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FIBER OPTIC OXYGEN SENSOR
No full textIn 1978 work was begun on development of a fiber optic oxygen partial
pressure sensor for physiological application. Originally a search
was made for an optical absorption indicator, but since one with
suitable stability could not be found, a sensor was developed based on
the fluorescence quenching principles demonstrated by Kautsky and
Hirsch.
The original sensor, based on a dye adsorbed on a hydrophobic support
enclosed in a porous envelope, has been further developed into a
needle form for physiological research applications.
Instrumentation to use the sensor has followed an evolutionary path.
The principal problem has been to obtain low drift and good stability
of the calibration. A computer operated instrument has just been
completed, which is expected to be suitable for a variety of research
applications.
A series of experiments to measure PO, in dogs' eyes were done with a
prototype instrument in comparison with a polarographic electrode, and
future work on human subjects is planned with the new instrument.
This requires operation of the sensor in a high ambient light level.
The instrumentation and measurements will be described
THE HUMAN FRONTIER SCIENCE PROGRAM
No full textHuman bodies and biobodies perform excellent superior functions such as
sophisticated information processing, the efficient transportation of
materials and energy conversion. By elucidating and applying these functions,
we will be able to develop new modes of science and technology
in harmony with nature and human society. Research on these biological
functions is a long-term project that will require interdisciplinary
cooperation at an international
resolved to pursue this project
tion in the concerned fields of
proposed the program called the
Venice Summit in June
GLUCOSE SENSOR: COMPARISON OF ENZYMATIC AND ELECTROCATALYTIC PRINCIPLES
No full textAn enzymatic glucose sensor using glucose oxidase (1) and especially
an electrocatalytic sensor oxidizing glucose directly (2) are under
investigation for the intracorporal measurement of glucose. Both are
based on electrochemical principle. Though we have mainly pursued the
latter one, both systems will be compared by presenting some experimental
results. The enzymatic sensor was designed in a simple way:
Pt-electrode/glucose oxidase solution/membrane. This sensor is featured
by the residual current due to direct oxidation of glucose at
the electrode, the effect of H20.2 which results as a product of enzymatic
oxidation of glucose and the presence or absence of oxygen
during the glucose measurement. In the electrocatalytic sensor, the
membrane covered Pt-electrode is subjected to a potential-jump in
cycle between a working and a rejuvenating potential. Either the
charge derived at the working potential or the impedance obtained at
two different frequencies for various potential steps is a measure
for the glucose concentration. Its performance is mainly determined
by the electrode poisoning and the membrane properties. However,
these conditions can be optimized and, as will be shown, glucose
still be measured in saline solutions, serum and blood. The electrocatalytic
sensor is promising because of its long term stability
though its selectivity poses a problem. It is just the opposite in
enzyme sensor since the enzyme is not stable over longer periods
MICRO ION-SELECTIVE ELECTRODES BASED ON ACTIVATED CARBON FIBERS
No full textConventional potentiometric microelectrodes which are used as
reference and/or ion-selective electrodes for biomedical and
physiological applications are usually based on glass capillary
supports. They can be made with a tip diameter of approximately 1 pa
by using a special glass capillary-pulling equipment. The resulting
resistance of the glass capillary tip is >100° \m and the relatively
high distributed capacitance across the glass capillary wall which
separates the interior solution from the outside solution causes the
long time constant and a low signal/noise ratio of these
microelectrodes. This can cause problens if fast changes in ion
concentration have to be measured, as for example during the
electrostimulation of cells
The "Chameleon Surface" : A New Concept for a Solid State Reference Electrode
No full textA new concept for an “all solid state” reference half-cell for use in aqueous solutions based on
mixed valent transition metal oxids is presented. XPS-surface analytical measurements demonstrate
the adaptation of the surface chemistry to the chemistry of the solution ("Chameleon Surface"). Thus
the driving force of the potential formation at the solid/liquid interface is significantly attenuated
which may explain the electrochemically observed sub-Nernst sensitivities (~ 10 mV/pH)
ENZYME SENSORS USING FLUORESCENCE BASED OXYGEN DETECTION
No full textAdvantages of the use of fluorescent sensor devices for oxygen measurements
in biological samples were described earlier li)
Basically these sensors (Optodes) consist of a polymeric (hydrophobic)
fluorescent layer, that is chemically attached to a transparent carrier.
Oxygen sensitivity follows the rules of dynamic quenching of fluores-
_cence and can be described by the Stern-Volmer equakıon (1)
ENGINEERING OF RNASE T 1
No full textRibonuclease Tl (RNase T1) was found in 1975 by Sato and Egamil from Aspergillus
oryzae. This enzyme catalyzes hydrolysis of single-stranded RNA at guanylic acid 3'-
phosphodiester sites. By this property RNase Tl is extremely useful for elucidation
of primary structure of RNA's together with pancreatic RNase. The amino acid sequence
of RNase Tl has been reported in 1965 , but it was corrected later in 1985.2 This
enzyme consists of 104 amino acids and two disulfide bridges between Cys 2 and 10, as
well as Cys6 and 103. RNase T1 is very stable towards heating and acidic conditions
and suitable for biochemical and physicochemical studies.3 Recently three dimensional
structure of this enzyme was elucidated by X-ray crystallography4:5 as a complex with
an inhibitor guanosine 2'-phosphate.
In this paper we attempted to obtain some details of structure-function relationship
of RNase Tl by means of protein engineering
Vorwort - Inhaltsverzeichnis
No full textIn den letzten Jahrzehnten erlebte die Fermentationstechnik, die sich
allmählich zur Biotechnologie entwickelt hatte, eine Renaissance, die
sie insbesondere den ihr zugetragenden neuen Aufgaben und den sich
abzeichnenden Erfolgen des "Genetic engineering" verdankt. Obwohl die
Verarbeitung der Fermentationsprodukte von großer wirtschaftlicher Bedeutung
ist, wurde der Isolierung und Reinigung der biotechnolegischen
Produkte an den Universitäten geringe Aufmerksamkeit gewidmet. Um das
Interesse der Kollegen aus dem Bereich der Grundlagenforschung für die
Probleme der Aufarbeitung zu wecken und die Fachleute aus den Universitäten
und Forschungsinstituten mit ihren Kollegen aus der Industrie
zusammenzubringen, wurde das 23. Bunsen-Kolloquium unter Mitwirkung
der Dechema und der GBF von der Bunsen-Gesellschaft für Physikalische
Chemie organisiert.
Wegen des großen Umfanges der Aufarbeitung biologischer Medien wurden
drei aktuelle Themenkreise ausgewählt: die Adsorption, die Extraktion
und die Schaumflotation.
Die rege Beteiligung aus der Industrie zeigt, daß man dort diesen
Trennverfahren große Bedeutung zumißt. Die interessanten Vorträge und
die ausführliche Diskussion der Themen sorgten für einen intensiven
Informationsaustausch zwischen den Teilnehmern,
Der Gesellschaft für Biotechnologische Forschung mbH wird für die
Überlassung des Vortragsraumes und die reibungslose Abwicklung des
Kolloquiums und Herrn Dr. J.-H. Walsdorff für seine Unterstützung bei
der Organisation gedankt
EXTRAKTIVE AUFARBEITUNG VON INTRAZELLULAREN ENZYMEN
No full textWäßrige Phasensysteme weisen einen hohen Wassergehalt auf, der sie fiir die Verteilung
von Biopolymeren geeignet macht. Durch selektive Extraktion in solchen Systemen
wurden bereits zahlreiche intrazelluläre Enzyme, z. T. auch im technischen
Maßstab, aufgearbeitet. In diesem Artikel wird eine kurze Übersicht über die
Grundlagen und den Entwicklungsstand der Technologie gegeben
SCANNING ELECTRON MICROSCOPY OF FRUITING BODY FORMATION BY STIGMATELLA AURANTICA AND CHONDROMYCES CROCATUS
No full textThe study to be presented consists of two related parts. Scanning. electron
microscopy was employed 1) to observe mature fruiting bodies of several
myxobacter genera and 2) to study details of fruiting body formation
by Stigmatella aurantica and Chondromyces crocatus. fiicrographs representative
of both parts will be shown.
Initially, technics for optimum fruiting body production.and for specimen
preparation were perfected on the structually less complex fruiting
bodies produced by species of Myxococcus and Cystobacter. These were
then modified to permit an in depth study of fruiting body formation by
pure cultures of S. aurantica and C. crocatus. In summary, vegetative
cells of the latter two species were grown and then transferred to a nonnutrient
medium for fructification. Fruiting‘body formation was interrupted
at various stages by fixation with glutaraldehyde vapours. Fixed
and dehydrated specimen were dried by the critical point method in liquid
C0,. Fruiting in both species begins with an aggregation center which
closely resembles a fried egg in appearance. It is after this stage that
significant and consistant differences occur in fruiting between the two
organisms., In S. aurantica, the "yolk region" of the fried egg stage extends
upward to form a column-like stalk which is nearly uniform in diameter
throughout its length. At maximum height the terminus of the stalk
develops into an irregular pattern of bud-like swellings which eventually
differentiate into sporangia. C. crocatus differs in chat the "yolk
region" enlarges into a large bulbous structure initially. The bulb anpears
to be lifted upward by a slender stalk which develops beneath. The
bulb differentiates into numerous bud-like swellings at maximum stalk
height, but unlike Stigmatella, the swellings and immature sporanoia are
arranged in a distinctive radial pattern. This symmetry is lost as more
sporangia develop and mature. Stalks of two week old mature fruiting
bodies of both species appear cellular in composition. Stereomicrographs
of cross sections of broken mature stalks suggest the cells are oriented
parallel to the long axis of the stalk