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MEMBRANE PROTEIN RECEPTORS IN SUPPORTED LIPID BILAYERS AS BIOSENSORS
No full textAcetylcholine receptors have been incorporated into planar lipid bilayers and
coupled to the surface of a silicon wafer. The binding of ligands to these receptors have been
quantified by measuring the concomitant changes of certain electrical properties of the
membrane such as impedance and capacitance. The results show that there is principle
feasibility to use membrane protein receptors as biosensors
DUAL-ANTIBODY SYSTEMS FOR THE CONSTRUCTION OF BIOSENSORS
No full textWe are reviewing a dual-antibody analytical system based on competitive immunoassay
methodologies. Two antibodies are immobilized at separate locations: one antibody (Ab-1)
recognizing the analyte and analyte-enzyme conjugate, and the other antibody (Ab-2) recognizing the
enzyme componentin the conjugate. This dual-antibody system provides twosignals, originating
from the analyte-enzyme conjugate bound to Ab-1 and Ab-2, in response to different analyte
concentrations in samples. A competitive immunoassay can be performed without separation of
bound and unboundanalyte-enzyme conjugate by the user. Three different modifications of the dualantibody
system are described: 1) operationin the irreversible mode under equilibrium conditions, 2)
measurement in the irreversible mode under non-equilibrium conditions, and 3) continuous
monitoring in the reversible mode. The first two modifications can be used for the developmentof
disposable probes. The secondsystem is particularly suitable for immunochromatographywith either
colorimetric or amperometric signal readout. Thethird principle makesuse ofthe reversibility of
binding for antigen-antibody complex formation and can be adapted for slow-response sensors for
the continuous measurementoffluctuating concentrations of small analytes in aqueous media streams
REAL TIME BIA. A NEW BIOSENSOR BASED TECHNOLOGY FOR THE DIRECT MEASUREMENT OF BIOMOLECULAR INTERACTIONS
No full textThis report descibes a system for real time biospecific
interaction analysis, using biosensor technology based on
the optical phenomenon surface plasmon resonance. The
biospecific interface is a sensor chip consisting of a thin
gold film deposited on a glass support and covered with a
dextran polymer. One component of the interaction being
studied is attached covalently to the dextran, and other
interactants are passed over the sensor chip assisted by a
flow injection liquid handling system. Sequential
interactions can be followed in real time in terms of
changes in the mass concentration of molecules at the sensor
interface. Surface concentrations down to 10 pg/mm2 can be
measured. Repeated analysis can be performed on the same
sensor chip by regeneration of the specific interaction.
With this system, the same general procedure can be used for
a wide range analytical methodology including: 1)
identification and classification, for example antigen
specificity and antibody subclass classification 2)
concentration and activity determination in crude samples 3)
affinity ranking 4) determination of relative association
and dissociation rate constants 5) label free detection of
multiple sequential interactions, for example epitope
mapping of antibody binding sites on an antigen
PIEZOELECTRIC (PZ) IMMUNOSENSORS AND THEIR APPLICATIONS
No full textThe recent development of piezoelectric immunosensors is
reviewed. The selectivity provided by the biological coatings
together with the inherent sensitivity of the PZ devices and the
ability to oscillate the crystal in liquid medium have induced a
rising interest in this class of sensors. Methods of coating and
several applications are reported including microgravimetric
immunoassays, microbial assays and gas phase immunosensors
NOVEL COVALENT AVIDIN IMMOBILIZATION ON GLASSY CARBON ELECTRODES USING A BIFUNCTIONAL REAGENT
No full textIt is generally accepted that the stability and performance of a biosensor is determined by the
way biocomponents are immobilized on the inorganic support. We present a covalent coupling
method of the anchor protein avidin to a glassy carbon electrode surface using the
heterobifunctional reagent m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS). Thus, a
nearly complete, biologically active monolayer of avidin was obtained which is suitable for the
immobilization of any biotinylated compound. These modified electrodes are potentially useful as
amperometric biosensors
Das Gensequenzanalysesystem DIANA
No full textDIANA (Dna Interactive Artificial Neural-network Analysis) is a software package for the
analysis of gene sequences. It allows a precise determination of splicing positions and coding
regions in the human genom. The method is based on cascading neural networks, which were
specially trained for the identification of human genes. DIANA has got a graphical user interface
that is easy to understand. The analysis of 100.000 base pairs takes only a few seconds on a
standard workstation. DIANAcanbe extendedfor further organisms
Statistical Significance of Local Alignments with Gaps
No full textRecent results on the statistical significance of local alignment with gaps are presented.
Parameters necessary for computation of the probability that an alignment achieves a
certain score can be approximated by a computationally fast simulation. We present
applications to database searching where there-sorting of the output bystatistical significance
instead of score leads to improved ability to distinguish sequences homologous to
the probe sequence from unrelated sequences
BIOSENSORS IN INDUSTRIAL BIOPROCESS CONTROL
No full textOur experiences in industrial bioprocess control have culminated in a
concept for the development of biosensors which distinguishes itself
from other, better known, approaches by treating the biosensor as a
component of a measuring technique used for the solution of an
analytical problem. The combination of flow injection analysis with
immobilized enzymes, for example, is already used today for the solution
of metrological problems in bioprocess control. The development of
biosensors must be accompanied by an improvement and/or simplification
of already-existing analysis systems. Only the parallel development of
biosensors and their complementary metrology can lead to industriallysound
analytical solutions.
Two examples are presented to support our concept:
- The development of a glucose sensor for the control of bioprocesses,
and
- The development of biosensors for the control of biological stages
in waste water treatment
SURFACE ANALYTICAL METHODS AS A POWERFUL TOOL IN DEVELOPMENT OF MODIFIED SURFACES FOR BIOSENSORS
No full textIt could be shown, that the thickness of layers and the chemical
composition of unmodified and modified silicon surfaces can be
well analyzed by Secondary Ion Mass Spectrometry (SIMS). The interpretation
of the results gives helpful hints for design of
surface layers useful for biosensor development
QUANTITATIVE DETECTION OF GASEOUS SUBSTANCES AT LOW ppm AND SUB-ppm LEVELS BY MEANS OF ENZYME DIFFUSION BADGES
No full textA family of diffusion dependent enzyme badges for measurement of
gaseous hydrogen peroxide, formaldehyde, acetaldehyde, and ethanol
is presented.
The main functional part of it is a porous solid support at the top
of which the required enzymes are applied, e.g. by lyophilization.
The badge is activated by dipping the enzyme-coated support into a
reagent solution. Capillary forces and evaporation produce a flow of
reagent solution to the surface resulting in a permanent water and
reagent supply as well as in concentrating the enzyme(s) at the
surface. The gaseous substrate molecules reach the surface by
diffusion. The high specifity of the badges results from the
catalytic conversion of the gaseous compounds by the enzymes. The
colored compounds finally produced by the combined enzymatic and
chemical reactions are concentrated at the surface because
evaporation prevents their diffusion into the support material.?)
This way a selective determination of the concentration of gaseous
enzyme substrates becomes feasible, simply by color comparison or by
reflectometry.
These badges allow simple, selective and reliable spot measurements
of hydrogen peroxide and formaldehyde down to 100 ppb after 15 min
exposure