Hydrogen-sensitive palladium-gate MOS structures heated above 150°C show sensitivity to ethanol vapor. The effect is probably due to catalytic dehydrogenation of adsorbed ethanol molecules on the surface of the palladium gate.
The epidermal growth factor receptor (EGFR) is fundamental for normal cell growth and organ development, but has also been implicated in various pathologies, notably tumors of epithelial origin. We have previously shown that the initial 13 amino acids (P13) within the intracellular juxtamembrane region (R645-R657) are involved in the interaction with calmodulin, thus indicating an important role for this region in EGFR function. Here we show that P13 is required for proper dimerization of the receptor. We expressed either the intracellular domain of EGFR (TKJM) or the intracellular domain lacking P13 (ΔTKJM) in COS-7 cells that express endogenous EGFR. Only TKJM was immunoprecipitated with an antibody directed against the extracellular part of EGFR, and only TKJM was tyrosine phosphorylated by endogenous EGFR. Using SK-N-MC cells, which do not express endogenous EGFR, that were stably transfected with either wild-type EGFR or recombinant full-length EGFR lacking P13 demonstrated that P13 is required for appropriate receptor dimerization. Furthermore, mutant EGFR lacking P13 failed to be autophosphorylated. P13 is rich in basic amino acids and in silico modeling of the EGFR in conjunction with our results suggests a novel role for the juxtamembrane domain (JM) of EGFR in mediating intracellular dimerization and thus receptor kinase activation and function. © 2004 Elsevier Inc. All rights reserved.
Calcium-calmodulin (CaM) binding to the epidermal growth factor receptor (EGFR) has been shown to both inhibit and stimulate receptor activity. CaM binds to the intracellular juxtamembrane (JM) domain (Met645-Phe688) of EGFR. Protein kinase C (PKC) mediated phosphorylation of Thr654 occurs within this domain. CaM binding to the JM domain inhibits PKC phosphorylation and conversely PKC mediated phosphorylation of Thr654 or Glu substitution of Thr654 inhibits CaM binding. A second threonine residue (Thr669) within the JM domain is phosphorylated by the mitogen-activated protein kinase (MAPK). Previous results have shown that CaM interferes with EGFR-induced MAPK activation. If and how phosphorylation of Thr669 affects CaM-EGFR interaction is however not known.In the present study we have used surface plasmon resonance (BIAcore) to study the influence of Thr669 phosphorylation on real time interactions between the intracellular juxtamembrane (JM) domain of EGFR and CaM. The EGFR-JM was expressed as GST fusion proteins in Escherichia coli and phosphorylation was mimicked by generating Glu substitutions of either Thr654 or Thr669. Purified proteins were coupled to immobilized anti-GST antibodies at the sensor surface and increasing concentration of CaM was applied. When mutating Thr654 to Glu654 no specific CaM binding could be detected. However, neither single substitutions of Thr669 (Gly669 or Glu669) nor double mutants Gly654/Gly669 or Gly654/Glu669 influenced the binding of CaM to the EGFR-JM. This clearly shows that PKC may regulate EGF-mediated CaM signalling through phosphorylation of Thr654 whereas phosphorylation of Thr669 seems to play a CaM independent regulatory role. The role of both residues in the EGFR-calmodulin interaction was also studied in silico. Our modelling work supports a scenario where Thr654 from the JM domain interacts with Glu120 in the calmodulin molecule. Phosphorylation of Thr654 or Glu654 substitution creates a repulsive electrostatic force that would diminish CaM binding to the JM domain. These results are in line with the Biacore experiments showing a weak binding of the CaM to the JM domain with Thr654 mutated to Glu. Furthermore, these results provide a hypothesis to how CaM binding to EGFR might both positively and negatively interfere with EGFR-activity. © 2006 Elsevier Inc. All rights reserved.
This communication reports the first steps in the construction of a novel, nanoparticle-based hybrid material for biomimetic and biosensor applications. Gold nanoparticles were modified with synthetic polypeptides to enable control of the particle aggregation state in a switchable manner, and particle aggregation was, in turn, found to induce folding of the immobilized peptides.
The spectral fingerprinting of the excitation emission matrix (EEM) of fluorescent substances is demonstrated using polychromatic light sources and tri-chromatic image detectors. A model of the measured fingerprints explaining their features and classification performance, based on the polychromatic excitation of the indicators is proposed.
Substantial amount of spectral information is retained in the fingerprints as corroborated by multivariate analysis and experimental conditions that favor such situation are identified.
In average, for five different substances, the model shows a fitting goodness measured by the Pearsons r coefficient and the root mean square deviation of 0.8541 and 0.0247 respectively, while principal component classification patterns satisfactorily compare with the EEM spectroscopy classification and respectively explain 96% and 93% of the information in the fist two principal components.
The measurements can be performed using regular computer screens as illumination and web cameras as detectors, which constitute ubiquitous and affordable platforms compatible with distributed evaluations, in contrast to regular instrumentation for EEM measurements.
In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be "portable" and "simple". In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8 h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30 min. The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities. © 2006 Elsevier B.V. All rights reserved.
Melanophores are pigmented cells in lower vertebrates capable of quick color changes and thereby suitable as whole cell biosensors. In the frog dermis skin layer, the large and dark pigmented melanophore surrounds a core of other pigmented cells. Upon hormonal stimulation the black-brown pigment organelles will redistribute within the melanophore, and thereby cover or uncover the core, making complex color changes possible in the dermis. Previously, melanophores have only been cultured on flat surfaces. Here we mimic the three dimensional biological geometry in the frog dermis by culturing melanophores on fluorescent plastic microbeads. To demonstrate biosensing we use the hormones melatonin and α-melanocyte stimulating hormone (α-MSH) as lightening or darkening stimuli, respectively. Cellular responses were successfully demonstrated on single cell level by fluorescence microscopy, and in cell suspension by a fluorescence microplate reader and a previously demonstrated computer screen photo-assisted technique. The demonstrated principle is the first step towards "single well/multiple read-out" biosensor arrays based on suspensions of different selective-responding melanophores, each cultured on microbeads with distinctive spectral characteristics. By applying small amount of a clinical sample, or a candidate substance in early drug screening, to a single well containing combinations of melanophores on beads, multiple parameter read-outs will be possible. © 2004 Elsevier B.V. All rights reserved.
The interaction of chemical species with molecular films of porphyrins causes variations of the work function of the film itself, as it has been recently demonstrated by using the Kelvin probe technique. This characteristic makes porphyrins films suitable to be used as sensitive layers in ChemFET sensors. In this paper, we present a preliminary report about the fabrication and testing of such gas sensitive devices. The technological solutions towards an optimised device are also illustrated and discussed. © 2001 Elsevier Science B.V.
In Xenopus melanophores, melatonin induce melanosome aggregation via activation of its receptor Mel1c, coupled to inhibitory G proteins, adenylate cyclase deactivation, cyclic adenosine 3':5'-monophosphate (cAMP) decrease, protein kinase A inhibition, protein phophatase 2A activation, and serine/threonine dephosphorylations. Myosin V is the motor protein responsible for transporting melanosomes along actin filaments. Myosin V has been demonstrated to be necessary for melanosome dispersion and to keep the dispersed state. We have previously shown that melatonin induce activation of phosphoinositide-3 kinase, mitogen-activated protein kinase and tyrosine phosphorylation of a 280-kDa protein. Here we characterize the kinetics of latrunculin A-induced aggregation, and show that latrunculin A aggregate melanophores with the same kinetics as melatonin. This indicates that the downstream mechanisms might be similar although their primary targets in the cells are totally different. We suggest that both drugs act by inhibiting myosin V, the rate-determinative step for melanosome aggregation. Our data suggest that dynein is not up regulated during aggregation, as previously suggested by others,
Field-effect devices with a catalytic metal gate are operated as gas sensors over a large temperature range by the use of 6H-silicon carbide (bandgap 2.9 eV) instead of silicon (1.1 eV) as the semiconducting material. We have produced metal-silicon dioxide-silicon carbide (MOSiC) capacitors with platinum as the gate metal that can be operated above 800-degrees-C. The sensitivity of the Pt-MOSiC devices to hydrogen and hydrocarbons was tested in various oxygen atmospheres. The response to mixtures of hydrogen and saturated hydrocarbons indicated the existence of two different sensing mechanisms.
Catalytic metal gate-silicon dioxide-silicon carbide (MOSiC) capacitors operating to about 800-degrees-C are used as high temperature gas sensor devices. Hydrogen or hydrogen containing molecules, which are dissociated on the catalytic metal surface, create a decrease of the flat band voltage of the MOS capacitor. The MOSiC devices with a platinum gate respond to saturated hydrocarbons in air at concentrations well below the explosion limits.
Drift is one of the most serious impairments afflicting gas sensors. It can be seen as a gradual change in the sensor response over a long period of time when the external conditions an constant. This paper presents a new simple drift counteraction method based on PCA and PLS. The basic idea is to remove the drift direction component from the measurements. The direction of the drift, p, is calculated from measurements for a reference gas. Projecting the sample gas measurements on this vector gives the score vector t. The drift component tp(T) can then he removed from the sample gas data, which we call component correction (CC). The method is tested on a data set based on a reduced factorial design with four gases and a concentration gradient of hydrogen. It is found that the method works efficiently for both cases. Copyright (C) 2000 John Wiley & Sons, Ltd.
A method for measuring a property of a test sample utilizing one of the test methods ellipsometry, surface plasmon resonance and nephelometry, wherein the method includes the steps; providing a test sample being an object with which an optical interaction with light takes place, illuminating said test sample using a program controlled display as a light source, which program controlled display is composed of at least one activated pixel providing an illumination from an illuminating area of said program controlled display, arranging said program controlled display to illuminate said test sample with polarized light, detecting light emerging from said test sample utilizing a detector coupled to said program and evaluating said property from signals from said detector.
Conducting polymers appear very attractive as sensor materials either as the gas-sensitive component or as a matrix for easy immobilization of a specific substrate. The planar Schottky barrier diode with poly(3-octylthiophene), P3OT, as the semiconductor is used as a sensor for the detection of different gas species. The shifts in the current-voltage (C-V) characteristics as well as the C-V characteristics of the diodes due to water and ethanol vapour, ammonia gas and nitric oxide gases are studied. Nitric oxide and ammonia give the largest and most specific changes of the C-V characteristics. Nitric oxide has a doping effect, which increases the reverse current, while ammonia is the only gas that causes a negative change in the forward bias current of the I-V curve. The planar configuration of the Schottky barrier diode facilitates the absorption of gaseous species in the environment, and provides a simple method for production of gas sensors.
Konferensbidrag (muntligt-1:a pris) vid "EUROPT(R)ODE VIII, Tübingen, Germany, 2-5 april
The separation of emission from transmitted light for the fingerprinting of fluorescent substances using a computer screen photo-assisted technique (CSPT) is demonstrated. CSPT is a technique for optical evaluation using a simple cell with just a standard computer set and a web camera as instrumentation. It has been demonstrated to be a versatile system for colorimetric and fluorescent fingerprinting. Here the omnidirectional property of fluorescent emission is utilized to separate it from the background, using a simple optical arrangement compatible with CSPT purposes. This enhances the classification capabilities and makes classification at sub-μM concentrations possible.
The ellipsometric measurement of thickness is demonstrated using a computer screen as a light source and a webcam as a detector, adding imaging off-null ellipsometry to the range of available computer screen photoassisted techniques. The results show good qualitative agreement with a simplified theoretical model and a thickness resolution in the nanometer range is achieved. The presented model can be used to optimize the setup for sensitivity. Since the computer screen serves as a homogeneous large area illumination source, which can be tuned to different intensities for different parts of the sample, a large sensitivity range can be obtained without sacrificing thickness resolution.
Detection of antibody-antigen reactions is demonstrated by measuring changes in reflectance of light polarized parallel to the plane of incidence, using a computer screen as light source and a web camera as detector, giving results similar to traditional off-null ellipsometry and in accordance with a simplified theoretical model.
Detection and classification of fluorescent dyes are demonstrated using a computer screen photo-assisted technique (CSPT). This technique has previously been demonstrated for analyzing fluorescence from 96 wells microtiterplates (200 µl per well) and from a single cuvette with some optics to enhance sensitivity. In this work a custom designed array of wells with a volume of approximately 1 mu;l is used. In order to measure such small volumes without saturating the detector, the transmitted light is masked by placing the sample between two crossed polarizers. This arrangement blocks nearly all the transmitted light, while the emitted light, which is nearly unpolarized, can still be detected. The lowest amount (concentration x volume) of analyte detectable in this setup is about 40 times smaller than in the previous setups.
Field effect sensors based on metal-oxide-silicon carbide (MOSiC) devices are used as high temperature gas sensors. They are sensitive to, for example, saturated hydrocarbons and hydrogen and can be operated up to at least 800 degrees C, which make them suitable for several types of combustion control. A metal gate with two layer platinum and a buffer layer of tantalum silicide in between gave a large increase in the long term stability of the sensors. At temperatures below 600 degrees C, the response to ethane in oxygen was shown to have a threshold at a ratio of about 0.38 for the ethane-to-oxygen concentrations. Below this ratio, the surface can be considered as mainly oxygen covered and the response is small. Above this ratio the metal surface is probably mainly hydrogen covered and the response is considerably larger.
Field effect devices based on catalytic metal-oxide-silicon carbide (MOSiC) structures can be used as high temperature gas sensors. The devices are sensitive to hydrocarbons and hydrogen and can be operated up to at least 900 degrees C, which make them suitable for several combustion applications, Simulated and real exhaust gases from a car engine have been studied at sensor temperatures from 200 to 650 degrees C, and it was round that the sensor signal is high for excess hydrocarbon and low for excess oxygen. The response time is less than 100 ms and only a small degradation of the devices was observed after several days of operation. The devices also react to changes of the gas composition In the fuel-rich and fuel-lean region. The devices show an interesting temperature dependence in the fuel rich region.
We report on a reversible hydrogen annealing effect observed in platinum-silicon dioxide-silicon carbide structures at temperatures above about 650 degrees C. It appears as a decrease of the inversion capacitance in the presence of hydrogen. This phenomenon is shown to depend on hydrogen atoms, created on the catalytic metal, that pass through the oxide and interact with charge generation sites at the oxide-silicon carbide interface. The consequence of the observation for chemical sensors based on silicon carbide is discussed. The results are phenomenological, since no details of the annealing chemistry could be developed from the present experiments. We find, however, that the annealing process and its reversal have activation energies of about 0.9 eV and 2.9 eV/site,respectively.
Rapid transitions in the response of platinum-based chemical sensors occurring at given hydrogen-oxygen concentration ratios are explained by kinetic phase transitions or switching phenomena on the catalytic metal surface. Below the transition point the response of platinum-insulator silicon carbide devices is small and above the transition it is large. It is found that the critical ratio depends on the operation temperature and the properties of the device. Three different cases are identified, namely, injection-, diffusion-, and reaction-rate-determined transitions. At sufficiently large temperatures the transition is injection limited and occurs at the stoichiometric ratio of hydrogen and oxygen in the gas mixture. The implications of the experimental observations on the applications of chemical sensors with catalytic sensing layers are discussed.
Rapid transitions in the response of platinum based chemical sensors occurring at given hydrogen-oxygen concentration ratios are explained by kinetic phase transitions or switching phenomena on the catalytic metal surface. Below the transition point the response of platinum-insulator silicon carbide devices is small and above the transition large and almost saturated. It is found that the critical ratio depends on the operation temperature and the properties of the device. Three different cases are identified, namely injection-, diffusion- and reaction rate determined transitions. At sufficiently large temperatures the transition is injection limited and occurs at the stoichiometric ratio of hydrogen and oxygen in the gas mixture. The implications of the experimental observations on the applications of chemical sensors with catalytic sensing layers are discussed.
The computer screen photo-assisted technique (CSPT) is a method for the classification of colorimetric assays utilizing ordinary computer sets and web cameras as instrumentation. In CSPT measurements the web camera captures the image of the assay under the screen illumination, and typically a spurious spatial distribution of intensities is overlapped on the image. This issue is examined here, focusing on the effect of the sample and illuminating colors on the spatial modulation of intensity. A method for the selection of colors composing an illuminating sequence that minimizes the spatial variability is proposed. The approach is tested for the classification of different color substances showing improvements up to 53% of the intra/inter cluster distance ratio measured in a PCA space, when compared to randomly chosen colors. © 2006 Elsevier B.V. All rights reserved.
Despite several types of fluorescent sensing molecules have been proposed and examined to signal Hg2+ ion binding, the development of fluorescence-based devices for in-field Hg2+ detection and screening in environmental and industrial samples is still a challenging task. Herein, we report the synthesis and characterization of three new coumarin-based fluorescent chemosensors featuring mixed thia/aza macrocyclic framework as receptors units, that is, ligands L1-L3. These probes revealed an OFF-ON selective response to the presence of Hg2+ ions in MeCN/H2O 4:1 (v/v), which allowed imaging of this metal ion in Cos-7 cells in vitro. Once included in silica core-polyethylene glycol (PEG) shell nanoparticles or supported on polyvinyl chloride (PVC)-based polymeric membranes, ligands L1-L3 can also selectively sense Hg2+ ions in pure water. In particular we have developed an optical sensing array tacking advantage of the fluorescent properties of ligand L3 and based on the computer screen photo assisted technique (CSPT). In the device ligand L3 is dispersed into PVC membranes and it quantitatively responds to Hg2+ ions in natural water samples.
Rapid quantitative determinations of creatinine, potassium and glucose, all important parameters in routine medical diagnostics, are demonstrated using a computer screen photo-assisted technique (CSPT). CSPT uses regular computer screens as light sources and web cameras as imaging detectors for supporting optical evaluations of diverse character. The ubiquity and versatility of the setup, makes CSPT an attractive candidate for point of care determinations. A robust procedure for the automatic selection of experimental conditions in CSPT evaluation, including camera channels and illuminating colors that minimize the measuring time up to 5 times is described. The method utilizes the correlation between experimental conditions and classification scores, obtained under a generic 50 color training session, to extract measuring sequences as short as 9 s. The extracted measuring conditions automatically adapted to the different tests provided a general, practical and fast approach for CSPT optimization in real scenarios. © 2008 Elsevier B.V. All rights reserved.
Poster på konferensen " Eurosensors XX, Göteborg, Sweden, 17-20 sept.
Photodesorption of thin films of fulvic acid adsorbed on planar iron oxide surfaces was monitored by ellipsometry. Description was first observed at 546 nm, and additional fractions of the adsorbed acid left the surfaces at 405 and 365 nm Similar kinetics for photodesorption was observed from metallic iron films and from porous iron oxide prepared electrochemically by deposition on porous silicon substrates. Soluble photoproducts leaving the surface H ere monitored by UV absorbance spectroscopy at 200 nm Gaseous products were not detected by mass spectrometry but the results seemed to indicate that net all of the photoproducts entered the liquid phase. Of the metal films tested which adsorbed fulvic acid from aqueous solution (Fe. Cr, Ni, Al, and Pt), it was only iron which exhibited a photodesorption effect. (C) 2001 Elsevier Science B.V. All rights reserved.
The sensor performance of MISiC (metal-insulator-silicon carbide) diode devices depends on their temperature pretreatment: an activation step at 600 degreesC leads to fast-responding devices with extraordinarily high signals but the devices fail when operated above 700 degreesC. The authors focus on the key role of nanoparticles in high-temperature gas sensor applications of these MISiC devices, presenting a model in which the interface dipole moment of nanoparticles is seen as the driving force and explaining the difference in response of capacitor-configuration and Schottky-diode-configuration devices.
This work reports on thermally isolated electronic components for gas sensing applications. The device is composed of an array of 4 MOSFET, a diode and a semiconductor resistor integrated on a micro-hotplate, which is fabricated using bulk micromachining of silicon. The thermal efficiency of the device is 2°C/mW with a thermal constant less than 100 ms. Holes are made in the passivation film over the gates of the MOSFET and gas sensitive films deposited on top of the gate insulator. The low thermal mass device realized allows new modes of operation for MOSFET gas sensors such as a combination of the field and thermal effects and a pulsed temperature mode of operation.
This paper reports on the design, fabrication, and characterization of the first low-power consumption MOSFET gas sensor. The novel MOSFET array gas sensor has been fabricated using anisotropic bulk silicon micromachining. A heating resistor, a diode used as temperature sensor, and four MOSFETs are located in a silicon island suspended by a dielectric membrane. The membrane has a low thermal conductivity coefficient and, therefore, thermally isolates the electronic components from the chip frame. This low thermal mass device allows the reduction of the power consumption to a value of 90 mW for an array of four MOSFETs at an operating temperature of 170 °C. Three of the MOSFETs have their gate covered with thin catalytic metals and are used as gas sensors. The fourth one has a standard gate covered with nitride and could act as a reference. The sensor was tested under different gaseous atmospheres and has shown good gas sensitivities to hydrogen and ammonia. The low-power MOSFET array gas sensor presented is suitable for applications in portable gas sensor instruments, electronic noses, and automobiles.
This communication presents a modulated mode of operation for MOSFET gas sensors. A low-power micromachined device allows pulsing the temperature of MOSFET gas sensors with a time constant less than 100ms. Modulating the temperature during the gas exposure modifies the kinetics of the gas reactions with the sensing film. The way the sensor response is modified by the temperature modulation depends on the sensor "history", on the nature of the surrounding gaseous atmosphere, and on the type of materials used as catalytic sensing film. Pulsing the temperature up just after the gas exposure can reduce the recovery time for specific applications, such as for hydrogen detection. Cycling the temperature can allow the discrimination between different gas mixtures. Discrimination was shown for gaseous mixtures of hydrogen and ammonia in air. The results obtained indicate that a "smart" combination of sample and temperature profile could be used to expand the information content in the sensor response. © 2003 Elsevier Science B.V. All rights reserved.
The application of pyrrole-substituted porphyrin electropolymers for simultaneous optical and electrochemical analysis of red-ox active analytes, namely diazo-conjugated dyes of Sudan family, is presented. Sudan colorants are widely used in many fields, but accurate screening of their consumption is required due to their high toxicity. The inherent electrochemical activity of Sudan dyes, as far as their intense coloration, makes possible to find the appropriate conditions of hybrid optical and electrochemical porphyrin electropolymer based sensor array system application. This approach allowed a significant increase in the chemical information, improving the analytical system performance in terms of selectivity and sensitivity, and permitted the fast and simple monitoring of Sudan dye analytes.
Global glycosylation changes of serum proteins in type 1 diabetic patients have in this paper been investigated based on the interaction of the saccharide moiety of serum proteins with different lectins. Lectins are proteins, which bind carbohydrates specifically and reversibly. Panels with lectins of various carbohydrate specificities were immobilized on gold surfaces. Sera from healthy individuals, newly diagnosed type 1 diabetes patients and type 1 diabetes patients having had the disease for 4–6 years, respectively, were applied to the lectin panel. The biorecognition was evaluated with null ellipsometry. Data obtained were related to an internal standard of lactoferrin. Multivariate data analysis (MVDA) techniques were used to analyze data.
Principal component analysis showed that the lectin panel enabled discrimination between sera from the three different above-mentioned groups. Using an artificial neuronal net (ANN), it was possible to correctly categorize unknown serum samples into one of the three groups.
Serum proteins of different species and of different human blood groups exhibit various protein glycosylation patterns. Sera from human, pig, sheep and guinea pig have been applied to a panel of eight different lectins immobilized on a gold wafer. The biorecognition has been evaluated with scanning ellipsometry and the two-dimensional matrices obtained have been treated with image analysis and MVDA for evaluation. The results showed a clear difference in protein binding pattern between the different species and thereby separation of the different sera could be made. Dendograms indicate that human and pig sera are the most related of the four different sera investigated.
In this work, simple microcontact printed gold-wafers were used to make a lectin panel for investigation and discrimination of different meat juices from fresh meat of cattle, chicken, pig, cod, turkey and lamb. Seven different lectins were thus attached to gold surfaces using the streptavidin–biotin method. Lectins recognize and bind specifically to carbohydrate structures present on different proteins. The biorecognition was evaluated with null ellipsometry and the data obtained was related to an internal standard of lactoferrin. The data was evaluated with multivariate data analysis techniques to identify possible discrimination or grouping of data. Scanning ellipsometry was used for visualization of the binding pattern of the lectins and the meat juice proteins. The two-dimensional images obtained could be used to visualize the protein distribution, furthermore, to exclude anomalies. The results showed that the different meat juices from the six different species: cattle, chicken, pig, cod, turkey and lamb could be discriminated from each other. The results showed to be more repetitive for the mammalian meat juices. Using a simple model based on an artificial neuronal net, it was also possible to classify meat juices from the mammals investigated.
The interaction of acetylene and ethylene with a clean and oxygen covered Pd surface has been studied at a temperature of 473 K. The measurements were performed on a hydrogen sensitive Pd-MOS structure making it possible to obtain direct information on the dissociation of both hydrogen and oxygen containing species on a palladium surface. Desorption studies were also performed as well as ultraviolet photoelectron spectroscopy and work function measurements. The studies show that both acetylene and ethylene adsorb dissociatively at this temperature leaving mainly carbon on the surface. When an oxygen covered Pd surface is exposed to C2H2 or C2H4 carbon dioxide and water will be formed and desorb until the surface is oxygen free. In the case of acetylene the presence of preadsorbed oxygen does not block or prevent the C2H2 dissociation on the surface. For C2H4, a large preadsorbed oxygen coverage ( 0.45) will have an impeding effect on the dissociation. The CO2 desorption is oxygen coverage dependent contrary to the H2O desorption. This is due to the fact that hydrogen has a large lateral mobility on the surface while carbon has not. Both the CO2 and H2O reactions are, however, due to the same type of mechanisms.
The photodissociative splitting of water has been studied in gas phase on a plane solid surface. A hydrogen sensitive Pd‐metal‐oxide‐semiconductor (MOS) structure was coated with 1–2 nm TiOx and exposed to water vapor and ultraviolet light. A natural separation of the produced hydrogen and oxygen occurs over the Pd film of the structure and the produced hydrogen is monitored by the electric behavior of the MOS device. The results suggest that suitably treated thin Pd membranes may be of interest for studying the continuous photodissociation of water.