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We present conventional detection of 2,4-dinitrophenol (DNP) for using the competitive reaction between DNP and DNP-conjugated albumin onto DNP antibody immobilized quartz crystal microbalance (QCM). This QCM method allows detection of DNP concentration in the range of 0.01 to 100 ng/ml; linear correlation obtains DNP concentration from 1 to 100 ng/ml.
It is well understood that the strong coupling of thickness-shear and flexural vibrations in piezoelectric crystal plates only occurs at specific length at which the vibration mode conversion, like the flexural mode gradually converting to thickness-shear mode while the thickness-shear mode converting to higher-order flexural mode, happens. It is important to avoid the strong coupling of modes in a crystal resonator that uses thickness-shear vibrations to enhance the energy trapping. To achieve such a design goal, the length of a crystal blank should be carefully chosen such that the coupling is at its weakest, which usually is in the middle of two strong coupling points. Through a closer examination of the frequency spectra, or the frequency-length relationship in this study, we can see that the strong coupling points appear periodically. This implies that we can find exact locations with the plate theory that predicts the resonance frequency. Based on this observation, we first use the first-order Mindlin plate theory with the precise thickness-shear frequency, which is normalized to one, to find corresponding wavenumbers. Then the length as a variable is solved from the coupled frequency equation for exact coupling points in a crystal plate of AT-cut quartz. The optimal length of a crystal blank in the simplest resonator model is calculated for the coupled thickness-shear, flexural, and extensional vibrations. The solutions and the method will be important in the determination of optimal length of a crystal blank in the resonator design process.
Grain boundary migration is an important mechanism of microstructural modification both in rocks and in metals. Combining detailed cathodoluminescence (CL) and electron backscatter diffraction (EBSD) analysis offers the opportunity to relate directly changes in crystallographic orientation to migrating boundaries. We observe the following features in naturally heated quartz grains from the thermal aureole of the Ballachulish Igneous Complex (Scotland, U.K.): (a) propagation of substructures and twin boundaries in swept areas both parallel and at an angle to the growth direction, (b) development of slightly different crystallographic orientations and new twin boundaries at both the growth interfaces and within the swept area and (c) a gradual change in crystallographic orientation in the direction of growth. All these features are compatible with a growth mechanism in which single atoms are attached and detached both at random and at preferential sites, i.e. crystallographically controlled sites or kinks in boundary ledges. Additionally, strain fields caused by defects and/or trace element incorporation may facilitate nucleation sites for new crystallographic orientations at distinct growth interfaces but also at continuously migrating boundaries. This study illustrates the usefulness of combined CL and EBSD in microprocess analysis. Further work in this direction may provide detailed insight into both the mechanism of static grain growth and the energies and mobilities of boundaries in terms of misorientation and grain boundary plane orientation.
We have found that a quartz-crystal microbalance is a facile and useful tool for detecting the specific aggregation of the amyloid-beta peptides responsible for Alzheimer's disease. This method greatly reduces the time and samples (corresponds to 1 Hz frequency decrease per 30 pg mass increase on a 4.9 mm(2) electrode) that are needed in the aggregation assay, and is also applicable to molecular interactions between smaller amyloid-beta fragment peptides such as the pentapeptide KLVFF.
The reduction of bacterial biofilm formation on stainless steel surfaces by N-acetyl-L-cysteine (NAC) is attributed to effects on bacterial growth and polysaccharide production, as well as an increase in the wettability of steel surfaces. In this report, we show that NAC-coated stainless steel and polystyrene surfaces affect both the initial adhesion of Bacillus cereus and Bacillus subtilis and the viscoelastic properties of the interaction between the adhered bacteria and the surface. A quartz crystal microbalance with dissipation was shown to be a powerful and sensitive technique for investigating changes in the applied NAC coating for initial cell surface interactions of bacteria. The kinetics of frequency and dissipation shifts were dependent on the bacteria, the life cycle stage of the bacteria, and the surface. We found that exponentially grown cells gave rise to a positive frequency shift as long as their cell surface hydrophobicity was zero. Furthermore, when the characteristics of binding between the cell and the surface for different growth phases were compared, the rigidity increased from exponentially grown cells to starved cells. There was a trend in which an increase in the viscoelastic properties of the interaction, caused by the NAC coating on stainless steel, resulted in a reduction in irreversibly adhered cells. Interestingly, for B. cereus that adhered to polystyrene, the viscoelastic properties decreased, while there was a reduction in adhered cells, regardless of the life cycle stage. Altogether, NAC coating on surfaces was often effective and could both decrease the initial adhesion and increase the detachment of adhered cells and spores. The most effective reduction was found for B. cereus spores, for which the decrease was caused by a combination of these two parameters.
Rats were exposed to quartz dust (about 90 mg/m3) for five hours a day, five times a week either throughout the 48 weeks of the experiment or for a total of 40 weeks plus eight weeks of "rest." Cytological study of bronchoalveolar lavage showed that at a certain level of silicotic changes in the lungs, a pronounced breakdown in pulmonary dust clearance by macrophages could be observed. There was, however, a concomitant compensatory increase in the contribution to pulmonary phagocytosis by the neutrophil leukocytes (NL). As a result, pulmonary dust kinetics could be mathematically described using a constant clearance rate both throughout the 48 weeks of exposure and during the eight weeks after the end of the 40 week exposure. It is shown in a separate experiment that enhanced recruitment of NL into the airways may be due not only to an attractant effect of the products of macrophage breakdown (PMB) themselves but also to the release of an NL attractant factor by viable macrophages activated under influence of the PMB.
A multicompartmental model for the kinetics of dust retention in the pulmonary region of the lung and in the tracheobronchial lymph nodes has been developed. The model reflects the following ideas concerning the basic features of this process: (1) penetration into the pulmonary interstitium and translocation to the lymph nodes are possible for non-phagocytized particles only; (2) these processes depend on the degree of damage to macrophages by dust and on the extent of compensatory enhancement in the recruitment of neutrophils taking part in the clearance of the pulmonary region free surface; (3) a certain proportion of initially penetrating particles is continuously returned to this surface together with recruited pulmonary macrophages. The model ensures a satisfactory approximation to experimental data on the retention of quartz in the lung and lymph nodes during long term inhalation exposure, and simulation of the kinetic effects associated with both the damage to and the protection of the macrophagal clearance mechanism.
The distribution of length and diameter and the aspect ratio of crocidolite asbestos, a mineral substitute for asbestos (wollastonite), a manmade mineral fibre (glass wool), and synthetic fibres (polypropylene and polyacrylonitrite) were determined by light microscopy with phase contrast and, for crocidolite, also with transmission electron microscopy. The synthetic organic fibres and manmade mineral fibre used were of a size exceeding that considered respirable. Respirable materials were given to rats by the intratracheal method and after exposure for a standard time interval the main indices of fibrogenic effects--the total hydroxyproline content, the wet weight of the lung, and the total lipid content in the lung--were estimated. For wollastonite there was a significant increase in these variables in comparison with the controls. The fibrogenicity was considerably less than that of crocidolite and quartz.
BACKGROUND: The penetration of different wavelengths of UV radiation through human skin is of major importance, especially for the determination of photoprotective properties of sunscreens and UV-protective clothes. OBJECTIVE: In this study we present a new method for the measurement of UV transmission through small skin specimens. METHODS: The transmission measurements were performed by using a UV spectrophotometer with an integrating sphere operating in the wavelength range of 280-390 nm. For the skin samples, special quartz glass cuvettes were developed which allowed measurements for very thin and small skin specimens. Furthermore, the cuvettes prevented dehydration of the specimens and guaranteed, by using an additional diaphragm, that the transmission data were derived solely from the small skin specimen examined. Specimens measuring 8 x 3 mm(2) with a thickness of 0.3 mm (histometric and sonographic control) were taken from the thighs of 10 subjects via shave biopsy. RESULTS: In the UVA range (315-390 nm) we obtained a mean transmission of 4.6% and for the UVB range (280-315 nm) of 0.9%. No significant (p >0.14) difference of UV transmission was found between the individual skin specimens. CONCLUSION: This new method seems to be well suitable for UV transmission measurements of small skin specimens. As UVA radiation has a much deeper penetration depth and in in vivo situations dermal hemoglobin could have an effect on UV penetration, the present method is better suitable for the investigation of UVB-induced biological adaptation mechanisms and the impact of topical agents on UVB transmission of the epidermis.
Epidemiological, clinical and serological data of uranium miners with symptoms of connective tissue diseases (CTD) were collected during the control examinations for occupational lung diseases since 1975. Twenty eight definite (four or more ARA criteria) and 15 probable (2-3 ARA criteria) SLE were diagnosed. The estimated prevalence among heavily silica exposed uranium miners was up to 93 in 100,000. The only significant differences to nonexposed SLE patients were decreased frequency of arthritis and photosensitivity and the absence of anti-Sm and anti-U1-RNP antibodies. ANA were found in all definite SLE patients examined with the following specificities: anti-dsDNA (in 44.4%), & anti-Ro/SSA (in 55.6%, four cases together with anti-dsDNA) and anti-La/SSB (in 22.2%). The autoantibody profiles of patients with probable SLE were similar, but with a lower frequency of ANA, anti-dsDNA and anti-Ro/SSA. Middle to high-titred autoantibodies to dsDNA, Ro/SSA and La/SSB were detected in 3.2% uranium miners with no (N = 1229) and in 20.6% with some symptoms (one ARA criterion and/or two or more of other CTD typical symptoms, N = 68) of CTD development. We conclude, that the strong exposure to dust with a high content of silica may predispose to or initiate the development of SLE. The detection of SLE-typical antibodies in quartz dust-exposed miners may indicate a higher risk for the development of systemic autoimmune disease.
We used an in vitro system that eliminates competing guidance cues found in embryos to determine whether substratum topography alone provides important neurite guidance information. Dissociated embryonic Xenopus spinal cord neurons and rat hippocampal neurons were grown on quartz etched with a series of parallel grooves. Xenopus neurites grew parallel to grooves as shallow as 14 nm and as narrow as 1 microm. Hippocampal neurites grew parallel to deep, wide grooves but perpendicular to shallow, narrow ones. Grooved substrata determined the sites at which neurites emerged from somas: Xenopus neurites sprouted from regions parallel to grooves but presumptive axons on rat hippocampal neurons emerged perpendicular to grooves and presumptive dendrites emerged parallel to them. Neurites grew faster in the favored direction of orientation and turned through large angles to align on grooves. The frequency of perpendicular alignment of hippocampal neurites depended on the age of the embryos from which neurons were isolated, suggesting that contact guidance is regulated in development. Collectively, the data indicate that substratum topography is a potent morphogenetic factor for developing CNS neurons and suggest that in addition to a role in pathfinding the geometry of the embryo assists in establishing neuronal polarity. In the companion paper (A. M. Rajnicek and C. D. McCaig (1997) J. Cell Sci. 110, 2915-2924) we explore the cellular mechanism for contact guidance of growth cones.
Raman spectra of alpha-quartz (Qz) grains of various size (250 microm to < 11 microm) and arrangement (individual and aggregated) have been investigated with a combination of confocal Raman and micro-Raman systems. Frequency downshift and line broadening of the 464 cm(-1), v,(Si-O-Si) band are observed in the smallest size group (< 11 microm, both individual grains and aggregates) because of laser-induced heating and are used to estimate the temperature of the sampled region. The intensity ratio of the anti-Stokes to Stokes Raman lines is also used to estimate the vibrational temperature of the samples under different excitation power. The degree of laser-induced heating is more noticeable in the aggregates than in the individual grains with the use of medium-level laser excitation (< or = 150 mW). Heating diminishes with increasing grain size, and it can only be detected in grain aggregates between 11 and 20 microm in diameter using 150 mW excitation. Intensity studies of the v(s)(Si-O-Si) band using individual grains show no noticeable signs of grain size effects. However, grain size effects become an important factor in the study of aggregates in which spectral intensity diminishes with respect to decreasing grain size.
BACKGROUND: The resurgence of the parasitic disease schistosomiasis calls for more efficient diagnostic tests. We developed a rapid, simple, portable, and sensitive immunoagglutination assay that uses SiO(2) particles and quartz crystal microbalance (QCM) for quantifying Schistosoma japonicum (Sj) antibodies (SjAb). METHODS: We prepared submicrometer-sized silica particles derivatized with Sj antigens as replacements for traditional latex microspheres to specifically agglutinate in the presence of SjAb targets, and we used the QCM monitor to measure the resulting frequency shifts. We optimized the assay medium by adding poly(ethylene glycol) (PEG) as a response accelerator of immunoagglutination. To minimize or eliminate any nonspecific agglutination or adsorption interferences, we conducted appropriate sealing procedures separately for silica particles and the QCM probe. RESULTS: The measured frequency changes were linearly related to the SjAb concentrations in infected rabbit serum. The PEG-assisted immunoagglutination system was quantitatively sensitive to SjAb concentrations ranging from approximately 0.70 to 32.31 mg/L, with a detection limit of approximately 0.46 mg/L. The obtained linear regression equation was: y=43.61 x+80.44 (r=0.9872). Several serum specimens were evaluated with the developed QCM immunoassay and the results were compared with ELISA, validating the feasibility of practical applications. CONCLUSIONS: This novel immunoagglutination-based QCM detection format is rapid, simple to use, and more portable than conventional diagnostic immunoassays, thus offering a promising alternative tool that can be used for point-of-care clinical diagnosis of schistosomiasis, particularly in epidemic situations.
To characterize silica-induced alveolitis in human subjects, we studied 22 workers in the granite stone cutting industry of Quebec and compared results with those of 22 manual workers without quartz exposure (group 1). All were nonsmokers and were of comparable age. On the basis of chest roentgenogram, seven were without disease (group 2), nine had silicosis without coalescence/conglomeration (group 3), and six had silicosis with coalescence/conglomeration (group 4). The alveolitis in subsets of silica-exposed workers with distinct clinical stages of disease was found to have distinct biologic characteristics.
We present a immunosensing system based on a quartz crystal microbalance (QCM) that allows detection and evaluation of a broad range of molecules relevant to medicine and biology. Soluble analyte is applied by injection into a flow-through chamber where receptor molecules are immobilized, thus enabling real-time measurement of the specific intermolecular interactions. This system can be used for detection purposes, e.g., screening for antibodies, and for determination of affinity constants including affinity evaluation of newly selected or designed aptamers, as kd and ka rates can be derived from the sensograms.
The piezoelectric quartz crystal impedance technique (QCI) was employed to monitor in situ the Pb2+-induced precipitation of BSA onto a gold electrode and the precipitate dissolution with EDTA in an aqueous solution. The critical precipitation concentration of Pb2+, at which the resonant frequency decreased significantly, was estimated to be 4.78 x 10(-4) mol/L. The saturated adherence of the precipitate on the electrode was observed when the concentration of Pb2+ was greater than 7.53 x 10(-2) mol/L. The frequency response was mainly caused by the mass effect of the precipitate adherence to the electrode, rather than the changes in the physico-chemical properties of the contacting liquid. An excess addition of Na2EDTA after the Pb2+-BSA dissolution led to new precipitation, probably due to the formation of an EDTA precipitate in this medium (pH approximately 3). The pH effect on the response of the resonant frequency was analyzed by using the sum of two exponential functions. A larger frequency response occurred at a pH greater than pI. These findings have been reasonably explained. Also, a decrease in the concentration of the background electrolyte increased the frequency response.
The interaction between metal ions and bovine serum albumin (BSA) was studied by using a piezoelectric quartz crystal (PQC) arranged in the electrode-separated configuration. A silanized surface of the PQC was coated with a BSA membrane via a coupling reaction with glutaraldehyde. The frequency shifts obtained from PQC coated with a BSA membrane suggested that various kinds of metal ions could be adsorbed onto the BSA membrane from aqueous solutions containing a low concentration of metal ions (2 or 10 micromol dm(-3)), only when the BSA was denatured with an alkaline solution. Anionic species of Pt(IV) and Au(III) were adsorbed onto the denatured BSA membrane from an acetic acid solution at pH 2.2, and cationic species of Cd(II), Zn(II), Co(II), Ni(II), Cu(II), and Ag(I), and cations, such as Ca2+, Ba2+, and Mg2+, were adsorbed from ammonia buffer at pH 9.5, whereas Al(III), Cr(III), Fe(III), Hg(II), and Pb(II) were hardly adsorbed. The adsorption mechanisms of these metal ions are discussed, based on the electrostatic interaction between the metal ions and the denatured BSA membrane, and complex formation between the metal ions and amino acid residues of the denatured BSA. Further, the PQC coated with a denatured BSA membrane was applied to the determination of Pt and Cd, using large frequency shifts for Pt(IV) and Cd(II).
The hydrolytic stability of a pre-activated MPS silane (Monobond-S) and a 2-component 4-META/ gamma-MPTS silane (Porcelain Liner M) to H202-etched quartz fiber posts was investigated using a modeling approach. Composite build-ups around silanized posts were stored dry for 24 hours, stored in deionized water at 37 degrees C for 24 hours, 1 week, 1 month or they were thermocycled. Sectioned specimens were prepared for microtensile bond testing and SEM examination; 4-META/gamma-MPTS silane produced a rapid decline in bond strength after 1 week and 1 month of water storage and after thermocycling. This was not apparent in pre-activated MPS silane. SEM revealed debonding along the post-composite interfaces, which were coupled with 2-component silane. The use of a hydrophilic resin monomer (4-META) for on-demand hydrolysis of the gamma-MPTS silane expedited interfacial water sorption and hydrolytic degradation, which may be prevented with alternative coupling strategies.