a corresponding change in quantum yield. A change in quantum yield of BSA tryptophan fluorophors implies that measuring adsorbed protein concentration by intrinsic fluorescence is unreliable.

Adsorption↗
PubMed2005

Quartz-crystal microbalance-dissipation technique for the study of initial adsorption of fibronectin onto tresyl chloride-activated titanium.

The immobilization of cell-adhesive proteins onto titanium implants improves biological response at the implant-tissue interface. Previous studies demonstrated the easy and direct attachment of fibronectin onto titanium with the use of a 2,2,2-trifluoroethanesulfonyl chloride (tresyl chloride) activation technique. The present study investigated the initial adsorption behavior of fibronectin on tresyl chloride-activated titanium by the quartz-crystal microbalance-dissipation (QCM-D) technique. The crystal resonant frequency and the dissipation shift of the oscillator were simultaneously measured by the injection of fibronectin/phosphate-buffered saline solution (pH = 7.4). The tresyl chloride-activated titanium surface showed a faster and greater decrease in frequency than that of untreated titanium, indicating that a greater amount of fibronectin was adsorbed in the former case during a 120-min adsorption. The dissipation-frequency plots revealed that, during the initial stage of adsorption, the bond between fibronectin and tresyl chloride-activated titanium is stronger than that between fibronectin and untreated titanium. The QCM-D technique can provide new insights into the adsorption mechanism of fibronectin.

Adsorption↗
PubMed2006

Measuring cell adhesion on RGD-modified, self-assembled PEG monolayers using the quartz crystal microbalance technique.

In this study, the suitability of a flow-through quartz crystal microbalance system for the detection of the adhesion of rMSCs and 3T3-L1 fibroblasts on different surfaces is demonstrated. Frequency shifts for rMSCs of -6.7 mHz x cell(-1) and -2.0 mHz x cell(-1) for 3T3-L1 cells could be detected on non-modified gold sensors, revealing that the frequency shift per cell is comparable to that of a static setup. Modifying the sensor surface with SAMs of thioalkylated omega-amine-terminated PEG derivatives led to cell-adhesion-resistant surfaces. Total frequency shifts of only -20 +/- 7 Hz showed that protein adsorption was also significantly reduced. Attaching 35 pmol x mm(-2) of the GRGDS cell adhesion motif to the SAMs induced specific cell adhesion due to RGD-integrin interactions; the resonance frequency dropped by 3.4 mHz x cell(-1). Furthermore, the kinetics of cell detachment could be determined. The corresponding processes were completed after 10 min for trypsin, and not before 90 min with GRGDS. Moreover, the detectability of cell adhesion was shown to increase after the addition of manganese cations. The total decrease in the resonance frequency was almost 80 Hz in the presence of Mn(2+) (6.4 mHz x cell(-1)). [image: see text] Staining the cytoskeleton of the rMSCs shows that the GRGDS-modified surfaces are almost completely covered with well-spread cells.

Animals↗
PubMed2001

Comparison of different protein immobilization methods on quartz crystal microbalance surface in flow injection immunoassay.

In this study, a quartz crystal microbalance (QCM) system operated repetitively in flow injection analysis (FIA) mode, is reported. Four immobilization approaches of seven different methods include: (i) physical adsorption; (ii) two thioamine thiolation methods, using cysteamine and cystamine for gold chemisorption and further coupling; (iii) two oxidized dextran spacer methods, coupling of cysteamine and cystamine thiolated QCM surface with periodate-oxidized dextran for further Schiff acid-base reaction; and (iv) two thiol-gold chemisorption-based self-assembled monolayer (SAM), applying short-chain, C(3), and long-chain, C(11), mercapto fatty acids to insolubilize human serum albumin (HSA) on QCM surface. Effects of these protein immobilization methods on FIA immunoassay of anti-HSA were compared. At the 0.01 mg/ml anti-HSA level, the lowest analyte concentration tested, the SAM using 11-mercaptoundecanoic acid as QCM surface activating agent generated a larger frequency shift than the other immobilization methods. This implied that the use of thiolated long-chain fatty acid constructed as self-assembled monolayer may thereby potentially be a useful protein immobilization method in QCM-FIA application.

Absorption↗
PubMed1994

Recognition of monosialoganglioside (GM3) reconstituted in sphingomyerin and glucosylceramide membranes against wheat germ agglutinin: quantitative analyses by a quartz crystal microbalance.

Specific binding of Wheat Germ Agglutinin (WGA) to GM3-containing mixed monolayer at the air-water interface was studied by using a quartz crystal microbalance to know the binding amount and initial binding rate of WGA to GM3. GM3 in the glucosylceramide matrix membrane showed the high recognizability compared to GM3 in sphingomyeline matrix membrane. It is demonstrated that matrix lipids surrounding GM3 regulated the recognition of GM3.

Binding Sites↗
PubMed2002

Covalent DNA immobilization on polymer-shielded silver-coated quartz crystal microbalance using photobiotin-based UV irradiation.

The use of a commercial, silver-coated quartz crystal microbalance (QCM) as a disposable, low-cost, and reliable DNA sensor is presented. This is an incorporation of polymer-based silver electrode shielding and photochemistry-based surface modification for covalent DNA immobilization. To prevent undesired oxidation, the silver electrodes are coated with thin polystyrene films. The polymer surfaces are then modified by a photoreactive biotin derivative (photobiotin) under UV irradiation. The resulting biotin residues on the polymer-shielded surface react with a tetrameric avidin. Consequently a biotin-labeled DNA probe can be immobilized through a biotin-avidin-biotin bridge. A 14-mer single-stranded biotin-DNA probe and a 70-mer single-stranded DNA fragment containing complementary or noncomplementary sequences are used as a model system for DNA hybridization assay on the proposed sensors. The shielding ability of the polystyrene coatings after photo irradiation is investigated. The DNA probe binding capacity, hybridization efficiency, and kinetics are also investigated.

Affinity Labels↗
PubMed2002

Study of adsorption behavior of bilirubin on human-albumin monolayer using a quartz crystal microbalance.

The quartz crystal microbalance was employed to study the adsorption behavior of bilirubin on human-albumin layer, which was chemically bound to the self-assembled monolayer of 4-aminothiophenol on the surface of a gold electrode of the crystal via glutaraldehyde. A long-time adsorption process of bilirubin that took place on a human-albumin-modified surface was observed, and the adsorption kinetic parameters were estimated from the in situ frequency measurements. The amount of adsorbed bilirubin increased with increasing of both hydrogen ions and bilirubin concentration and was larger than that estimated based on the conclusion that there are two affinity sites for bilirubin per albumin molecule. With the present method, the displacement of bilirubin from an albumin layer caused by aspirin was also examined. QCM measurement provides a facile method for in situ monitoring of the adsorption/desorption of bilirubin on proteins layers.

Adsorption↗
PubMed1977

The asymmetric adsorption of alpha-aminopropionitrile on D-quartz.

alpha-Aminopropionitrile was adsorbed on the powdered D-quartz, recovered as N-trifluoro-acetylalanyl-(+)-secondarybutyl ester, and analyzed by means of gas chromatography. The asymmetric result supporting the preferential adsorption of L-antipode was obtained and its significance in chemical evolution has been discussed.

Adsorption↗